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How were pulsars discovered? · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: What is the moment of scientific discovery actually? Like I mean,
0:14
Speaker 1: in the movies, it always seems so crisp. Scientists find
0:18
Speaker 1: something in her data or an experiment suddenly dramatically works.
0:22
Speaker 1: We go from ignorance to knowledge in a moment, from
0:25
Speaker 1: failure to success. That kind of drama works for the
0:29
Speaker 1: movie screen, But how does it happen in real life?
0:33
Speaker 1: Is it a slow and steady march rather than a
0:36
Speaker 1: sudden leap, or are there actually real moments of insight
0:41
Speaker 1: where all of a sudden light penetrates the darkness and
0:44
Speaker 1: the scientists learned something new about the universe that no
0:48
Speaker 1: human has ever known before. Hi, I'm Daniel. I'm a
1:07
Speaker 1: particle physicist and I've been doing particle physics experiments for
1:11
Speaker 1: decades but never discovered a new particle. And Welcome to
1:16
Speaker 1: the podcast. Daniel and Jorge explain the Universe, in which
1:20
Speaker 1: we examine everything about the universe, from its origins to
1:24
Speaker 1: its ends, from its biggest things to its smallest things,
1:28
Speaker 1: from all of its mysteries and all of our discoveries.
1:31
Speaker 1: Our goal in this podcast is to open our minds
1:34
Speaker 1: to all of the craziest, biggest, deepest, most important questions
1:39
Speaker 1: the one that frame the context of being human, the
1:42
Speaker 1: ones that tell us what it means to be in
1:44
Speaker 1: this universe and how this universe works. We tackle all
1:48
Speaker 1: of those questions and we go right to the forefront
1:51
Speaker 1: of scientific knowledge. We take you right to the edge
1:54
Speaker 1: where scientists are currently working, and we explain all of
1:57
Speaker 1: it to you in a way that we hope it
1:59
Speaker 1: makes and maybe even occasionally makes you laugh. My co
2:03
Speaker 1: host Orgy him the Creative PhD Comics, can't be here today,
2:06
Speaker 1: so I'm gonna share with you one of my favorite
2:08
Speaker 1: stories of scientific discovery. And I mentioned earlier on that
2:13
Speaker 1: I have never discovered a new particle. That's not a true.
2:17
Speaker 1: My career and particle physics spans from the mid nineteen
2:21
Speaker 1: nineties till today, and in the mid nineteen nineties was
2:24
Speaker 1: the discovery of the top cork or and I did
2:27
Speaker 1: a really fun episode about that whole, amazing, hilarious, dramatic story.
2:31
Speaker 1: But I just would have joined the field right when
2:33
Speaker 1: that had already happened, So I wasn't around when the
2:36
Speaker 1: top cork was discovered. I didn't get to participate in
2:38
Speaker 1: that moment of discovery. I was, however, part of the
2:42
Speaker 1: team that discovered the Higgs boson. But you have to understand,
2:45
Speaker 1: this was a really big group of people, thousands of
2:48
Speaker 1: thousands of people who all contributed little bits here and there,
2:52
Speaker 1: and there wasn't really a dramatic moment when we said,
2:55
Speaker 1: ah ha, the Higgs is there. It's solely emerged out
2:59
Speaker 1: of the a a sort of the way a treasure
3:01
Speaker 1: chest might be revealed in the sand of a beach,
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Speaker 1: as a tide pulls out inch by inch, showing you
3:06
Speaker 1: more and more of it. That was sort of the
3:08
Speaker 1: way the Higgs boson discovery went. We saw a little peak,
3:11
Speaker 1: we thought it might be it. It got bigger and
3:13
Speaker 1: bigger and bigger, and there was never really a moment
3:16
Speaker 1: of than the official announcement when we could say, now
3:19
Speaker 1: we have discovered the Higgs. But that sort of was
3:21
Speaker 1: a bureaucratic choice and artificial choice. There was no single
3:25
Speaker 1: aha moment. And part of that is because we knew
3:28
Speaker 1: what we were looking for. We suspect that the Higgs
3:31
Speaker 1: was there, we knew how to find it, we knew
3:33
Speaker 1: how to look for it, we knew what to expect,
3:35
Speaker 1: and so when we saw it, it was just sort
3:37
Speaker 1: of this slow creeping realization that we had found what
3:41
Speaker 1: we had been hunting. But that doesn't mean it's always
3:44
Speaker 1: like that. There are moments of discovery in science. Usually
3:48
Speaker 1: they happen when we're more surprised, when we see something
3:52
Speaker 1: we didn't expect, when you go looking for one thing
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Speaker 1: and you find something else. Moments, for example, like the
3:58
Speaker 1: discovery of the cosmic microwave back round that we talked
4:00
Speaker 1: about a few episodes ago. Today, we're going to tell
4:03
Speaker 1: the story of one of those moments when discovery came quickly,
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Speaker 1: when someone went looking for one thing and found something else,
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Speaker 1: something alarming and astonishing, a moment of insight about the universe. Actually,
4:16
Speaker 1: we're gonna tell a story of two of those moments,
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Speaker 1: because this discovery has multiple parts, and for one of
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Speaker 1: those parts, we happen to have real historical audio of
4:28
Speaker 1: those scientists realizing their discovery in real time as it happens,
4:33
Speaker 1: so you'll get to hear what it actually sounds like
4:36
Speaker 1: when scientists are astonished when they make a real life discovery.
4:41
Speaker 1: So that's super fun, and for me, it's always really
4:43
Speaker 1: interesting to try to understand what it was like to
4:47
Speaker 1: make that discovery. You know, it's easy in hindsight to say,
4:51
Speaker 1: all these things exist, here's how you look for them
4:54
Speaker 1: that when did it bad? A boom but being done.
