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Can Anything Really Travel Faster Than Light? · The Quark Side - Quantum Physics Podcast

• 0:01
  Speaker 1: Welcome to the quark Side. Quantum Physics podcast, an exploration
• 0:05
  Speaker 1: of the fundamental structure of reality, where quantum laws govern matter, energy,
• 0:11
  Speaker 1: and information. Here, uncertainty is a feature, not a flaw,
• 0:16
  Speaker 1: and understanding begins at the smallest scales.
• 0:27
  Speaker 2: Picture this. You're sitting in the driver's seat.
• 0:30
  Speaker 3: Of your car, Okay, a nice fast car hopefully.
• 0:33
  Speaker 2: Right, Yeah, a sports car, and you merge onto this
• 0:36
  Speaker 2: completely empty, perfectly straight highway and you just press your
• 0:41
  Speaker 2: foot down on the gas pedal.
• 0:43
  Speaker 3: The best feeling it really is.
• 0:44
  Speaker 2: You hear the engine roar, You feel all that torque,
• 0:47
  Speaker 2: and your body gets pressed back into the seat. Yeah,
• 0:50
  Speaker 2: and you give it more energy and you go faster.
• 0:53
  Speaker 2: Simple as that, exactly. You push the pedal closer to
• 0:56
  Speaker 2: the floor, the engine pumps more fuel, burns more energy,
• 1:00
  Speaker 2: and the speedometer needle just climbs sixty eighty one hundred
• 1:04
  Speaker 2: miles an hour.
• 1:05
  Speaker 1: Right.
• 1:05
  Speaker 2: It's just you know, it's one of the most intuitive,
• 1:08
  Speaker 2: deeply ingrained physical experiences we have as human beings. More
• 1:12
  Speaker 2: energy equals more speed.
• 1:13
  Speaker 3: It makes total logical sense to our brains.
• 1:15
  Speaker 2: Yeah, it feels like absolute common sense that if you
• 1:17
  Speaker 2: just had a big enough engine, right, and an infinite
• 1:20
  Speaker 2: supply of fuel and a road that just went on forever.
• 1:22
  Speaker 2: You could just keep accelerating like.
• 1:25
  Speaker 3: Forever, to keep pushing the pedal.
• 1:27
  Speaker 2: Yeah, you could hit a million miles an hour, a billion,
• 1:29
  Speaker 2: a trillion, as long as you kept pumping energy into
• 1:31
  Speaker 2: the system. But you can't. You absolutely fundamentally cannot.
• 1:36
  Speaker 3: You really can't. It's a very comforting illusion, you know,
• 1:38
  Speaker 3: the idea of limitless acceleration, because eventually you hit a wall,
• 1:42
  Speaker 3: a very specific wall, right, And we need to be
• 1:44
  Speaker 3: incredibly precise about what kind of wall this actually is,
• 1:48
  Speaker 3: because it's not it's not a wall of engineering. It's
• 1:52
  Speaker 3: not a limitation of your engine's thermal efficiency or you know,
• 1:55
  Speaker 3: the aerodynamics of your car's chassis, or friction from the tires, right.
• 1:59
  Speaker 2: It's not something a better mechanic can fix, exactly.
• 2:01
  Speaker 3: It is a hard, unbreakable structural limit that is just
• 2:06
  Speaker 3: built into the very fabric of the universe itself.
• 2:08
  Speaker 2: And that limit is approximately two hundred and ninety nine million,
• 2:11
  Speaker 2: seven hundred and ninety two four hundred and fifty eight
• 2:14
  Speaker 2: meters per.
• 2:14
  Speaker 3: Second, the cosmic speed limit.
• 2:16
  Speaker 2: The speed of light in a vacuum. Now, we are
• 2:20
  Speaker 2: not just here today to state that nothing goes faster
• 2:22
  Speaker 2: than light, because I mean, anyone with a passing interest
• 2:25
  Speaker 2: in science already knows that trivia.
• 2:26
  Speaker 3: Fact, right, Yeah, you learned that in high school, right.
• 2:29
  Speaker 2: Our mission today is to completely deconstruct exactly why that
• 2:33
  Speaker 2: limit exists, how we actually proved it, and what happens
• 2:37
  Speaker 2: to the fabric of reality when you try to.
• 2:39
  Speaker 3: Test it, because it is so much stranger than you'd think.
• 2:41
  Speaker 2: Oh it's wild. It's so much more profound than just
• 2:45
  Speaker 2: a rule about how fast things can move. We are
• 2:48
  Speaker 2: going to explore how this specific number isn't some you know,
• 2:52
  Speaker 2: arbitrary hurdle waiting to be solved by the warp drives
• 2:55
  Speaker 2: of the future.
• 2:56
  Speaker 3: No warp drives are saving us here, right.
• 2:58
  Speaker 2: It's the very glue holding space, time, mass, and cause
• 3:02
  Speaker 2: and effect together.
• 3:03
  Speaker 3: It really operates as the foundational code of reality. And
• 3:07
  Speaker 3: if you try to hack that code, like if you
• 3:09
  Speaker 3: try to force a physical object with mass past that
• 3:12
  Speaker 3: specific numerical speed limit, the universe doesn't just you know,
• 3:16
  Speaker 3: gently push back with a bit of wind resistance.
• 3:18
  Speaker 2: It shuts you down.
• 3:19
  Speaker 3: It mathematically and physically bankrupts you completely. But to truly
• 3:22
  Speaker 3: understand why we can't break this limit, and why the
• 3:25
  Speaker 3: universe enforces it with such such extreme prejudice. We have
• 3:30
  Speaker 3: to unlearn almost everything we experience.
• 3:32
  Speaker 2: In our daily lives, which is hard to do.
• 3:34
  Speaker 3: Very hard. We need to travel back to the late
• 3:36
  Speaker 3: nineteenth century, right before the year nineteen oh five, to
• 3:40
  Speaker 3: understand a deeply fundamentally flawed assumption humanity held about how
• 3:45
  Speaker 3: time and space actually work.
• 3:47
  Speaker 2: Right, Because before ever Einstein came along and essentially well
• 3:51
  Speaker 2: ruin everyone's common sense, physics was totally dominated by classical mechanics.
• 3:55
  Speaker 3: We lived in Isaac Newton's universe.
• 3:57
  Speaker 2: Exactly, and under Newton's view, time was this incredibly comforting,
• 4:02
  Speaker 2: universal absolute thing. A second was just a second.
• 4:06
  Speaker 3: It was reliable.
• 4:06
  Speaker 2: Yeah, if you had a grandfather clock ticking away in
• 4:09
  Speaker 2: your living room on Earth, you could trust that a
• 4:11
  Speaker 2: second on that clock was exactly identical to a second
• 4:15
  Speaker 2: ticking by on some I don't know, hypothetical alien clock
• 4:18
  Speaker 2: floating in the middle of the Andromeda galaxy.
• 4:20
  Speaker 3: Right, Newton gave us a universe that made intuitive sense
• 4:23
  Speaker 3: to our primate brains. He described space as a passive
• 4:27
  Speaker 3: fixed stage, so think of it like a massive empty theater.
• 4:31
  Speaker 2: Okay, I'm picturing it.
• 4:32
  Speaker 3: The stage itself never changes its dimensions, right, the actors, so,
• 4:37
  Speaker 3: the planets, the stars, the comets, you and me, We
• 4:40
  Speaker 3: move around on this rigid stage, and the grand clock
• 4:44
  Speaker 3: on the wall of the theater just ticks away at
• 4:47
  Speaker 3: a constant, unyielding universal rate for everyone.
• 4:50
  Speaker 2: Everywhere, forever, exactly, and for hundreds of years that worked perfectly.
• 4:55
  Speaker 2: It predicted the orbits of planets. It helped us build bridges.
• 4:58
  Speaker 2: It literally made the end dro a revolution.
• 5:00
  Speaker 3: Possible, because it makes total sense. If I walk across
• 5:04
  Speaker 3: a room, the room doesn't suddenly change size, and my
• 5:06
  Speaker 3: watch doesn't randomly slow down. But then there's a crisis
• 5:10
  Speaker 3: in physics in the late eighteen hundreds. Yeah, because another
• 5:13
  Speaker 3: giant of physics, James Clark Maxwell, comes along and he
• 5:16
  Speaker 3: figures out electricity and magnetism, and his equations spit out
• 5:20
  Speaker 3: a massive, massive problem.
• 5:22
  Speaker 2: Yeah, that is the exact moment that crack in Newton's
• 5:24
  Speaker 2: Grand Theater appears. Maxwell formulated the equations for electromagnetism, and
• 5:29
  Speaker 2: he discovered that light is an electromagnetic wave. Okay, but
• 5:32
  Speaker 2: the truly shocking part of Maxwell's equations was that they
• 5:34
  Speaker 2: predicted a specific fixed speed for these waves approximately three
• 5:39
  Speaker 2: hundred thousand kilometers per second.
• 5:41
  Speaker 3: Which is fast, obvious, very fast. But the problem was
• 5:44
  Speaker 3: Maxwell's math didn't say what that speed was relative to,
• 5:48
  Speaker 3: and in Newton's world, a speed only makes sense relative
• 5:51
  Speaker 3: to something else, like.
• 5:52
  Speaker 2: A cargoes sixty miles per hour relative to the asphalt
• 5:55
  Speaker 2: on the road exactly.
• 5:56
  Speaker 3: So physicists totally panicked. They assumed there just had to
• 6:00
  Speaker 3: be an invisible, stationary substance filling the entire universe that
• 6:05
  Speaker 3: light traveled through, which they called the lumiferous ether.
• 6:09
  Speaker 2: They just invented a ghost substance just to save Newton's
• 6:12
  Speaker 2: idea of absolute space.
• 6:14
  Speaker 3: They absolutely did. They couldn't let go of the rigid stage.
• 6:17
  Speaker 3: And then in eighteen eighty seven, Albert Michaelson and Edward
• 6:20
  Speaker 3: Morley ran one of the most famous failed experiments in
• 6:23
  Speaker 3: the entire history of.
• 6:24
  Speaker 2: Science, the Michaelson Morley experiment.
