Latest / Boring Science / Can Humans Ever Reach Voyager 1_s Distance_ _ Science For Sleep

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Can Humans Ever Reach Voyager 1_s Distance_ _ Science For Sleep · Boring Science

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  Speaker 1: On November 18th, 2026, at two in the morning Pacific time,
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  Speaker 1: something happened that had never happened before in the history
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  Speaker 1: of human technology. A spacecraft crossed a threshold, not a
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  Speaker 1: physical boundary marked by any wall or line, but a distance,
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  Speaker 1: 16 billion miles from Earth, the distance light itself travels
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  Speaker 1: in exactly 24 hours, one light day. Humanity's most distant
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  Speaker 1: machine quietly passed this mark while most of the world
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  Speaker 1: was asleep and almost nobody noticed. That spacecraft is Voyager 1.
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  Speaker 1: It has been moving outward continuously since September of 1977,
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  Speaker 1: which means it had been travelling for nearly 50 years
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  Speaker 1: before it reached this point. The milestone sounds abstract at first.
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  Speaker 1: A light day. What does that mean in terms a
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  Speaker 1: person can actually hold? Light moves at roughly 186,000 miles
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  Speaker 1: per second. In one second, it crosses the continental United
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  Speaker 1: States about 60 times. In eight minutes, it covers the
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  Speaker 1: distance from the sun to the Earth. In 24 hours,
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  Speaker 1: it travels 16 billion miles. That is the distance Voyager
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  Speaker 1: crossed on November 18th. Not a speed, a distance. 16
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  Speaker 1: billion miles of empty space between a spinning planet and
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  Speaker 1: a machine roughly the size of a small car. The
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  Speaker 1: reason this threshold matters is not purely symbolic. It changes
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  Speaker 1: the practical reality of communicating with the spacecraft in a
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  Speaker 1: way that feels almost impossible to accept. When Voyager was
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  Speaker 1: younger and closer, signals traveling at the speed of light
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  Speaker 1: still took minutes to arrive, then hours. Mission controllers could
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  Speaker 1: send a command and receive a response the same day.
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  Speaker 1: That is no longer true. At one light day, a
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  Speaker 1: signal sent from the Jet Propulsion Laboratory in California takes
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  Speaker 1: a full 24 hours to reach Voyager. Then Voyager has
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  Speaker 1: to process whatever instruction it received and transmit a response.
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  Speaker 1: That response also takes 24 hours to travel back. A
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  Speaker 1: single exchange, one question, one answer, now takes two full days.
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  Speaker 1: A complete rotation of the Earth passes between the moment
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  Speaker 1: a command leaves the antenna and the moment the team
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  Speaker 1: learns whether it worked. Think about what that means in practice.
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  Speaker 1: If something goes wrong aboard Voyager on a Monday morning
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  Speaker 1: and engineers send a corrective command immediately, they will not
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  Speaker 1: know whether it solved the problem until Wednesday morning. If
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  Speaker 1: the first command didn't work, the next attempt adds another
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  Speaker 1: two days. There is no quick reaction possible. There is
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  Speaker 1: no real-time control. Every decision made by the team on
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  Speaker 1: the ground has to be correct, or nearly correct, before
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  Speaker 1: it is sent, because the cost of a mistake is
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  Speaker 1: measured not in seconds, but in days. The spacecraft is
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  Speaker 1: on its own between transmissions in a way that no
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  Speaker 1: other operational machine in human history has ever been, and
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  Speaker 1: yet Voyager is still operational, still transmitting. The signal it
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  Speaker 1: sends back to Earth is extraordinarily faint, far weaker than
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  Speaker 1: the power of a refrigerator light bulb. But the Deep
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  Speaker 1: Space Network's large antennas can still detect it. Scientists are
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  Speaker 1: still receiving data from instruments that have been running continuously
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  Speaker 1: for five decades. There is something almost difficult to process
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  Speaker 1: about that fact. The spacecraft was built with 1970s technology,
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  Speaker 1: launched before personal computers existed in any recognisable form, and
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  Speaker 1: it is still alive in interstellar space, still telling us
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  Speaker 1: what it finds out there in the dark between the stars.
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  Speaker 1: The one light-day milestone is also a reminder of the
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  Speaker 1: gap between what Voyager is and where it sits. Voyager
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  Speaker 1: is not large. It is not powerful. By modern standards,
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  Speaker 1: its computers are laughably primitive. But it crossed into interstellar
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  Speaker 1: space in 2012, became the first human-made object to do so,
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  Speaker 1: and has been moving deeper into that territory ever since.
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  Speaker 1: No other machine has gone farther. Nothing else we have
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  Speaker 1: built is even close. The nearest competitor is Voyager 2.
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  Speaker 1: also launched in 1977. Also still operational, but trailing its
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  Speaker 1: twin by billions of miles. When the clock ticked past 2.16
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  Speaker 1: in the morning on November 18th, and Voyager reached that threshold,
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  Speaker 1: it raised a question that is harder to answer than
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  Speaker 1: it sounds. People have always asked whether we could follow
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  Speaker 1: our machines into space. where the humans could eventually go
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  Speaker 1: where our probes have gone. We sent robots to the moon,
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  Speaker 1: then sent people. We sent robots to Mars, and now
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  Speaker 1: serious plans exist to send people there too. So it
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  Speaker 1: seems natural to ask the same question about Voyager. We
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  Speaker 1: sent a spacecraft to interstellar space. Could humans ever follow?
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  Speaker 1: Could anything we build reach the place where Voyager now sits,
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  Speaker 1: in any time frame that would mean something to the
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  Speaker 1: civilization that launched it? And that question, whether we could
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  Speaker 1: ever actually reach the place Voyager 1 now sits, is
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  Speaker 1: not a simple one to answer. Voyager 1 is not
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  Speaker 1: a large spacecraft. It weighs about 722 kilograms, roughly the
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  Speaker 1: mass of a small car. though its shape looks nothing
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  Speaker 1: like one. The main body is a 10-sided aluminum frame
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  Speaker 1: about 47 centimeters tall with a large dish antenna dominating
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  Speaker 1: one side. That dish is 3.7 meters across, about the
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  Speaker 1: width of a large living room, and it is the
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  Speaker 1: feature that makes everything else possible. The one component that
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  Speaker 1: allows a machine in interstellar space to whisper back to
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  Speaker 1: a planet it left behind in 1977. Extending outward from
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  Speaker 1: the central frame are booms carrying scientific instruments, magnetometers, the
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  Speaker 1: three radioisotope thermoelectric generators that have been slowly converting heat
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  Speaker 1: from decaying plutonium into electricity for nearly five decades. From
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  Speaker 1: the tip of one boom to the far end of another,
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  Speaker 1: spacecraft spans roughly 12 meters. Sitting on a launch pad
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  Speaker 1: it would not be remarkable to look at. It looks
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  Speaker 1: like something assembled from components that engineers had on hand,
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  Speaker 1: because in many ways it was. It launched on September
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  Speaker 1: 5th 1977 from Cape Canaveral aboard a Titan II IIE rocket.
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  Speaker 1: The mission at that point had a clear and bounded purpose.
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  Speaker 1: Scientists had discovered in the 1960s that a rare alignment
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  Speaker 1: of the outer planets would occur in the late 1970s,
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  Speaker 1: one that would not repeat for another 176 years. Jupiter, Saturn,
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  Speaker 1: Uranus and Neptune would be positioned in such a way
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  Speaker 1: that a single spacecraft, using each planet's gravity to redirect
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  Speaker 1: itself toward the next, could visit all four in sequence
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  Speaker 1: without needing an impossibly large fuel supply. The window to
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  Speaker 1: launch was narrow. NASA moved quickly. The mission was called
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  Speaker 1: the Voyager program. Two spacecraft were built, both on tight
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  Speaker 1: timelines and tighter budgets. Voyager 1's specific assignment was a
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  Speaker 1: flyby of Jupiter and Saturn, with particular attention to Saturn's
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  Speaker 1: moon Titan. that astronomers suspected had a substantial atmosphere. Because
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  Speaker 1: the trajectory required to get a close look at Titan
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  Speaker 1: bent the spacecraft's path sharply out of the plane of
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  Speaker 1: the solar system. Voyager 1 could not continue onto Uranus
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  Speaker 1: and Neptune. That work fell to Voyager 2. Voyager 1's mission,
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  Speaker 1: as officially designed, would end with Saturn. The spacecraft would
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  Speaker 1: fly past, gather data, transmit everything back, then continue moving
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  Speaker 1: outward into space where there was nothing left to study,
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  Speaker 1: nothing planned and nothing expected. The mission would be complete.
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  Speaker 1: What no one publicly committed to, at least not in
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  Speaker 1: official documentation, was what might come after. But a small
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  Speaker 1: group of scientists and engineers at the Jet Propulsion Laboratory
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  Speaker 1: understood that, If the planetary mission succeeded, the spacecraft would
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  Speaker 1: still be functional. It would still have power. it would
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  Speaker 1: still be transmitting, and it would be moving through a
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  Speaker 1: region of space that no human instrument had ever entered.
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  Speaker 1: Physicist Ed Stone, who served as the Voyager project scientist,
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  Speaker 1: a handful of colleagues pushed to keep the mission funded
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  Speaker 1: beyond the planetary encounters. What followed wasn't an accident exactly.
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  Speaker 1: It was a persistent argument that a working spacecraft in
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  Speaker 1: unexplored territory represented an opportunity that no civilization with any
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  Speaker 1: scientific conscience could simply abandon. The instruments aboard supported that argument.
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  Speaker 1: Voyager 1 carries equipment designed to measure magnetic fields, low
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  Speaker 1: energy charged particles, plasma waves, cosmic rays, the properties of
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  Speaker 1: the solar wind. These instruments were built to study the
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  Speaker 1: outer planets, but they were also precisely the tools needed
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  Speaker 1: to detect what the solar system looks like at its boundary,
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  Speaker 1: where the sun's influence fades and interstellar space begins. The
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  Speaker 1: spacecraft was, almost by design, equipped to answer questions nobody
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  Speaker 1: had fully thought to ask when it was built. There
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  Speaker 1: is also the golden record. Each Voyager spacecraft carries a
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  Speaker 1: 12-inch gold-plated copper disc containing sounds and images selected to
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  Speaker 1: represent life and culture on Earth. It includes greetings in
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  Speaker 1: 55 languages, music from dozens of cultures, The sounds of
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  Speaker 1: rain and wind and surf and a human heartbeat, photographs
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  Speaker 1: of human anatomy in planetary landscapes. Mathematical diagrams intended to
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  Speaker 1: allow an intelligent recipient to decode the contents. Carl Sagan
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  Speaker 1: chaired the committee that assembled it. The record was not
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  Speaker 1: a navigation instrument. It was not a scientific sensor. It
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  Speaker 1: served no operational purpose in the mission as originally planned.
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  Speaker 1: It was a message placed aboard a spacecraft that its
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  Speaker 1: creators understood might one day leave the solar system and
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  Speaker 1: drift through interstellar space for billions of years. Someone thought
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  Speaker 1: carefully enough about that possibility to spend time and resources
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  Speaker 1: building and including it. That tells you something about the
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  Speaker 1: people who built this machine. By the time Voyager 1
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  Speaker 1: completed its Saturn flyby in November of 1980, it had
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  Speaker 1: already returned more data about the outer solar system than
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  Speaker 1: had been gathered in all of prior human history. It
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  Speaker 1: revealed that Jupiter's moon Io was volcanically active, a discovery
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  Speaker 1: nobody anticipated, It returned detailed images of Saturn's rings that
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  Speaker 1: transformed understanding of how planetary ring systems form and behave.
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  Speaker 1: It measured the atmosphere of Titan and found it denser
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  Speaker 1: than Earth's. The mission, by any reasonable standard, had already
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  Speaker 1: succeeded beyond what anyone promised it would deliver. And then
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  Speaker 1: it kept going. Not dramatically. There was no ceremony marking
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  Speaker 1: the point where the planetary mission ended and something else began.
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  Speaker 1: The spacecraft simply continued outward, still transmitting, still drawing power
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  Speaker 1: from its generators, still being tracked by the deep space
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  Speaker 1: network's enormous antennas. The team that stayed with it shrank
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  Speaker 1: over the years, then grew again when the mission's discoveries
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  Speaker 1: commanded attention. the spacecraft became something different from what it
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  Speaker 1: had been designed to be. Not through any single decision
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  Speaker 1: or announcement, but through the accumulation of years and distance,
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  Speaker 1: and the refusal of the people watching it to stop
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  Speaker 1: paying attention. What it became, eventually, was the first human-made
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  Speaker 1: object to cross into interstellar space. To leave the Sun's
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  Speaker 1: plasma bubble, and enter the region between stars. That crossing
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  Speaker 1: happened in August 2012, 35 years after launch, in a
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  Speaker 1: region of space nobody had a photograph of. Measured by
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  Speaker 1: instruments that were already older than most people working on
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  Speaker 1: the mission at the time. For nearly 50 years, it
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  Speaker 1: has been moving outward without stopping. It has no mechanism
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  Speaker 1: to stop, even if anyone wanted it to. The reason
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  Speaker 1: Voyager 1 moves as fast as it does has almost
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  Speaker 1: nothing to do with how powerful its rockets were. The
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  Speaker 1: rockets that launched it in September of 1977 were impressive
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  Speaker 1: by any human standard. They had to be. Getting a
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  Speaker 1: 722 kilogram spacecraft off the surface of Earth and out
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  Speaker 1: of its gravitational well requires an enormous expenditure of energy.
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  Speaker 1: But those rockets burned out long before Voyager reached anything interesting,
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  Speaker 1: and the velocity they provided was nowhere near enough to
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  Speaker 1: carry the spacecraft to the distances it has now covered.
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  Speaker 1: Something else did that, something that costs no fuel at all.
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  Speaker 1: The technique is called a gravity assist, and it is
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  Speaker 1: one of the most elegant ideas in the history of spaceflight.
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  Speaker 1: The basic principle sounds almost like a trick. spacecraft falls
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  Speaker 1: toward a massive planet curves around it under the influence
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  Speaker 1: of gravity and then flies away if done correctly the
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  Speaker 1: spacecraft emerges from that encounter moving faster than it entered
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  Speaker 1: no fuel burned in the process no engine fired the
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  Speaker 1: planet simply handed over some of its momentum and the
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  Speaker 1: spacecraft took it to understand why this works you have
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  Speaker 1: to think about what is actually happening during the encounter.
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  Speaker 1: The planet is not sitting still. It is orbiting the
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  Speaker 1: Sun at its own speed, carrying enormous momentum simply by
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  Speaker 1: virtue of its mass. Jupiter, for instance, orbits the Sun
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  Speaker 1: at roughly 13 kilometers per second and contains more mass
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  Speaker 1: than all the other planets combined. When Voyager fell into
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  Speaker 1: Jupiter's gravitational field, It was essentially catching a ride on
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  Speaker 1: something moving. The geometry of the approach determines how much
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  Speaker 1: speed the spacecraft picks up and in what direction. Get
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  Speaker 1: the angle right and the spacecraft slingshots away carrying a
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  Speaker 1: fraction of the planet's orbital energy. The planet slows down
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  Speaker 1: by an immeasurably tiny amount. The spacecraft speeds up by
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  Speaker 1: an amount that matters enormously on human scales. This is
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  Speaker 1: not a loophole or an approximation. The physics is exact.
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  Speaker 1: Momentum is conserved between the planet and the spacecraft across
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  Speaker 1: the entire encounter. The planet loses what the spacecraft gains.
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  Speaker 1: Because Jupiter is so incomprehensibly massive, its slowdown from Voyager's
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  Speaker 1: flyby is a number so small it could never be measured.
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  Speaker 1: But Voyager's speed gain was real. significant and permanent. Voyager
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  Speaker 1: 1 flew past Jupiter in March of 1979. The flyby
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  Speaker 1: served the mission's scientific goals. Cameras captured the first close
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  Speaker 1: images of Jupiter's cloud bands and its moon Io in
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  Speaker 1: volcanic eruption. But the flyby also did something to Voyager's
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  Speaker 1: velocity that no rocket aboard could have matched. Jupiter's gravity
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  Speaker 1: bent the spacecraft's path and accelerated it considerably. The exact
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  Speaker 1: numbers shifted depending on the precise geometry of the encounter,
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  Speaker 1: but Voyager left Jupiter moving substantially faster than it had arrived.
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  Speaker 1: The outer solar system, which had seemed distant before, was
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  Speaker 1: now within reach on a reasonable timeline. Saturn came next.
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  Speaker 1: Voyager 1 reached Saturn in November of 1980 and passed
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  Speaker 1: within about 124,000 kilometers of its cloud tops. The Saturn
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  Speaker 1: flyby was the one that mattered for Voyager's long-term trajectory
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  Speaker 1: in a second important way. It did not just add speed,
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  Speaker 1: it bent the spacecraft's path sharply northward, out of the
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  Speaker 1: flat plane of the solar system where all the planets orbit.
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  Speaker 1: This was a deliberate choice, not an accident. Mission planners
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  Speaker 1: knew that passing close enough to Saturn's moon Titan required
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  Speaker 1: a trajectory that would fling Voyager out of the ecliptic entirely.
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  Speaker 1: They chose Titan. They accepted the consequence. That consequence was that,
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  Speaker 1: after Saturn, there were no more planets in Voyager's path.
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  Speaker 1: Uranus and Neptune were not accessible from that trajectory. any
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  Speaker 1: hope of additional gravity assists was gone. What Voyager carried
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  Speaker 1: away from that Saturn encounter was essentially everything it would
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  Speaker 1: ever have. After November of 1980 the spacecraft entered a
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  Speaker 1: long coast that has never ended. No engine has fired
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  Speaker 1: in any meaningful sense since then. No planet has offered
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  Speaker 1: another gravitational handshake. For over four decades Voyager has been
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  Speaker 1: moving on momentum it borrowed from two planets and has
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  Speaker 1: not returned. The speed it's settled into after those encounters
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  Speaker 1: works out to roughly 17 kilometers per second relative to
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  Speaker 1: the sun. That number deserves a moment. 17 kilometers per
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  Speaker 1: second means Voyager covers about 1.5 million kilometers every day.
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  Speaker 1: It means that in the time it takes you to
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  Speaker 1: read a single paragraph aloud, the spacecraft has moved roughly
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  Speaker 1: 50 kilometers farther from Earth. It is fast enough that
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  Speaker 1: the continental United States, coast to coast, would pass beneath
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  Speaker 1: it in approximately three minutes. A commercial airliner flying the
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  Speaker 1: same route takes around five hours. Voyager would cross the
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  Speaker 1: same distance before the airliner finished its safety announcement. And
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  Speaker 1: yet this speed, which took extraordinary planning and two planetary
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  Speaker 1: encounters to achieve, barely registers against the scale of the universe.
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  Speaker 1: The speed of light is approximately 300,000 kilometers per second.
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  Speaker 1: Voyager is moving at 17. That is a little under 0.006%
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  Speaker 1: of light speed. At this velocity, it would take Voyager
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  Speaker 1: roughly 73,000 years to reach Proxima Centauri, the nearest star
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  Speaker 1: to our Sun. Not 73,000 years of gradual slowing. Not 73,000
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  Speaker 1: years with occasional pauses. 73,000 years of continuous travel at
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  Speaker 1: maximum velocity, arriving at the closest possible destination. The 17
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  Speaker 1: kilometers per second that Jupiter and Saturn gave to this
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  Speaker 1: spacecraft represents the ceiling of what gravitational assistance and chemical
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  Speaker 1: propulsion together could achieve in 1977. Engineers squeezed everything available
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  Speaker 1: out of the planetary alignment that made the Grand Tour possible,
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  Speaker 1: an alignment that recurs only once every 176 years. They
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  Speaker 1: will not get another opportunity like it for generations. What
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  Speaker 1: Voyager carries is not just data and a golden record.