4:56
Speaker 1: But you have to go back to what it was
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Speaker 1: like before we knew it was there, to put yourself
5:01
Speaker 1: back in that mental position of ignorance, not knowing whether
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Speaker 1: something is out there, not understanding whether you live in
5:07
Speaker 1: the universe where it's real or where it's just an idea,
5:10
Speaker 1: not knowing which direction human knowledge and science will take.
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Speaker 1: Science is so easy in hindsight and so difficult in foresight.
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Speaker 1: When you stand in the forefront of human ignorance, you
5:22
Speaker 1: don't know necessarily which way to go. So it's really
5:25
Speaker 1: valuable to revisit these moments when we took a step forward,
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Speaker 1: when we went from ignorance to knowledge, and understand what
5:33
Speaker 1: was required, how it happened, and the bravery it took
5:36
Speaker 1: to make that claim to say I have found something new.
5:39
Speaker 1: I now know something about the universe that no human
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Speaker 1: ever knew before. And so today we're gonna be telling
5:45
Speaker 1: one of my favorite stories of discovery, one about a
5:48
Speaker 1: really weird kind of star, a very fast, very dense,
5:53
Speaker 1: very bizarre kind of star that we've talked about on
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Speaker 1: the podcast before and so today's episode we'll be answering
5:59
Speaker 1: the question how we're pulsars discovered? And so, as usual,
6:08
Speaker 1: before we dig into the topic and tell you the
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Speaker 1: story today, I wanted to know how much people already
6:14
Speaker 1: knew about this sort of famous story. So I went
6:17
Speaker 1: out and solicited volunteers from the internet to tell us
6:20
Speaker 1: what they knew about various questions and science of this
6:23
Speaker 1: being one of them. So thank you to all of
6:25
Speaker 1: those who participated and give us their speculation without the
6:28
Speaker 1: opportunity to look into any reference material whatsoever on the
6:32
Speaker 1: honor system. Of course, if you'd like to participate and
6:36
Speaker 1: hear your voice on the podcast in the future, please
6:39
Speaker 1: don't be shy. I promise you it's fun. Send me
6:42
Speaker 1: an email to questions at Daniel and Jorge dot com.
6:46
Speaker 1: But in the meantime, think to yourself, do you know
6:48
Speaker 1: the story of how pulsars were discovered? Here's what people
6:52
Speaker 1: had to say. I am a d percent sure that
6:56
Speaker 1: pulsels were discovered when they stuck a stepiscope pots to
7:00
Speaker 1: the whole space telescope. I'm guessing pulsars were discovered by
7:05
Speaker 1: scientists who observed these stars that were kind of flashing,
7:10
Speaker 1: so dimming and brightening in these regular pulses. Hence the
7:17
Speaker 1: name pulsar. I realized I just described what a pulsar is,
7:23
Speaker 1: not how they were discovered, so sorry about that. UM.
7:28
Speaker 1: For what a pulsar is, I would say it was
7:31
Speaker 1: discovered as a rapidly blinking source of light in the sky. Um.
7:36
Speaker 1: They were discovered by I think she was a graduate
7:42
Speaker 1: student ince in the sixties. Something they were They discovered
7:50
Speaker 1: through listening to some radio signals, and first they thought
7:58
Speaker 1: there was extracted see in life, because they called that
8:03
Speaker 1: little Green Men l g M. But I always confused
8:07
Speaker 1: pulsars and quasars. I'm going to guess that someone saw
8:15
Speaker 1: repetition of light in some part of the sky over
8:19
Speaker 1: and over and that led to an investigation that found
8:23
Speaker 1: the pulsars. Pulsars were discovered by a woman, and I
8:28
Speaker 1: believe it was in the nineties seventies, but I'm not
8:31
Speaker 1: sure how or why or where even There was a
8:36
Speaker 1: woman astronomer radio astronomer whose name, unfortunately I cannot remember,
8:42
Speaker 1: was doing some sort of sky survey when she noticed
8:45
Speaker 1: a set of pulses that were incredibly regularly spaced. She
8:52
Speaker 1: actually annotated them as l g M for Little Green Men.
8:56
Speaker 1: That one time they thought it might have been discovery
8:59
Speaker 1: of aliens, but later they discovered that it was actually
9:05
Speaker 1: a rotating uh neutron star and the magnetic field was
9:11
Speaker 1: exciting the gas molecules molecules around it and giving off
9:15
Speaker 1: radio energy. Alright, so congratulations to our excellently informed listeners. Together,
9:21
Speaker 1: they really do have most of the story there. There's
9:24
Speaker 1: a lot of really insightful stuff and a lot of
9:26
Speaker 1: bits of the story are there in pieces here and there.
9:29
Speaker 1: So let's dig into it and to really understand how
9:32
Speaker 1: pulsars were discovered, we have to understand, of course, first
9:35
Speaker 1: what a pulsar is, how we came to the idea
9:39
Speaker 1: of it existing in the universe, and that will help
9:41
Speaker 1: us understand how it was seen and how we knew
9:43
Speaker 1: what we were seeing, all right, So first of all,
9:47
Speaker 1: what is a pulsar. A pulsar is a very very
9:50
Speaker 1: compact object. Neutron stars and white dwarfs are more famous
9:55
Speaker 1: as the sort of like densest things in the universe,
9:58
Speaker 1: and a pulsar is a version of these. It's most
10:02
Speaker 1: commonly considered to be a version of a neutron star,
10:05
Speaker 1: but it can also be a white dwarf, but both
10:07
Speaker 1: of them are essentially are the end points of stars.