• 6:27
  Speaker 3: Right, they built an incredibly sensitive device using mirrors to
• 6:31
  Speaker 3: measure how the speed of light changed as the Earth
• 6:33
  Speaker 3: moved through this supposed ether. They fully expected to measure
• 6:37
  Speaker 3: a headwind of light when Earth moved one way and
• 6:39
  Speaker 3: a tailwind would have moved another.
• 6:40
  Speaker 2: Like driving a car into the wind versus with the
• 6:42
  Speaker 2: wind exactly like that. But they found nothing, just a
• 6:45
  Speaker 2: null result. No matter which way the Earth was moving
• 6:48
  Speaker 2: in its orbit, no matter what time of year it was,
• 6:51
  Speaker 2: the speed of light was exactly the.
• 6:52
  Speaker 3: Same always, which brings us to nineteen oh five and
• 6:56
  Speaker 3: Einstein's theory of special relativity. Einstein looks at the Michaelson
• 7:00
  Speaker 3: Morley experiment, he looks at Maxwell's equations, and he decides
• 7:03
  Speaker 3: to just take a sledgehammer to Newton's Grand Theater, just
• 7:07
  Speaker 3: smashes it, oh completely. He does it by putting forward
• 7:10
  Speaker 3: two core postulates, two rules that completely dismantle the absolute clock.
• 7:16
  Speaker 3: The first postulate basically states that the laws of physics
• 7:20
  Speaker 3: are the same in all non accelerating frames of reference.
• 7:23
  Speaker 3: In physics terminology, we call these inertial frames.
• 7:26
  Speaker 2: Okay, let's translate that for everyday experience, because inertial frame
• 7:29
  Speaker 2: sounds heavy. A non accelerating frame of reference just means
• 7:32
  Speaker 2: you are moving at a constant speed in a straight line,
• 7:35
  Speaker 2: or you are perfectly still. You aren't stepping on the gas,
• 7:38
  Speaker 2: you aren't hitting the brakes, and you aren't taking a
• 7:40
  Speaker 2: sharp turn.
• 7:41
  Speaker 3: That's the crucial distinction. If you are in a train car, right,
• 7:46
  Speaker 3: and let's say the windows are blacked out and you're
• 7:48
  Speaker 3: moving at a perfectly smooth, constant speed over perfectly smooth track,
• 7:53
  Speaker 3: no bumps, right, no bumps. You can bounce a tennis
• 7:55
  Speaker 3: ball on the floor. You can pour a cup of
• 7:57
  Speaker 3: hot coffee, you can play a game of pool, and
• 8:00
  Speaker 3: all the mechanical physics will play out exactly the same
• 8:03
  Speaker 3: as if the train were parked at the station.
• 8:05
  Speaker 2: I would spill my coffee.
• 8:07
  Speaker 3: Nope, there is absolutely no mechanical experiment you could run
• 8:11
  Speaker 3: inside that closed train car to prove you were moving.
• 8:15
  Speaker 3: Movement at a constant velocity is completely relative.
• 8:19
  Speaker 2: Okay, I'm tracking with that. That's postulate one, and it
• 8:21
  Speaker 2: feels pretty grounded. It makes sense. But then we hit
• 8:25
  Speaker 2: postulate two, which is where Einstein demands we throw all
• 8:28
  Speaker 2: human logic out the window.
• 8:30
  Speaker 3: Yeah, this is the brain breaker.
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  Speaker 2: He stated that the speed of light in a vacuum,
• 8:34
  Speaker 2: which we denote with the letter C, is always measured
• 8:37
  Speaker 2: at the exact same value, regardless of the motion of
• 8:39
  Speaker 2: the observer or the source of the light.
• 8:41
  Speaker 3: I really want to pause here because we need to
• 8:44
  Speaker 3: appreciate how deeply offensive this is. To our everyday experience.
• 8:48
  Speaker 3: Galilean relativity. You know, the math we've used since the
• 8:51
  Speaker 3: Renaissance tells us that velocities are.
• 8:54
  Speaker 2: Additive additive, meaning they stack.
• 8:56
  Speaker 3: Right. If you are running on a moving walkway at
• 8:59
  Speaker 3: the airport, your speed is your running speed plus the
• 9:02
  Speaker 3: speed of the walkway.
• 9:03
  Speaker 2: Right. Let me set up a classic thought experiment for this,
• 9:05
  Speaker 2: but let's elevate it a bit. Imagine you are riding
• 9:08
  Speaker 2: on a high speed maglev train and it's moving at
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  Speaker 2: one hundred miles per hour.
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  Speaker 3: Okay, fast train.
• 9:13
  Speaker 2: You are standing in the aisle and you throw a
• 9:15
  Speaker 2: baseball forward toward the front of the train at fifty
• 9:18
  Speaker 2: miles per hour. Now, from your perspective inside the train,
• 9:21
  Speaker 2: the ball leaves your hand at fifty miles per hour.
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  Speaker 3: Yep. And if an observer is standing outside on the
• 9:27
  Speaker 3: station platform watching this translucent train go by, they do
• 9:31
  Speaker 3: the simple additive math. The train is moving at one hundred,
• 9:35
  Speaker 3: the ball is moving forward inside the train at.
• 9:37
  Speaker 2: Fifty, so one hundred plus fifty.
• 9:39
  Speaker 3: Right, the observer on the platform sees a baseball flying
• 9:42
  Speaker 3: through the air at one hundred and fifty miles per hour.
• 9:45
  Speaker 2: Makes total sense. But now you replace the baseball with
• 9:49
  Speaker 2: a laser pointer. You stand in the aisle of that
• 9:51
  Speaker 2: one hundred mile per hour train, You point the laser forward,
• 9:54
  Speaker 2: and you click it on. According to Newton and according
• 9:56
  Speaker 2: to our airport walkway logic, the beam of light should
• 9:59
  Speaker 2: leave the laser the speed of light plus the one
• 10:01
  Speaker 2: hundred miles per hoer of the train. The observer on
• 10:03
  Speaker 2: the platform should see the light moving at C plus
• 10:06
  Speaker 2: one hundred.
• 10:07
  Speaker 3: But the Migelsinrley experiment and Einstein's second post till It
• 10:10
  Speaker 3: tell us they absolutely don't. When the observer on the
• 10:13
  Speaker 3: platform measures that beam of light, they clock it at
• 10:16
  Speaker 3: exactly see two hundred and ninety nine million, seven hundred
• 10:19
  Speaker 3: and ninety two, four hundred and fifty eight meters per second.
• 10:22
  Speaker 3: No extra one hundred miles per.
• 10:23
  Speaker 2: Hour, which is weird, right, But maybe you could argue
• 10:26
  Speaker 2: the light just has a hard physical cap, like it
• 10:28
  Speaker 2: just can't go faster. But here is the part that
• 10:30
  Speaker 2: actually breaks your brain. When you standing inside the moving
• 10:34
  Speaker 2: train measure that exact same beam of light leaving your
• 10:37
  Speaker 2: laser pointer, you also measure it moving at exactly see.
• 10:41
  Speaker 3: Let the paradox of that really sink in for a second.
• 10:44
  Speaker 3: You and the observer on the platform are moving it
• 10:46
  Speaker 3: entirely different speeds relative to.
• 10:48
  Speaker 2: Each other, right, one hundred mile an hour difference.
• 10:50
  Speaker 3: Yet you both measure the exact same beam of light
• 10:53
  Speaker 3: passing you at the exact same speed. If light speed
• 10:56
  Speaker 3: rigidly refuses to add up, if it completely or is
• 11:00
  Speaker 3: the motion of the train and the motion of the platform,
• 11:03
  Speaker 3: it means there is a massive systemic problem with the
• 11:06
  Speaker 3: fundamental equation of speed itself.
• 11:09
  Speaker 2: Okay, let's open up that equation. Because speed is incredibly basic.
• 11:13
  Speaker 2: It is literally just distance divided by time miles per hour,
• 11:17
  Speaker 2: meters per second. It is a ratio of space over time.
• 11:20
  Speaker 3: Right. And if the output of that equation, the speed
• 11:23
  Speaker 3: of light is fundamentally fixed and it can never ever
• 11:26
  Speaker 3: change for any observer, no matter how fast they are
• 11:29
  Speaker 3: running toward or away from the light source, then the
• 11:31
  Speaker 3: variables on the other side of the equal sign must
• 11:34
  Speaker 3: be the things changing.
• 11:35
  Speaker 2: The space and the time.
• 11:36
  Speaker 3: Exactly, the space being traversed and the time it takes
• 11:39
  Speaker 3: to traverse it are no longer rigid.
• 11:41
  Speaker 2: So Newton's grand theater stage and his universal ticking clock
• 11:44
  Speaker 2: are entirely shattered to protect this cosmic speed limit. Space
• 11:48
  Speaker 2: and time have to literally flex, stretch, and warp they merge.
• 11:53
  Speaker 3: It was actually Einstein's former professor, this mathematician named Hermann Minkowski,
• 11:58
  Speaker 3: who realized the profound my own geometric implication of Einstein's work.
• 12:02
  Speaker 3: A few years later, Oh really yeah, Minkowski realized you
• 12:05
  Speaker 3: could no longer treat space and time as separate entities.
• 12:09
  Speaker 3: They form a unified four dimensional fabric known as Minkowski
• 12:12
  Speaker 3: space time. You are never just moving through space or
• 12:15
  Speaker 3: just moving through time. You're always navigating a combined pass
• 12:19
  Speaker 3: through space time.
• 12:20
  Speaker 2: I like to visualize it using a really strict road
• 12:23
  Speaker 2: trip scenario.
• 12:24
  Speaker 3: Let's hear it.
• 12:25
  Speaker 2: Imagine you're driving across the country and there is a bizarre,
• 12:29
  Speaker 2: unbreakable cosmic traffic law. Your arrival time is mathematically locked.