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  Speaker 1: It carries the absolute limit of what that approach to
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  Speaker 1: propulsion could do. 17 kilometers per second is the fastest
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  Speaker 1: any human-made object has ever traveled. And it is not
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  Speaker 1: nearly fast enough. One astronomical unit is the distance between
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  Speaker 1: Earth and the Sun. which works out to about 93
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  Speaker 1: million miles. That number is already difficult to hold in
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  Speaker 1: your mind. Light, traveling at 186,000 miles per second, takes
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  Speaker 1: about eight minutes to cover it. A commercial airliner flying
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  Speaker 1: without pause would need roughly 19 years to complete that
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  Speaker 1: single leg. And Voyager 1 sits 170 of those units
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  Speaker 1: away from us right now. which means the arithmetic alone
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  Speaker 1: should give you pause before you even try to picture it.
• 23:28
  Speaker 1: Start with something familiar. A standard American football field runs
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  Speaker 1: 100 yards from end zone to end zone. Suppose you
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  Speaker 1: shrink the entire Earth-Sun distance down to that length, 93
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  Speaker 1: million miles compressed into 100 yards. On that scale, where
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  Speaker 1: would Voyager 1 be? Not at the other end of
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  Speaker 1: the field. Not in the parking lot outside, about three
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  Speaker 1: miles down the road. You would need to walk for
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  Speaker 1: an hour to reach it. And on that same scale,
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  Speaker 1: the nearest star to our sun, Proxima Centauri, would be
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  Speaker 1: sitting roughly 4,000 miles away. Somewhere around Iceland, if you
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  Speaker 1: started in New York. The football field gets you to Voyager.
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  Speaker 1: The nearest star puts you on a different continent. Try
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  Speaker 1: it another way. Imagine drawing a map of the solar
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  Speaker 1: system on a single sheet of paper. You put the
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  Speaker 1: Sun at the center and you draw the orbits of
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  Speaker 1: the planets working outward. Mercury close in. Venus a little farther. Earth, Mars,
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  Speaker 1: the asteroid belt. Jupiter at the midpoint of the page, roughly.
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  Speaker 1: Saturn somewhere toward the outer third. Uranus and Neptune pushed
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  Speaker 1: toward the edges. On a map like that, With Neptune
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  Speaker 1: near the margin, Voyager 1 would fall just off the
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  Speaker 1: edge of the page, maybe an inch or two beyond
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  Speaker 1: the border you drew. It sounds impressive. The nearest star
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  Speaker 1: on that same map would be hanging on the wall
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  Speaker 1: a mile down the hallway, not in the next room,
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  Speaker 1: not at the end of the building, a mile away.
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  Speaker 1: The sheet of paper represents everything humanity has ever physically reached.
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  Speaker 1: The nearest star does not fit in the building. These
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  Speaker 1: comparisons are not decorative. They are load-bearing, because 170 AU
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  Speaker 1: sounds like a number you can reason about, and without
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  Speaker 1: anchoring it to something physical, the mind accepts it on
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  Speaker 1: trust and moves on. And that is precisely the wrong response.
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  Speaker 1: Here is what 170 AU means in terms of travel
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  Speaker 1: time at different speeds. The fastest passenger aircraft in commercial
• 25:55
  Speaker 1: service moves at roughly 600 miles per hour. At that speed,
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  Speaker 1: reaching Voyager 1 from Earth would take about 1,800 years.
• 26:06
  Speaker 1: A traveler who departed during the fall of the Roman
• 26:09
  Speaker 1: Empire would be arriving about now. The Apollo spacecraft that
• 26:14
  Speaker 1: carried astronauts to the moon traveled at around 25,000 miles
• 26:17
  Speaker 1: per hour. far faster than any airliner. At that speed,
• 26:24
  Speaker 1: the journey to Voyager's current position would take roughly 100 years.
• 26:30
  Speaker 1: A mission launched today, moving at the velocity of the
• 26:33
  Speaker 1: Apollo capsule, would arrive sometime in the 220s, and the
• 26:38
  Speaker 1: engineers who built it would have been dead for generations
• 26:41
  Speaker 1: before it got there. Voyager itself covers about 38,000 miles
• 26:46
  Speaker 1: per hour, faster than Apollo, faster than anything humans have ridden,
• 26:53
  Speaker 1: and it has been running for nearly 50 years to
• 26:56
  Speaker 1: reach this distance. That number, 50 years, is worth sitting with.
• 27:02
  Speaker 1: The spacecraft launched in 1977. The engineers who designed it
• 27:08
  Speaker 1: were working on slide rules and early computer systems. The
• 27:12
  Speaker 1: mission required calculations done by hand that would take modern
• 27:17
  Speaker 1: software seconds. And after all that time and all that velocity,
• 27:22
  Speaker 1: the distance covered is 170 AU. Now consider light. Light
• 27:29
  Speaker 1: does not have a cruising speed or a fuel budget.
• 27:32
  Speaker 1: It simply moves at 186,000 miles per second, the fastest
• 27:38
  Speaker 1: anything in the universe can travel. If you stood on
• 27:42
  Speaker 1: Earth and aimed a flashlight directly at Voyager's current position,
• 27:47
  Speaker 1: The beam would take over 22 hours to reach it.
• 27:51
  Speaker 1: Not days. Not weeks. But also not minutes. Not the
• 27:56
  Speaker 1: 8 minutes it takes to reach the Sun. And not
• 28:00
  Speaker 1: the 1.3 seconds it takes to reach the Moon. 22 hours!
• 28:05
  Speaker 1: A signal sent in the morning arrives the following morning.
• 28:08
  Speaker 1: And that is the speed of light. That is the ceiling.
• 28:12
  Speaker 1: Nothing moves faster. Everything humanity has built and launched and
• 28:17
  Speaker 1: steered through space is slower by orders of magnitude, which
• 28:22
  Speaker 1: means that for any spacecraft traveling at realistic velocities, 22
• 28:27
  Speaker 1: light hours of distance translates into journey times measured in
• 28:31
  Speaker 1: decades or centuries. This is the central paradox Voyager forces
• 28:37
  Speaker 1: into view. It sits at 170 AU. A distance that
• 28:43
  Speaker 1: staggers every human intuition about what far means. The scale models,
• 28:49
  Speaker 1: the travel time calculations, the light speed delay, they all
• 28:54
  Speaker 1: point in the same direction. This is genuinely far. And
• 28:59
  Speaker 1: then you look at where 170 AU places Voyager in
• 29:03
  Speaker 1: the broader context of the galaxy, and the ground shifts
• 29:07
  Speaker 1: under you. The Milky Way is roughly 100,000 light years across.
• 29:13
  Speaker 1: One light year is about 63,000 astronomical units. Voyager 1,
• 29:19
  Speaker 1: at 170 AU, has covered less than three thousandths of
• 29:24
  Speaker 1: a single light year. The nearest star is 4.2 light
• 29:28
  Speaker 1: years away, roughly 265 thousandth of a single light year.
• 29:34
  Speaker 1: Voyager is about 1 15th of 1% of the way
• 29:38
  Speaker 1: there after 50 years of continuous travel. The galaxy contains
• 29:43
  Speaker 1: somewhere between 200 billion and 400 billion stars. The distances
• 29:49
  Speaker 1: between them are not smaller than the distance to Proxima Centauri.
• 29:54
  Speaker 1: Many are larger and beyond the Milky Way Hundreds of
• 29:59
  Speaker 1: billions of other galaxies stretch outward across distances that make
• 30:03
  Speaker 1: interstellar distances look like the football field comparison all over again.
• 30:09
  Speaker 1: Voyager 1 holds two simultaneous truths at once, and both
• 30:14
  Speaker 1: are real. It is the farthest object humanity has ever
• 30:18
  Speaker 1: sent into space. No other human-made artefact has ever been
• 30:23
  Speaker 1: this remote from the planet where it was built. That
• 30:26
  Speaker 1: is a genuine fact about human achievement, and it is
• 30:30
  Speaker 1: not diminished by anything else. And simultaneously, 170 AU is
• 30:37
  Speaker 1: cosmically negligible. It places Voyager barely beyond the doorstep, in
• 30:43
  Speaker 1: a universe where the nearest neighbors are separated by distances 1,500
• 30:48
  Speaker 1: times greater than Voyager's entire journey. The same number, 170,
• 30:57
  Speaker 1: can produce wonder or vertigo depending on which direction you look.
• 31:02
  Speaker 1: Look back toward Earth and it represents 50 years of
• 31:06
  Speaker 1: unbroken motion, the farthest reach of human technology, a machine
• 31:12
  Speaker 1: still alive and still transmitting from interstellar space. Look outward
• 31:17
  Speaker 1: toward the stars and it represents almost nothing. A single
• 31:22
  Speaker 1: step in a journey that would require millions of steps
• 31:25
  Speaker 1: at the same pace, over timescales longer than our species
• 31:30
  Speaker 1: has existed. Both perspectives are accurate. Neither cancels the other out.
• 31:37
  Speaker 1: The number 170 sounds manageable until you understand what the
• 31:42
  Speaker 1: unit actually means, and then it stops being manageable at all.
• 31:47
  Speaker 1: Here is a way to feel the distance rather than
• 31:50
  Speaker 1: just understand it. Imagine you need to ask Voyager 1
• 31:54
  Speaker 1: to do something. A routine task. Turn a sensor. Adjust
• 32:00
  Speaker 1: an antenna angle. Run a diagnostic on one of its
• 32:03
  Speaker 1: remaining instruments. You sit down at a console at the
• 32:07
  Speaker 1: Jet Propulsion Laboratory in Pasadena on a Monday morning and
• 32:11
  Speaker 1: you send the command. That signal leaves Earth traveling at
• 32:16
  Speaker 1: the speed of light The fastest anything in the universe
• 32:20
  Speaker 1: can move, and it still takes a full day to arrive.
• 32:23
  Speaker 1: 24 hours of light speed travel just to deliver the instruction.
• 32:29
  Speaker 1: Voyager receives it Tuesday morning. It executes the command and
• 32:34
  Speaker 1: sends a response back. That response also takes a full
• 32:38
  Speaker 1: day to cross the same distance in reverse. You get
• 32:42
  Speaker 1: your answer Wednesday morning. a two-day wait for a single exchange.
• 32:48
  Speaker 1: A conversation that on Earth would take three seconds has
• 32:53
  Speaker 1: become a commitment measured in calendar days. This is not
• 32:57
  Speaker 1: a theoretical problem. This is the operational reality the Voyager
• 33:02
  Speaker 1: flight team works inside every single time they interact with
• 33:06
  Speaker 1: the spacecraft. Compare this to other distances humanity has reached
• 33:11
  Speaker 1: with signals. When Apollo astronauts were standing on the moon,
• 33:16
  Speaker 1: mission controllers in Houston had to wait about 1.3 seconds
• 33:21
  Speaker 1: for a signal to make the round trip. Long enough
• 33:24
  Speaker 1: to notice, short enough that a real conversation was still possible.
• 33:30
  Speaker 1: Controllers could hear something go wrong and respond within two seconds.
• 33:36
  Speaker 1: Mars is much farther. Depending on where the two planets
• 33:40
  Speaker 1: sit in their orbits, a one-way signal to Mars takes
• 33:44
  Speaker 1: anywhere from 3 minutes to 24 minutes. That delay makes
• 33:49
  Speaker 1: real-time control impossible, which is why Mars rovers operate on
• 33:54
  Speaker 1: pre-programmed sequences sent hours in advance. But even a 24-minute
• 34:00
  Speaker 1: one-way delay means a round trip under an hour. If
• 34:04
  Speaker 1: a Mars rover gets into trouble, engineers can diagnose the problem,
• 34:09
  Speaker 1: send a fix, and know whether it worked inside a
• 34:12
  Speaker 1: single afternoon. With Voyager, that same cycle takes 48 hours minimum.
• 34:19
  Speaker 1: There is no version of this where you get a
• 34:21
  Speaker 1: quick answer. There is no version where you catch a
• 34:25
  Speaker 1: problem in the morning and know by lunch whether your
• 34:28
  Speaker 1: fix worked. The distance has fundamentally changed the nature of
• 34:33
  Speaker 1: the relationship between the spacecraft and the people responsible for it.
• 34:38
  Speaker 1: In late 2023, That relationship was tested in a way
• 34:42
  Speaker 1: that made every engineer on the team understand exactly what
• 34:47
  Speaker 1: one light day means in practice. Voyager 1 started sending
• 34:51
  Speaker 1: back garbled data. Not silence. The spacecraft was still transmitting.
• 34:57
  Speaker 1: But the information arriving at JPL was scrambled, unreadable, coming
• 35:03
  Speaker 1: from one of the flight data system computers aboard the probe.
• 35:07
  Speaker 1: Something had gone wrong with the chip responsible for encoding
• 35:10
  Speaker 1: the science and engineering data before transmission. The spacecraft itself
• 35:15
  Speaker 1: appeared to be functioning. The signal was strong, but the
• 35:20
  Speaker 1: data was meaningless. The team had to figure out what
• 35:24
  Speaker 1: had failed on a machine that was nearly a light
• 35:27
  Speaker 1: day away. A machine nobody could see, nobody could touch,
• 35:32
  Speaker 1: nobody could hook up to a diagnostic terminal. Everything they
• 35:37
  Speaker 1: knew about Voyager's condition came through that garbled stream of signals,
• 35:42
  Speaker 1: and interpreting what had actually broken required weeks of careful analysis.
• 35:48
  Speaker 1: They could not just reboot the system and see what happened.
• 35:52
  Speaker 1: A reboot attempt, if it went wrong, might silence the
• 35:56
  Speaker 1: spacecraft permanently. Every command carried consequences that would only reveal
• 36:02
  Speaker 1: themselves two days later. What they eventually determined was that
• 36:07
  Speaker 1: a single chip in the flight data system had corrupted
• 36:11
  Speaker 1: the memory it was responsible for storing. The solution they
• 36:15
  Speaker 1: developed was precise and painstaking. Rather than trying to repair
• 36:20
  Speaker 1: the chip, they re-routed the affected code, broke it into
• 36:24
  Speaker 1: pieces and distributed those pieces across other memory locations in
• 36:29
  Speaker 1: different parts of the computer. locations that had not been
• 36:33
  Speaker 1: used since Voyager launched in 1977. They then sent that
• 36:38
  Speaker 1: rerouted code to the spacecraft in sections, because the full
• 36:42
  Speaker 1: set of changes was too large to transmit at once.
• 36:46
  Speaker 1: Each transmission required waiting. Send the command. Wait a day
• 36:52
  Speaker 1: for it to arrive. Wait another day for Voyager to confirm.
• 36:56
  Speaker 1: Then send the next sections. The entire process unfolded over weeks,
• 37:01
  Speaker 1: with the team working through each step without being able
• 37:05
  Speaker 1: to directly observe what was happening aboard the spacecraft between responses.
• 37:10
  Speaker 1: On April 20th, 2024, Voyager returned its first coherent data
• 37:16
  Speaker 1: in five months. The fix had worked. But think about
• 37:21
  Speaker 1: what that actually required. Engineers diagnosing a hardware failure by
• 37:27
  Speaker 1: inference alone across a gap that light itself takes 22
• 37:32
  Speaker 1: hours to cross, sending instructions to a computer that runs
• 37:36
  Speaker 1: on technology from the early 1970s, with no margin for error,
• 37:42
  Speaker 1: no ability to course correct in real time, and no
• 37:46
  Speaker 1: fallback if the solution made things worse. The isolation of
• 37:50
  Speaker 1: that situation is difficult to fully convey. Ground-based engineers working
• 37:56
  Speaker 1: on complex systems can run tests, swap components, try again
• 38:02
  Speaker 1: within minutes. The Voyager team was operating something closer to
• 38:06
  Speaker 1: surgery by telegraph, sending instructions into the dark and waiting
• 38:12
  Speaker 1: two days to learn whether the patient survived the procedure.
• 38:16
  Speaker 1: This is what one light day means operationally. It is
• 38:21
  Speaker 1: not just a number. It is a specific kind of
• 38:24
  Speaker 1: helplessness that the Voyager team has learned to manage through
• 38:29
  Speaker 1: extraordinary care and patience. Every command is weighed carefully before
• 38:35
  Speaker 1: it is sent because there is no quick recovery from
• 38:39
  Speaker 1: a mistake. Every response is analyzed thoroughly because the next
• 38:44
  Speaker 1: question won't be answerable for another two days. The pace
• 38:49
  Speaker 1: of work is governed entirely by the speed of light.
• 38:53
  Speaker 1: And the speed of light, fast as it is, is
• 38:56
  Speaker 1: not fast enough to allow anything resembling normal engineering at
• 39:00
  Speaker 1: this distance. Every exchange with Voyager is a two-day commitment,
• 39:06
  Speaker 1: and the team has been making those commitments for decades.
• 39:11
  Speaker 1: In April of 2026, four astronauts aboard the Orion capsule
• 39:16
  Speaker 1: travelled farther from Earth than any humans had ever gone.
• 39:20
  Speaker 1: The mission was Artemis II. It launched on April 1st
• 39:25
  Speaker 1: from Kennedy Space Center, and over the course of 10
• 39:29
  Speaker 1: days it carried its crew on a wide loop around
• 39:33
  Speaker 1: the moon and back. On April 6th the capsule reached
• 39:37
  Speaker 1: its maximum distance from Earth, 406,773 kilometers. That number broke
• 39:41
  Speaker 1: a record that had stood for 56 years since Apollo
• 39:51
  Speaker 1: 13 swung around the far side of the Moon in
• 39:54
  Speaker 1: April of 1970 and found itself further from home than
• 39:59
  Speaker 1: any human crew before or since. The Artemis 2 astronauts
• 40:04
  Speaker 1: finally took that record back. It is worth pausing on
• 40:07
  Speaker 1: what 407,000 kilometers actually looks like in space. The Moon
• 40:14
  Speaker 1: sits roughly 384,000 kilometers from Earth on average. Artemis II
• 40:20
  Speaker 1: went slightly past that, looped behind it, and came home.
• 40:26
  Speaker 1: On any map of the solar system drawn to scale,
• 40:29
  Speaker 1: the Moon is so close to Earth that the two
• 40:32
  Speaker 1: are almost touching. The entire Apollo program, every mission that
• 40:37
  Speaker 1: flew there, all the distance traveled to reach another world
• 40:41
  Speaker 1: and walk on its surface, fits inside a region that
• 40:45
  Speaker 1: on a full solar system map would be invisible. Artemis
• 40:49
  Speaker 1: the Stu pushed past that boundary by about 23,000 kilometers.
• 40:55
  Speaker 1: In human terms, that is a profound achievement. In solar
• 40:59
  Speaker 1: system terms, the crew barely stepped off the porch. Now
• 41:04
  Speaker 1: consider Voyager 1. As of late 2026, Voyager sits approximately 25.9
• 41:09
  Speaker 1: billion kilometers from Earth. The Artemis 2 record is 407,000 kilometers.
• 41:19
  Speaker 1: To compare those two numbers directly, you divide one by
• 41:22
  Speaker 1: the other. The answer is roughly 63,600. Voyager is about 63,600
• 41:31
  Speaker 1: times farther from Earth than any human being has ever travelled.
• 41:37
  Speaker 1: That ratio is not a gap in degree. It is
• 41:41
  Speaker 1: a gap in kind. Here is one way to hold
• 41:44
  Speaker 1: both numbers in your head at once. Draw a map.
• 41:48
  Speaker 1: Place Earth on one end. Make Artemis II's record distance
• 41:53
  Speaker 1: exactly one inch on paper. At that scale, where would
• 41:58
  Speaker 1: Voyager 1 be? It would be sitting roughly one mile
• 42:02
  Speaker 1: away from you. One inch versus one mile. That is
• 42:06
  Speaker 1: the present distance between human spaceflight and robotic deep space exploration.
• 42:12
  Speaker 1: Both measured from the same starting point. both launched by
• 42:17
  Speaker 1: the same civilization, both products of the same engineering tradition,
• 42:22
  Speaker 1: and yet separated by a mile of open paper. What
• 42:26
  Speaker 1: makes that ratio even more striking is how recently Artemis
• 42:31
  Speaker 1: II flew. This was not a record from the 1970s
• 42:35
  Speaker 1: sitting untouched because no one tried. It was broken in
• 42:39
  Speaker 1: April 2026 by a brand new spacecraft, representing decades of
• 42:45
  Speaker 1: development and billions of dollars in investment, carrying the most
• 42:50
  Speaker 1: advanced life support systems and communications equipment human engineers have produced.