10:11
Speaker 1: Stars have these incredible life cycles where you start out
10:14
Speaker 1: as a big molecular cloud, huge blob of gas and
10:18
Speaker 1: dust that somehow shocked to collapse into a hot and
10:21
Speaker 1: dense object a star, which burns for billions and billions
10:25
Speaker 1: of years in this incredible, incredible balance between gravity that's
10:29
Speaker 1: pulling it together, trying to turn it into a black
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Speaker 1: hole or something very very dense, and fusion which is
10:35
Speaker 1: erupting and sending radiation out to prevent the collapse of
10:39
Speaker 1: that star. And it always amazes me that these things
10:41
Speaker 1: go on for so long, these two cosmic forces so different,
10:45
Speaker 1: both so powerful, can be so balanced for so many
10:49
Speaker 1: billions of years. Well, at some point the star gives
10:52
Speaker 1: up because it's burned most of its fuel and its
10:54
Speaker 1: core has become very very heavy, and it's filled with
10:57
Speaker 1: things that it can no longer fuse. When the war
11:00
Speaker 1: of the star is filled with iron, for example, I
11:02
Speaker 1: using iron doesn't generate heat, it actually costs energy, so
11:06
Speaker 1: it cools the star. So now the star no longer
11:09
Speaker 1: has that power from fusion to resist gravity, and it collapses.
11:13
Speaker 1: There's some intermediate stages in there will skip over, such
11:15
Speaker 1: as it becoming a red giant, but depending on the
11:17
Speaker 1: size of the star, this collapse generally triggers a supernova.
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Speaker 1: So you have this collapse where the materials racing inwards,
11:24
Speaker 1: which then causes that back reaction outwards, a massive explosion
11:29
Speaker 1: where a huge chunk of the stuff that used to
11:31
Speaker 1: be the star is now spread out into a new nebula,
11:34
Speaker 1: like a big sprawling cloud of gas and dust. At
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Speaker 1: the core of it, however, is a very dense, very
11:41
Speaker 1: hot remnant, and that remnant can either be a white
11:44
Speaker 1: dwarf or a neutron star or a black hole, depending
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Speaker 1: on the mass of the original star. So smaller stars
11:52
Speaker 1: end up as white dwarfs, which are basically just like
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Speaker 1: huge hot chunks of metal that are resisting collapsing because
12:00
Speaker 1: their fermions and they don't like to overlap too much,
12:03
Speaker 1: or if they are larger, they become neutron stars, where
12:06
Speaker 1: gravity now pushes them together and forces all of the
12:09
Speaker 1: protons and the electrons together into forming new neutrons, and
12:13
Speaker 1: you have this really weird material that's sort of like
12:16
Speaker 1: the nucleus of an atom, but the size of a mountain.
12:19
Speaker 1: So it's incredibly dense, incredibly weird stuff, something we even
12:23
Speaker 1: still today do not understand in detail. And then, of course,
12:25
Speaker 1: if the star is more massive, it would become a
12:28
Speaker 1: black hole. So the gravity totally wins and nothing prevents
12:32
Speaker 1: the collapse and it becomes a black hole. But it's
12:34
Speaker 1: the first two categories that are more interested in. And
12:36
Speaker 1: let's focus on the neutron star category because that's the
12:39
Speaker 1: majority of pulsars. So you have this very dense object, right,
12:42
Speaker 1: and the object is a huge chunk of the material
12:44
Speaker 1: that used to be a star, not all of it.
12:46
Speaker 1: Some of the material is lost in the supernova and
12:49
Speaker 1: some of it remains in this cloud that surrounds the
12:51
Speaker 1: neutron star. But this neutron star is a very very
12:54
Speaker 1: dense object and very very small because gravity is really
12:58
Speaker 1: pulled it together. And with that means is that it's
13:00
Speaker 1: spinning really fast. Why is it spinning fast, Well, the
13:04
Speaker 1: star itself was spinning because everything in the universe is spinning.
13:08
Speaker 1: And the reason is simple is because angular momentum is conserved.
13:13
Speaker 1: You know how momentum is conserved. If you push on something,
13:16
Speaker 1: it stays in motion until something else pushes on it,
13:19
Speaker 1: or if you don't push on something, it stays still
13:22
Speaker 1: until something does push on it. That's conservation of momentum.
13:25
Speaker 1: Those are Newton's laws. Well, there are similar laws for
13:29
Speaker 1: angular momentum. That is that something spinning tends to keep spinning,
13:33
Speaker 1: and to make something spin, you've gotta give it a push.
13:35
Speaker 1: So if you leave something alone, it will keep spinning
13:38
Speaker 1: the way it's always been spinning. Right, that's conservation of
13:42
Speaker 1: angular momentum. And so the original gas cloud that formed
13:45
Speaker 1: that star had some spin to it, and that spin
13:48
Speaker 1: can't go away. It needs to stick around. And as
13:52
Speaker 1: the gas cloud gets smaller and smaller and turns into
13:54
Speaker 1: a star, the star spins faster. Now that might sound
13:58
Speaker 1: like it violates conservation of because the momentum because it's
14:01
Speaker 1: spinning faster. Right, Well, the velocity of the star's spin
14:04
Speaker 1: is not what's conserved. It's the angular momentum, which is
14:07
Speaker 1: the product of the velocity and their radius. So things
14:11
Speaker 1: that are larger spin slower with the same angular momentum
14:15
Speaker 1: as things that are smaller than spin faster. You know
14:18
Speaker 1: this because if you're a figure skater and you pull
14:20
Speaker 1: your arms in, you spin faster. You have the same
14:24
Speaker 1: angular momentum. You're not pushing against anything to spin faster,
14:27
Speaker 1: but you spin faster because your radius is smaller. So
14:30
Speaker 1: to have the same angular momentum, you've got to go faster.
14:33
Speaker 1: That's why the star spins faster than the original gas cloud.