• 12:34
  Speaker 2: You must arrive at your final destination at exactly three
• 12:37
  Speaker 2: point zero zero PM, no earlier, no later. Okay, Now,
• 12:39
  Speaker 2: let's say you decide to ignore the speed limit. You
• 12:41
  Speaker 2: press the gas pedal to the floor, and you drive
• 12:43
  Speaker 2: twice as fast. In our normal universe, driving faster over
• 12:47
  Speaker 2: the same distance means you arrive earlier, say at one
• 12:49
  Speaker 2: point thirty pm. But this cosmic law doesn't allow that
• 12:53
  Speaker 2: the arrival time of three point zero zero pm is fixed,
• 12:55
  Speaker 2: much like the speed of light is fixed.
• 12:57
  Speaker 3: So reality has to intervene to ensure the mass balances
• 13:01
  Speaker 3: out at the destination.
• 13:02
  Speaker 2: Exactly to make sure you still arrive at exactly three
• 13:05
  Speaker 2: zero zero pm despite driving way faster, the physical road
• 13:09
  Speaker 2: itself has to literally stretch out in front of you,
• 13:12
  Speaker 2: creating vastly more distance for you to cover, and simultaneously,
• 13:16
  Speaker 2: the clock on your dashboard and the watch on your
• 13:18
  Speaker 2: wrist and the beating of your heart has to start
• 13:21
  Speaker 2: ticking slower.
• 13:22
  Speaker 3: Sounds like a bad dream, right.
• 13:24
  Speaker 2: You are driving incredibly fast, but because the road elongated
• 13:28
  Speaker 2: and your personal flow of time became sluggish, you still
• 13:30
  Speaker 2: pull in at exactly three zero zero pm.
• 13:33
  Speaker 3: That is a brilliant way to conceptualize the twin phenomena
• 13:36
  Speaker 3: of length contraction and time dilation. And we really must
• 13:41
  Speaker 3: emphasize to anyone listening that these are not optical illusions.
• 13:44
  Speaker 3: They are not mechanical defects of the clocks themselves.
• 13:46
  Speaker 2: It's not your dashboard clock malfunctioning because you.
• 13:49
  Speaker 3: Hit a pothole exactly. It is a mechanical, biological, and
• 13:52
  Speaker 3: atomic reality of the universe. Time itself is passing at
• 13:55
  Speaker 3: a fundamentally different rate for the person in motion compared
• 13:58
  Speaker 3: to the observer standing still.
• 14:00
  Speaker 2: This is the point where people demand proof, you know,
• 14:02
  Speaker 2: because it sounds like science fiction magic. How do we
• 14:05
  Speaker 2: actually know time slows down for moving objects?
• 14:09
  Speaker 3: We have proven it repeatedly, but perhaps the most elegant
• 14:12
  Speaker 3: demonstration was the Hafiel Keating experiment in nineteen seventy one.
• 14:16
  Speaker 2: The atomic clocks on planes.
• 14:18
  Speaker 3: Right, Yes, Physicists Joseph Hafeel and Richard Keating took four
• 14:23
  Speaker 3: incredibly precise caesium atomic clocks. They left one set of
• 14:28
  Speaker 3: clocks on the ground at the US Naval Observatory as
• 14:30
  Speaker 3: a control reference. Then they loaded the other atomic clocks
• 14:34
  Speaker 3: onto commercial Boeing seven forty seven airliners and flew them
• 14:37
  Speaker 3: completely around the world twice, once eastward and once westward.
• 14:42
  Speaker 2: Just buying plane tickets for clocks, pretty much. And when
• 14:44
  Speaker 2: they brought the flying clocks back to the observatory and
• 14:47
  Speaker 2: compared them to the clocks that stayed on the ground, the.
• 14:49
  Speaker 3: Flying clocks disagreed with the ground clocks. And they didn't
• 14:52
  Speaker 3: just disagree randomly. They differed by the exact fractions of
• 14:56
  Speaker 3: a nanosecond that Einstein's equations of special and general relativeivity predicted. Yeah,
• 15:02
  Speaker 3: the clocks that traveled eastward, moving in the direction of
• 15:05
  Speaker 3: earth rotation, thus moving faster relative to the center of
• 15:08
  Speaker 3: the Earth, had ticked slower less time had passed for them.
• 15:12
  Speaker 3: They had literally traveled into the future of the ground clocks,
• 15:16
  Speaker 3: albeit by a microscopic amount.
• 15:18
  Speaker 2: And we deal with this daily, don't we. It's not
• 15:20
  Speaker 2: just an esoteric experiment from the seventies. This literally affects
• 15:24
  Speaker 2: the technology in our pockets right now.
• 15:26
  Speaker 3: Absolutely. The Global Positioning System GPS is the ultimate daily
• 15:31
  Speaker 3: proof of relativity. We have a constellation of satellites orbiting
• 15:35
  Speaker 3: the Earth at roughly fourteen thousand kilometers per hour, which
• 15:38
  Speaker 3: is zooming, right, And because they are moving so fast
• 15:41
  Speaker 3: relative to us on the ground, special relativity dictates their
• 15:45
  Speaker 3: onboard atomic clocks should tick slower by about seven microseconds
• 15:48
  Speaker 3: a day.
• 15:49
  Speaker 2: But wait, they are also further away from Earth's gravity, right,
• 15:52
  Speaker 2: which gets into general relativity meeting, they should tick faster.
• 15:55
  Speaker 3: Correct. The weaker gravity up there speeds their clocks up
• 15:59
  Speaker 3: by about forty five microseconds a day. So when you
• 16:02
  Speaker 3: combine those two relativistic effects, the satellite clocks run fast
• 16:06
  Speaker 3: by a net total of thirty eight microseconds every single day.
• 16:09
  Speaker 3: Compared to our clocks on the ground.
• 16:11
  Speaker 2: Thirty eight microseconds sounds like nothing.
• 16:14
  Speaker 3: It sounds like nothing but light and the radio signals.
• 16:16
  Speaker 3: GPS uses travel about three hundred meters in a single microsecond.
• 16:20
  Speaker 3: If our smartphones and satellites didn't actively run Einstein's equations
• 16:24
  Speaker 3: to correct for that thirty eight microsecond time dilation every
• 16:27
  Speaker 3: single day, your GPS navigation would drift by roughly ten
• 16:31
  Speaker 3: kilometers over six miles every day.
• 16:33
  Speaker 2: Oh my god.
• 16:34
  Speaker 3: Yeah, the entire global navigation system would be completely useless
• 16:37
  Speaker 3: in under a week.
• 16:38
  Speaker 2: It is staggering to think that every time you use
• 16:40
  Speaker 2: your phone to find like a coffee shop, you are
• 16:43
  Speaker 2: practically relying on the flexible nature of space time to
• 16:45
  Speaker 2: get you there. You really are, so reality will actively bend, stretch,
• 16:49
  Speaker 2: and warp time to ensure that light always goes at
• 16:51
  Speaker 2: sea for everyone, everywhere. But this brings us to a
• 16:54
  Speaker 2: massive practical roadblock. The big question, right, what happens if
• 16:59
  Speaker 2: a physical object, something made of matter, like a spaceship,
• 17:03
  Speaker 2: a probe, or even just a single proton, tries to
• 17:06
  Speaker 2: actually accelerate to see. If space time is so flexible
• 17:10
  Speaker 2: and accommodating, can't you just build a powerful enough engine
• 17:13
  Speaker 2: and force your way through you cannot.
• 17:15
  Speaker 3: You hit a catastrophic physical barrier. And this is where
• 17:18
  Speaker 3: we transition from the conceptual weirdness of shifting clocks into
• 17:22
  Speaker 3: the realm of infinite crushing mathematical barriers. We really need
• 17:26
  Speaker 3: to talk about the mass barrier and why energy becomes
• 17:29
  Speaker 3: your absolute worst enemy.
• 17:30
  Speaker 2: Let's do it, going back to our starting hook, the
• 17:33
  Speaker 2: gas pedal on the highway. Under classical Newtonian mechanics, kinetic
• 17:37
  Speaker 2: energy is a very straightforward linear concept. The equation is
• 17:40
  Speaker 2: e equals one half envy SQUAREDO classic the kinetic energy
• 17:44
  Speaker 2: of an object is half its mass times its velocity squared.
• 17:47
  Speaker 2: So if you want to go faster, you just add
• 17:49
  Speaker 2: a predictable amount of force.
• 17:51
  Speaker 3: Right in that classical model, adding force steadily and perpetually
• 17:54
  Speaker 3: grows your velocity. If you keep burning fuel, the velocity
• 17:58
  Speaker 3: just keeps climbing theoretically toward infinity. But Einstein's special relativity
• 18:02
  Speaker 3: proved that this classical equation is actually an incomplete approximation.
• 18:07
  Speaker 2: Wait, in complete, Yes, it.
• 18:10
  Speaker 3: Works fine for walking, driving cars, and even launching space shuttles,
• 18:13
  Speaker 3: because those speeds are so incredibly slow compared to light.
• 18:16
  Speaker 3: But as you approach shieldbacha, that classical equation breaks down completely.
• 18:21
  Speaker 2: Because the energy required stops scaling linearly.
• 18:24
  Speaker 3: Exactly as an object nears the speed of light, it's
• 18:27
  Speaker 3: total relativistic energy in its relativistic momentum scale nonlinearly. They
• 18:31
  Speaker 3: are governed by a mathematical multiplier called the Lorentz factor,
• 18:35
  Speaker 3: represented by the Greek letter.
• 18:36
  Speaker 2: Gamma ah gamma.
• 18:38
  Speaker 3: Hendrick Lorenz, the physicist is named after, actually developed these
• 18:42
  Speaker 3: mathematical transformations that Einstein later integrated into the core of relativity.
• 18:46
  Speaker 2: Okay, let's look under the hood of reality. Here we
• 18:49
  Speaker 2: need to dissect the actual math of the Lorentz factor,
• 18:52
  Speaker 2: because understanding the components of this specific fraction is the
• 18:56
  Speaker 2: only way to understand how the brick wall is built.
• 18:58
  Speaker 3: The total relativistic energy of a moving object equals its
• 19:02
  Speaker 3: rest mass multiplied by the speed of light squared, and
• 19:06
  Speaker 3: then that whole thing is multiplied by the Lorentz factor.