• 42:57
  Speaker 1: And it went one inch. This is not a failure.
• 43:01
  Speaker 1: That point deserves emphasis. Sending four human beings around the
• 43:06
  Speaker 1: moon and returning them safely to Earth is one of
• 43:09
  Speaker 1: the hardest things any organisation has ever done. The engineering
• 43:14
  Speaker 1: required to keep a crew alive through the radiation environment
• 43:18
  Speaker 1: of cislunar space, to manage the thermal extremes, to handle
• 43:23
  Speaker 1: re-entry at lunar return velocities, is genuinely extraordinary. The Artemis
• 43:30
  Speaker 1: II crew demonstrated that humans can again venture into deep
• 43:34
  Speaker 1: cislunar space. That matters enormously for everything that comes next.
• 43:40
  Speaker 1: including eventual crewed missions to the lunar surface and eventually Mars.
• 43:46
  Speaker 1: But robotic spacecraft and crewed spacecraft are solving fundamentally different problems.
• 43:53
  Speaker 1: Voyager 1 is a 722 kilogram machine with no crew requirements.
• 43:59
  Speaker 1: It carries no food, no water, no air, no medical systems,
• 44:05
  Speaker 1: no radiation shielding sized for a living nervous system. does
• 44:10
  Speaker 1: not need to slow down, turn around or return anyone home.
• 44:15
  Speaker 1: When something breaks, engineers can send a software patch and
• 44:19
  Speaker 1: wait two days for the result. Nobody dies if the
• 44:23
  Speaker 1: diagnosis is wrong on the first attempt. The mission can
• 44:26
  Speaker 1: absorb a failure and try again. Crewed missions carry none
• 44:31
  Speaker 1: of those flexibilities. Every kilogram of life support equipment is
• 44:37
  Speaker 1: a kilogram that requires more propulsion, which requires more fuel,
• 44:42
  Speaker 1: which requires more propulsion to carry that fuel. The constraints
• 44:46
  Speaker 1: compound in ways that make the two disciplines almost incomparable.
• 44:52
  Speaker 1: Voyager also had something that no crewed mission has been
• 44:55
  Speaker 1: able to replicate. It borrowed its speed from Jupiter and Saturn.
• 45:01
  Speaker 1: Those gravitational assists were available because the outer planets aligned
• 45:06
  Speaker 1: in a configuration that won't repeat for roughly another 175 years.
• 45:12
  Speaker 1: A crewed mission launched today could not follow the same
• 45:16
  Speaker 1: path and receive the same boost. It would have to
• 45:20
  Speaker 1: generate that velocity some other way, carrying its energy source
• 45:25
  Speaker 1: with it, which brings the propulsion problem back immediately. and
• 45:30
  Speaker 1: makes it much worse than anything Voyager's engineers ever had
• 45:34
  Speaker 1: to solve. There is also the question of what the
• 45:38
  Speaker 1: Artemis II record represents in the long arc of spaceflight history.
• 45:43
  Speaker 1: Apollo 13's record stood for 56 years. Not because humanity
• 45:49
  Speaker 1: gave up on deep space, but because the Moon was
• 45:52
  Speaker 1: as far as chemical rockets and life support systems could
• 45:56
  Speaker 1: reasonably take a crew in a short mission window. Artemis
• 46:00
  Speaker 1: II pushed past it, but only marginally. The ceiling on
• 46:05
  Speaker 1: crewed spaceflight distance is not primarily a function of ambition
• 46:10
  Speaker 1: or political will. It is a function of physics and time.
• 46:15
  Speaker 1: A crewed mission to Mars, if it flies in the
• 46:18
  Speaker 1: 2030s or 2040s, will shatter the Artemis II record by
• 46:23
  Speaker 1: an enormous margin. Mars at closest approach sits roughly 55
• 46:29
  Speaker 1: million kilometers from Earth. That would push the crew distance
• 46:34
  Speaker 1: record by a factor of 135 beyond where it sits today.
• 46:40
  Speaker 1: And even then, the crew would still be 470 times
• 46:44
  Speaker 1: closer to Earth than Voyager 1 is right now. The
• 46:48
  Speaker 1: distinction matters because it reframes the question of whether humans
• 46:53
  Speaker 1: can reach Voyager's distance It is not simply a question
• 46:57
  Speaker 1: of building bigger rockets or summoning more political commitment. The
• 47:02
  Speaker 1: gap is rooted in what human bodies need to survive,
• 47:06
  Speaker 1: what physics permits, and what the universe's scale imposes on
• 47:11
  Speaker 1: anything that has mass and requires care. Robotic exploration and
• 47:16
  Speaker 1: crude exploration are complementary, not competing, but they operate on
• 47:22
  Speaker 1: entirely different distance scales. and nothing about the history of
• 47:27
  Speaker 1: either discipline suggests that gap will close quickly or easily.
• 47:32
  Speaker 1: The gap between where humans have been and where Voyager
• 47:35
  Speaker 1: sits is not a gap you can close with ambition alone.
• 47:40
  Speaker 1: The problem with sending humans to where Voyager 1 now
• 47:44
  Speaker 1: sits is not any single obstacle. It is that the
• 47:48
  Speaker 1: obstacles stack on top of each other in ways that
• 47:51
  Speaker 1: make each one harder to solve. Start with the most
• 47:55
  Speaker 1: fundamental one. To move a spacecraft, you burn fuel and
• 48:00
  Speaker 1: throw the exhaust out the back. The faster you want
• 48:04
  Speaker 1: to go, the more fuel you need. But fuel has mass,
• 48:09
  Speaker 1: and mass requires more fuel to accelerate. That additional fuel
• 48:14
  Speaker 1: has its own mass, which requires still more fuel on
• 48:18
  Speaker 1: top of that. This is the Tsiolkovsky rocket equation. worked
• 48:23
  Speaker 1: out in the late 19th century. It describes a vicious
• 48:27
  Speaker 1: compounding cycle that gets worse the more velocity you demand.
• 48:33
  Speaker 1: Double the target velocity and the required fuel mass does
• 48:36
  Speaker 1: not double, it grows exponentially. A spacecraft designed to reach
• 48:42
  Speaker 1: Voyager's current distance in any reasonable time frame would need
• 48:46
  Speaker 1: to leave Earth moving significantly faster than Voyager itself does.
• 48:52
  Speaker 1: Voyager reached its speed by borrowing momentum from Jupiter and Saturn.
• 48:57
  Speaker 1: Those planets are not going anywhere, but their geometry only
• 49:01
  Speaker 1: lines up in useful ways on timescales of decades. A
• 49:06
  Speaker 1: crewed spacecraft cannot be designed around a planetary alignment that
• 49:11
  Speaker 1: may not cooperate with a launch window. Starting from Earth
• 49:15
  Speaker 1: without those assists means carrying the energy that Jupiter once provided.
• 49:21
  Speaker 1: The fuel mass required to do that with chemical propulsion
• 49:25
  Speaker 1: would be staggering. Not impractical in the way that an
• 49:28
  Speaker 1: expensive project is impractical. Impractical in the way that the
• 49:33
  Speaker 1: numbers become physically absurd before you finish writing them down.
• 49:38
  Speaker 1: Now add the life support problem and watch the first
• 49:41
  Speaker 1: problem get worse. Voyager 1 weighs roughly 722 kilograms. It
• 49:49
  Speaker 1: carries no food, no water, no air, no medical equipment,
• 49:55
  Speaker 1: no psychological space for the people who are not aboard
• 49:58
  Speaker 1: it because there are no people aboard it. A crewed
• 50:02
  Speaker 1: spacecraft is a different category of object entirely. Humans require
• 50:08
  Speaker 1: breathable air on a continuous cycle. That means scrubbers and
• 50:13
  Speaker 1: filters and backup systems for the scrubbers and filters. They
• 50:17
  Speaker 1: require water, which must either be carried or recycled with
• 50:21
  Speaker 1: near-perfect efficiency because there is nowhere to resupply. They require calories,
• 50:28
  Speaker 1: which means either carrying food for the entire journey or
• 50:32
  Speaker 1: developing a closed-loop agricultural system that has never been built
• 50:37
  Speaker 1: for the duration and scale a 50-year voyage demands. They
• 50:42
  Speaker 1: require medical equipment because injuries and illness do not pause
• 50:47
  Speaker 1: for the convenience of deep space. They require physical space.
• 50:53
  Speaker 1: This was because confinement sufficient to drive a person into
• 50:57
  Speaker 1: psychological breakdown is not a spacecraft. It is a slow catastrophe.
• 51:03
  Speaker 1: Every item on this list adds mass. Every kilogram of
• 51:08
  Speaker 1: mass added to a crude spacecraft makes the propulsion problem
• 51:13
  Speaker 1: from the first paragraph more severe. The two problems are
• 51:17
  Speaker 1: not independent. They feed each other in a loop that
• 51:21
  Speaker 1: punishes every solution you attempt. Then there is the question
• 51:26
  Speaker 1: of time. That is its own kind of obstacle, even
• 51:30
  Speaker 1: if the physics somehow cooperated. At Voyager's current speed of
• 51:35
  Speaker 1: roughly 17 kilometers per second, a spacecraft launched today would
• 51:41
  Speaker 1: need approximately 50 years to cover the same distance Voyager
• 51:45
  Speaker 1: has covered since 1977. 50 years in transit. A crew
• 51:51
  Speaker 1: member who launches at 30 years old arrives. If everything
• 51:56
  Speaker 1: goes perfectly, at 80. Many would not survive the journey
• 52:01
  Speaker 1: simply due to age. Those who did would arrive having
• 52:05
  Speaker 1: spent essentially their entire adult lives inside a vehicle smaller
• 52:10
  Speaker 1: than most apartments, cut off from Earth except for the
• 52:14
  Speaker 1: slow trickle of radio signals that take over 20 hours
• 52:18
  Speaker 1: to arrive. The psychological architecture of such a mission has
• 52:23
  Speaker 1: no precedent. Humans are social animals built for environments that change,
• 52:29
  Speaker 1: for communities larger than a handful of people, for a
• 52:33
  Speaker 1: sky that is something other than a fixed field of
• 52:36
  Speaker 1: cold stars visible through a porthole. Six months on the
• 52:41
  Speaker 1: International Space Station produces measurable psychological stress in carefully selected,
• 52:48
  Speaker 1: rigorously trained astronauts. Multiply that duration by a factor of
• 52:53
  Speaker 1: 100 and the comparison becomes almost meaningless. The longest any
• 52:58
  Speaker 1: human has spent continuously in space is a little over
• 53:02
  Speaker 1: a year. A mission to Voyager's distance at current speeds
• 53:07
  Speaker 1: would require 50 times that. The fourth obstacle is radiation,
• 53:13
  Speaker 1: and it may be the most stubborn of all. Inside
• 53:16
  Speaker 1: the protective bubble of Earth's magnetic field, radiation exposure is manageable.
• 53:22
  Speaker 1: out past that boundary in deep space. The environment is
• 53:27
  Speaker 1: saturated with galactic cosmic rays, high energy particles accelerated by
• 53:33
  Speaker 1: distant supernovae and other violent events across the galaxy, arriving
• 53:38
  Speaker 1: from every direction simultaneously. These are not the kind of
• 53:43
  Speaker 1: radiation that a lead sheet stops. Galactic cosmic rays carry
• 53:48
  Speaker 1: enough energy to pass straight through most shielding materials. When
• 53:53
  Speaker 1: they do, they interact with the shield itself and produce
• 53:57
  Speaker 1: secondary particles that can be as damaging as the original ray.
• 54:02
  Speaker 1: More shielding, paradoxically, can make the secondary radiation problem worse
• 54:08
  Speaker 1: rather than better. Long-duration exposure to galactic cosmic rays at
• 54:13
  Speaker 1: the levels found in deep space is associated with elevated
• 54:18
  Speaker 1: rates of cancer, damage to the central nervous system, degradation
• 54:24
  Speaker 1: of cognitive function, the very functions a crew would need
• 54:28
  Speaker 1: to operate a spacecraft, diagnose problems, make decisions across a
• 54:34
  Speaker 1: 50-year mission. There is no solution to this problem sitting
• 54:38
  Speaker 1: on a shelf waiting to be implemented. The shielding that
• 54:42
  Speaker 1: would meaningfully block galactic cosmic rays at high energies would
• 54:48
  Speaker 1: be so massive, that it would make the propulsion problem
• 54:52
  Speaker 1: catastrophically worse. Researchers are exploring pharmaceutical approaches, genetic selection, and
• 55:00
  Speaker 1: advanced materials, but nothing in the current experimental landscape suggests
• 55:07
  Speaker 1: a near-term answer. What makes this genuinely difficult to convey
• 55:12
  Speaker 1: is that each of these four problems would be a
• 55:15
  Speaker 1: career-defining engineering challenge on its own. The rocket equation alone
• 55:21
  Speaker 1: has occupied the finest engineering minds in the space industry
• 55:25
  Speaker 1: for a century. Life support systems for long-duration spaceflight represent
• 55:31
  Speaker 1: a field of ongoing research with no solved examples at
• 55:36
  Speaker 1: the timescale of a mission to Voyager. The psychology of
• 55:40
  Speaker 1: multi-decade confinement is barely understood at the one-year mark, let
• 55:46
  Speaker 1: alone fifty. The radiation problem may require a breakthrough in materials,
• 55:51
  Speaker 1: science or medicine that does not yet have a clear
• 55:54
  Speaker 1: path forward. But no one of these problems exists in isolation.
• 56:00
  Speaker 1: Solving the life support challenge adds mass that worsens the
• 56:04
  Speaker 1: propulsion challenge. Solving the radiation challenge adds mass that worsens
• 56:09
  Speaker 1: the propulsion challenge. The propulsion challenge in turn constrains how
• 56:15
  Speaker 1: much mass can be allocated to solving everything else. They
• 56:19
  Speaker 1: are not four separate walls. They are four walls of
• 56:23
  Speaker 1: the same room. The room gets smaller every time you
• 56:27
  Speaker 1: address one of them. Voyager 1 is in interstellar space.
• 56:31
  Speaker 1: Because it was small, it had no crew. It carried
• 56:35
  Speaker 1: no life support. It had two enormous planets to borrow
• 56:40
  Speaker 1: speed from. at precisely the right moment in history. None
• 56:45
  Speaker 1: of those conditions apply to a crewed mission. Solve any
• 56:50
  Speaker 1: one of these problems and you still have three more waiting.
• 56:54
  Speaker 1: Chemical rockets work by burning fuel and throwing the exhaust
• 56:58
  Speaker 1: out the back, which sounds simple because it is. Two
• 57:02
  Speaker 1: chemicals combine. The reaction releases energy. The exhaust flies out
• 57:08
  Speaker 1: one end. and the rocket moves the other direction. This
• 57:12
  Speaker 1: is Newton's third law applied to combustion, and it has
• 57:16
  Speaker 1: carried every human being who has ever left Earth. It
• 57:20
  Speaker 1: put 12 people on the moon. It launched Voyager itself.
• 57:25
  Speaker 1: The principle is elegant, and the engineering behind it, after
• 57:29
  Speaker 1: decades of refinement, is genuinely extraordinary. But elegant principles have limits.
• 57:36
  Speaker 1: And the limit on chemical propulsion is not an engineering
• 57:40
  Speaker 1: problem waiting to be solved. It is written into the
• 57:44
  Speaker 1: molecular structure of the fuel itself. The measure of a
• 57:48
  Speaker 1: rocket engine's efficiency is called specific impulse. Think of it
• 57:53
  Speaker 1: as miles per gallon for rockets. How much thrust you
• 57:57
  Speaker 1: extract from each unit of propellant you burn. The higher
• 58:01
  Speaker 1: the specific impulse, the more efficient the engine. Chemical rockets
• 58:06
  Speaker 1: have been chasing higher specific impulse for the better part
• 58:09
  Speaker 1: of a century. The best engines ever built, running on
• 58:13
  Speaker 1: liquid hydrogen and liquid oxygen, achieve a specific impulse of
• 58:18
  Speaker 1: around 450 seconds. That number represents something close to the
• 58:24
  Speaker 1: absolute ceiling for chemical combustion. Hydrogen and oxygen produce more
• 58:30
  Speaker 1: energy per kilogram than almost any other chemical reaction available.
• 58:36
  Speaker 1: There is nowhere meaningfully higher to go. The reaction is
• 58:40
  Speaker 1: nearly as energetic as chemistry permits and we are already
• 58:44
  Speaker 1: burning it. This ceiling matters enormously once you try to
• 58:48
  Speaker 1: move a spacecraft to serious speeds. The exhaust velocity of
• 58:53
  Speaker 1: a hydrogen-oxygen engine tops out around 4.4 kilometers per second.
• 58:59
  Speaker 1: Voyager 1 is currently moving at roughly 17 kilometers per second.
• 59:05
  Speaker 1: That speed did not come from chemical combustion alone. It
• 59:09
  Speaker 1: came from two planetary gravity assists from Jupiter and Saturn,
• 59:15
  Speaker 1: which added velocity that no onboard engine provided. Strip those
• 59:20
  Speaker 1: assists away. Imagine trying to reach 17 kilometers per second
• 59:25
  Speaker 1: from a standing start using only chemical fuel. The numbers
• 59:31
  Speaker 1: become almost surreal. This is where the rocket equation comes in.
• 59:36
  Speaker 1: Formulated by Konstantin Tsiolkovsky in 1903, it describes the relationship
• 59:42
  Speaker 1: between a rocket's exhaust velocity, its final speed, and the
• 59:47
  Speaker 1: ratio of its starting mass to its ending mass. The
• 59:51
  Speaker 1: equation is not complicated, but its implications are brutal. To
• 59:55
  Speaker 1: go faster you need more fuel, but more fuel means
• 59:59
  Speaker 1: more mass. More mass means you need even more fuel
• 1:00:03
  Speaker 1: to accelerate that fuel. The cycle compounds on itself exponentially.
• 1:00:08
  Speaker 1: For every increment of additional velocity, the required fuel mass
• 1:00:13
  Speaker 1: does not grow linearly. It grows as a rising exponential curve.
• 1:00:18
  Speaker 1: Here is what that means in practice. If you wanted
• 1:00:21
  Speaker 1: to accelerate a crewed spacecraft of roughly 100 tons, a
• 1:00:27
  Speaker 1: conservative estimate for anything capable of sustaining humans over a
• 1:00:32
  Speaker 1: long journey, to just half of Voyager's current speed using
• 1:00:37
  Speaker 1: a hydrogen-oxygen engine, you would need a fuel mass that
• 1:00:41
  Speaker 1: dwarfs the spacecraft itself by a factor that makes the
• 1:00:45
  Speaker 1: entire exercise absurd. Some calculations for reaching even modest fractions
• 1:00:51
  Speaker 1: of interstellar velocity with chemical propulsion produce fuel requirements larger
• 1:00:57
  Speaker 1: than anything humanity has ever constructed. The Saturn V, the
• 1:01:02
  Speaker 1: most powerful rocket ever launched, had a fully fuelled mass
• 1:01:07
  Speaker 1: of about 2,900 tonnes. The fuel requirements to chemically push
• 1:01:13
  Speaker 1: a crewed vehicle to meaningful interstellar speeds would exceed this
• 1:01:18
  Speaker 1: by orders of magnitude, and you would need to launch
• 1:01:22
  Speaker 1: all of that mass from Earth's gravity well which requires
• 1:01:26
  Speaker 1: more fuel still. The Saturn V got to the moon.
• 1:01:30
  Speaker 1: It did not get close to Voyager's speed. The engines
• 1:01:34
  Speaker 1: were magnificent. The fuel was as good as fuel gets.
• 1:01:38
  Speaker 1: The physics simply did not permit it. What Voyager did
• 1:01:43
  Speaker 1: is instructive precisely because it is not a template for
• 1:01:47
  Speaker 1: crewed missions. Voyager 1 at launch had a mass of
• 1:01:51
  Speaker 1: about 722 kilograms. roughly the weight of a small car.