14:37
Speaker 1: And that's why the super compact, dense, little neutron star
14:41
Speaker 1: that has a huge chunk of the star's mass but
14:43
Speaker 1: is much much smaller. We're talking about something only kilometers
14:46
Speaker 1: in size, you know, maybe ten fifteen kilometers, has to
14:50
Speaker 1: be spinning really really fast to have the same angular
14:53
Speaker 1: momentum as most of the original star. So that's why
14:56
Speaker 1: these things are spinning so fast because they are so
14:59
Speaker 1: small as they are so dense. In addition, some of
15:02
Speaker 1: these things are highly magnetic. There's a magnetic field of
15:05
Speaker 1: these stars, just like every star and most planets have
15:08
Speaker 1: a magnetic field, and that's because the motion of charged
15:11
Speaker 1: particles inside it. A neutron star is mostly neutrons, but
15:14
Speaker 1: there are protons and there are electrons, and they are
15:17
Speaker 1: moving around sometimes on the surface, and the flux of
15:19
Speaker 1: the particles on the inside can create these magnetic fields.
15:23
Speaker 1: So you have this object that's spinning really really fast,
15:26
Speaker 1: and it has a magnetic field. In addition, it's generating
15:30
Speaker 1: a huge amount of radiation. The magnetic field of the
15:34
Speaker 1: thing is rotating, which generates an electric field which accelerates
15:37
Speaker 1: the protons and the electrons on the surface of the
15:39
Speaker 1: neutron star, and that creates a bunch of radiation because
15:43
Speaker 1: when you accelerate particles, they radiate photons. So you have
15:46
Speaker 1: this magnetic fields on this neutron star that's rotating and
15:50
Speaker 1: is generating an electric field which pushes the electrons and
15:53
Speaker 1: protons on the surface of the star, creating a lot
15:55
Speaker 1: of radiation. And that radiation doesn't go in every direction
15:58
Speaker 1: because there's a strong magnetic field. That radiation tends to
16:02
Speaker 1: go along the magnetic north and the magnetic south because
16:06
Speaker 1: magnetic fields are really good at bending the path of
16:10
Speaker 1: charged particles. The reason that we don't get a lot
16:12
Speaker 1: of radiation from space is because we have a magnetic
16:15
Speaker 1: field here on Earth, and when particles come from space,
16:19
Speaker 1: they are bent around those magnetic field lines. The magnetic
16:23
Speaker 1: field lines are sort of like the lines on a
16:24
Speaker 1: basketball right they run from north to south, and if
16:27
Speaker 1: a particle comes from space, it gets bent by those
16:30
Speaker 1: magnetic fields and goes out in another direction where sometimes
16:33
Speaker 1: they loop around those magnetic field lines all the way
16:36
Speaker 1: up to the north or the south pole, and then
16:38
Speaker 1: they can slip in between the magnetic field lines. And
16:41
Speaker 1: that's for example, why we have the Northern lights and
16:44
Speaker 1: the Southern lights, because magnetic fields guide charged particles in
16:49
Speaker 1: the same way. If you generate radiation on the surface
16:52
Speaker 1: of the planet, it's also bound by those magnetic fields,
16:56
Speaker 1: and so in this case, the magnetic fields are even
16:58
Speaker 1: much more powerful, and essentially all of the radiation from
17:01
Speaker 1: the neutron star gets guided towards the north or the
17:05
Speaker 1: south pole of the magnetic field. So you get these
17:08
Speaker 1: beams of radiation shooting off of this crazy neutron star.
17:12
Speaker 1: Right like it's not crazy enough, it's already super hot,
17:16
Speaker 1: super dense, super small, spinning, super fast, really magnetized, and
17:21
Speaker 1: now on top of that, it's shining these two crazy
17:24
Speaker 1: flashlights out into the universe, one from its magnetic north
17:28
Speaker 1: pole and the other from its magnetic south pole. And
17:30
Speaker 1: these beams don't come for free. They are very bright,
17:33
Speaker 1: they cost a lot of energy, and this energy comes
17:36
Speaker 1: from the spinning of the neutron star. Because that's what's
17:39
Speaker 1: generating this electric field, the rotation of the magnetic field,
17:43
Speaker 1: and eventually it's going to slow it down. Like these pulsars,
17:46
Speaker 1: they generate these beams and they last for maybe ten
17:49
Speaker 1: or a hundred million years, but they don't last for
17:52
Speaker 1: their whole lifetime. At some point the beams turned off
17:55
Speaker 1: because the neutron star has slowed down, it's not generating
17:58
Speaker 1: that radiation anymore. What that means is that for most
18:01
Speaker 1: of a lifetime, the pulsar is actually quiet. They don't
18:04
Speaker 1: emit these beams, and so something like nine percent of
18:08
Speaker 1: the pulsars out there aren't actually emitting any radiation anymore.
18:12
Speaker 1: They are quiet. The universe is filled with dead pulsars,
18:16
Speaker 1: pulsars that have gone quiet. So we've explained what a
18:19
Speaker 1: pulsar is and how it emits these beams. But why
18:22
Speaker 1: do we call it a pulsar. Are these beams themselves
18:26
Speaker 1: like pulsing? Do they turn on and off? The beams
18:29
Speaker 1: don't turn on and off. I mean, they last for
18:31
Speaker 1: millions of years and they eventually fade, but they don't
18:34
Speaker 1: like flicker on and off. The reason we call it
18:36
Speaker 1: a pulsar is because we only see those beams as
18:40
Speaker 1: they pass by the Earth, because the beam is shooting
18:43
Speaker 1: up and down along the magnetic field lines. But that's
18:46
Speaker 1: not necessarily the same as the axis that the pulsar
18:49
Speaker 1: is spinning around. So if it were, if the magnetic
18:53
Speaker 1: north and the magnetic south were the same as the
18:56
Speaker 1: north and south of the actual stars, so it was
18:59
Speaker 1: spinning around on the north pole, then it would always
19:01
Speaker 1: be shooting the beam north and the beam south. However,
19:05
Speaker 1: if instead the magnetic field is tilted so that it's
19:08
Speaker 1: like spinning along one axis, but it's beams are shooting
19:11
Speaker 1: off a little bit skewed, then when it spins around,
19:15
Speaker 1: the direction of that beam changes right. It's like if
19:18
Speaker 1: you're holding a flashlight and you point it straight up
19:21
Speaker 1: and then spin, the direction of the flashlight doesn't change.