• 19:08
  Speaker 3: The Lorentz factor itself is a fraction.
• 19:10
  Speaker 2: Okay, fraction.
• 19:11
  Speaker 3: Yes, the numertor on top is just the number one.
• 19:14
  Speaker 3: It is the denominator on the bottom where the curse lies.
• 19:16
  Speaker 2: Let's spell out that denominator carefully. It is the square
• 19:19
  Speaker 2: root of one minus the ratio of your velocity squared
• 19:23
  Speaker 2: divided by the speed of light squared. Mathematically, it's the
• 19:26
  Speaker 2: square root of one minus V squared over C square.
• 19:30
  Speaker 3: That ratio V squared over C squared is the crucial part.
• 19:33
  Speaker 3: It is comparing your current speed to the absolute speed limit.
• 19:37
  Speaker 3: Let's walk through what happens to that denominator as your
• 19:39
  Speaker 3: velocity V gets closer.
• 19:41
  Speaker 2: And closer to see, I'm going to take you through
• 19:43
  Speaker 2: the terrifying math of this Lorentz factor progression, because seeing
• 19:47
  Speaker 2: how the numbers explode is the only way to really
• 19:49
  Speaker 2: feel the barrier. Let's say humanity unites. We build an
• 19:53
  Speaker 2: incredible fusion powered spaceship, and you get it moving at
• 19:56
  Speaker 2: ten percent of the speed of.
• 19:58
  Speaker 3: Light, which is roughly thirty thousand k per second, vastly
• 20:01
  Speaker 3: faster than anything we've ever built.
• 20:03
  Speaker 2: Right, So, at a velocity of point one, see, we
• 20:05
  Speaker 2: look at our ratio point one square is boring zero one,
• 20:08
  Speaker 2: so we subtract that from one. The denominator becomes the
• 20:10
  Speaker 2: square root of zero point nine to nine. When you
• 20:13
  Speaker 2: calculate the whole fraction, the Lorentz factor gamma comes out
• 20:16
  Speaker 2: to about one point zero zero five.
• 20:18
  Speaker 3: Right, And what does the Lorentz factor of one point
• 20:20
  Speaker 3: zero zero five actually mean for our ship's engines.
• 20:23
  Speaker 2: It means that to maintain that acceleration you only need
• 20:27
  Speaker 2: about a half percent energy penalty compared to what classical
• 20:30
  Speaker 2: Newtonian physics would predict.
• 20:32
  Speaker 3: So at ten percent, the speed of light physics is
• 20:33
  Speaker 3: still acting mostly normal. You push the gas, you go faster,
• 20:37
  Speaker 3: and the energy cost is entirely manageable.
• 20:39
  Speaker 2: Okay, the engineers on Earth are thrilled. They build a
• 20:42
  Speaker 2: better antimatter engine. You push the throttle, you reach fifty
• 20:45
  Speaker 2: percent of the speed of light, halfway to the absolute limit.
• 20:48
  Speaker 3: Now the math starts to bite. At point five c.
• 20:51
  Speaker 3: Your ratio is point twenty five one minus point twenty
• 20:54
  Speaker 3: five is point seven five. The square root of that
• 20:57
  Speaker 3: shrinks the denominator. The Lorentz factor jumps to one point
• 21:00
  Speaker 3: one five five.
• 21:01
  Speaker 2: Wow.
• 21:02
  Speaker 3: Okay, you now require roughly fifteen point five percent more
• 21:05
  Speaker 3: energy to keep accelerating than you would classically expect. The
• 21:08
  Speaker 3: engine's burning hotter, the fuel is draining faster, but you know,
• 21:11
  Speaker 3: it still feels like an engineering problem you can.
• 21:13
  Speaker 2: Solve, so you really floor it. You engage the experimental hyperdrives.
• 21:18
  Speaker 2: You hit ninety percent of the speed of light. You
• 21:20
  Speaker 2: are cruising. Time dilation is heavily in effect. You are
• 21:23
  Speaker 2: aging slower than the people on Earth, and you are
• 21:25
  Speaker 2: blazing across the Solar system.
• 21:27
  Speaker 3: Here is where the math turns vicious and exponential. At
• 21:31
  Speaker 3: ninety percent of st the Lorentz factor leaps to two
• 21:34
  Speaker 3: point two ninety.
• 21:35
  Speaker 2: Four, meaning you need more than double the expected energy
• 21:38
  Speaker 2: just to maintain your rate of acceleration. The universe is
• 21:41
  Speaker 2: now actively aggressively resisting your attempts to go faster.
• 21:45
  Speaker 3: But human ambition is boundless.
• 21:47
  Speaker 2: Yeah.
• 21:47
  Speaker 3: Right, You want to reach one hundred percent. You want
• 21:50
  Speaker 3: to ride alongside a beam of light, so you pump
• 21:51
  Speaker 3: unimaginable power into the system. You've reached ninety nine percent
• 21:55
  Speaker 3: of the speed of light, and.
• 21:56
  Speaker 2: The Lorentz factor spikes to seven point zero eight nine.
• 21:59
  Speaker 2: You need over seven times the base energy, but you
• 22:03
  Speaker 2: keep pushing. Let's say you reach ninety nine point ninety
• 22:06
  Speaker 2: nine percent of the speed of light. You are right
• 22:08
  Speaker 2: on the jagged.
• 22:08
  Speaker 3: Edge the Lorentz factor at ninety nine point nine to
• 22:11
  Speaker 3: nine percent is seventy point seventy one. You now need
• 22:14
  Speaker 3: seventy times the energy to squeeze out that final tiny
• 22:17
  Speaker 3: fraction of a percent. And this is where we have
• 22:19
  Speaker 3: to look at the denominator that equation one last time.
• 22:22
  Speaker 3: The square root of one minus V squared over C squared. Okay,
• 22:25
  Speaker 3: as your velocity V approaches c, that ratio of V
• 22:28
  Speaker 3: squared over C squared approaches one.
• 22:30
  Speaker 2: Right, Because you are dividing C squared by C squared,
• 22:32
  Speaker 2: which is exactly one.
• 22:33
  Speaker 3: And one minus one is zero. The square root of
• 22:36
  Speaker 3: zero is zero, so.
• 22:37
  Speaker 2: The denominator, the Lorentz factor, becomes a strict absolute zero.
• 22:41
  Speaker 2: You are trying to divide the numerator the number one
• 22:44
  Speaker 2: by zero.
• 22:44
  Speaker 3: Which is mathematically undefined. You cannot divide by zero in algebra,
• 22:48
  Speaker 3: and you absolutely cannot divide by zero in reality in
• 22:51
  Speaker 3: the context of physics and energy limits. As the denominator
• 22:55
  Speaker 3: shrinks towards zero, the resulting fraction, the Lorentz factor, shoots infinitive.
• 23:00
  Speaker 2: And since gamma is the multiplier for the total energy
• 23:03
  Speaker 2: you need to accelerate, the required energy shoots to infinity.
• 23:07
  Speaker 3: This is the ultimate cosmic veto it is a mathematical
• 23:11
  Speaker 3: dead end. It means that to accelerate any object with
• 23:14
  Speaker 3: even the tiniest fraction of rest mass up to exactly
• 23:17
  Speaker 3: V equal C, you must supply an infinite amount of energy.
• 23:21
  Speaker 2: I really want to emphasize the word infinite here. Infinite
• 23:23
  Speaker 2: energy does not just mean a lot of energy. It
• 23:26
  Speaker 2: doesn't mean more energy than humanity currently knows how to generate.
• 23:30
  Speaker 2: It means a quantity without boundary or end.
• 23:32
  Speaker 3: To put a definitive, sobering scale on this, the observable
• 23:36
  Speaker 3: universe contains a finite amount of mass and a finite
• 23:39
  Speaker 3: amount of energy. You could hypothetically build a dice and
• 23:41
  Speaker 3: sphere around every single star in our Milky Way galaxy
• 23:45
  Speaker 3: and harvest one hundred percent of their energy. You can
• 23:48
  Speaker 3: combine that with the energy of every star in the
• 23:50
  Speaker 3: Andromeda galaxy. You could harvest the rotational power of every
• 23:54
  Speaker 3: supermassive black hole, collect every photon, and consume every speck
• 23:58
  Speaker 3: of dust in the entire obsc servable.
• 24:00
  Speaker 2: Cosmos, and it still wouldn't be enough to accelerate a
• 24:03
  Speaker 2: single microscopic electron to the state of light, let alone
• 24:06
  Speaker 2: a huge starship. The universe mathematically bankruptcy.
• 24:10
  Speaker 3: The closer you get, we actually see this happening every
• 24:12
  Speaker 3: single day here on Earth. By the way, it's not
• 24:14
  Speaker 3: just theoretical math on a chalkboard.
• 24:16
  Speaker 2: Oh. The particle accelerator.
• 24:17
  Speaker 3: Yes, places like the Large Hadron Collider in Switzerland. We
• 24:21
  Speaker 3: use massive superconducting electromagnets to accelerate protons around a twenty
• 24:26
  Speaker 3: seven kilometer ring, and they get fast, very fast. We
• 24:29
  Speaker 3: can get those protons up to ninety nine point nine
• 24:33
  Speaker 3: percent of the speed of light. But to do that
• 24:36
  Speaker 3: we have to pump the electrical equivalent of a small
• 24:38
  Speaker 3: city into the magnets. Every fraction of percent closer to
• 24:42
  Speaker 3: keep requires exponentially more megawatts of power unbelieva. The protons
• 24:46
  Speaker 3: gain immense relativistic mass energy, but they never ever hit c.
• 24:52
  Speaker 3: The curve is an asymptote.
• 24:53
  Speaker 2: It's a crushing reality for a lot of our favorite
• 24:56
  Speaker 2: science fiction concepts, isn't it. We all want the warp core.
• 24:58
  Speaker 2: We want to sit in Captain's chair, say engage and
• 25:01
  Speaker 2: watch the stars stretch into long white streaks. But it's
• 25:04
  Speaker 2: not a matter of just waiting for a genius engineer
• 25:07
  Speaker 2: to build a bigger engine or find a denser more
• 25:10
  Speaker 2: exotic fuel source.