• 1:01:57
  Speaker 1: It carried no crew, no life support, no food, no
• 1:02:02
  Speaker 1: water recycling, no radiation shielding for human bodies, no medical equipment,
• 1:02:10
  Speaker 1: no psychological space. It carried a few scientific instruments and
• 1:02:15
  Speaker 1: a golden record. The entire spacecraft was designed to be
• 1:02:20
  Speaker 1: as light as possible, because even at that mass, Getting
• 1:02:25
  Speaker 1: it to the speeds required for the planetary tour demanded
• 1:02:28
  Speaker 1: careful planning and the gravitational assistance of two of the
• 1:02:33
  Speaker 1: largest planets in the solar system. Without Jupiter and Saturn,
• 1:02:38
  Speaker 1: Voyager would not be where it is. It would be
• 1:02:41
  Speaker 1: somewhere in the outer solar system, moving considerably slower. A
• 1:02:46
  Speaker 1: crewed mission cannot borrow the same momentum. Jupiter and Saturn
• 1:02:50
  Speaker 1: are still there, and gravity assists are still available. But
• 1:02:55
  Speaker 1: the physics of a gravity assist ties the velocity gain
• 1:02:58
  Speaker 1: to the planet's orbital speed, not to the spacecraft's mass.
• 1:03:03
  Speaker 1: The assist available from Jupiter is fixed. A spacecraft massing
• 1:03:08
  Speaker 1: thousands of tons for crew and life support gains the
• 1:03:12
  Speaker 1: same absolute velocity increment as Voyager. But that increment represents
• 1:03:18
  Speaker 1: a far smaller fraction of what a crewed vehicle actually needs.
• 1:03:24
  Speaker 1: You cannot compound assists indefinitely. After Saturn, there are no
• 1:03:29
  Speaker 1: more giant planets on the trajectory that took Voyager out
• 1:03:32
  Speaker 1: of the solar system. The spacecraft coasted from there on
• 1:03:37
  Speaker 1: borrowed momentum, and that option runs out. So a crewed
• 1:03:42
  Speaker 1: chemical rocket mission aimed at Voyager's current position would face
• 1:03:46
  Speaker 1: this situation. It would launch from Earth with an enormous
• 1:03:50
  Speaker 1: fuel mass that is almost certainly unbuildable with any existing infrastructure.
• 1:03:56
  Speaker 1: It would conduct what gravity assists it could manage. And
• 1:04:00
  Speaker 1: then it would coast, at a speed well below Voyager's
• 1:04:05
  Speaker 1: 17 kilometers per second, across a distance that currently takes
• 1:04:10
  Speaker 1: radio signals more than 22 hours to cross. At a
• 1:04:15
  Speaker 1: realistic speed achievable by a heavy crewed vehicle using chemical
• 1:04:20
  Speaker 1: propulsion and planetary assists, reaching Voyager's current position would take
• 1:04:25
  Speaker 1: not 50 years but several centuries, by which point Voyager
• 1:04:31
  Speaker 1: would be vastly farther away. There is something clarifying about
• 1:04:35
  Speaker 1: this comparison. Voyager left in 1977. It was small. It
• 1:04:42
  Speaker 1: had the planets working in its favor. Nobody was aboard
• 1:04:46
  Speaker 1: and it still took nearly 50 years to reach one
• 1:04:50
  Speaker 1: light day. A crewed mission with chemical propulsion does not
• 1:04:54
  Speaker 1: arrive at that distance in 50 years. It does not
• 1:04:58
  Speaker 1: arrive in a hundred. The crew would be long dead
• 1:05:02
  Speaker 1: before the spacecraft covered half the distance. And the spacecraft
• 1:05:06
  Speaker 1: would need to have been launched with life support systems
• 1:05:10
  Speaker 1: capable of sustaining people for a timeframe longer than most
• 1:05:14
  Speaker 1: existing nations have governed themselves. Chemical rockets are not a failure.
• 1:05:19
  Speaker 1: They are a profound achievement. They represent decades of engineering
• 1:05:24
  Speaker 1: ingenuity and have transformed humanity's relationship with space. The space
• 1:05:30
  Speaker 1: shuttle flew over 130 missions, The Saturn V remains one
• 1:05:35
  Speaker 1: of the most impressive machines ever assembled. The Falcon 9
• 1:05:40
  Speaker 1: has made orbital access routine. These accomplishments are real and
• 1:05:45
  Speaker 1: they matter, but they are accomplishments built for a particular
• 1:05:49
  Speaker 1: regime of spaceflight, reaching orbit, reaching the moon, reaching nearby planets.
• 1:05:56
  Speaker 1: In that regime, Chemical propulsion is competitive and often unmatched
• 1:06:01
  Speaker 1: in simplicity and reliability. The regime that begins beyond the
• 1:06:06
  Speaker 1: planets is different. The distances change in character. The time
• 1:06:12
  Speaker 1: scales change in character. The energy requirements change in character.
• 1:06:18
  Speaker 1: And in that regime, chemical propulsion runs out of answer
• 1:06:22
  Speaker 1: before the question is even fully asked. The rocket equation
• 1:06:27
  Speaker 1: is not a challenge to be engineered around. It is
• 1:06:30
  Speaker 1: a mathematical fact about how much energy is available from chemistry,
• 1:06:35
  Speaker 1: and chemistry ran out of headroom a long time ago.
• 1:06:39
  Speaker 1: Voyager 1 crossed the heliopause in August of 2012, which
• 1:06:44
  Speaker 1: is the moment many headlines called leaving the solar system.
• 1:06:50
  Speaker 1: The heliopause is the boundary where the Sun's stream of
• 1:06:53
  Speaker 1: charged particles, the solar wind, finally loses pressure against the
• 1:06:59
  Speaker 1: surrounding interstellar medium. Inside that boundary, the Sun's plasma dominates.
• 1:07:06
  Speaker 1: Outside it, the wider galaxy takes over. Voyager crossed from
• 1:07:11
  Speaker 1: one regime into the other, and the instruments aboard confirmed
• 1:07:15
  Speaker 1: the change in particle density and magnetic field orientation. It
• 1:07:20
  Speaker 1: was a real boundary. The crossing was real. And the
• 1:07:24
  Speaker 1: headlines were not wrong, exactly. But they were describing one
• 1:07:29
  Speaker 1: definition of the solar system, while quietly ignoring another, more
• 1:07:33
  Speaker 1: demanding one. The Sun's gravitational reach does not end at
• 1:07:38
  Speaker 1: the heliopause. Not even close. Gravity follows different rules than plasma.
• 1:07:46
  Speaker 1: The solar wind runs out of pressure at roughly 120
• 1:07:50
  Speaker 1: astronomical units from the Sun, which is approximately where Voyager
• 1:07:55
  Speaker 1: crossed in 2012. Gravity, though, extends outward almost without limit,
• 1:08:02
  Speaker 1: weakening with distance but never truly vanishing. What it weakens into,
• 1:08:07
  Speaker 1: at the outermost edges of the Sun's domain, is a
• 1:08:11
  Speaker 1: vast and nearly empty region that astronomers call the Oort Cloud.
• 1:08:16
  Speaker 1: This is not a place anyone has ever seen directly.
• 1:08:20
  Speaker 1: No telescope has resolved it. Most spacecraft has reached it.
• 1:08:26
  Speaker 1: The Oort Cloud is theoretical in the sense that its
• 1:08:29
  Speaker 1: existence is inferred from the behaviour of comets that occasionally
• 1:08:33
  Speaker 1: fall inward toward the Sun on long, slow orbits that
• 1:08:37
  Speaker 1: trace back to enormous distances. Something has to be sending them.
• 1:08:43
  Speaker 1: That something is the Oort cloud. The structure itself is
• 1:08:48
  Speaker 1: thought to be a roughly spherical shell surrounding the entire
• 1:08:52
  Speaker 1: solar system, beginning somewhere around 2,000 astronomical units from the
• 1:08:58
  Speaker 1: Sun and extending out perhaps as far as 100,000 astronomical units.
• 1:09:05
  Speaker 1: That outer edge puts it at roughly one to two
• 1:09:08
  Speaker 1: light years from the Sun. The nearest star, Proxima Centauri,
• 1:09:13
  Speaker 1: sits about 4.2 light years away. The Oort cloud, at
• 1:09:18
  Speaker 1: its outermost reach, gets you nearly halfway there. The Sun's
• 1:09:23
  Speaker 1: gravitational domain, properly measured, extends almost to the doorstep of
• 1:09:29
  Speaker 1: the next star system. What lies between the stars is
• 1:09:33
  Speaker 1: not empty, unclaimed space. It is in large part still
• 1:09:38
  Speaker 1: our solar system, loosely held, barely populated, but gravitationally bound
• 1:09:44
  Speaker 1: to the same star that warms Earth. What the Oort
• 1:09:48
  Speaker 1: cloud actually contains is not easy to picture. It is
• 1:09:52
  Speaker 1: not a ring like Saturn's, not a belt like the
• 1:09:56
  Speaker 1: asteroid belt, not a region where you would see rocks
• 1:10:00
  Speaker 1: and ice crowding close together. The distances between individual objects
• 1:10:05
  Speaker 1: in the Oort cloud are enormous. A traveller passing through
• 1:10:10
  Speaker 1: it would almost certainly never come close to a single body.
• 1:10:14
  Speaker 1: It is better understood as an almost impossibly thin haze
• 1:10:18
  Speaker 1: of icy material. Billions of cometary nuclei distributed across a
• 1:10:24
  Speaker 1: shell so vast that the average distance between any two
• 1:10:29
  Speaker 1: objects is likely measured in astronomical units. The Sun formed
• 1:10:34
  Speaker 1: from a collapsing cloud of gas and dust roughly 4.6
• 1:10:37
  Speaker 1: billion years ago. And during the chaotic early period of
• 1:10:43
  Speaker 1: the solar system's formation, gravitational interactions between the giant planets
• 1:10:49
  Speaker 1: scattered enormous quantities of icy debris outward. Some of that
• 1:10:54
  Speaker 1: debris was ejected entirely, lost to interstellar space. Some of
• 1:11:00
  Speaker 1: it settled into these remote, slowly drifting orbits at the
• 1:11:04
  Speaker 1: edge of the sun's reach. That is the Oort Cloud.
• 1:11:08
  Speaker 1: It is the solar system's debris field, preserved in cold
• 1:11:13
  Speaker 1: storage at the farthest edges of what the Sun can hold.
• 1:11:17
  Speaker 1: Voyager 1, at 170 astronomical units, has not reached it.
• 1:11:24
  Speaker 1: The inner edge of the Oort cloud begins somewhere around
• 1:11:27
  Speaker 1: 2000 AU, though estimates vary and the boundary is not sharp.
• 1:11:33
  Speaker 1: At its current speed, Voyager will not reach that inner
• 1:11:37
  Speaker 1: edge for roughly 300 years. Three centuries of continuous travel
• 1:11:44
  Speaker 1: at 17 km per second just to arrive at the
• 1:11:48
  Speaker 1: beginning of a region we have not yet confirmed with
• 1:11:51
  Speaker 1: direct observation. The outer edge of the Oort cloud at
• 1:11:56
  Speaker 1: perhaps 100,000 AU is farther still. At Voyager's pace, clearing
• 1:12:02
  Speaker 1: the outer boundary would take something in the range of 30,000 years.
• 1:12:08
  Speaker 1: This is a number that is worth sitting with. Voyager
• 1:12:11
  Speaker 1: 1 crossed what most people would call the edge of
• 1:12:14
  Speaker 1: the solar system in 2012. It entered interstellar space by
• 1:12:19
  Speaker 1: the plasma definition, the one that made the headlines. And yet,
• 1:12:25
  Speaker 1: by the gravitational definition, The one that asks how far
• 1:12:29
  Speaker 1: the sun's influence actually extends. Voyager is at 170 AU
• 1:12:36
  Speaker 1: out of a journey that will require something approaching 100,000
• 1:12:40
  Speaker 1: AU to complete. It has covered less than a fifth
• 1:12:45
  Speaker 1: of 1% of the distance to the Oort cloud's outer edge.
• 1:12:49
  Speaker 1: It is not past the front door. It is standing
• 1:12:53
  Speaker 1: in the entryway. The Oort cloud also reframes the question
• 1:12:57
  Speaker 1: of what it would mean to truly reach Voyager's distance
• 1:13:01
  Speaker 1: with a crewed mission. When someone asks whether humans can
• 1:13:05
  Speaker 1: reach where Voyager now sits, they usually mean the heliopause,
• 1:13:10
  Speaker 1: or the current position at 170 AUO, or the general
• 1:13:14
  Speaker 1: idea of interstellar space. But Voyager's position is inside a
• 1:13:19
  Speaker 1: solar system that extends far beyond it. The Sun's gravity,
• 1:13:25
  Speaker 1: weak as it is at those distances, still touches Voyager,
• 1:13:30
  Speaker 1: still touches the inner Oort cloud, still touches objects nearly
• 1:13:35
  Speaker 1: halfway to the next star. Our solar system is not
• 1:13:39
  Speaker 1: a small neighborhood with clear streets and clean boundaries. It
• 1:13:43
  Speaker 1: is a gravitational basin so large that our best spacecraft,
• 1:13:49
  Speaker 1: moving faster than anything humanity has ever built, has been
• 1:13:53
  Speaker 1: travelling for nearly 50 years and covered a small fraction
• 1:13:58
  Speaker 1: of it. Long period comets that fall towards the Sun
• 1:14:01
  Speaker 1: from the Oort cloud take thousands to millions of years
• 1:14:06
  Speaker 1: to complete a single orbit. They spend almost their entire
• 1:14:10
  Speaker 1: existence moving slowly through a region so remote that the
• 1:14:15
  Speaker 1: Sun appears as just a bright star among many. The
• 1:14:19
  Speaker 1: occasional nudge from a passing star or a giant molecular
• 1:14:23
  Speaker 1: cloud can knock one of them loose from its distant
• 1:14:27
  Speaker 1: orbit and send it plunging inward. That plunge, which can
• 1:14:32
  Speaker 1: take millions of years, is what eventually produces the bright
• 1:14:36
  Speaker 1: comet visible from Earth for a few weeks. The comet
• 1:14:40
  Speaker 1: people see from a suburban backyard has been travelling toward
• 1:14:44
  Speaker 1: that moment for longer than humans have existed as a species.
• 1:14:49
  Speaker 1: Voyager is at 170 AU. The Oort cloud begins at
• 1:14:54
  Speaker 1: roughly 2,000 and ends near 100,000. The nearest star is
• 1:15:00
  Speaker 1: at approximately 270,000 AU. The solar system's gravitational shadow reaches
• 1:15:07
  Speaker 1: almost to the halfway point of that distance. By every
• 1:15:11
  Speaker 1: measure that treats gravity as the definition of ownership, Voyager
• 1:15:17
  Speaker 1: is still deep inside our solar system, moving through the
• 1:15:21
  Speaker 1: same gravitational basin it left Earth from in 1977. By
• 1:15:27
  Speaker 1: the time Voyager clears the true outer edge of our
• 1:15:31
  Speaker 1: solar system, every human alive today will have been dead
• 1:15:36
  Speaker 1: for approximately 30,000 years. Proxima Centauri is the nearest star
• 1:15:42
  Speaker 1: to our sun, sitting 4.2 light years away. That number
• 1:15:47
  Speaker 1: sounds almost manageable after the numbers that have come before it. 4.2. Small. Contained.
• 1:15:56
  Speaker 1: But a light year is the distance light covers in
• 1:15:58
  Speaker 1: a full year, travelling at 186,000 miles per second without stopping. 4.2
• 1:16:07
  Speaker 1: of those years. The actual distance works out to roughly
• 1:16:11
  Speaker 1: 25 trillion miles, or in the units we have been using,
• 1:16:17
  Speaker 1: about 270,000 astronomical units. Voyager 1, after nearly 50 years
• 1:16:25
  Speaker 1: of continuous travel, has covered 170 of those units. To
• 1:16:30
  Speaker 1: reach Proxima Centauri at its current speed, Voyager would need
• 1:16:35
  Speaker 1: approximately 70,000 years. Sit with that number for a moment.
• 1:16:41
  Speaker 1: Not 70 years. Not 700. 70,000. 70,000 years ago, anatomically
• 1:16:50
  Speaker 1: modern humans existed, but just barely in any recognizable sense.
• 1:16:55
  Speaker 1: Small bands were beginning to move out of Africa, following
• 1:16:59
  Speaker 1: coastlines and river valleys into territory no human had ever entered.
• 1:17:04
  Speaker 1: They had fire, they had stone tools, though crude ones.
• 1:17:09
  Speaker 1: Some of them were beginning to paint on cave walls,
• 1:17:13
  Speaker 1: pressing pigment into rock with their hands, to leave a
• 1:17:17
  Speaker 1: mark that something had been there. There were no cities,
• 1:17:21
  Speaker 1: there was no writing, there was no agriculture, no wheel,
• 1:17:27
  Speaker 1: no metal, no mathematics. The entire concept of civilization, everything
• 1:17:34
  Speaker 1: that separates the world you inhabit from that world of
• 1:17:37
  Speaker 1: painted cave walls and hand-chipped stones, had not yet begun.
• 1:17:43
  Speaker 1: And the window between that moment and right now, the
• 1:17:47
  Speaker 1: complete span of everything humanity has ever built or discovered
• 1:17:52
  Speaker 1: or destroyed or written down, is roughly 1 15th of
• 1:17:56
  Speaker 1: the time Voyager would need just to reach the nearest star.
• 1:18:01
  Speaker 1: Every language ever spoken, every empire ever raised and collapsed,
• 1:18:08
  Speaker 1: every war ever fought over borders that no longer exist,
• 1:18:12
  Speaker 1: every scientific discovery from the first recognition that certain plants
• 1:18:18
  Speaker 1: could be grown deliberately to the moment someone figured out
• 1:18:22
  Speaker 1: that the earth orbits the sun and not the other
• 1:18:24
  Speaker 1: way around to the equations that let us build a
• 1:18:28
  Speaker 1: spacecraft in the first place all of it the complete
• 1:18:33
  Speaker 1: record of human thought and achievement across the entire arc
• 1:18:37
  Speaker 1: of recorded history That entire span fits 15 times into
• 1:18:42
  Speaker 1: the journey Voyager is not even making, because here is
• 1:18:47
  Speaker 1: the detail that makes this stranger still. Voyager 1 is
• 1:18:51
  Speaker 1: not headed toward Proxima Centauri. Its trajectory bent northward by
• 1:18:57
  Speaker 1: Saturn's gravity decades ago carries it toward the constellation Camelopardis.
• 1:19:04
  Speaker 1: In roughly 40,000 years it will pass within about 1.7
• 1:19:10
  Speaker 1: light years of a dim red star called AC plus
• 1:19:15
  Speaker 1: 79 3888. That approach is as close as Voyager will
• 1:19:20
  Speaker 1: get to any star for an extraordinarily long time. And
• 1:19:25
  Speaker 1: when it does pass, nothing will happen. There will be
• 1:19:29
  Speaker 1: no signal. No one will be watching. The spacecraft will
• 1:19:33
  Speaker 1: not slow down or alter course. It will simply drift
• 1:19:38
  Speaker 1: through the dark at 17 km per second, invisible, silent,
• 1:19:44
  Speaker 1: carrying its golden record past a star that has no
• 1:19:48
  Speaker 1: planets capable of receiving it, and continue outward into a
• 1:19:52
  Speaker 1: galaxy that has no reason to notice. The 270,000 AU
• 1:19:58
  Speaker 1: figure is worth breaking down further to feel its full weight.
• 1:20:02
  Speaker 1: Voyager covers roughly 3.4 AU per year. At that rate,
• 1:20:07
  Speaker 1: reaching 270,000 AU requires dividing one number by the other.
• 1:20:14
  Speaker 1: The answer does not change no matter how many times
• 1:20:17
  Speaker 1: you run it. The math is patient and indifferent. What
• 1:20:21
  Speaker 1: Voyager has done in 50 years represents about 0.06% of
• 1:20:25
  Speaker 1: the distance to the nearest star. Not 6%. Not 1%. 0.06%.