19:24
Speaker 1: But if you hold a flashlight straight out and then
19:26
Speaker 1: spin right, then what happens. Then Your flashlight's gonna sweep
19:30
Speaker 1: around three sixty degrees every time you rotate. And what
19:34
Speaker 1: does somebody see if they're standing in front of you
19:37
Speaker 1: watching you spin, they see a flash. They see a
19:40
Speaker 1: pulse of light only when the flashlight is pointed in
19:43
Speaker 1: your direction. So it's this difference between the direction of
19:47
Speaker 1: the pulsars magnetic field and it's actual spin axis, which
19:52
Speaker 1: makes it a pulse. Are right, that's what makes it
19:54
Speaker 1: appear to pulse. They don't actually pulse. They're sending bright
19:58
Speaker 1: streams of light contain usually out into the universe until
20:01
Speaker 1: they fade. But we see them pulsing because that beam
20:05
Speaker 1: sweeps across Earth and that's what we see. So that's
20:08
Speaker 1: what a pulsar is. An introduction to these weird things
20:11
Speaker 1: in the universe. Next, we're gonna talk about why we
20:14
Speaker 1: suspect that they might exist and how they were actually found.
20:17
Speaker 1: But first let's take a quick break. All right, we're
20:33
Speaker 1: back and we're talking about the incredible story of the
20:35
Speaker 1: discovery of pulsars. And we reminded ourselves that pulsars are
20:39
Speaker 1: a tiny, very hot, very dense, very quickly spinning stars
20:44
Speaker 1: the left over heart of a supernova. They're shooting a
20:47
Speaker 1: beam of light out into the universe, and they are
20:49
Speaker 1: also spinning, and so that beam of light passes over
20:52
Speaker 1: the Earth and looks like pulsations. It looks like pulses
20:56
Speaker 1: from something out there in the universe. And before we
21:00
Speaker 1: discovered these things, we had a suspicion that they existed.
21:04
Speaker 1: People have been thinking about the life cycle of stars,
21:06
Speaker 1: and in nineteen thirty four people suggested that when you
21:10
Speaker 1: had a supernova, it might not all blow out into
21:13
Speaker 1: the universe, that you might get this small, dense core
21:17
Speaker 1: left over, and if so, it would have this really
21:20
Speaker 1: weird state of matter. These neutrons would form, that would
21:23
Speaker 1: be in a really dense state, this thing that's sort
21:25
Speaker 1: of like nuclear matter, the things in the heart of atoms,
21:29
Speaker 1: but now on the sides of like a mountain, something
21:31
Speaker 1: kilometers wide. Imagine that the nucleus of an atom, but
21:35
Speaker 1: kilometers wide. So this was a novelty, but nobody had
21:38
Speaker 1: ever seen one before. We didn't know if neutron stars
21:41
Speaker 1: existed in nineteen thirty four, and they would be difficult
21:43
Speaker 1: to detect because these things don't have fusion anymore. They
21:47
Speaker 1: don't glow the same way that very bright stars do.
21:50
Speaker 1: So to see neutron stars seemed like a puzzle. But
21:53
Speaker 1: then decades later people said, well, you know, they might
21:55
Speaker 1: have very strong magnetic fields, and if so, they might
21:59
Speaker 1: be rotating, and if so, then they might be pulsing.
22:03
Speaker 1: And so this idea sort of came into existence in
22:07
Speaker 1: the sixties idea the pulsars as weird, spinning, magnetized, beaming
22:13
Speaker 1: light neutron stars might be out there. But you have
22:16
Speaker 1: to remember that there are lots of crazy ideas for
22:19
Speaker 1: what might be out there. The astronomy literature is filled
22:22
Speaker 1: with people speculating maybe these things exist, maybe boson stars exist,
22:26
Speaker 1: maybe these other things exist. Now, with a hindsight of history,
22:29
Speaker 1: we can go back and trace the development of this
22:32
Speaker 1: one thread of an idea that turned out to describe
22:34
Speaker 1: something in the actual universe. But don't forget it was
22:37
Speaker 1: buried at the time in a forest of other crazy,
22:41
Speaker 1: wrong ideas about what might be out there in the universe.
22:44
Speaker 1: You know, pulsars exist, and if you took a time
22:47
Speaker 1: machine back to the sixties, you might say, I know
22:49
Speaker 1: these things exist, and I know how to find them.
22:51
Speaker 1: It's not actually that hard. But without the hindsight of
22:53
Speaker 1: that history, of course, it's hard to pick the wheat
22:56
Speaker 1: from the chaff. So let's get to the story of
22:58
Speaker 1: how they were actually discovered. They were found by a
23:00
Speaker 1: graduate student at the University of Cambridge, a woman named
23:04
Speaker 1: Joscelynn Bell, and she was not looking for pulsars. In fact,
23:07
Speaker 1: she wasn't looking for stars at all. She was trying
23:11
Speaker 1: to study quasars. Quasars are at the heart of really
23:15
Speaker 1: large galaxies. They are the accretion disks around black holes,
23:20
Speaker 1: the stuff that has not yet fallen into the black
23:22
Speaker 1: hole but is swirling around. And because of the tidal
23:25
Speaker 1: forces and the incredible gravity, these things get really hot
23:29
Speaker 1: and they radio a lot of light. And we had
23:31
Speaker 1: seen these things, and we knew that they were very,
23:33
Speaker 1: very far away, because these quasars have existed for a
23:36
Speaker 1: long time. They were formed in the very early universe,
23:39
Speaker 1: like a billion years after the Big Bang, but they're
23:42
Speaker 1: still super duper bright. And for a long time they
23:44
Speaker 1: were big mystery because people thought, well, what could it
23:47
Speaker 1: be that is so incredibly bright and so far away,
23:52
Speaker 1: so at its source, it's got to be like mind
23:54
Speaker 1: bogglingly bright. What could that even be? People thought for
23:57
Speaker 1: a long time, this was a mistake. It's not really
24:00
Speaker 1: a thing. We must be misunderstanding how these things work.