• 25:11
  Speaker 3: No, the universe's accounting system fundamentally prohibits it. You cannot
• 25:15
  Speaker 3: divide by zero.
• 25:16
  Speaker 2: The mass barrier is absolute and it is final for
• 25:20
  Speaker 2: anything that possesses mass. But this immediately raises a huge,
• 25:24
  Speaker 2: glaring question.
• 25:25
  Speaker 3: I think I know where you're going.
• 25:26
  Speaker 2: If having even a fraction of a gram of mass
• 25:29
  Speaker 2: requires infinite energy to reach ce, how in the world
• 25:32
  Speaker 2: does light do it? Light is traveling at the speed
• 25:34
  Speaker 2: of light. It's right there in the name. Why doesn't
• 25:36
  Speaker 2: a beam of light require infinite energy from the double
• 25:39
  Speaker 2: A batteries inside my flashlight?
• 25:41
  Speaker 3: That is the absolutely necessary follow up question, and it
• 25:44
  Speaker 3: brings us to the VIPs of the universe, the exclusive
• 25:47
  Speaker 3: club of massless particles. The entire secret to traveling at
• 25:51
  Speaker 3: the cosmic speed limit relies on a concept called rest mass.
• 25:55
  Speaker 2: Let's define rest mass because earlier we said protons get
• 25:58
  Speaker 2: heavier or gain relativistic mass as they speed up.
• 26:01
  Speaker 3: Right. Rest mass, often denoted as M zero in the equations,
• 26:05
  Speaker 3: is the intrinsic fundamental mass of a particle when it
• 26:08
  Speaker 3: is completely stationary, when it's perfectly at rest relative to
• 26:11
  Speaker 3: an observer. It is the baseline mass that you me,
• 26:15
  Speaker 3: a starship, a carbon atom, and an electron all possess.
• 26:19
  Speaker 3: But there is a very small, highly exclusive family of
• 26:22
  Speaker 3: fundamental particles in the standard model of physics that possess
• 26:25
  Speaker 3: absolutely zero rest mass.
• 26:27
  Speaker 2: Photons, which are the fundamental quantum particles of light, gluons,
• 26:31
  Speaker 2: which are the particles that carry the strong nuclear force
• 26:33
  Speaker 2: responsible for holding the quarks inside atoms together, and gravitational waves,
• 26:37
  Speaker 2: which are reaples in the fabric of spacetime itself.
• 26:39
  Speaker 3: Exactly, for these entities, M zero is precisely zero, and
• 26:44
  Speaker 3: because their rest mass is zero, their relativistic energy equation
• 26:48
  Speaker 3: completely bypasses the Lorentz factor trap.
• 26:51
  Speaker 2: Oh, because of the multiplication.
• 26:53
  Speaker 3: Yes, think back to the equation we just discussed. Energy
• 26:56
  Speaker 3: equals res mass time c squared times the Lorentz factor.
• 26:59
  Speaker 3: If you're rest mass is zero, you are multiplying the
• 27:02
  Speaker 3: infinite Lorentz factor by zero.
• 27:04
  Speaker 2: And anything multiplied by zero is zero. The infinite energy
• 27:07
  Speaker 2: toll just suddenly vanishes.
• 27:09
  Speaker 3: They are completely exempt from the esump tote. But this
• 27:12
  Speaker 3: exemption comes with a very bizarre, inflexible set of rules
• 27:15
  Speaker 3: for their existence. Because they have no rest mass, they
• 27:18
  Speaker 3: can never ever be at rest.
• 27:20
  Speaker 2: This is one of the most mind bending details for
• 27:22
  Speaker 2: me to really wrap my head around, because we are
• 27:25
  Speaker 2: so deeply accustomed to the concept of acceleration. We think
• 27:28
  Speaker 2: of a sports car going from zero to sixty. We
• 27:30
  Speaker 2: think of rockets slowly lifting off a pad and gaining speed.
• 27:34
  Speaker 2: But massless particles never actually accelerate.
• 27:36
  Speaker 3: They possess no mechanism for acceleration.
• 27:38
  Speaker 2: They don't go from zero miles per hour up to
• 27:40
  Speaker 2: one hundred, up to a million, and eventually settle at sea.
• 27:43
  Speaker 2: The exact precise, infinitesimal microsecond that a photon is born,
• 27:48
  Speaker 2: whether it's created deep in the nuclear fusion furnace of
• 27:51
  Speaker 2: the Sun's core or just emitted by the glowing tungsten
• 27:54
  Speaker 2: filament of a cheap desk lamp, the very instant of
• 27:57
  Speaker 2: its creation, it is already propagating through space at exactly
• 28:01
  Speaker 2: two hundred and ninety nine million, seven hundred and ninety
• 28:04
  Speaker 2: two four hundred and fifty eight meters per second.
• 28:07
  Speaker 3: It is the existential reality of being a massless particle.
• 28:10
  Speaker 3: To exist is to move at s There is no
• 28:13
  Speaker 3: alternative state. They can never slow down while in a vacuum,
• 28:16
  Speaker 3: they can never pause, and they can never be stationary.
• 28:19
  Speaker 2: They just pop into existence, already moving at the absolute
• 28:22
  Speaker 2: maximum speed the universe allows.
• 28:23
  Speaker 3: And because they travel at exactly the speed of light,
• 28:26
  Speaker 3: we were forced to revisit the consequences of space time
• 28:28
  Speaker 3: flexing that we discussed earlier, the time dilation.
• 28:31
  Speaker 2: Right the road trip analogy, where the faster you drive,
• 28:34
  Speaker 2: the slower your dashboard clock ticks to compensate.
• 28:36
  Speaker 3: We established that if you are an object with mass
• 28:39
  Speaker 3: approaching C, your clock ticks slower and slower toward a crawl.
• 28:43
  Speaker 3: But a photon is traveling at exactly C. If we
• 28:47
  Speaker 3: plug V equal C into the time dilation formula, the
• 28:50
  Speaker 3: time dilation stretches.
• 28:51
  Speaker 2: To infinity, meaning what exactly the clock on the photon
• 28:55
  Speaker 2: stops completely.
• 28:56
  Speaker 3: Yes, from the perspective of a photon or any massless
• 28:59
  Speaker 3: part article, time fund metally does not exist. The flow
• 29:03
  Speaker 3: of time is entirely halted. They do not experience duration, aging,
• 29:06
  Speaker 3: or the passage of time in their own frame of reference.
• 29:09
  Speaker 2: That is heavy. We'll definitely come back to the philosophical
• 29:11
  Speaker 2: implications of a timeless perspective at the end of this discussion,
• 29:14
  Speaker 2: but for now we've firmly established the how the universe
• 29:17
  Speaker 2: physically prevents mass from reaching sea via this infinite energy
• 29:21
  Speaker 2: math trap, while letting massless particles prove freely because they
• 29:24
  Speaker 2: have no rest mass. Right, But we still need to
• 29:26
  Speaker 2: ask why is the universe just being stingy with its
• 29:29
  Speaker 2: energy reserves. Why is there a speed limit at all?
• 29:32
  Speaker 2: Why not infinite speed?
• 29:33
  Speaker 3: The energy barrier, the Lorentz factor. All of that is
• 29:35
  Speaker 3: just the mechanical enforcer of the law, The actual underlying
• 29:40
  Speaker 3: reason for the cosmic speed limit. The reason reality demands
• 29:43
  Speaker 3: a cap on velocity is about protecting the foundation of logic.
• 29:47
  Speaker 2: Itself, protecting reality from breaking.
• 29:50
  Speaker 3: Yes, it is about protecting causality.
• 29:52
  Speaker 2: Causality cause and effect literally the most basic assumption we
• 29:56
  Speaker 2: make about the world. You drop a glass coffee mug,
• 29:58
  Speaker 2: it hits the tile floor, and it shatters. The cause
• 30:02
  Speaker 2: dropping it always precedes the effect the shattering.
• 30:05
  Speaker 3: It seems obvious to the point of being mundane. But
• 30:09
  Speaker 3: causality requires that a cause must always precede its effect
• 30:13
  Speaker 3: for every observer, everywhere in the universe, no matter how
• 30:15
  Speaker 3: fast they are moving or where they are located. If
• 30:18
  Speaker 3: we allow cause and effect to swap places, the universe
• 30:21
  Speaker 3: descends into profound logical chaos.
• 30:23
  Speaker 2: But wait, let me push back on this a little.
• 30:25
  Speaker 2: Didn't we say earlier when we were talking about space,
• 30:27
  Speaker 2: time flexing, and relativity, that event timing is relative, that
• 30:31
  Speaker 2: two things happening at the same time for me might
• 30:33
  Speaker 2: not happen at the same time for you.
• 30:34
  Speaker 3: We did, and that relativistic shifting of time is exactly
• 30:38
  Speaker 3: where the danger lies. Because space and time bend, two
• 30:42
  Speaker 3: events that appear simultaneous to you standing still on Earth
• 30:45
  Speaker 3: might look like they happen in a distinct sequence to
• 30:48
  Speaker 3: someone flying past Earth in a high speed spaceship. Okay,
• 30:51
  Speaker 3: The mathematical rules that govern how event coordination and timing
• 30:54
  Speaker 3: change between different moving frames of reference are called the
• 30:58
  Speaker 3: Lorentz transformations.
• 30:59
  Speaker 2: Are bringing back Lorentz.
• 31:01
  Speaker 3: He was instrumental in building the math that Einstein relied upon.
• 31:04
  Speaker 3: We specifically need to look at the transformation equation for
• 31:07
  Speaker 3: time intervals, which physicists call delta t prime. This formula
• 31:12
  Speaker 3: calculates the amount of time that passes between two events
• 31:15
  Speaker 3: as measured by an observer who is moving relative to
• 31:18
  Speaker 3: those events.
• 31:19
  Speaker 2: Without getting bogged down and doing algebra on air. Let's
• 31:21
  Speaker 2: look at the mechanical components of that equation. The formula
• 31:24
  Speaker 2: takes the time interval that you measure between two events,
• 31:28
  Speaker 2: and it subtracts a chunk of time based on how
• 31:30
  Speaker 2: fast the other person is moving and how far apart
• 31:33
  Speaker 2: the events are in space.