• 1:20:36
  Speaker 1: If you drew a line on a piece of paper
• 1:20:40
  Speaker 1: representing the full distance to Proxima Centauri, the portion Voyager
• 1:20:45
  Speaker 1: has covered so far would be invisible. You could not
• 1:20:50
  Speaker 1: render it at that scale with any pen that exists.
• 1:20:54
  Speaker 1: This is not a flaw in the mission. Voyager was
• 1:20:57
  Speaker 1: never designed to go to another star. It was designed
• 1:21:01
  Speaker 1: to visit Jupiter and Saturn, and then keep going, and
• 1:21:05
  Speaker 1: by any reasonable measure, it has succeeded beyond what anyone
• 1:21:10
  Speaker 1: in 1977 had a right to expect. But the distance
• 1:21:15
  Speaker 1: to even the nearest star is so vast that a
• 1:21:19
  Speaker 1: spacecraft travelling at the fastest speed any human-made object has
• 1:21:24
  Speaker 1: ever achieved, launched nearly half a century ago, has covered
• 1:21:29
  Speaker 1: something close to nothing in those terms. It has crossed
• 1:21:33
  Speaker 1: the heliopause. It has entered interstellar space by the definition
• 1:21:38
  Speaker 1: that matters for plasma physics. It is genuinely beyond the
• 1:21:43
  Speaker 1: Sun's bubble of charged particles. And still, measured against the
• 1:21:48
  Speaker 1: distance to the nearest star, it might as well have
• 1:21:52
  Speaker 1: not moved. There is a specific way this scale punishes intuition.
• 1:21:58
  Speaker 1: When people hear that Voyager is in interstellar space, The
• 1:22:02
  Speaker 1: natural conclusion is that it is somewhere between the stars,
• 1:22:06
  Speaker 1: well on its way, making progress toward something. The word
• 1:22:11
  Speaker 1: interstellar suggests travel between stellar destinations. But Voyager is not
• 1:22:18
  Speaker 1: between stars in any meaningful navigational sense. It is barely
• 1:22:23
  Speaker 1: off the porch. The gap between our solar system and
• 1:22:27
  Speaker 1: the next nearest star is not like the gap between continents,
• 1:22:32
  Speaker 1: where a long voyage eventually gets you somewhere. It is
• 1:22:35
  Speaker 1: a gap so enormous that the fastest machine humanity has
• 1:22:40
  Speaker 1: ever built, travelling continuously for 50 years, has crossed less
• 1:22:45
  Speaker 1: than a thousandth of it. Astronomers sometimes describe interstellar distances
• 1:22:51
  Speaker 1: as the universe's way of enforcing isolation. Every star is
• 1:22:56
  Speaker 1: essentially sealed off from every other star by distances that
• 1:23:01
  Speaker 1: require time scales longer than human civilization to cross at
• 1:23:05
  Speaker 1: any speed we have ever achieved. The stars are not
• 1:23:09
  Speaker 1: far away the way distant mountains are far away, where
• 1:23:14
  Speaker 1: the distance is real but crossable with enough effort. They
• 1:23:18
  Speaker 1: are far away in a way that requires either a
• 1:23:21
  Speaker 1: completely different relationship with time or a completely different kind
• 1:23:26
  Speaker 1: of machine? Possibly both. What Voyager's trajectory toward AC plus
• 1:23:33
  Speaker 1: 79 3888 illustrates most clearly is that even the closest
• 1:23:39
  Speaker 1: approach any human object will make to another star within
• 1:23:42
  Speaker 1: the next 40,000 years is not actually a close approach. 1.7
• 1:23:49
  Speaker 1: light years is still an almost unimaginable distance That flyby,
• 1:23:55
  Speaker 1: if it can even be called that, will happen at
• 1:23:57
  Speaker 1: a separation larger than many people imagine the entire solar
• 1:24:01
  Speaker 1: system to be. The spacecraft will pass by without any
• 1:24:06
  Speaker 1: awareness of the star, without any capacity to study it,
• 1:24:10
  Speaker 1: without any signal returning to Earth. The closest encounter between
• 1:24:16
  Speaker 1: a human-made object and another stellar system in the foreseeable
• 1:24:20
  Speaker 1: future will be completely silent and completely unnoticed from both ends.
• 1:24:28
  Speaker 1: Voyager 1 has done something genuinely historic that is not
• 1:24:33
  Speaker 1: in question. It has traveled farther than anything humanity has
• 1:24:37
  Speaker 1: ever launched. It has crossed a physical boundary that most
• 1:24:42
  Speaker 1: spacecraft will never approach. It has been sending data for
• 1:24:46
  Speaker 1: nearly 50 years from a place no instrument has ever
• 1:24:51
  Speaker 1: reached before. And measured against the nearest star, that achievement
• 1:24:56
  Speaker 1: represents a fraction so small it strains any analogy we
• 1:25:00
  Speaker 1: can reach for. Even for a spacecraft we consider the
• 1:25:04
  Speaker 1: most successful long-distance mission in human history, the nearest star
• 1:25:10
  Speaker 1: might as well be on the other side of a
• 1:25:12
  Speaker 1: wall we have no way to cross. If you want
• 1:25:15
  Speaker 1: to move a spacecraft significantly faster than Voyager without invoking
• 1:25:20
  Speaker 1: physics we don't understand, nuclear propulsion is where serious engineers
• 1:25:26
  Speaker 1: tend to end up. Not because it is elegant, and
• 1:25:30
  Speaker 1: not because it is cheap, because the math actually closes.
• 1:25:35
  Speaker 1: Chemical rockets have a ceiling baked into the nature of
• 1:25:39
  Speaker 1: chemical bonds, and that ceiling is nowhere near high enough.
• 1:25:44
  Speaker 1: Nuclear energy releases roughly a million times more energy per
• 1:25:48
  Speaker 1: unit of mass than any chemical reaction can. That gap
• 1:25:53
  Speaker 1: is not an incremental advantage. It changes what is possible
• 1:25:58
  Speaker 1: in a fundamental way. The most straightforward version of nuclear
• 1:26:03
  Speaker 1: propulsion is the nuclear thermal rocket. The concept is simpler
• 1:26:08
  Speaker 1: than it sounds. Instead of burning fuel and throwing hot
• 1:26:12
  Speaker 1: exhaust out the back, You run a propellant, usually liquid hydrogen,
• 1:26:17
  Speaker 1: through a nuclear reactor. The reactor heats the hydrogen to
• 1:26:21
  Speaker 1: temperatures no combustion chamber could survive. The hydrogen expands and
• 1:26:27
  Speaker 1: fires through a nozzle at velocities two to three times
• 1:26:30
  Speaker 1: higher than the best chemical engines can manage. You are
• 1:26:34
  Speaker 1: not changing the physics of rocket propulsion. You are just
• 1:26:38
  Speaker 1: heating the propellant far more efficiently. NASA tested working nuclear
• 1:26:43
  Speaker 1: thermal rocket engines in the 1960s under a program called NERVA.
• 1:26:49
  Speaker 1: The engines ran. They produced thrust. They were then shelved,
• 1:26:54
  Speaker 1: partly due to political concerns about launching nuclear reactors, partly
• 1:27:00
  Speaker 1: because the Apollo program was already succeeding with chemical rockets
• 1:27:05
  Speaker 1: and there was no mission that demanded something better. The
• 1:27:08
  Speaker 1: technology did not fail. The ambition behind it ran out
• 1:27:13
  Speaker 1: of funding before it ran out of ideas. A nuclear
• 1:27:17
  Speaker 1: thermal rocket could realistically cut travel times to the outer
• 1:27:21
  Speaker 1: solar system by half or more. That matters for missions
• 1:27:25
  Speaker 1: to Jupiter, Saturn, the heliopause. For interstellar distances, though, even
• 1:27:32
  Speaker 1: a nuclear thermal rocket is not fast enough. It improves
• 1:27:37
  Speaker 1: on chemical propulsion significantly. It does not change the order
• 1:27:42
  Speaker 1: of magnitude. To close the gap between Voyager's speed and
• 1:27:47
  Speaker 1: the fraction of light speed you would actually need for
• 1:27:50
  Speaker 1: interstellar travel, you have to go further. You have to
• 1:27:54
  Speaker 1: look at something wilder. In the late 1950s, a group
• 1:27:59
  Speaker 1: of physicists and engineers at General Atomics began studying what
• 1:28:03
  Speaker 1: is probably the most audacious propulsion concept ever worked out
• 1:28:08
  Speaker 1: in genuine engineering detail. Project Orion proposed that a spacecraft
• 1:28:13
  Speaker 1: could be driven by detonating a rapid series of nuclear
• 1:28:17
  Speaker 1: bombs directly behind it. A thick steel pusher plate at
• 1:28:22
  Speaker 1: the rear of the vehicle would absorb the blast. Shock
• 1:28:26
  Speaker 1: absorbers between the plate and the spacecraft would cushion the impulse.
• 1:28:31
  Speaker 1: Each explosion would shove the vehicle forward. Fire enough of
• 1:28:35
  Speaker 1: them in sequence, and the spacecraft accelerates to velocities no
• 1:28:40
  Speaker 1: chemical engine could approach. The concept sounds like something from
• 1:28:45
  Speaker 1: a fever dream. The engineering behind it was not. Freeman
• 1:28:50
  Speaker 1: Dyson worked on Orion. He was serious about it. Studies
• 1:28:55
  Speaker 1: showed that a sufficiently large Orion vehicle could theoretically reach
• 1:28:59
  Speaker 1: a few percent of the speed of light. Dyson himself
• 1:29:03
  Speaker 1: believed it could have reached Alpha Centauri within a human
• 1:29:07
  Speaker 1: lifetime if the political will had existed to build it.
• 1:29:11
  Speaker 1: The Partial Nuclear Test Ban Treaty of 1963, which prohibited
• 1:29:16
  Speaker 1: nuclear detonations in space, ended the program before a prototype flew.
• 1:29:22
  Speaker 1: It remains one of the stranger might-have-beens in the history
• 1:29:26
  Speaker 1: of space exploration. Orion was never built. What came after it,
• 1:29:32
  Speaker 1: in terms of serious engineering study, was Project Daedalus. In
• 1:29:37
  Speaker 1: the 1970s, the British Interplanetary Society gathered a team of
• 1:29:42
  Speaker 1: engineers and physicists and gave them an unusual assignment. Design
• 1:29:48
  Speaker 1: a real spacecraft, not a concept sketch. not a feasibility
• 1:29:53
  Speaker 1: study hedged with qualifications. An actual engineering design for an
• 1:29:58
  Speaker 1: unmanned probe capable of reaching another star within 50 years
• 1:30:03
  Speaker 1: of launch, using only technology that could plausibly be developed
• 1:30:07
  Speaker 1: from what existed at the time. The target they chose
• 1:30:11
  Speaker 1: was Barnard's star, roughly six light years away. The result,
• 1:30:17
  Speaker 1: published in 1978 after five years of work, was Project Daedalus.
• 1:30:22
  Speaker 1: The design used nuclear fusion rather than fission. Specifically, inertial
• 1:30:29
  Speaker 1: confinement fusion. Tiny pellets of deuterium and helium-3 would be
• 1:30:34
  Speaker 1: bombarded by electron beams, triggering fusion reactions, and the resulting
• 1:30:40
  Speaker 1: plasma would be directed out of a magnetic nozzle at
• 1:30:44
  Speaker 1: exhaust velocities far beyond anything achievable with fission or chemistry.
• 1:30:50
  Speaker 1: The spacecraft would fire these fusion pulses 250 times per
• 1:30:56
  Speaker 1: second during its acceleration phase. Over roughly four years of
• 1:31:02
  Speaker 1: continuous burn, it would reach approximately 12% of the speed
• 1:31:07
  Speaker 1: of light. At that velocity, the journey to Barnard's Star
• 1:31:12
  Speaker 1: would take about 46 years. A human lifetime, start to finish.
• 1:31:18
  Speaker 1: for the first interstellar probe in history. The numbers in
• 1:31:22
  Speaker 1: the Daedalus report are staggering in their specificity. The total
• 1:31:27
  Speaker 1: mass of the vehicle at launch was calculated at roughly 54,000 tons.
• 1:31:34
  Speaker 1: Of that, approximately 50,000 tons was fuel. The spacecraft itself,
• 1:31:41
  Speaker 1: the payload, the engines, the structure, accounted for only a
• 1:31:45
  Speaker 1: small fraction of the total mass. This is the inescapable
• 1:31:50
  Speaker 1: logic of propulsion at high velocities. Fuel dominates everything. The
• 1:31:56
  Speaker 1: payload Daedalus would have delivered to Barnard's star was about
• 1:32:00
  Speaker 1: 450 tonnes of scientific instruments, designed to take readings during
• 1:32:06
  Speaker 1: a flyby lasting a few hours before the probe vanished
• 1:32:10
  Speaker 1: into the dark beyond. The helium-3 requirement is where Daedalus
• 1:32:15
  Speaker 1: runs into its deepest problems. Helium-3 is extraordinarily rare on Earth.
• 1:32:22
  Speaker 1: The entire global supply accumulated over decades of nuclear research
• 1:32:28
  Speaker 1: amounts to a few hundred kilograms. Daedalus required roughly 30,000
• 1:32:33
  Speaker 1: tons of it. The proposed solution was to mine it
• 1:32:38
  Speaker 1: from the upper atmosphere of Jupiter, where it exists in
• 1:32:42
  Speaker 1: far greater quantities. using a fleet of automated mining platforms
• 1:32:47
  Speaker 1: operating over decades. This is not a violation of any
• 1:32:51
  Speaker 1: physical law. It is also not something any existing civilization
• 1:32:56
  Speaker 1: has come close to doing. The infrastructure required to extract
• 1:33:01
  Speaker 1: and refine helium-3 from a gas giant at the scale
• 1:33:05
  Speaker 1: Daedalus demanded would itself represent an engineering project larger than
• 1:33:11
  Speaker 1: anything humans have built. The math worked. Given the fuel,
• 1:33:16
  Speaker 1: given the engineering resources to construct something that large, the
• 1:33:20
  Speaker 1: laws of physics permitted the journey. The British Interplanetary Society
• 1:33:26
  Speaker 1: was not writing science fiction. They were doing engineering with
• 1:33:31
  Speaker 1: real equations, real materials, real projected performance numbers. Daedalus is
• 1:33:38
  Speaker 1: taken seriously precisely because it did not cheat. It did
• 1:33:42
  Speaker 1: not invoke any physics that wasn't understood. It asked only
• 1:33:47
  Speaker 1: for resources and manufacturing capability at a scale humanity does
• 1:33:52
  Speaker 1: not currently possess and has no near-term plan to develop.
• 1:33:57
  Speaker 1: That distinction matters. There is a difference between a problem
• 1:34:01
  Speaker 1: that is physically impossible and a problem that is merely
• 1:34:04
  Speaker 1: expensive beyond any scale we can currently imagine. Project Daedalus
• 1:34:10
  Speaker 1: showed that the physics of reaching another star in a
• 1:34:13
  Speaker 1: human lifetime is not impossible, just extraordinarily, almost incomprehensibly expensive.
• 1:34:22
  Speaker 1: There is one proposed propulsion method that takes the rocket
• 1:34:26
  Speaker 1: equation entirely off the table, and it does not look
• 1:34:30
  Speaker 1: like any rocket you have ever seen. Every propulsion system
• 1:34:34
  Speaker 1: discussed before this one shares a common burden. The spacecraft
• 1:34:39
  Speaker 1: carries its own energy source. Nuclear thermal, nuclear pulse, chemical.
• 1:34:45
  Speaker 1: All of them require the ship to bring its fuel
• 1:34:48
  Speaker 1: along for the ride. This is the fundamental trap. Fuel
• 1:34:52
  Speaker 1: has mass. Mass requires more fuel to accelerate. The rocket
• 1:34:57
  Speaker 1: equation punishes you for every kilogram you add. And a
• 1:35:01
  Speaker 1: fuel tank is always adding kilograms. The laser sail concept
• 1:35:06
  Speaker 1: escapes this trap by doing something almost obvious once you
• 1:35:10
  Speaker 1: hear it. Leave the energy source at home. The principle
• 1:35:14
  Speaker 1: is this. A large, highly reflective sail is attached to
• 1:35:18
  Speaker 1: a small spacecraft. Back on Earth, or in orbit around Earth,
• 1:35:24
  Speaker 1: an enormous array of lasers fires a concentrated beam at
• 1:35:28
  Speaker 1: that sail. Light carries momentum. When photons strike a reflective
• 1:35:34
  Speaker 1: surface and bounce back, they transfer twice their momentum to
• 1:35:38
  Speaker 1: whatever they hit. Repeat this across trillions upon trillions of photons,
• 1:35:44
  Speaker 1: sustained over minutes of continuous laser fire, and the sail accelerates.
• 1:35:50
  Speaker 1: No fuel burned, no exhaust expelled, the spacecraft is pushed
• 1:35:55
  Speaker 1: the way a leaf is pushed across water, by a
• 1:35:59
  Speaker 1: breath of air. except the breath is a focused beam
• 1:36:02
  Speaker 1: of coherent light and the leaf is moving toward another star.
• 1:36:07
  Speaker 1: The key insight that makes this more than a thought
• 1:36:10
  Speaker 1: experiment is exactly what it removes from the equation. The
• 1:36:15
  Speaker 1: laser stays on Earth. The ship carries nothing to generate
• 1:36:20
  Speaker 1: its own thrust. What it carries instead is the sail itself.
• 1:36:25
  Speaker 1: As thin and light as engineers can possibly make it,
• 1:36:29
  Speaker 1: whatever small payload is attached strip the mission down to
• 1:36:33
  Speaker 1: its minimum and suddenly the mass problem transforms into something
• 1:36:38
  Speaker 1: that might actually be solvable in 2016 this concept found
• 1:36:43
  Speaker 1: a serious champion physicist Philip Lubin at the University of
• 1:36:48
  Speaker 1: California Santa Barbara had been developing the theoretical framework for
• 1:36:53
  Speaker 1: laser propulsion for years that year The billionaire science philanthropist
• 1:36:59
  Speaker 1: Yuri Milner announced he was committing $ 100 million to turning
• 1:37:03
  Speaker 1: those ideas into something real. The project was called Breakthrough Starshot.
• 1:37:10
  Speaker 1: Stephen Hawking stood on the stage at the announcement. The
• 1:37:14
  Speaker 1: goal was not modest. The proposal was to send probes
• 1:37:18
  Speaker 1: to Alpha Centauri, the nearest star system at roughly 4.2
• 1:37:23
  Speaker 1: light years away. within a human lifetime. Not within a
• 1:37:28
  Speaker 1: thousand years, within roughly 20 years of travel time. To
• 1:37:32
  Speaker 1: do that, the probes would need to reach approximately 20%
• 1:37:37
  Speaker 1: of the speed of light. No human-made object has ever
• 1:37:41
  Speaker 1: exceeded a small fraction of 1%. Voyager 1, fast as
• 1:37:46
  Speaker 1: it is, moves at roughly 0.006% of light speed. Breakthrough
• 1:37:53
  Speaker 1: Starshot was proposing to exceed that by a factor of
• 1:37:56
  Speaker 1: more than 3,000. The way to achieve this speed is
• 1:38:00
  Speaker 1: to make the spacecraft almost nothing at all. The proposal
• 1:38:04
  Speaker 1: centred on what the team called star chips, probes massing
• 1:38:09
  Speaker 1: only a few grams, roughly the weight of a paperclip,
• 1:38:13
  Speaker 1: carrying miniaturised cameras, sensors and communication hardware etched onto a
• 1:38:18
  Speaker 1: single chip. Attach one of these chips to a sail,
• 1:38:22
  Speaker 1: perhaps a few meters wide, made from material only a
• 1:38:26
  Speaker 1: few hundred atoms thick, and a laser array of sufficient
• 1:38:30
  Speaker 1: power could accelerate the whole assembly to a fifth of
• 1:38:34
  Speaker 1: the speed of light within minutes. The laser array required
• 1:38:38
  Speaker 1: would itself be staggering. Early estimates pointed toward a system
• 1:38:43
  Speaker 1: generating roughly 100 gigawatts of power, fired in a coordinated
• 1:38:48
  Speaker 1: beam from a large array of individual laser units acting
• 1:38:52
  Speaker 1: in concert. For context, the total electrical generating capacity of
• 1:38:58
  Speaker 1: the United States is somewhere around 1,000 gigawatts. This laser
• 1:39:04
  Speaker 1: would consume roughly a tenth of that, fired in a burst,
• 1:39:08
  Speaker 1: to push something the size of a postage stamp to
• 1:39:11
  Speaker 1: interstellar speeds. The thermal management alone Dissipating the heat generated
• 1:39:17
  Speaker 1: by firing such a system is an engineering challenge with
• 1:39:21
  Speaker 1: no solved precedent. Then there is the alignment problem. The
• 1:39:26
  Speaker 1: laser must hit the sail. As the sail accelerates and
• 1:39:30
  Speaker 1: the distance between it and Earth grows, keeping the beam
• 1:39:34
  Speaker 1: precisely centered becomes exponentially harder. Any drift in the beam,
• 1:39:40
  Speaker 1: any atmospheric distortion, any slight misalignment in the laser array
• 1:39:46
  Speaker 1: and the sail either tumbles or receives uneven pressure that
• 1:39:49
  Speaker 1: sends it off course. Engineers have proposed placing the array
• 1:39:54
  Speaker 1: at high altitude or in orbit to reduce atmospheric interference.