24:04
Speaker 1: And Jocelyn Bell was trying to understand these quasars. She
24:07
Speaker 1: was trying to understand how these quasars twinkle, how they scintillate.
24:11
Speaker 1: You know that when you look at a star in
24:13
Speaker 1: the sky, you see a twinkling, and that's mostly because
24:16
Speaker 1: the stuff between you and the star is interfering with
24:20
Speaker 1: the star light. That's why planets, for example, don't twinkle,
24:23
Speaker 1: but stars do because the light from the star has
24:26
Speaker 1: to go really really far. So quasars kind of twinkle
24:29
Speaker 1: as well. They do this thing called scintillation, and it's
24:33
Speaker 1: due to fluctuations in the densities of particles in the
24:36
Speaker 1: solar wind. So the way we see quasars is not
24:39
Speaker 1: by looking usually at visible light, but by looking at
24:42
Speaker 1: radio waves. These things come from really really far away
24:44
Speaker 1: and with their best seen in the radio spectrum. And
24:47
Speaker 1: in the radio spectrum, an obstacle is the solar wind.
24:51
Speaker 1: Remember that the Sun doesn't just shoot out photons. It
24:54
Speaker 1: also shoots out a bunch of charge particles, protons and
24:57
Speaker 1: electrons and other crazy stuff, and this is what we
25:00
Speaker 1: call the solar wind. And when a radio photon enters
25:04
Speaker 1: our solar system from somewhere really really far away, it
25:07
Speaker 1: hits this barrage of radiation coming from the Sun and
25:11
Speaker 1: interact with it. It's radio signal made of light and
25:14
Speaker 1: electromagnetic radiation. Essentially, photons comes from these quasars billions of
25:19
Speaker 1: years away, they sometimes get deflected or interfered with by
25:23
Speaker 1: these particles in the solar wind, and so that's what
25:26
Speaker 1: makes these quasars scintillate. So she wanted to study this
25:29
Speaker 1: because she wanted to understand quasars. People at that time
25:32
Speaker 1: didn't know that black holes were real, so they didn't
25:35
Speaker 1: know what was powering these quasars. What could possibly be
25:38
Speaker 1: generating so much radiation from so far away. So she
25:41
Speaker 1: built a radio telescope. And a radio telescope is just
25:45
Speaker 1: a bunch of antennas. But the thing about radio waves
25:48
Speaker 1: is that their wavelength is very, very long. They could
25:51
Speaker 1: be meters or hundreds of meters. So to capture a
25:54
Speaker 1: radio photon, you need a big antenna, you need something large.
25:59
Speaker 1: So she builds some thing which was four and a
26:01
Speaker 1: half acres, Like this thing is big. She spent two years,
26:05
Speaker 1: and for her, doing astronomy meant every day pounding fence
26:09
Speaker 1: posts into the ground and stringing wire among them. Imagine
26:13
Speaker 1: one of those old fashioned TV antennas. It was like
26:15
Speaker 1: a grid of metal that could capture a signal. That's
26:18
Speaker 1: essentially what she built. And she strung hundred and twenty
26:22
Speaker 1: miles of wire over two years to build her radio
26:25
Speaker 1: telescope to capture the signal from these quasars to look
26:28
Speaker 1: at them scintillating. She wanted to see the fluctuations in
26:32
Speaker 1: these signals. And that's really key because what she did
26:35
Speaker 1: is get these radio signals and look at them and
26:37
Speaker 1: develop her own personal sense for what this data should
26:41
Speaker 1: look like. She was looking for characteristic wiggles changes in
26:45
Speaker 1: this data as they studied the pulsar. And this is
26:48
Speaker 1: back in the day before they had computers and before
26:51
Speaker 1: people could just like you know, dump the data onto
26:54
Speaker 1: the screen and analyze it bump bump bump. Her data
26:57
Speaker 1: came out directly onto a printer like her radio telescope
27:01
Speaker 1: captured this turned it into an electrical signal which was
27:03
Speaker 1: directly sent to a printer which dumped it onto paper.
27:07
Speaker 1: So her output from her telescope was stored on a
27:10
Speaker 1: hundred feet per day of printer paper, which is like
27:14
Speaker 1: came out steadily and she would stand there and look
27:17
Speaker 1: at it. She would get to know it. She was
27:18
Speaker 1: like a natural neural network where she learned if I'm
27:22
Speaker 1: looking over here that I'm going to see this thing
27:24
Speaker 1: which we're pointing at the sun, and I'm gonna see
27:26
Speaker 1: this kind of radio waves. And this isn't the kind
27:28
Speaker 1: of thing that she could easily point right. This thing
27:30
Speaker 1: is just something you build in the ground. But the
27:33
Speaker 1: earth turns, and as the Earth turns, this thing is
27:36
Speaker 1: essentially pointed in a new direction. She herself is like
27:39
Speaker 1: sweeping her instrument across the sky, examining different parts of
27:43
Speaker 1: the universe. And you can get some directional information from
27:47
Speaker 1: a radio antenna based on like when the signal arrives,
27:50
Speaker 1: does it arrive first on the eastern part of the
27:53
Speaker 1: antenna or first on the western part of the antenna.