• 31:34
  Speaker 3: Crucially, I want to emphasize the minus sign in that equation.
• 31:37
  Speaker 3: As the velocity of the moving observer increases, the chunk
• 31:41
  Speaker 3: of time being subtracted gets larger and larger. Now, as
• 31:44
  Speaker 3: long as the velocity of the observer or the signal
• 31:46
  Speaker 3: is less than the skew of light, so a V
• 31:48
  Speaker 3: is less than C, the mag stays safe.
• 31:51
  Speaker 2: So no paradox yet, right.
• 31:53
  Speaker 3: The order events might shift slightly, maybe they see the
• 31:55
  Speaker 3: glass chatter or a fraction of a secut later than
• 31:57
  Speaker 3: you do, but the cause always still happens before the effect.
• 32:00
  Speaker 2: What if we pretend we have a magic warp drive.
• 32:03
  Speaker 2: What if an object or even just a radio signal
• 32:05
  Speaker 2: carrying data went faster than light If velocity V is
• 32:09
  Speaker 2: strictly greater than C.
• 32:11
  Speaker 3: If V is greater than C, the term being subtracted
• 32:14
  Speaker 3: in the Lorentz transformation becomes so massively large that it
• 32:17
  Speaker 3: completely overtakes and swallows the original time interval. The resulting
• 32:21
  Speaker 3: time interval delta t prime ceases to be positive, it
• 32:25
  Speaker 3: becomes a negative number.
• 32:26
  Speaker 2: Hold on, if the time interval between me pressing a
• 32:29
  Speaker 2: launch button and a missile firing becomes a negative number.
• 32:33
  Speaker 2: Are you saying that going faster than light is literally
• 32:36
  Speaker 2: mathematically synonymous with traveling backward in time?
• 32:39
  Speaker 3: I am saying exactly that, in the physical framework of
• 32:42
  Speaker 3: special relativity, there are not two different science fiction concepts.
• 32:46
  Speaker 3: Faster than light travel and backward time travel are mathematically,
• 32:49
  Speaker 3: physically and geometrically identical. You cannot have one without the other.
• 32:54
  Speaker 2: Okay, we need to break that down because a negative
• 32:56
  Speaker 2: time interval is really hard to visualize. How does that
• 33:00
  Speaker 2: actually play out in real life or at least in
• 33:03
  Speaker 2: a thought experiment.
• 33:04
  Speaker 3: If you possess a device that can transmit a signal
• 33:07
  Speaker 3: faster than light in your own reference frame, the math
• 33:10
  Speaker 3: of space time guarantees that there exists another perfectly valid
• 33:13
  Speaker 3: inertial frame of reference, say a spaceship flying by at
• 33:17
  Speaker 3: a specific sublight speed, where an observer will see that
• 33:21
  Speaker 3: signal arrive at its destination before you ever sent it.
• 33:24
  Speaker 2: Before the effect precedes the cause. Yes, let's illustrate this
• 33:28
  Speaker 2: because the logical paradox here is incredible, and it shows
• 33:31
  Speaker 2: exactly why the universe forbids it. Let's walk through what
• 33:34
  Speaker 2: physicists call the transmitter paradox or the tachyonic anti telephone
• 33:38
  Speaker 2: a great thought experiment. Imagine you and I are on
• 33:40
  Speaker 2: two different planets light years apart, and I have somehow
• 33:43
  Speaker 2: managed to invent a faster than light radio, a subspace
• 33:46
  Speaker 2: communicator like the use in Star Trek.
• 33:48
  Speaker 3: Okay, you have an FTO radio on your desk.
• 33:51
  Speaker 2: Send signals instantaneously or at least massively faster than the
• 33:54
  Speaker 2: speed of light. I want to test it out. I
• 33:57
  Speaker 2: have a big red button on my desk. When I
• 33:59
  Speaker 2: press the button, sends a faster than light signal to
• 34:02
  Speaker 2: your planet.
• 34:03
  Speaker 3: And let's say my receiver on my planet is wired
• 34:05
  Speaker 3: directly to an automated planetary defense system. When I receive
• 34:09
  Speaker 3: your signal, my system automatically and instantly fires a faster
• 34:13
  Speaker 3: than light missile back at your planet, aimed directly at
• 34:16
  Speaker 3: your radio transmitter.
• 34:17
  Speaker 2: Perfect setup. So I sit down on my desk at
• 34:19
  Speaker 2: exactly twelve five zero pm, I press the red button.
• 34:22
  Speaker 2: The signal shoots to you faster than light, arriving at
• 34:25
  Speaker 2: say twelve four to h one pm. Your automated system
• 34:28
  Speaker 2: receives it and instantly fires the faster than light missile
• 34:31
  Speaker 2: back at me.
• 34:32
  Speaker 3: Now we apply the Lorentz transformations we just discussed. Because
• 34:36
  Speaker 3: of the negative time interval created by the faster than
• 34:38
  Speaker 3: light speeds the signal in the missile from a certain
• 34:41
  Speaker 3: valid geometric perspective in the universe, that return missile is
• 34:45
  Speaker 3: traveling back in time relative to your initial button press.
• 34:49
  Speaker 2: So the missile crosses the void of space and arrives
• 34:51
  Speaker 2: at my desk at eleven five nine AM, one full
• 34:55
  Speaker 2: minute before I press the button exactly.
• 34:57
  Speaker 3: The missile strikes your transmitter at eleven thirty nine AM
• 35:00
  Speaker 3: and completely destroys it.
• 35:02
  Speaker 2: But if my transmitter is blown to pieces at eleven
• 35:04
  Speaker 2: to five nine AM, I can never press the red
• 35:06
  Speaker 2: button at twelve zero zero PM.
• 35:08
  Speaker 3: And if your transmitter is a pile of ash, you
• 35:10
  Speaker 3: never press the button, which means you never send the
• 35:12
  Speaker 3: initial signal to me.
• 35:14
  Speaker 2: And if I never send the signal, your automated system
• 35:16
  Speaker 2: never receives anything, and you never fire the missile.
• 35:19
  Speaker 3: If I never fire the missile, your transmitter is never
• 35:21
  Speaker 3: destroyed at eleven fifty nine AM.
• 35:22
  Speaker 2: Which means it's sitting there perfectly intact on my desk
• 35:25
  Speaker 2: at twelve zero PM. So I reach out and I press.
• 35:27
  Speaker 3: The button, and the loop begins again. The logic completely
• 35:30
  Speaker 3: eats itself. It is a fundamental structural breakdown of reality.
• 35:35
  Speaker 3: It is a temporal paradox.
• 35:36
  Speaker 2: It's essentially the classic grandfather paradox, you know, going back
• 35:41
  Speaker 2: in time and killing your own grandfather, so you are
• 35:43
  Speaker 2: never born, but just executed with an FTL radio and
• 35:46
  Speaker 2: a missile instead of a time machine. If I can
• 35:49
  Speaker 2: send a signal to disable my own transmitter before I
• 35:51
  Speaker 2: push the start button, logic collapses. The universe stops making sense.
• 35:56
  Speaker 3: This is exactly why the cosmic speed limit exists. The
• 36:00
  Speaker 3: speed of light isn't just a physical property of how
• 36:02
  Speaker 3: fast a photon can run through a vacuum. See is
• 36:05
  Speaker 3: the maximum permitted speed of information and causality in the universe.
• 36:10
  Speaker 3: It is an absolute air tight lock on reality designed
• 36:13
  Speaker 3: to prevent the universe from breaking into a chaotic mess
• 36:16
  Speaker 3: of contradictory temporal paradoxes.
• 36:18
  Speaker 2: It's the universe's immune system. It's saying, I will literally
• 36:21
  Speaker 2: enforce infinite energy requirements to stop you from creating a paradox.
• 36:24
  Speaker 3: Precisely causality must remain inviolable for a universe of function.
• 36:28
  Speaker 2: Okay, so we've established that it is an air tight physical, mathematical,
• 36:32
  Speaker 2: and logical lock on reality. Nothing with mass can reach it,
• 36:36
  Speaker 2: nothing can exceed it, or the universe mathematically breaks. Yet
• 36:42
  Speaker 2: if you open a popular science magazine or read science
• 36:45
  Speaker 2: headlines online, you constantly see things claiming they are breaking
• 36:49
  Speaker 2: the speed of light.
• 36:49
  Speaker 3: You do see that quite often scientists transmit data faster
• 36:53
  Speaker 3: than light or distant galaxy observe breaking the cosmic speed limit.
• 36:57
  Speaker 2: It can be deeply confusing for people. If the speed
• 37:00
  Speaker 2: limit is absolute and paradoxes are forbidden, what are these
• 37:03
  Speaker 2: headlines actually talking about. We really need to look at
• 37:06
  Speaker 2: the phenomena that appear to be loopholes, but aren't They.
• 37:09
  Speaker 3: Are apparent faster than light phenomena. There are a few
• 37:12
  Speaker 3: famous examples that always come up in these discussions. They
• 37:14
  Speaker 3: are fascinating edge cases of physics, but none of them
• 37:18
  Speaker 3: actually violate special relativity, and most importantly, none of them
• 37:22
  Speaker 3: transfer information faster than sea, meaning causality is always protected.
• 37:27
  Speaker 2: Let's tackle the one you hear about most often in
• 37:29
  Speaker 2: astronomy and cosmology, the expansion of the universe. We point
• 37:33
  Speaker 2: our most powerful telescopes like Hubble or James Webb at
• 37:36
  Speaker 2: the furthest edges of the cosmos at galaxies billions of
• 37:40
  Speaker 2: light years away, and we can measure via redshift that
• 37:43
  Speaker 2: they are moving away from us.
• 37:45
  Speaker 3: And if you calculate their recession velocity based on that
• 37:47
  Speaker 3: red shift, they're moving away from at speeds vastly exceeding
• 37:52
  Speaker 3: two hundred and ninety nine million, seven hundred ninety two
• 37:55
  Speaker 3: four hundred and fifty eight meters per second.