• 1:39:59
  Speaker 1: The precision required for sustained targeting across growing distances is
• 1:40:05
  Speaker 1: at the edge of what current optical technology can even conceive.
• 1:40:10
  Speaker 1: The sail itself presents a separate problem. It must be
• 1:40:14
  Speaker 1: reflective enough to catch the beam efficiently. It must be
• 1:40:18
  Speaker 1: thin enough to have almost no mass. And it must
• 1:40:22
  Speaker 1: survive the intensity of a beam powerful enough to push
• 1:40:25
  Speaker 1: it to 20% of the speed of light without burning,
• 1:40:29
  Speaker 1: tearing or warping. The energy density at the sail surface
• 1:40:34
  Speaker 1: during acceleration would be extreme. Any imperfection in the material,
• 1:40:40
  Speaker 1: any hotspot in the beam, and the sail fails. Building
• 1:40:44
  Speaker 1: a material that is simultaneously near transparent in mass, mechanically stable,
• 1:40:51
  Speaker 1: and capable of enduring that energy flux is an open
• 1:40:55
  Speaker 1: material science problem. Assume the probe reaches Alpha Centauri in
• 1:41:00
  Speaker 1: 20 years. What happens when it gets there? It flies
• 1:41:04
  Speaker 1: through the system at one fifth the speed of light
• 1:41:07
  Speaker 1: and keeps going. There are no breaks. The laser cannot
• 1:41:12
  Speaker 1: decelerate it from four light years away. The probe will
• 1:41:15
  Speaker 1: have perhaps hours, perhaps less, to collect data and images
• 1:41:20
  Speaker 1: as it passes through the star system at roughly 60,000
• 1:41:24
  Speaker 1: kilometers per second. Whatever it sees, it must transmit back
• 1:41:28
  Speaker 1: to Earth as it goes, which raises the communication problem.
• 1:41:33
  Speaker 1: A gram-scale chip carrying a miniaturized transmitter with almost no
• 1:41:39
  Speaker 1: power budget attempting to send a signal from four light
• 1:41:43
  Speaker 1: years away. The signal would take over four years to
• 1:41:47
  Speaker 1: reach Earth, and the signal itself would be so faint
• 1:41:51
  Speaker 1: that detecting it would require receiver arrays far larger than
• 1:41:56
  Speaker 1: anything currently built. The team has proposed large optical receiver telescopes,
• 1:42:02
  Speaker 1: but pulling a signal from a chip-scale transmitter across four
• 1:42:06
  Speaker 1: light years of space is at the outer boundary of
• 1:42:10
  Speaker 1: what physics allows, even with ideal equipment. None of these
• 1:42:14
  Speaker 1: problems have been solved. The materials don't exist yet. The
• 1:42:19
  Speaker 1: laser array doesn't exist. The sail fabrication techniques don't exist.
• 1:42:26
  Speaker 1: The chip-scale spacecraft don't exist in the form required. Breakthrough
• 1:42:31
  Speaker 1: Starshot's $ 100 million funded early research, not construction. The timeline
• 1:42:39
  Speaker 1: for actually launching anything under this framework likely runs to
• 1:42:43
  Speaker 1: mid-century at the earliest, under optimistic assumptions. And yet, what
• 1:42:49
  Speaker 1: separates this concept from warp drives and wormholes is that
• 1:42:54
  Speaker 1: none of the obstacles are physics problems. Light does carry momentum.
• 1:42:59
  Speaker 1: Reflection does transfer it. Thin sails can be pushed. These
• 1:43:05
  Speaker 1: are not theoretical propositions. They are observed phenomena. Solar sails
• 1:43:10
  Speaker 1: have flown in space already. Small ones, pushed by sunlight,
• 1:43:15
  Speaker 1: not lasers, but the principle is identical. The path from
• 1:43:19
  Speaker 1: where we are to a functional laser sail mission runs
• 1:43:23
  Speaker 1: through difficult engineering, extreme precision, and enormous expense. The engineering
• 1:43:30
  Speaker 1: problems are real and enormous. But they are engineering problems.
• 1:43:36
  Speaker 1: which is a different category of problem than physics problems.
• 1:43:41
  Speaker 1: One way to reach another star without inventing new physics
• 1:43:46
  Speaker 1: is to simply accept that the journey will take longer
• 1:43:49
  Speaker 1: than any one human lifetime. Laser sails and nuclear fusion
• 1:43:55
  Speaker 1: engines are attempts to compress the journey into a span
• 1:43:59
  Speaker 1: a single crew could survive. The generation ship takes the
• 1:44:03
  Speaker 1: opposite approach. It does not try to solve the time problem.
• 1:44:08
  Speaker 1: It folds the time problem into the mission itself and
• 1:44:12
  Speaker 1: asks a different question. What if the spacecraft were not
• 1:44:16
  Speaker 1: a vehicle but a world? The concept is straightforward to
• 1:44:21
  Speaker 1: describe and almost incomprehensible to actually build. You launch a
• 1:44:27
  Speaker 1: spacecraft large enough to sustain a human population across several
• 1:44:32
  Speaker 1: centuries of travel. The people aboard live out their lives.
• 1:44:37
  Speaker 1: They have children. Those children grow up, have their own children.
• 1:44:42
  Speaker 1: Those generations carry the mission forward until somewhere between 500
• 1:44:49
  Speaker 1: and 1,000 years later. Descendants who share no living memory
• 1:44:54
  Speaker 1: with the original crew arrive at another star. The engineering
• 1:44:59
  Speaker 1: requirements alone would dwarf anything humanity has ever constructed. a
• 1:45:04
  Speaker 1: functional biosphere, self-contained agriculture capable of feeding hundreds or thousands
• 1:45:11
  Speaker 1: of people indefinitely, water recycling, atmosphere management, waste processing, medical
• 1:45:19
  Speaker 1: facilities capable of handling everything from routine illness to surgery
• 1:45:24
  Speaker 1: to childbirth across centuries with no resupply. Every system would
• 1:45:29
  Speaker 1: need redundancy. The redundancy would need redundancy. This was because
• 1:45:35
  Speaker 1: a single catastrophic failure in the air recycling system or
• 1:45:39
  Speaker 1: the food supply does not end emission. It ends everyone.
• 1:45:45
  Speaker 1: The population question is one that researchers have actually calculated.
• 1:45:50
  Speaker 1: To avoid genetic bottlenecks, the slow collapse of genetic diversity
• 1:45:55
  Speaker 1: that happens when a breeding population is too small, Estimates
• 1:45:59
  Speaker 1: suggest you need somewhere between a few hundred and several
• 1:46:03
  Speaker 1: thousand people at minimum. Some studies have placed the lower
• 1:46:08
  Speaker 1: bound at around 160 individuals if mating is carefully managed.
• 1:46:14
  Speaker 1: Others put the safe number much higher, closer to 40,000,
• 1:46:19
  Speaker 1: when accounting for random genetic drift across multiple generations without
• 1:46:24
  Speaker 1: any management at all. The range is wide because the
• 1:46:28
  Speaker 1: problem is genuinely hard and involves assumptions about how rigorously
• 1:46:33
  Speaker 1: the population would be willing to govern its own reproduction. 40,000
• 1:46:39
  Speaker 1: people travelling between stars is not a spacecraft. It is
• 1:46:44
  Speaker 1: a city. Then there is the social architecture problem, which
• 1:46:49
  Speaker 1: may be harder than the genetic one. Nations that have
• 1:46:53
  Speaker 1: lasted 500 years are rare. Institutions that have maintained coherent
• 1:46:59
  Speaker 1: purpose and direction across that span without fracturing, splitting or
• 1:47:05
  Speaker 1: reversing course entirely are almost non-existent in the historical record.
• 1:47:11
  Speaker 1: A generation ship would need to accomplish this in a
• 1:47:14
  Speaker 1: sealed container with no outside contact, no immigration, no trade,
• 1:47:21
  Speaker 1: no new ideas from anywhere beyond its own hull. The
• 1:47:25
  Speaker 1: founders of the mission, the people who chose to go,
• 1:47:29
  Speaker 1: will be dead within the first generation or two. They
• 1:47:33
  Speaker 1: cannot enforce their intentions from the grave. Whatever social contract
• 1:47:39
  Speaker 1: they established at launch has to survive in a community
• 1:47:43
  Speaker 1: that grows increasingly distant from the original decision. Among people
• 1:47:48
  Speaker 1: who never consented to any of it, This is the
• 1:47:51
  Speaker 1: philosophical problem at the centre of the generation ship concept.
• 1:47:56
  Speaker 1: It does not have an obvious answer. The crew members
• 1:48:00
  Speaker 1: born into the third generation of a 500 year voyage
• 1:48:04
  Speaker 1: did not choose to be there. They were born into
• 1:48:07
  Speaker 1: a trajectory someone else set toward a destination they will
• 1:48:12
  Speaker 1: likely never see. For reasons that must have seemed pressing
• 1:48:17
  Speaker 1: to people who lived and died before their grandparents. were born.
• 1:48:21
  Speaker 1: Whether that constitutes an ethical problem is a question that
• 1:48:25
  Speaker 1: philosophers and ethicists have been arguing about without resolution for decades.
• 1:48:31
  Speaker 1: Whether it constitutes a practical problem is more certain. History
• 1:48:36
  Speaker 1: suggests that populations under sustained pressure with no exit, shrinking
• 1:48:42
  Speaker 1: connection to the original purpose of their confinement, do not
• 1:48:47
  Speaker 1: reliably maintain institutional stability. They fracture, they revolt, they reinterpret
• 1:48:55
  Speaker 1: the mission. In the middle of interstellar space with no
• 1:48:58
  Speaker 1: way to course correct from Earth, a fractured society aboard
• 1:49:03
  Speaker 1: a generation ship is a disaster with nowhere to go.
• 1:49:07
  Speaker 1: What political structure survives 500 years? Democracies as currently practiced
• 1:49:14
  Speaker 1: tend to shift in priorities election by election. Autocracies are
• 1:49:19
  Speaker 1: stable until they are not. And when they collapse, they
• 1:49:23
  Speaker 1: often collapse violently. Technocratic governance by an engineering class might
• 1:49:29
  Speaker 1: maintain the ship's systems. But it is not clear it
• 1:49:33
  Speaker 1: could maintain social cohesion across generations of people who may
• 1:49:38
  Speaker 1: come to regard the mission itself as an inherited prison
• 1:49:43
  Speaker 1: rather than a shared purpose. Some theorists have proposed that
• 1:49:47
  Speaker 1: the answer involves religion, that only a system of belief
• 1:49:51
  Speaker 1: capable of rendering the mission sacred could sustain commitment across
• 1:49:56
  Speaker 1: the timescales involved. Others have suggested constitutional frameworks specifically designed
• 1:50:03
  Speaker 1: for closed system governance, with amendment processes deliberately constrained to
• 1:50:10
  Speaker 1: prevent the mission from being voted out of existence by
• 1:50:13
  Speaker 1: a generation that simply wants to turn around. None of
• 1:50:18
  Speaker 1: these proposals have been tested. This was because no society
• 1:50:22
  Speaker 1: has ever been asked to hold itself together in a
• 1:50:25
  Speaker 1: sealed box for five centuries without contact with the outside world.
• 1:50:31
  Speaker 1: If the destination proves inhospitable, if the planet the founders
• 1:50:35
  Speaker 1: targeted turns out to be sterile or poisonous or simply
• 1:50:40
  Speaker 1: wrong in ways a telescope four light years away could
• 1:50:43
  Speaker 1: not detect, the people who arrive have nowhere to go.
• 1:50:48
  Speaker 1: The people who launched made a decision that cannot be undone.
• 1:50:52
  Speaker 1: The descendants bear the consequences of a bet they had
• 1:50:56
  Speaker 1: no vote on. The stars surrounding them are not places
• 1:51:00
  Speaker 1: they can easily redirect toward. The mission parameters were fixed
• 1:51:05
  Speaker 1: at launch by people centuries dead. The generation ship is
• 1:51:10
  Speaker 1: not really an engineering problem. It is a question about
• 1:51:15
  Speaker 1: what kind of society you can build inside a sealed
• 1:51:19
  Speaker 1: container for 500 years and whether it stays pointed in
• 1:51:23
  Speaker 1: the right direction. If a generation ship puts the burden
• 1:51:27
  Speaker 1: of the journey on your descendants, hibernation offers a different
• 1:51:31
  Speaker 1: kind of answer. Put the burden on chemistry instead. The
• 1:51:36
  Speaker 1: appeal is not hard to understand. A generation ship requires
• 1:51:40
  Speaker 1: you to solve civilization at a small scale. to build
• 1:51:44
  Speaker 1: social structures that hold together across centuries, to convince people
• 1:51:49
  Speaker 1: born into a voyage they never chose to keep pointing
• 1:51:52
  Speaker 1: the ship in the right direction. Hibernation sidesteps all of that.
• 1:51:58
  Speaker 1: If the crew spends most of the journey in a
• 1:52:01
  Speaker 1: dormant state, there are no generations born aboard, no political fractures,
• 1:52:08
  Speaker 1: no slow drift away from the mission. The people who
• 1:52:12
  Speaker 1: wake up at the destination are the same people who launched.
• 1:52:16
  Speaker 1: They remember Earth. They remember why they went. The psychological
• 1:52:22
  Speaker 1: continuity that a generation ship cannot guarantee. Hibernation delivers by
• 1:52:28
  Speaker 1: simply removing the problem from the equation. The question is
• 1:52:33
  Speaker 1: whether the biology cooperates. What medicine currently has is therapeutic hypothermia.
• 1:52:41
  Speaker 1: In certain surgeries in cardiac emergencies, doctors lower a patient's
• 1:52:46
  Speaker 1: core body temperature by several degrees to slow metabolism and
• 1:52:51
  Speaker 1: reduce the brain's demand for oxygen. This buys time. It
• 1:52:56
  Speaker 1: allows surgeons to pause the body in a controlled way
• 1:53:00
  Speaker 1: for hours while they work. Patients have survived and recovered
• 1:53:05
  Speaker 1: with their cognitive function intact. This is real and it works.
• 1:53:10
  Speaker 1: and it has been used for decades. But the time
• 1:53:13
  Speaker 1: scale involved is hours, occasionally a day. The longest applications
• 1:53:19
  Speaker 1: of therapeutic hypothermia in clinical settings are measured not in weeks,
• 1:53:24
  Speaker 1: but in hours. Scaling that to decades is a different
• 1:53:29
  Speaker 1: problem in almost every dimension. The first challenge is metabolic.
• 1:53:35
  Speaker 1: During therapeutic hypothermia, the body is not fully shut down.
• 1:53:40
  Speaker 1: It is slowed. The heart still beats. The lungs still
• 1:53:45
  Speaker 1: process oxygen. The brain is still active, just suppressed. For
• 1:53:51
  Speaker 1: a long duration hibernation lasting years or decades, researchers would
• 1:53:56
  Speaker 1: need to maintain this reduced metabolic state continuously, keeping every
• 1:54:02
  Speaker 1: organ system functional enough to survive, but running at a
• 1:54:06
  Speaker 1: fraction of its normal rate. No one has done this
• 1:54:10
  Speaker 1: in humans for more than a few days, and the
• 1:54:13
  Speaker 1: physiology of truly extended suppression is largely unknown territory. Radiation
• 1:54:20
  Speaker 1: is a serious complication. In deep space, galactic cosmic rays
• 1:54:25
  Speaker 1: arrive from every direction, and they pass through most shielding
• 1:54:29
  Speaker 1: materials without much difficulty. An active immune system provides some
• 1:54:35
  Speaker 1: defense against cellular damage. A hibernating crew, by definition, has
• 1:54:40
  Speaker 1: a suppressed immune system. The radiation exposure that accumulates over
• 1:54:45
  Speaker 1: a 20-year voyage while the body's defenses are dialed down
• 1:54:50
  Speaker 1: to nearly nothing is a problem that nobody has modeled
• 1:54:53
  Speaker 1: with much confidence. Radiation causes damage at the cellular and
• 1:54:59
  Speaker 1: DNA level, and that damage compounds over time. Whether a
• 1:55:03
  Speaker 1: dormant body could survive two decades of deep space radiation
• 1:55:08
  Speaker 1: without catastrophic cellular breakdown is genuinely unknown. Muscle and bone
• 1:55:14
  Speaker 1: loss add another layer of difficulty. Even with a fully
• 1:55:18
  Speaker 1: active crew aboard a spacecraft, preventing atrophy requires hours of
• 1:55:23
  Speaker 1: daily exercise and careful nutritional management. A hibernating crew cannot exercise.
• 1:55:30
  Speaker 1: Bone density would drop. muscle tissue would waste. The degree
• 1:55:35
  Speaker 1: of atrophy that accumulates over years of dormancy could leave
• 1:55:40
  Speaker 1: crew members physically incapable of functioning when revived, assuming revival
• 1:55:46
  Speaker 1: is even possible at that point. There are proposals for
• 1:55:50
  Speaker 1: electrical muscle stimulation systems that could fire muscle groups periodically
• 1:55:55
  Speaker 1: during hibernation without waking the crew, But these remain theoretical
• 1:56:00
  Speaker 1: and untested at any meaningful duration. The brain presents perhaps
• 1:56:05
  Speaker 1: the deepest uncertainty. Neurons are fragile in ways that other
• 1:56:10
  Speaker 1: cells are not. Even short periods of reduced oxygen can
• 1:56:14
  Speaker 1: cause lasting cognitive damage. Cooling the brain slows its metabolism,
• 1:56:21
  Speaker 1: but it does not stop the slow background processes of
• 1:56:24
  Speaker 1: cellular aging and biochemical decay. What happens to human cognition
• 1:56:30
  Speaker 1: after 20 years of suppressed brain activity is not something
• 1:56:34
  Speaker 1: science has any data on. Animal hibernation offers some analogies. Bears,
• 1:56:41
  Speaker 1: ground squirrels and several other species hibernate for months with
• 1:56:45
  Speaker 1: no apparent cognitive damage. But the physiological mechanisms involved in
• 1:56:50
  Speaker 1: animal hibernation are quite different from the therapeutic hypothermia used
• 1:56:55
  Speaker 1: in human medicine. And scaling from a bear's winter dormancy
• 1:57:00
  Speaker 1: to a human's 20-year interstellar sleep requires bridging a gap
• 1:57:05
  Speaker 1: that current biology does not know how to bridge. And
• 1:57:08
  Speaker 1: then there is the question of what happens when something
• 1:57:11
  Speaker 1: breaks while everyone is asleep. A generation ship has people aboard, conscious,
• 1:57:18
  Speaker 1: capable of responding to emergencies. A hibernation ship does not.