27:55
Speaker 1: But it's not great at telling where something is coming
27:58
Speaker 1: from exactly. So she came really good analyzing these signals,
28:01
Speaker 1: and then one day, November nineteen sixty seven, she saw
28:06
Speaker 1: the signal that she did not understand, something she had
28:09
Speaker 1: never seen before. What she saw were pulses separated by
28:13
Speaker 1: one and the third seconds. So it was like whoop,
28:17
Speaker 1: poop poop, and she would get these pulses of radio waves,
28:22
Speaker 1: and the regularity of it, the exact distance between the
28:25
Speaker 1: pulses is what made it seem really weird. And at
28:28
Speaker 1: first she thought, oh, this must be a signal from
28:30
Speaker 1: something here. On Earth, because, of course, there are lots
28:34
Speaker 1: of sources of radio waves here on Earth. Almost everything
28:38
Speaker 1: we do with our electronics generates radio noise. Every time
28:42
Speaker 1: you turn on your television, certainly every time you use
28:44
Speaker 1: your cell phone, and of course there are radio transmitters
28:47
Speaker 1: all over the planet. And so first she had to
28:50
Speaker 1: rule out various sources of human interference, like other radio astronomers,
28:55
Speaker 1: people sending pulses off the Moon to measure the distance
28:58
Speaker 1: to the Moon, television signals, beeps from orbiting satellites, even
29:02
Speaker 1: like you know, possible effects from large corrugated metal buildings
29:06
Speaker 1: near the telescopes. She went through this whole list, and
29:09
Speaker 1: you gotta do that when you see something weird in
29:11
Speaker 1: your data, you gotta first look for the boring explanation like, oh, well,
29:15
Speaker 1: maybe I'm just measuring what happens when somebody turns on
29:18
Speaker 1: the microwave in the break room or something like that.
29:20
Speaker 1: You don't go straight to I've discovered something new in
29:23
Speaker 1: the universe. So she very carefully went through all these
29:26
Speaker 1: different explanations and eventually even borrowed somebody else's radio telescope
29:30
Speaker 1: to confirm her observations. She wanted to make sure it
29:33
Speaker 1: wasn't just like some weird blip in her telescope, so
29:36
Speaker 1: she knew it wasn't just her telescope. She ruled out
29:39
Speaker 1: all sources of human earth bound interference, and she saw
29:43
Speaker 1: that it tracted with a particular location in the sky.
29:46
Speaker 1: And that's a great clue that tells you that it's
29:48
Speaker 1: not from Earth, because if it's from Earth, then it
29:51
Speaker 1: doesn't matter which direction the Earth is pointed. If it's
29:54
Speaker 1: not from Earth, then you will only see it when
29:57
Speaker 1: the Earth is pointed in a certain direction, only when
29:59
Speaker 1: the mess it itself sweeped across your radio telescope. So
30:02
Speaker 1: where did their minds go? The strange regularity of it,
30:06
Speaker 1: the fact that it came like every one and a
30:08
Speaker 1: third seconds, made them think not of some new after
30:13
Speaker 1: physical object, because nature is not often that precise, right.
30:17
Speaker 1: Nature is messy. When you go out into the world.
30:20
Speaker 1: You don't see like rocks that are exactly square. You
30:23
Speaker 1: don't see like ten rocks exactly the same size. You
30:27
Speaker 1: don't see the sort of regular patterns. I mean, sometimes
30:29
Speaker 1: you do in crystals and other places, but nature is
30:33
Speaker 1: more often messy than precise and regular. So their media
30:37
Speaker 1: thought was like, wow, maybe this is alien intelligence, you know,
30:42
Speaker 1: she says, quote, we did not really believe that we
30:45
Speaker 1: had picked up signals from another civilization, but obviously the
30:48
Speaker 1: idea had crossed our minds, and we had no proof
30:51
Speaker 1: that it was an entirely natural radio emission. It is
30:54
Speaker 1: an interesting problem if one thinks one may have detected
30:58
Speaker 1: life elsewhere in the universe, how does one announced the
31:00
Speaker 1: results responsibly? So they really didn't know what they had.
31:04
Speaker 1: They were wondering, is this something weird and new? Are
31:07
Speaker 1: these aliens? Or is this some natural source of radio
31:10
Speaker 1: emission that's weirdly regular. So in their internal notes they
31:14
Speaker 1: called this thing l g M, one for Little Green Men.
31:18
Speaker 1: And so here you can see the process of discovery
31:21
Speaker 1: in motion, like there existed in the literature, the speculation
31:25
Speaker 1: that these things might be out there, that spinning neutron
31:29
Speaker 1: stars might generate pulses, and here they are discovering pulses
31:33
Speaker 1: in the radio spectrum, essentially exactly what was predicted. But
31:36
Speaker 1: they couldn't put it together because, as we mentioned before,
31:40
Speaker 1: there are lots of predictions out there in the literature,
31:42
Speaker 1: only in hindsights you know exactly who to listen to.
31:46
Speaker 1: It's like picking one of Nostradamis's predictions. Right, most of
31:50
Speaker 1: them are nonsense, and if you look back through all
31:52
Speaker 1: of them, you can always find one that seems to
31:54
Speaker 1: make sense. So what they did was they kept looking,
31:58
Speaker 1: and pretty soon they found in other pulsars somewhere else
32:01
Speaker 1: in the sky. And I told him it's probably not aliens,
32:05
Speaker 1: because their signals coming from two very different, very distant
32:09
Speaker 1: locations in the universe, so probably it's a natural source.