• 37:57
  Speaker 2: How is that possible? We literally just spent the last
• 38:00
  Speaker 2: half hour establishing that no mass can go faster than Sigh.
• 38:03
  Speaker 2: How is an entire galaxy full of billions of massive stars, dust,
• 38:07
  Speaker 2: and planets casually breaking the limit?
• 38:09
  Speaker 3: It's all about, precisely what is actually doing the moving.
• 38:12
  Speaker 3: The galaxies themselves are not firing massive cosmic rocket engines
• 38:15
  Speaker 3: and traveling through space faster than light. What is actually
• 38:18
  Speaker 3: happening is that the physical fabric of space existing between
• 38:20
  Speaker 3: us and those distant galaxies is stretching.
• 38:23
  Speaker 2: The metric space itself is expanding.
• 38:24
  Speaker 3: Yes, A common analogy is baking raisin bread.
• 38:27
  Speaker 2: Okay, I like baking.
• 38:28
  Speaker 3: Imagine a ball of dough with raisins scattered throughout it.
• 38:31
  Speaker 3: The raisins represent galaxies, and the dough represents the space
• 38:35
  Speaker 3: time between them. As the dough bakes and rises, it
• 38:39
  Speaker 3: expands in all directions, the reasons move further apart from
• 38:42
  Speaker 3: each other. But the raisins aren't actively swimming or moving
• 38:45
  Speaker 3: through the dough. The dough itself is swelling, pushing them apart.
• 38:49
  Speaker 2: And because space itself is just the fabric, it's the
• 38:51
  Speaker 2: stage we talked about earlier, not an actor.
• 38:54
  Speaker 3: It has no mass exactly, Space itself carries absolutely zero mass,
• 38:58
  Speaker 3: and because it has no mass, it is entirely unconstrained
• 39:01
  Speaker 3: by the mass barrier and the Lorentz factor of special relativity.
• 39:06
  Speaker 3: Space time can stretch, expand, and inflate at any arbitrary
• 39:09
  Speaker 3: speed it wants to. The galaxies are just along for
• 39:11
  Speaker 3: the ride, embedded in the stretching fabric in their own
• 39:15
  Speaker 3: local neighborhood of space. They might barely be moving at all.
• 39:18
  Speaker 3: No local speed limit is broken, and most importantly, no
• 39:21
  Speaker 3: information is being transmitted between the galaxies faster than light.
• 39:25
  Speaker 2: That makes a lot of sense. It feels like a technicality,
• 39:27
  Speaker 2: but it's a mathematically profound one. Okay, Let's look at
• 39:31
  Speaker 2: another apparent loophole. This is the one that always gets
• 39:33
  Speaker 2: brought up in sci fi forums and late night physics debates.
• 39:37
  Speaker 2: Quantum entanglement.
• 39:39
  Speaker 3: Uh yes, the quantum realm. This is the phenomenon that
• 39:42
  Speaker 3: Albert Einstein famously and somewhat grumpily referred to as spooky
• 39:47
  Speaker 3: action at a distance. He hated it because it seemed
• 39:51
  Speaker 3: to violate his precious speed limit.
• 39:52
  Speaker 2: Let me set up how entanglement works and you can
• 39:55
  Speaker 2: correct my quantum mechanics. You take two quantum particles, let's
• 39:58
  Speaker 2: say two electrons. You interact them in a way that
• 40:01
  Speaker 2: entangles them, which permanently links their quantum states. Then you
• 40:05
  Speaker 2: separate them. You put one electron in a containment lab
• 40:08
  Speaker 2: on Earth, and you fly the other electron out to
• 40:11
  Speaker 2: a lab on Mars.
• 40:12
  Speaker 3: Or to a lab on a planet in the Andromeda galaxy.
• 40:15
  Speaker 3: The physical distance between them no longer matters once they
• 40:18
  Speaker 3: are entangled.
• 40:19
  Speaker 2: Right, And the spooky part is that the moment you
• 40:21
  Speaker 2: measure the state of the electron on Earth, say you
• 40:24
  Speaker 2: measure its quantum spin and it collapses into a spin
• 40:27
  Speaker 2: up state, You instantaneously determine the state of the electron
• 40:31
  Speaker 2: on Mars, it will immediately in that exact same millisecond,
• 40:35
  Speaker 2: collapse into a spin down state, instantaneously, vastly faster than
• 40:39
  Speaker 2: the speed of light could ever travel between Earth and Mars.
• 40:42
  Speaker 3: The state determination is indeed instantaneous across the universe. Experiments
• 40:47
  Speaker 3: have proven this correlation exists and happens faster than light
• 40:51
  Speaker 3: could traverse the distance. So it feels like a massive,
• 40:54
  Speaker 3: glaring violation of the cosmic speed limit. If they're communicating
• 40:58
  Speaker 3: their state faster than light, shouldn't that create the exact
• 41:01
  Speaker 3: temporal paradox we just talked about.
• 41:03
  Speaker 2: Yeah, why can't I use entangled electrons to build my
• 41:06
  Speaker 2: FTL radio and send my time traveling missile signal? It
• 41:09
  Speaker 2: seems like the perfect mechanism.
• 41:11
  Speaker 3: You can't because of a very strict fundamental rule in
• 41:14
  Speaker 3: quantum mechanics known as the no communication theorem. It all
• 41:17
  Speaker 3: comes down to the nature of quantum randomness.
• 41:20
  Speaker 2: Unpack the no communication theorem for me, how does randomness
• 41:23
  Speaker 2: stop me from sending a message?
• 41:24
  Speaker 3: When you measure your entangled electron on Earth, you cannot
• 41:28
  Speaker 3: force it to be spin up or spin down. The
• 41:31
  Speaker 3: outcome of a quantum measurement is fundamentally inherently random. It's
• 41:35
  Speaker 3: a coin flip governed by probability.
• 41:38
  Speaker 2: Okay, so I measure it, and I just get what
• 41:39
  Speaker 2: I get.
• 41:40
  Speaker 3: Right, So you measure your particle. It comes up heads,
• 41:43
  Speaker 3: spin up. You immediately know with one hundred percent certainty
• 41:48
  Speaker 3: that the particle on Mars is tails spin down. But
• 41:52
  Speaker 3: because you didn't choose heads, because you couldn't manipulate the outcome,
• 41:56
  Speaker 3: you cannot encode a message into that measurement. You can't
• 41:59
  Speaker 3: use it to send more code. You can't assign spin
• 42:01
  Speaker 3: up to mean fire the missile and spin down to
• 42:04
  Speaker 3: mean a board, because you have no control over which
• 42:06
  Speaker 3: instruction is generated.
• 42:07
  Speaker 2: Ah, because if I tried to send a coherent message,
• 42:10
  Speaker 2: I'd just be generating a string of completely random static
• 42:13
  Speaker 2: on both ends.
• 42:15
  Speaker 3: Exactly, the particles share a deeply correlated state. But because
• 42:19
  Speaker 3: you lack the ability to control the outcome of the measurement,
• 42:22
  Speaker 3: no usable data, no code, and no information can be
• 42:25
  Speaker 3: transmitted between the two locations. And if no information can
• 42:29
  Speaker 3: be transmitted, causality remains completely safe. Remember, the speed of
• 42:33
  Speaker 3: light is the maximum speed of information. Quantum entanglement does
• 42:37
  Speaker 3: not transfer information, so the paradox is avoided and the
• 42:41
  Speaker 3: speed limit stands absolute.
• 42:42
  Speaker 2: It's like the universe handed us to magic eight balls
• 42:45
  Speaker 2: that always show opposite answers, but strictly prohibited us from
• 42:49
  Speaker 2: ever actually choosing the answer they give. You know what
• 42:52
  Speaker 2: the other person is seeing, but you can't use it
• 42:53
  Speaker 2: to talk to them.
• 42:54
  Speaker 3: That is a very apt analogy. The correlation is an
• 42:57
  Speaker 3: instantaneous but communication is still limited to c All.
• 43:00
  Speaker 2: Right, let's explore a third apparent loophole. This one is
• 43:04
  Speaker 2: less cosmic and abstract and more terrestrial and visual. If
• 43:07
  Speaker 2: you've ever seen a photograph or a video of the
• 43:10
  Speaker 2: inside of a nuclear reactor core, specifically a core that
• 43:13
  Speaker 2: is submerged in a pool of cooling water, there is
• 43:15
  Speaker 2: this incredibly eerie, bright, glowing blue light emanating from it.
• 43:20
  Speaker 3: Charin CoV radiation discovered by Soviet's physicist Pavel charin CoV
• 43:25
  Speaker 3: in nineteen thirty four, for which he later won the
• 43:27
  Speaker 3: Nobel Prize.
• 43:28
  Speaker 2: Yes, and my understanding of Cherenkov radiation is that this
• 43:31
  Speaker 2: blue glow is explicitly caused by particles traveling faster than
• 43:35
  Speaker 2: the speed of light.
• 43:36
  Speaker 3: It is caused by particles traveling faster than light in
• 43:38
  Speaker 3: that specific medium, But it absolutely does not violate the
• 43:42
  Speaker 3: universal constantcy Let's.
• 43:45
  Speaker 2: Break that distinction down carefully, because to a layman, faster
• 43:49
  Speaker 2: than light but doesn't violate the speed of light sounds
• 43:52
  Speaker 2: like a direct contradiction.
• 43:53
  Speaker 3: It comes back to our very precise definitions. Remember, at
• 43:56
  Speaker 3: the very beginning of our discussion, when we define the
• 43:58
  Speaker 3: cosmic speed limit, we explicitly define C as the speed
• 44:02
  Speaker 3: of light in a perfect vacuum empty space two hundred
• 44:05
  Speaker 3: ninety nine million, seven hundred ninety two four hundred and
• 44:08
  Speaker 3: fifty eight meters per second.
• 44:09
  Speaker 2: Right, the vacuum is the key.