• 1:57:24
  Speaker 1: The automation required to manage a vessel across decades of
• 1:57:28
  Speaker 1: deep space travel, monitoring life support, maintaining the hibernation systems,
• 1:57:34
  Speaker 1: diagnosing hardware failures, executing repairs would need to function without
• 1:57:40
  Speaker 1: human oversight for the entire journey. A single point of
• 1:57:44
  Speaker 1: failure in the hibernation pods, in the power system, in
• 1:57:48
  Speaker 1: the thermal regulation that keeps the crew at the right temperature,
• 1:57:52
  Speaker 1: could kill everyone aboard before any alarm reached a conscious mind.
• 1:57:57
  Speaker 1: The engineering standard required for that level of autonomous reliability
• 1:58:02
  Speaker 1: over two or more decades of continuous operation is far
• 1:58:07
  Speaker 1: beyond anything currently deployed. Spacecraft systems fail. Voyager's own team
• 1:58:14
  Speaker 1: dealt with serious computer problems in 2023, and diagnosing those
• 1:58:20
  Speaker 1: required months of careful work by a large team of engineers.
• 1:58:25
  Speaker 1: In a hibernation scenario, those engineers are asleep. None of
• 1:58:29
  Speaker 1: this means hibernation is impossible. Some of the physiological barriers
• 1:58:34
  Speaker 1: may prove more manageable than current data suggests. Research into
• 1:58:40
  Speaker 1: torpor induction, ways of chemically triggering a hibernation-like state in
• 1:58:45
  Speaker 1: mammals that don't naturally hibernate, has shown some early promise.
• 1:58:50
  Speaker 1: NASA has funded preliminary studies. The field is not stagnant,
• 1:58:55
  Speaker 1: but the distance between where this science stands today and
• 1:58:59
  Speaker 1: where it would need to stand before anyone trusted it
• 1:59:02
  Speaker 1: with a crew on a 20-year voyage is very large.
• 1:59:07
  Speaker 1: The gap between short-duration medical hibernation and sleeping through a
• 1:59:12
  Speaker 1: 20-year interstellar voyage is not a gap that has a
• 1:59:16
  Speaker 1: clear bridge yet. Every proposed method for reaching another star
• 1:59:21
  Speaker 1: eventually runs into the same wall, no matter how different
• 1:59:26
  Speaker 1: the approach looks on the surface. nuclear propulsion, laser sails,
• 1:59:32
  Speaker 1: generation ships, hibernation. Each approach has its own set of
• 1:59:37
  Speaker 1: engineering challenges. Each one has been examined in detail by
• 1:59:42
  Speaker 1: serious researchers. But underneath all of them, no matter how
• 1:59:46
  Speaker 1: you slice the problem, there is a single constraint that
• 1:59:50
  Speaker 1: none of them escape. Energy. The amount of energy required
• 1:59:55
  Speaker 1: to push anything to interstellar velocities is so far beyond
• 2:00:00
  Speaker 1: what humanity currently produces that the gap does not feel
• 2:00:04
  Speaker 1: like a technical shortfall. It feels like a different category
• 2:00:09
  Speaker 1: of problem entirely. Here is a number worth sitting with.
• 2:00:14
  Speaker 1: Accelerating one ton of mass to 10% of the speed
• 2:00:18
  Speaker 1: of light requires approximately 125 terawatt hours of energy. In
• 2:00:22
  Speaker 1: the early 2000s, The entire world consumed roughly that amount
• 2:00:31
  Speaker 1: of energy in a single year. Every power plant, every car,
• 2:00:36
  Speaker 1: every factory, every heated home on the planet, all of it,
• 2:00:41
  Speaker 1: added together for 12 months, buys you enough energy to
• 2:00:45
  Speaker 1: push one tonne to one tenth light speed. One tonne
• 2:00:49
  Speaker 1: is roughly the mass of a small car. A crewed
• 2:00:53
  Speaker 1: interstellar spacecraft does not mass one tonne. It masses thousands
• 2:00:57
  Speaker 1: of tons. This was because humans need food, water, air,
• 2:01:02
  Speaker 1: radiation shielding, medical equipment, structural integrity across decades of travel.
• 2:01:09
  Speaker 1: The energy math scales with mass. A spacecraft massing 5,000
• 2:01:15
  Speaker 1: tons requires 5,000 times the energy of that single ton calculation.
• 2:01:22
  Speaker 1: That is 5,000 years of current global energy production for
• 2:01:27
  Speaker 1: a single departure burn. And departure is only half the problem.
• 2:01:33
  Speaker 1: If the spacecraft arrives at Proxima Centauri at 10% of
• 2:01:37
  Speaker 1: light speed and cannot stop, it conducts a flyby lasting
• 2:01:42
  Speaker 1: a few hours before vanishing into the dark on the
• 2:01:45
  Speaker 1: other side. A useful crewed mission has to decelerate. Deceleration
• 2:01:51
  Speaker 1: requires the same energy as acceleration, assuming you are not
• 2:01:56
  Speaker 1: using some external braking mechanism at the destination. Double the
• 2:02:00
  Speaker 1: energy requirement. Now the mission to Proxima Centauri demands not 5,000
• 2:02:06
  Speaker 1: years of global energy production, but closer to 10,000. That
• 2:02:12
  Speaker 1: is at the optimistic velocity of 10% light speed. That
• 2:02:17
  Speaker 1: is already far beyond anything we have demonstrated. The nearest
• 2:02:23
  Speaker 1: star is the easiest possible target. It is the shortest
• 2:02:28
  Speaker 1: interstellar distance that exists from our position. If the energy
• 2:02:32
  Speaker 1: requirements for a crewed mission to Proxima Centauri are that extreme,
• 2:02:38
  Speaker 1: every other destination in the galaxy is worse by a
• 2:02:41
  Speaker 1: proportional margin. This is not a problem where incremental engineering
• 2:02:46
  Speaker 1: improvements close the gap. The gap is measured in orders
• 2:02:50
  Speaker 1: of magnitude. What makes this harder is where humanity currently
• 2:02:55
  Speaker 1: gets its energy. The overwhelming majority of global power generation
• 2:03:01
  Speaker 1: still comes from burning fossil fuels. That combustion is already
• 2:03:06
  Speaker 1: destabilizing the planet's climate system in ways that will demand
• 2:03:10
  Speaker 1: enormous resources to manage across the coming centuries. The civilization
• 2:03:16
  Speaker 1: that would need to build interstellar energy infrastructure is the
• 2:03:20
  Speaker 1: same civilization currently struggling to decarbonize its electrical grid. The
• 2:03:27
  Speaker 1: energy required to launch one crewed interstellar mission would necessitate
• 2:03:32
  Speaker 1: an industrial base that does not exist, powered by sources
• 2:03:37
  Speaker 1: that have not been fully developed, built over a timeframe
• 2:03:41
  Speaker 1: that no existing institution could plan across. Some estimates suggest
• 2:03:46
  Speaker 1: the energy infrastructure alone, not the spacecraft, not the mission,
• 2:03:52
  Speaker 1: just the power generation capacity required to fuel the departure burn.
• 2:03:58
  Speaker 1: would take centuries to construct under the most optimistic assumptions
• 2:04:02
  Speaker 1: about economic growth and technological development. Nuclear fusion is the
• 2:04:08
  Speaker 1: most commonly cited answer to the energy supply side of
• 2:04:12
  Speaker 1: this problem. Fusion produces far more energy per unit of
• 2:04:17
  Speaker 1: fuel than any combustion reaction. Its fuel sources, isotopes of hydrogen,
• 2:04:23
  Speaker 1: are essentially limitless. The challenge is that controlled fusion power
• 2:04:29
  Speaker 1: has been under development for roughly 70 years and remains
• 2:04:33
  Speaker 1: commercially unavailable. Progress has accelerated in recent years. Several private
• 2:04:40
  Speaker 1: companies and major government programs are pursuing fusion reactors with
• 2:04:45
  Speaker 1: genuine optimism. There is real possibility that fusion power grids
• 2:04:50
  Speaker 1: could exist within this century. But fusion reactors on Earth
• 2:04:55
  Speaker 1: producing electricity for cities are a different proposition from fusion reactors,
• 2:05:01
  Speaker 1: compact and powerful enough to serve as spacecraft propulsion systems.
• 2:05:06
  Speaker 1: The engineering distance between those two applications is significant. There
• 2:05:12
  Speaker 1: is also the question of what 10% of light speed
• 2:05:15
  Speaker 1: actually buys. At that velocity, the trip to Proxima Centauri
• 2:05:20
  Speaker 1: takes about 42 years. The crew ages 42 years before arrival.
• 2:05:27
  Speaker 1: They need to survive the journey in good health, conduct
• 2:05:30
  Speaker 1: a meaningful mission. If anyone ever wants the data before
• 2:05:34
  Speaker 1: a century has passed, transmit their findings back at the
• 2:05:38
  Speaker 1: speed of light. That takes another four years to return.
• 2:05:43
  Speaker 1: This is a best-case scenario that requires solving the energy problem,
• 2:05:48
  Speaker 1: the propulsion problem, the radiation problem, the life support problem,
• 2:05:54
  Speaker 1: the hibernation or generation ship problem simultaneously. Each of those
• 2:05:59
  Speaker 1: problems is individually enormous. The energy problem is the one
• 2:06:04
  Speaker 1: that underlies all the others. This was because every proposed
• 2:06:09
  Speaker 1: solution to every other problem costs energy. Some researchers have
• 2:06:14
  Speaker 1: suggested that the only realistic path is to first solve
• 2:06:17
  Speaker 1: the problem of essentially unlimited clean energy on Earth. Allow
• 2:06:22
  Speaker 1: that infrastructure to mature across centuries, then build outward from
• 2:06:27
  Speaker 1: that base toward interstellar capability. This is not a pessimistic answer, exactly.
• 2:06:35
  Speaker 1: It is a realistic sequencing of what has to happen
• 2:06:38
  Speaker 1: before departure becomes conceivable. It also means that anyone alive today,
• 2:06:44
  Speaker 1: or anyone likely to be alive within the next several generations,
• 2:06:49
  Speaker 1: is not going to see a crude interstellar mission launch.
• 2:06:53
  Speaker 1: The mathematics of energy are that unforgiving. The energy problem
• 2:06:58
  Speaker 1: does not have an engineering solution that anyone has found yet.
• 2:07:02
  Speaker 1: It has a civilization solution. That is a different kind
• 2:07:06
  Speaker 1: of problem entirely. There is a category of proposed solutions
• 2:07:11
  Speaker 1: to the interstellar travel problem that lives in a strange
• 2:07:15
  Speaker 1: space between serious physics and science fiction. These are not
• 2:07:20
  Speaker 1: ideas from novels or films that physicists politely ignore. They
• 2:07:25
  Speaker 1: are mathematical structures that emerge from Einstein's own equations, peer-reviewed
• 2:07:31
  Speaker 1: and published in serious journals, taken seriously by serious people.
• 2:07:38
  Speaker 1: They are also completely unbuildable with anything humanity currently has
• 2:07:43
  Speaker 1: or can foresee having. combination makes them genuinely difficult to categorize.
• 2:07:51
  Speaker 1: In 1994 a physicist named Miguel Alcubierre published a paper
• 2:07:55
  Speaker 1: that caused considerable excitement in certain corners of theoretical physics.
• 2:08:01
  Speaker 1: He had found a solution to Einstein's field equations, describing
• 2:08:05
  Speaker 1: something that looked, on paper, like a faster-than-light drive. The
• 2:08:11
  Speaker 1: idea was not to accelerate a spacecraft through space in
• 2:08:15
  Speaker 1: the conventional sense, because relativity forbids that for any object
• 2:08:20
  Speaker 1: with mass. Instead, the Alcubierre solution described a bubble of spacetime.
• 2:08:27
  Speaker 1: The space in front of the bubble would contract. The
• 2:08:31
  Speaker 1: space behind it would expand. The spacecraft inside the bubble
• 2:08:35
  Speaker 1: would not be moving through space so much as space
• 2:08:39
  Speaker 1: itself would be moving around it. The occupants inside the
• 2:08:43
  Speaker 1: bubble would feel nothing. No acceleration. no crushing g-forces, no
• 2:08:49
  Speaker 1: violation of relativity from their own frame of reference. On paper,
• 2:08:55
  Speaker 1: the bubble could move at any speed. The problem arrives
• 2:08:58
  Speaker 1: immediately after the excitement. To create the Alcubierre bubble, you
• 2:09:03
  Speaker 1: need something called negative energy density. This is not just
• 2:09:08
  Speaker 1: a very cold material or a very low energy state.
• 2:09:12
  Speaker 1: Negative energy density means something with less energy than empty vacuum.
• 2:09:17
  Speaker 1: which is a condition that has never been observed in
• 2:09:20
  Speaker 1: any laboratory and may not correspond to anything that can
• 2:09:24
  Speaker 1: actually exist in the physical universe. The initial estimates for
• 2:09:29
  Speaker 1: how much exotic matter the Alcibiere Drive would require were staggering.
• 2:09:35
  Speaker 1: Early calculations suggested energy equivalent to the mass of Jupiter
• 2:09:41
  Speaker 1: converted entirely to this exotic form. Some researchers have since
• 2:09:46
  Speaker 1: revisited those calculations and found configurations that require smaller amounts,
• 2:09:52
  Speaker 1: which is genuinely interesting. But smaller than a planet's worth
• 2:09:56
  Speaker 1: of impossible material is still impossible material. No revised estimate
• 2:10:03
  Speaker 1: has brought the requirement anywhere near something a civilization might
• 2:10:07
  Speaker 1: plausibly create. Wormholes present a similar picture. A wormhole is
• 2:10:14
  Speaker 1: a theoretical tunnel through space-time connecting two points that might
• 2:10:19
  Speaker 1: be separated by enormous distances in normal space. The concept
• 2:10:24
  Speaker 1: has been part of the mathematical toolkit of general relativity
• 2:10:29
  Speaker 1: for nearly a century, appearing in solutions to Einstein's equations
• 2:10:34
  Speaker 1: dating back to work by Einstein and Nathan Rosen in 1935.
• 2:10:38
  Speaker 1: A traversable wormhole one that something could actually pass through
• 2:10:45
  Speaker 1: without being destroyed, was shown by Kip Thorne and colleagues
• 2:10:49
  Speaker 1: in the 1980s to be theoretically possible under specific conditions.
• 2:10:54
  Speaker 1: Those conditions again involve exotic matter with negative energy density,
• 2:11:00
  Speaker 1: required to hold the wormhole open and prevent it from
• 2:11:04
  Speaker 1: pinching shut the instant anything tries to pass through. Without
• 2:11:08
  Speaker 1: that exotic matter, the wormhole collapses, the throat closes, whatever
• 2:11:15
  Speaker 1: was inside ceases to exist in any navigable sense. There
• 2:11:20
  Speaker 1: is a distinction worth being careful about here, and physicists
• 2:11:25
  Speaker 1: tend to be careful about it even when popular coverage
• 2:11:28
  Speaker 1: is not. These concepts are not forbidden by physics in
• 2:11:33
  Speaker 1: the way that, say, perpetual motion is forbidden. Perpetual motion
• 2:11:38
  Speaker 1: violates thermodynamics, which is a closed case. The Alcubierre drive
• 2:11:43
  Speaker 1: and traversable wormholes violate nothing in general relativity. They emerge
• 2:11:49
  Speaker 1: from general relativity. What they require is exotic matter, and
• 2:11:54
  Speaker 1: the status of exotic matter is not forbidden, but unknown.
• 2:11:59
  Speaker 1: Small quantities of negative energy density have actually been observed
• 2:12:04
  Speaker 1: in quantum systems, the Casimir effect being the most familiar example.
• 2:12:10
  Speaker 1: where two uncharged metal plates held close together in a
• 2:12:14
  Speaker 1: vacuum experience a force caused by the suppression of quantum
• 2:12:19
  Speaker 1: fluctuations between them. This produces a region of slightly negative
• 2:12:24
  Speaker 1: energy density. It is real. It is also fantastically smaller
• 2:12:30
  Speaker 1: than anything the Alcubierre drive would need, by many orders
• 2:12:35
  Speaker 1: of magnitude that beggar any comparisons. So the honest answer
• 2:12:41
  Speaker 1: about warp drives and wormholes is neither dismissal nor encouragement.
• 2:12:47
  Speaker 1: They are real solutions to real equations. They describe geometries
• 2:12:53
  Speaker 1: of space-time that would, if instantiated, do what the equations
• 2:12:59
  Speaker 1: say they would do. What physics cannot currently say is
• 2:13:04
  Speaker 1: whether the matter required to build them can exist in
• 2:13:07
  Speaker 1: the quantities required or whether quantum gravity effects that no
• 2:13:12
  Speaker 1: current theory fully describes would simply prevent these geometries from
• 2:13:17
  Speaker 1: forming at all. That is a substantial and unresolved uncertainty.
• 2:13:23
  Speaker 1: For any mission planner thinking about reaching Voyager 1's distance
• 2:13:28
  Speaker 1: or reaching the nearest star in the next hundred years,
• 2:13:33
  Speaker 1: none of this is useful. Not because the physics is wrong,
• 2:13:37
  Speaker 1: but because there is no engineering path from here to there.
• 2:13:41
  Speaker 1: A concept requires more than valid mathematics to become a spacecraft.
• 2:13:47
  Speaker 1: It requires materials, energy sources and construction techniques that either
• 2:13:53
  Speaker 1: exist or can be extrapolated from things that exist. Warp
• 2:13:58
  Speaker 1: drives and wormholes currently connect to none of that, They
• 2:14:03
  Speaker 1: float in a space that physics has not closed off,
• 2:14:06
  Speaker 1: but engineering cannot enter. The math is real. The exotic
• 2:14:11
  Speaker 1: matter is not. And right now, that gap is the
• 2:14:15
  Speaker 1: size of everything we don't know about physics. While astronomers
• 2:14:19
  Speaker 1: and engineers debate how humanity might someday travel to interstellar distances,
• 2:14:25
  Speaker 1: Voyager 1 itself is running out of time. The spacecraft's
• 2:14:30
  Speaker 1: power has always had a deadline. Three radioisotope thermoelectric generators
• 2:14:37
  Speaker 1: aboard Voyager convert heat released by decaying plutonium-238 into electricity.
• 2:14:45
  Speaker 1: They have been doing this since 1977. The plutonium decays
• 2:14:50
  Speaker 1: whether anyone wants it to or not, and as it decays,
• 2:14:55
  Speaker 1: less heat is available. which means less power reaching the instruments.
• 2:15:00
  Speaker 1: Each year, the output drops by roughly 4 watts. That
• 2:15:05
  Speaker 1: sounds small. Over nearly five decades, it adds up to
• 2:15:09
  Speaker 1: a machine that is slowly going dark, one system at
• 2:15:13
  Speaker 1: a time, with no way to recharge or refuel from
• 2:15:17
  Speaker 1: 25 billion kilometres away. The decisions this forces on the
• 2:15:23
  Speaker 1: mission team are painful in a specific way. In 2025,
• 2:15:29
  Speaker 1: engineers shut off the Cosmic Ray subsystem. This was not
• 2:15:34
  Speaker 1: a minor instrument. It was the instrument that detected the
• 2:15:37
  Speaker 1: change in particle environment that confirmed Voyager had crossed into
• 2:15:42
  Speaker 1: interstellar space in 2012. The subsystem that provided the defining
• 2:15:48
  Speaker 1: scientific moment of the entire mission was switched off to
• 2:15:52
  Speaker 1: buy the remaining instruments a little more time. Each of
• 2:15:56
  Speaker 1: these shutoffs is permanent. There is no switching something back
• 2:16:01
  Speaker 1: on when the power budget improves. Because the power budget
• 2:16:05
  Speaker 1: does not improve. The trajectory only goes one direction. What
• 2:16:11
  Speaker 1: the team is doing is rationing. They are deciding, carefully
• 2:16:16
  Speaker 1: and systematically, which measurements are worth more than others. Which
• 2:16:21
  Speaker 1: questions about interstellar space are important enough to keep a
• 2:16:25
  Speaker 1: heater or a sensor or a transmitter alive for another
• 2:16:29
  Speaker 1: year or two? These are not easy calculations. The data
• 2:16:34
  Speaker 1: coming back from Voyager is irreplaceable. No other instrument is
• 2:16:38
  Speaker 1: where Voyager is. There is no backup. Every reading it
• 2:16:43
  Speaker 1: takes exists nowhere else in the history of human science.