• 44:10
  Speaker 3: But light doesn't only travel in a vacuum. It travels
• 44:14
  Speaker 3: through the Earth's atmosphere. It travels through the glass lenses
• 44:16
  Speaker 3: of our glasses, and it travels through water. And when
• 44:19
  Speaker 3: a photon enters a physical medium, it doesn't just glide
• 44:22
  Speaker 3: through empty space anymore. It interacts with the electromagnetic fields
• 44:26
  Speaker 3: of the atoms in that material. It gets absorbed, delayed,
• 44:29
  Speaker 3: and re emitted as it bounces around through the atomic structure.
• 44:32
  Speaker 3: This complex process slows the overall phase velocity, the propagation
• 44:36
  Speaker 3: speed of the light beamed down.
• 44:38
  Speaker 2: Right, there is an equation for this V equals C
• 44:41
  Speaker 2: over n where n is the refractive index of the material.
• 44:45
  Speaker 3: Exactly in pure water, the refractive index is about one
• 44:48
  Speaker 3: point three to three. This means that light travels through
• 44:51
  Speaker 3: water at roughly two hundred and twenty five billsand meters
• 44:53
  Speaker 3: per second. That is still incredibly fast, obviously, but it
• 44:57
  Speaker 3: is significantly slower than the absolute vacuum limit of seas.
• 45:00
  Speaker 2: So to use our earlier analogy, the absolute speed limit
• 45:02
  Speaker 2: of the highway is still three hundred thousand kilometers a second,
• 45:05
  Speaker 2: but light is currently driving through a construction zone in
• 45:08
  Speaker 2: the water, so it has to slow down to two
• 45:09
  Speaker 2: hundred twenty five thousand.
• 45:11
  Speaker 3: Yes. Now, inside an active nuclear reactor, you have high
• 45:14
  Speaker 3: energy particles like electrons or beta particles being violently shot
• 45:18
  Speaker 3: out of radioactive decay, and these particles are ejected at
• 45:22
  Speaker 3: a huge fraction of sea in a vacuum. Let's say
• 45:24
  Speaker 3: they are ejected at ninety nine percent of s.
• 45:26
  Speaker 2: And when those super fast ninety nine percent of sea
• 45:29
  Speaker 2: particles slam into the surrounding pool of cooling.
• 45:32
  Speaker 3: Water, they're suddenly traveling faster than light can travel in
• 45:35
  Speaker 3: that specific water. The electron is blazing through at ninety
• 45:38
  Speaker 3: nine percent of the vacuum speed of light, but the
• 45:41
  Speaker 3: photons of light in the water are only managing about
• 45:43
  Speaker 3: seventy five percent of the vacuum skied. The physical particle
• 45:47
  Speaker 3: successfully outpaces the light wave.
• 45:49
  Speaker 2: And what happens mechanically when a physical object outpaces a
• 45:52
  Speaker 2: wave in a medium.
• 45:53
  Speaker 3: We can use a very familiar acoustic analogy. Think of
• 45:56
  Speaker 3: a supersonic fighter jet flying faster than the speed of
• 45:59
  Speaker 3: sound in the air. As it pushes through the air
• 46:01
  Speaker 3: faster than the sound waves can propagate away from it,
• 46:03
  Speaker 3: it compresses the air and creates a massive conical pressure wave,
• 46:08
  Speaker 3: a sonic boom.
• 46:09
  Speaker 2: So the glowing blue light in the reactor is an
• 46:12
  Speaker 2: optical sonic boom.
• 46:13
  Speaker 3: It is the exact electromagnetic equivalent of a sonic boom.
• 46:17
  Speaker 3: The charge particle is displacing the electromagnetic field in the
• 46:20
  Speaker 3: water faster than the field can react and send light
• 46:23
  Speaker 3: waves ahead to clear the way. The waves bunch up constructively,
• 46:27
  Speaker 3: interfere with each other, and propagate outward as a shockwave
• 46:30
  Speaker 3: cone of blue light that is Cherenkov.
• 46:33
  Speaker 2: Radiation that is brilliant. So the particle is indeed going
• 46:36
  Speaker 2: faster than light in the water, but it is still
• 46:39
  Speaker 2: strictly bound by and traveling vastly slower than the absolute
• 46:43
  Speaker 2: vacuum limit of sea.
• 46:44
  Speaker 3: Special relativity remains completely intact. The true cosmic speed limit
• 46:48
  Speaker 3: is never broken. It is a local speed limit that
• 46:50
  Speaker 3: is exceeded, not the universal one.
• 46:52
  Speaker 2: It's honestly amazing how resilient this rule is. You try
• 46:55
  Speaker 2: to push through it with sheer mass and acceleration, and
• 46:58
  Speaker 2: the universe mathematically throws infinite energy requirements at you to
• 47:02
  Speaker 2: stop you. You try to circumvent it with the instantaneous
• 47:06
  Speaker 2: nature of quantum entanglement, and the universe throws fundamental quantum
• 47:10
  Speaker 2: randomness at you to STARp you from sending usable messages.
• 47:14
  Speaker 2: You try to outrace light in a medium, and you
• 47:16
  Speaker 2: just create a blue shock wave while remaining well under
• 47:19
  Speaker 2: the true limit. It really is the ultimate unbreakable boundary
• 47:23
  Speaker 2: of reality.
• 47:24
  Speaker 3: It is when you step back and look at the
• 47:26
  Speaker 3: big picture we've painted today. The assertion that nothing can
• 47:29
  Speaker 3: travel faster than light is not just an arbitrary speed
• 47:32
  Speaker 3: limit set by incomplete engineering. It's not a temporary hurdle.
• 47:36
  Speaker 3: It's not about lacking the right fuel or the right
• 47:38
  Speaker 3: aerodynamic shape.
• 47:39
  Speaker 2: Right. We aren't just waiting for a better spark plug
• 47:41
  Speaker 2: or a fictional warp drive to.
• 47:43
  Speaker 3: Solve this exactly. It is a fundamental structural law built
• 47:46
  Speaker 3: into the geometric fabric of space time itself. Massless particles
• 47:50
  Speaker 3: like photons travel at exactly C because they have no
• 47:54
  Speaker 3: inertial burden tying them down. They are the purest expression
• 47:57
  Speaker 3: of energy propagating through space.
• 48:00
  Speaker 2: N The object possessing mass U me a planet, a starship,
• 48:05
  Speaker 2: requires an infinite supply of energy to reach SKI, effectively
• 48:08
  Speaker 2: trapping us in the sub light universe.
• 48:10
  Speaker 3: And most importantly, the invariance of C, the fact that
• 48:14
  Speaker 3: it acts as this absolute unbending threshold for everyone everywhere
• 48:19
  Speaker 3: ensures that cause always inherently precedes effect across the entire cosmos.
• 48:24
  Speaker 3: It locks our reality into a coherent, predictable sequence of events.
• 48:29
  Speaker 3: Without this absolute speed limit on information, the universe wouldn't
• 48:32
  Speaker 3: be a place we could exist in, let alone a
• 48:34
  Speaker 3: place we could try to understand. It would be a
• 48:37
  Speaker 3: chaotic soup of paradoxes.
• 48:39
  Speaker 2: It's the thing keeping the universe from devolving into a
• 48:41
  Speaker 2: contradictory mess of time travel nonsense. That is a deeply
• 48:45
  Speaker 2: comforting thought. Honestly, it's nice to know the universe has
• 48:47
  Speaker 2: rules that protect us from logical collapse. But before we
• 48:50
  Speaker 2: wrap up today's exploration, I want to leave you with
• 48:52
  Speaker 2: one final mind expanding idea to ponder. It goes back
• 48:55
  Speaker 2: to something we touched on earlier with those VIP massless.
• 48:58
  Speaker 3: Particles, the extreme time dilation at the speeder light.
• 49:01
  Speaker 2: Yes, we learned that photons, because they travel at exactly sagay,
• 49:05
  Speaker 2: experience absolute infinite time dilation. They experience zero time. The
• 49:10
  Speaker 2: clock is entirely stopped. No time passes for them at all, ever.
• 49:15
  Speaker 3: None, They are entirely exempt from the flow of time.
• 49:17
  Speaker 2: So imagine a single particle of light, a photon created
• 49:22
  Speaker 2: in the blazing, unimaginable fury of the Big Bang at
• 49:25
  Speaker 2: the very dawn of the universe, roughly thirteen point eight
• 49:29
  Speaker 2: billion years ago. It shoots out into the rapidly expanding
• 49:33
  Speaker 2: void of space. It travels across the cosmos, dodging newly
• 49:36
  Speaker 2: forming galaxies, weaving through vast nebulas, surviving the birth and
• 49:40
  Speaker 2: death of stars for billions and billions of years, and
• 49:43
  Speaker 2: then finally, tonight, you step outside, You look up at
• 49:45
  Speaker 2: the dark sky, and that exact ancient photon hits the
• 49:48
  Speaker 2: retin of your eye and it is absorbed its long
• 49:50
  Speaker 2: journey ends.
• 49:51
  Speaker 3: From our human perspective, grounded in mass and time, that
• 49:54
  Speaker 3: journey took thirteen point eight billion.
• 49:56
  Speaker 2: Years, but from the perspective of that photon. Because it
• 49:59
  Speaker 2: fundamentally does not experience time, the exact instant of its
• 50:03
  Speaker 2: birth at the dawn of time, and the exact instant
• 50:05
  Speaker 2: of its death hitting Uretina happen at the exact same
• 50:08
  Speaker 2: simultaneous instant.
• 50:09
  Speaker 3: Its beginning and its end are one and the same moment.
• 50:12
  Speaker 2: There was no journey, There was no passage of billions
• 50:15
  Speaker 2: of years from its frame of reference. There was just
• 50:18
  Speaker 2: a singular, timeless flash of existence, connecting the birth of
• 50:21
  Speaker 2: the universe directly to your eye, which leaves you with
• 50:24
  Speaker 2: this incredible lingering thought. If light is the primary messenger
• 50:29
  Speaker 2: of the cosmos, bringing us all the information we have
• 50:31
  Speaker 2: about the stars, the galaxies, and the deep past, what
• 50:35
  Speaker 2: does the universe actually look like when you don't experience
• 50:37
  Speaker 2: time at all.