• 2:16:47
  Speaker 1: because no human instrument has ever been in that region
• 2:16:51
  Speaker 1: of space before, and none will be again for decades
• 2:16:55
  Speaker 1: at minimum. Current estimates place the end of meaningful science
• 2:17:00
  Speaker 1: sometime in the late 2020s. The remaining instruments will exhaust
• 2:17:05
  Speaker 1: whatever power margin is left, and they will go quiet.
• 2:17:10
  Speaker 1: After that, Voyager does not die immediately. The transmitter can
• 2:17:15
  Speaker 1: still function on less power than a full scientific sweep requires,
• 2:17:20
  Speaker 1: and for a few years after the instruments fall silent,
• 2:17:23
  Speaker 1: the spacecraft can still send back what engineers call a heartbeat,
• 2:17:28
  Speaker 1: a signal, proof of existence. No measurements, no data about
• 2:17:34
  Speaker 1: magnetic fields or plasma density or particle counts. Just the
• 2:17:39
  Speaker 1: fact that it is still out there, still moving, still transmitting.
• 2:17:44
  Speaker 1: a machine checking in from interstellar space to report that
• 2:17:48
  Speaker 1: it has not stopped. By roughly 2036, that signal is
• 2:17:52
  Speaker 1: expected to go quiet as well. The power will fall
• 2:17:56
  Speaker 1: below the threshold needed to transmit anything detectable across the distance.
• 2:18:02
  Speaker 1: And at that point, something strange happens, or rather, something
• 2:18:08
  Speaker 1: stops happening. Voyager 1 will continue traveling outward at 17
• 2:18:13
  Speaker 1: kilometers per second. It will not slow down. Nothing out
• 2:18:18
  Speaker 1: there is dense enough to slow it meaningfully. It will
• 2:18:22
  Speaker 1: keep moving for billions of years, pushing deeper into interstellar space,
• 2:18:28
  Speaker 1: eventually drifting into regions of the galaxy that no human
• 2:18:31
  Speaker 1: instrument has ever touched and no human mission is planned
• 2:18:35
  Speaker 1: to reach. It will pass through the Oort cloud over
• 2:18:39
  Speaker 1: the next 30,000 years. In about 40,000 years it will
• 2:18:44
  Speaker 1: pass within 1.7 light years of a star in the
• 2:18:48
  Speaker 1: constellation Camelopardalis. It will not stop there. It has no
• 2:18:53
  Speaker 1: mechanism to stop. The golden record bolted to its side
• 2:18:57
  Speaker 1: will still be there. Encoded on it are sounds and
• 2:19:01
  Speaker 1: images meant to describe Earth to whoever might someday find
• 2:19:06
  Speaker 1: the spacecraft. Greetings in 55 languages. Music from across human cultures.
• 2:19:14
  Speaker 1: The sound of rain, of surf, of a mother speaking
• 2:19:17
  Speaker 1: to a child. Mathematical diagrams intended to help an unknown
• 2:19:22
  Speaker 1: reader understand what kind of creature sent this object into
• 2:19:26
  Speaker 1: the dark. That record will outlast every institution that created it,
• 2:19:32
  Speaker 1: every language spoken on it, or most certainly the planet
• 2:19:36
  Speaker 1: it describes. It is the longest lasting artefact humanity has
• 2:19:41
  Speaker 1: ever produced, and after 2036 it will be moving through
• 2:19:47
  Speaker 1: space without anyone on Earth knowing precisely where it is.
• 2:19:51
  Speaker 1: The tracking will stop being meaningful. The last known position
• 2:19:56
  Speaker 1: and velocity can be extrapolated forward indefinitely using orbital mechanics,
• 2:20:03
  Speaker 1: so in a mathematical sense its location can always be calculated.
• 2:20:08
  Speaker 1: But there will be no confirmation, no signal bouncing back
• 2:20:12
  Speaker 1: to verify the math, just an equation running forward in time,
• 2:20:18
  Speaker 1: predicting where a silent machine should be based on where
• 2:20:21
  Speaker 1: it was when it stopped talking. There is something in
• 2:20:25
  Speaker 1: that timeline that resists easy description. A spacecraft built with
• 2:20:31
  Speaker 1: 1970s technology, launched before most of the engineers who now
• 2:20:36
  Speaker 1: operate it were born, still functioning in interstellar space nearly
• 2:20:40
  Speaker 1: 50 years later, and now approaching the end of what
• 2:20:45
  Speaker 1: it can tell us while still being nowhere near the
• 2:20:48
  Speaker 1: end of its journey. The science stops long before the
• 2:20:52
  Speaker 1: travelling does. The machine outlasts its ability to report back.
• 2:20:58
  Speaker 1: After roughly 2036, it will keep going in silence and
• 2:21:03
  Speaker 1: we will have no way of knowing where it is
• 2:21:06
  Speaker 1: or what it is passing through. There is an odd
• 2:21:09
  Speaker 1: possibility buried in the history of the Voyager program that
• 2:21:13
  Speaker 1: has a direct bearing on whether we can reach where
• 2:21:16
  Speaker 1: Voyager sits today. When Voyager 1 launched in September of 1977,
• 2:21:23
  Speaker 1: It was not the farthest human-made object in space. Pioneer
• 2:21:27
  Speaker 1: 10 had launched five years earlier, in 1972, and was
• 2:21:32
  Speaker 1: already well ahead of it in terms of raw distance
• 2:21:35
  Speaker 1: from Earth. Pioneer 10 was first. It held the record.
• 2:21:40
  Speaker 1: And then it didn't. Voyager 1 took a different trajectory,
• 2:21:45
  Speaker 1: swung past Jupiter and Saturn on a path that extracted
• 2:21:48
  Speaker 1: more velocity from those encounters. and gradually closed the gap.
• 2:21:53
  Speaker 1: By 1998, Voyager 1 had passed Pioneer 10 and taken
• 2:21:59
  Speaker 1: the title of most distant human-made object. It has held
• 2:22:03
  Speaker 1: that title ever since. The lesson here is simple but
• 2:22:08
  Speaker 1: worth sitting with. Distance records in space are not permanent.
• 2:22:13
  Speaker 1: They can be taken by a later machine that moves faster,
• 2:22:17
  Speaker 1: even if that machine started behind. This precedent matters because
• 2:22:22
  Speaker 1: the same logic applies going forward. Voyager 1 is currently
• 2:22:27
  Speaker 1: coasting at roughly 17 km per second, and nothing is
• 2:22:32
  Speaker 1: gaining on it yet. But that could change. Any spacecraft
• 2:22:37
  Speaker 1: launched in the coming decades with significantly higher velocity would,
• 2:22:42
  Speaker 1: given enough time, eventually cross the distance Voyager has already
• 2:22:47
  Speaker 1: covered and push past it. The physics are straightforward. If
• 2:22:52
  Speaker 1: something leaves Earth traveling at, say, three times Voyager's speed,
• 2:22:57
  Speaker 1: it closes the gap at a predictable rate. It would
• 2:23:01
  Speaker 1: not need to catch Voyager in motion, only cross the
• 2:23:05
  Speaker 1: same threshold first. A probe fast enough could reach 170
• 2:23:10
  Speaker 1: astronomical units in a fraction of the 50 years it
• 2:23:14
  Speaker 1: took Voyager. The record would transfer Humanity's most distant object
• 2:23:21
  Speaker 1: would be something newer, something faster, something we haven't built yet.
• 2:23:27
  Speaker 1: What would that spacecraft actually look like? This is not
• 2:23:31
  Speaker 1: entirely hypothetical. NASA has studied the question seriously. A mission
• 2:23:37
  Speaker 1: concept called the Interstellar Probe has been discussed within the
• 2:23:41
  Speaker 1: scientific community for years. And formal studies have evaluated what
• 2:23:46
  Speaker 1: it would take to reach 1,000 astronomical units within 50 years. 1,000
• 2:23:52
  Speaker 1: AU in 50 years. For context, Voyager covered roughly 170
• 2:23:58
  Speaker 1: AU in 50 years. The interstellar probe concept envisions approximately
• 2:24:05
  Speaker 1: six times that rate of travel. The approach involves nuclear
• 2:24:10
  Speaker 1: electric propulsion combined with a close solar flyby, where the
• 2:24:15
  Speaker 1: spacecraft swings extremely close to the Sun and fires its
• 2:24:20
  Speaker 1: engines at the moment of maximum gravitational acceleration, extracting a
• 2:24:25
  Speaker 1: large velocity boost. This technique, called an Oberth maneuver, is
• 2:24:31
  Speaker 1: far more efficient than burning fuel in open space, because
• 2:24:35
  Speaker 1: the kinetic energy gained is amplified by the gravitational field.
• 2:24:40
  Speaker 1: The result in the models is a probe moving fast
• 2:24:44
  Speaker 1: enough to reach interstellar space within a decade and cover
• 2:24:48
  Speaker 1: distances that took Voyager half a century in a fraction
• 2:24:52
  Speaker 1: of that time. The scientific case for such a mission
• 2:24:56
  Speaker 1: is strong. Voyager's instruments were designed in the 1960s, and
• 2:25:01
  Speaker 1: built with technology that was already aging when the spacecraft launched,
• 2:25:06
  Speaker 1: its power is nearly gone. Whatever it can tell us
• 2:25:10
  Speaker 1: about the interstellar medium, it is almost finished telling us.
• 2:25:14
  Speaker 1: A modern probe with 21st century sensors and actual bandwidth
• 2:25:19
  Speaker 1: to transmit detailed data would reveal things about the boundary
• 2:25:23
  Speaker 1: between the solar system and interstellar space that Voyager could
• 2:25:27
  Speaker 1: never have measured, the heliosphere's structure. the density and composition
• 2:25:33
  Speaker 1: of the interstellar medium, the magnetic field environment beyond the heliopause.
• 2:25:38
  Speaker 1: These are open questions, and Voyager's dimming instruments cannot answer
• 2:25:43
  Speaker 1: them now. A faster, better equipped successor could. But here
• 2:25:49
  Speaker 1: is where the perspective has to widen. Even 1000 AU
• 2:25:53
  Speaker 1: is a number that sounds large and isn't, not in
• 2:25:57
  Speaker 1: the context of what actually lies beyond the solar system.
• 2:26:00
  Speaker 1: 1000 AU is still well inside the Oort cloud. The
• 2:26:06
  Speaker 1: outer edge of the Oort cloud extends to perhaps 100,000 AU.
• 2:26:11
  Speaker 1: The nearest star sits at roughly 270,000 AU. A probe
• 2:26:17
  Speaker 1: reaching 1000 AU in 50 years is, by the definition
• 2:26:22
  Speaker 1: that actually matters, still entirely within our own solar system.
• 2:26:27
  Speaker 1: It would be farther than Voyager, yes, It would be
• 2:26:31
  Speaker 1: the most distant human-made object, yes, and it would still
• 2:26:35
  Speaker 1: be nowhere near anything else. This is the pattern that
• 2:26:39
  Speaker 1: keeps recurring at every scale of this problem. Each time
• 2:26:44
  Speaker 1: a new capability or new proposal is examined, it produces
• 2:26:49
  Speaker 1: a number that is genuinely impressive and still almost nothing
• 2:26:54
  Speaker 1: compared to what the universe requires. Voyager reaching one light
• 2:26:59
  Speaker 1: day was a milestone. A future probe reaching 1000 ANU
• 2:27:04
  Speaker 1: would be a milestone. Both milestones sit inside the same
• 2:27:09
  Speaker 1: fundamental constraint, that the solar system is vast, the space
• 2:27:14
  Speaker 1: between stars is incomprehensibly vaster, and every step forward humanity
• 2:27:20
  Speaker 1: has managed so far leaves the real distances essentially untouched.
• 2:27:25
  Speaker 1: The records will continue to fall. Pioneer gave way to Voyager.
• 2:27:31
  Speaker 1: Voyager will give way to something else. The distance those
• 2:27:35
  Speaker 1: records represent will keep growing, and the fraction of what
• 2:27:39
  Speaker 1: actually needs to be crossed will remain stubbornly, almost mockingly small.
• 2:27:45
  Speaker 1: The most distant object in space has changed before, and
• 2:27:50
  Speaker 1: it will change again. The question is, what kind of
• 2:27:54
  Speaker 1: machine takes that title next, and how much faster it
• 2:27:58
  Speaker 1: actually gets there? So can we ever reach how far
• 2:28:02
  Speaker 1: Voyager 1 has reached? The answer splits immediately into two
• 2:28:07
  Speaker 1: very different questions. Which one you're asking changes everything about
• 2:28:12
  Speaker 1: what the answer looks like. For robotic spacecraft, the answer
• 2:28:17
  Speaker 1: is almost certainly yes. Not tomorrow, and not without serious
• 2:28:22
  Speaker 1: engineering work. But the outlines of how it gets done
• 2:28:25
  Speaker 1: are already visible. Nuclear propulsion concepts exist on paper with
• 2:28:31
  Speaker 1: math that closes. Laser sail proposals have received real funding
• 2:28:36
  Speaker 1: and real attention from serious researchers. A dedicated interstellar probe
• 2:28:42
  Speaker 1: launched sometime in the next several decades, built with propulsion
• 2:28:47
  Speaker 1: systems already under active study, could cross the one light
• 2:28:51
  Speaker 1: day threshold faster than Voyager did. It took Voyager nearly
• 2:28:56
  Speaker 1: 50 years to reach that mark. A more capable successor
• 2:29:01
  Speaker 1: might do it in 20. The physics does not forbid it.
• 2:29:06
  Speaker 1: The engineering is hard, but hard is a different category
• 2:29:10
  Speaker 1: than impossible. For humans, the answer is something else entirely.
• 2:29:16
  Speaker 1: Reaching Voyager's current position with a crewed mission requires solving
• 2:29:21
  Speaker 1: problems that don't have solutions yet. Not partial solutions. Not
• 2:29:27
  Speaker 1: solutions that need refinement. But answers that don't exist in
• 2:29:31
  Speaker 1: any laboratory or blueprint on Earth right now. The propulsion problem.
• 2:29:37
  Speaker 1: The radiation problem. The life support problem. The time problem.
• 2:29:43
  Speaker 1: Each one alone would define an era of engineering effort.
• 2:29:48
  Speaker 1: Stacked together. They describe a challenge that sits somewhere beyond
• 2:29:52
  Speaker 1: the horizon of anything we can currently plan. That doesn't
• 2:29:57
  Speaker 1: mean it stays there. It means nobody can tell you
• 2:30:00
  Speaker 1: when it moves. Here is what makes the question strange.
• 2:30:05
  Speaker 1: Voyager's distance, one light day, roughly 170 astronomical units, is
• 2:30:12
  Speaker 1: simultaneously an almost incomprehensible achievement and a completely trivial position
• 2:30:19
  Speaker 1: in the context of the universe. The nearest star is 270,000
• 2:30:25
  Speaker 1: astronomical units away. Voyager has covered less than one-tenth of
• 2:30:30
  Speaker 1: one percent of that distance in 50 years. When you
• 2:30:34
  Speaker 1: ask whether we can reach where Voyager sits, you're asking
• 2:30:39
  Speaker 1: whether we can reach a point that is, by cosmic standards,
• 2:30:43
  Speaker 1: essentially on our doorstep. The universe does not grade on
• 2:30:47
  Speaker 1: that curve, though curve. Doorstep is relative to a scale
• 2:30:52
  Speaker 1: that makes the entire history of human civilization look like
• 2:30:56
  Speaker 1: a rounding error. What Voyager actually represents is a specific
• 2:31:01
  Speaker 1: kind of human achievement. It was built in the 1970s
• 2:31:06
  Speaker 1: with computing power that a modern wristwatch eclipses without effort.
• 2:31:12
  Speaker 1: It was launched on a mission designed to last four years.
• 2:31:16
  Speaker 1: The people who added the Golden Record, who aimed it
• 2:31:20
  Speaker 1: toward interstellar space, who calculated the gravity assists that gave
• 2:31:25
  Speaker 1: it the velocity to leave the solar system entirely, they
• 2:31:29
  Speaker 1: made decisions that extended the machine's purpose across five decades
• 2:31:35
  Speaker 1: they would not all live to see complete. The spacecraft
• 2:31:39
  Speaker 1: that crossed into interstellar space in 2012 was in many
• 2:31:44
  Speaker 1: ways running on ambition from 1977. And it is still
• 2:31:49
  Speaker 1: out there, still transmitting, still returning data from a place
• 2:31:54
  Speaker 1: no human has ever been and no human could currently survive.
• 2:31:59
  Speaker 1: That gap between what we built and what the universe
• 2:32:03
  Speaker 1: requires is the real answer to the question, We built
• 2:32:07
  Speaker 1: something that reached interstellar space. We could not have gone
• 2:32:11
  Speaker 1: with it. The stars are not places beyond our imagination.
• 2:32:16
  Speaker 1: They are places beyond our current physical form, beyond our
• 2:32:20
  Speaker 1: current energy supply, beyond our current understanding of how to
• 2:32:24
  Speaker 1: keep a human body alive across the timescales that interstellar
• 2:32:28
  Speaker 1: distances demand. Whether that changes depends on things that are
• 2:32:32
  Speaker 1: genuinely unknown. whether nuclear fusion propulsion reaches the performance levels
• 2:32:38
  Speaker 1: its proponents project, whether hibernation technology advances from short surgical
• 2:32:45
  Speaker 1: applications to decade-long dormancy, whether the energy infrastructure of human
• 2:32:51
  Speaker 1: civilization eventually reaches the scale that interstellar missions would require.
• 2:32:58
  Speaker 1: None of those things are impossible in the way that
• 2:33:00
  Speaker 1: traveling faster than light is impossible. They are difficult in
• 2:33:05
  Speaker 1: the way that landing on the moon was difficult in 1940.
• 2:33:07
  Speaker 1: Not yet. Not with what we have. But the physics
• 2:33:13
  Speaker 1: allows it, and the question is whether the will and
• 2:33:16
  Speaker 1: the time and the resources align. For crude interstellar flight,
• 2:33:21
  Speaker 1: the timeline is not decades. It is probably not this century.
• 2:33:27
  Speaker 1: It might be the next one. It might be longer.
• 2:33:31
  Speaker 1: The honest answer is that nobody actually knows. What is
• 2:33:35
  Speaker 1: not in question is that something built by human hands
• 2:33:40
  Speaker 1: is already there, already past the boundary where the sun's
• 2:33:44
  Speaker 1: plasma gives way to interstellar space, already in the dark
• 2:33:49
  Speaker 1: between the stars. Even if the nearest star is still
• 2:33:53
  Speaker 1: thousands of years of travel away at its current speed,
• 2:33:57
  Speaker 1: The golden record aboard Voyager carries greetings in 55 languages.
• 2:34:03
  Speaker 1: Music from dozens of cultures, sounds of rain and wind
• 2:34:07
  Speaker 1: and surf and laughter and a child's first words. It
• 2:34:12
  Speaker 1: carries a diagram of where Earth sits in the galaxy,
• 2:34:16
  Speaker 1: in case anyone finds it and wonders where it came from.
• 2:34:20
  Speaker 1: Nobody expects anyone to find it. The record is less
• 2:34:24
  Speaker 1: a message than a statement. that something from here reached
• 2:34:28
  Speaker 1: out that far, that we made something capable of crossing
• 2:34:32
  Speaker 1: that boundary even when we could not cross it ourselves.
• 2:34:37
  Speaker 1: Right now, in interstellar space, a golden record is moving
• 2:34:43
  Speaker 1: through the dark at 17 kilometers per second, carrying the
• 2:34:48
  Speaker 1: sounds of Earth to a universe that does not know
• 2:34:52
  Speaker 1: we exist. It has been doing this since before most
• 2:34:56
  Speaker 1: people alive today were born.