32:13
Speaker 1: And then by Christmas of nineteen sixty seven, right just
32:16
Speaker 1: like weeks after the first discovery, they had found four
32:21
Speaker 1: of these things, so four pulsars, and early the next
32:24
Speaker 1: year they publicized their results and they wrote a nice
32:27
Speaker 1: paper and this was a huge discovery, and then everybody
32:31
Speaker 1: with the radio telescope started looking at these things, like, wow,
32:34
Speaker 1: oh my gosh, these things are out there. The incredible
32:36
Speaker 1: thing is that once you know to look for them,
32:39
Speaker 1: they're not that hard to find. Pulsars are pretty bright.
32:42
Speaker 1: Radio telescopes were kind of new. Optical astronomy was dominant
32:46
Speaker 1: at the time, but there were a lot of radio
32:48
Speaker 1: telescopes out there, and by the end of nineteen dozens
32:52
Speaker 1: of these things had been found, and it was another scientist,
32:55
Speaker 1: a guy named Thomas Gold, that put the story together,
32:59
Speaker 1: who said, Ah, these pulsars are the rotating neutron stars
33:03
Speaker 1: that we've been thinking about. What these folks have seen
33:06
Speaker 1: out there in the universe is exactly what we thought
33:10
Speaker 1: might happen in some circumstances at the end of a supernova.
33:13
Speaker 1: So that was a really incredible moment to say, like, Wow,
33:16
Speaker 1: these things, these crazy, weird little blobs that we've predicted
33:20
Speaker 1: might be there as like the tombstone on the end
33:23
Speaker 1: of a supernova, actually are out there and they do
33:26
Speaker 1: this weird thing that lets us find them. I think
33:29
Speaker 1: the discovery that really put a pin in it was
33:32
Speaker 1: the discovery of a pulsar at the heart of the
33:34
Speaker 1: crab Nebula. Crab Nebula is a huge cloud of gas
33:37
Speaker 1: and dust. It's the remnant of an old supernova star
33:41
Speaker 1: that blew up and spread most of its stuff out
33:44
Speaker 1: there in the universe. So then when we looked with
33:46
Speaker 1: the radio and we saw that at the heart of
33:48
Speaker 1: crab Nebula was a pulsar, we thought, that's what this is,
33:52
Speaker 1: and that completes the story that tells us that at
33:55
Speaker 1: the heart of many nebula there may be these neutron stars.
33:58
Speaker 1: Not all of them become all stars, but pulsars tell
34:01
Speaker 1: us that the neutron stars are there, that this supernova
34:05
Speaker 1: remnant has this hard little nub at the core of it.
34:08
Speaker 1: But remember that we're using radio waves so far to
34:11
Speaker 1: find these pulsars, and radio waves are not very good
34:14
Speaker 1: at telling the direction of a signal. It's not like
34:17
Speaker 1: an optical telescope, where the photons of very short frequencies nanometers,
34:22
Speaker 1: and you can capture them with a telescope point in
34:24
Speaker 1: one specific direction and you can tell exactly where on
34:26
Speaker 1: the lens it hit. These things are captured by very
34:29
Speaker 1: large antenna and it's hard to tell what direction they're
34:32
Speaker 1: coming from. So while we say we saw a pulsar
34:34
Speaker 1: in the direction of the crab nebula, it's not like
34:37
Speaker 1: we could really pin down its location exactly. So there's
34:40
Speaker 1: a second part of this discovery story, a part that
34:43
Speaker 1: was caught on audio tape that I want to share
34:45
Speaker 1: with you. But first let's take another break, all right.
35:01
Speaker 1: So we are in the late sixties and the field
35:04
Speaker 1: of astronomy was very excited because people had been discovering pulsars.
35:07
Speaker 1: But these pulsars had been seen in the radio frequency,
35:11
Speaker 1: which means they were hard to pin down exactly where
35:13
Speaker 1: they were, and people were wondering, are their pulsars out
35:16
Speaker 1: there where? The beams of light that they are shooting
35:18
Speaker 1: are visible light, not just a radio noise, but like
35:22
Speaker 1: actual visible beams that our eyes and our telescopes could see. Well,
35:26
Speaker 1: most pulsars, we think are brightest in the radio or
35:29
Speaker 1: in the X ray. But the idea was that there
35:31
Speaker 1: might be some optical pulsars. So there are a couple
35:34
Speaker 1: of theorists named John Cook and Mike Disney, and these
35:37
Speaker 1: were not experienced astronomers, but they were curious about whether
35:40
Speaker 1: or not you could see one of these pulsars in
35:43
Speaker 1: the optical So they decided, hey, let's give this thing
35:45
Speaker 1: a shot. Let's sign up for some telescope time pointed
35:48
Speaker 1: at one of these pulsars and see if we can
35:50
Speaker 1: see any flashes. So these guys not experimentalists, right, they
35:54
Speaker 1: didn't really know how to use a telescope. This their
35:56
Speaker 1: first time using like real serious astronomical scientific equipment, and
36:01
Speaker 1: they went down to kid Peak near Tucson, and they
36:03
Speaker 1: signed up for a couple of days of observing time,
36:05
Speaker 1: and what they had going for them was that they
36:07
Speaker 1: were going to point this thing at the crab nebula,
36:10
Speaker 1: and they already knew the frequency of the pulsar, so
36:13
Speaker 1: they knew like what frequency of light flashes to look for.
36:16
Speaker 1: So what they did is they pointed this telescope at
36:19
Speaker 1: the crab nebula and then they looked at the light
36:21
Speaker 1: that came in. But remember that this again was before
36:24
Speaker 1: like dedicated computers where you could rapidly inflexibly analyze your data.
36:28
Speaker 1: But they needed was some sort of like dedicated electronics
36:31
Speaker 1: that could turn their flashes of light into blips that
36:34
Speaker 1: they could study. So there was a guy there who
36:36
Speaker 1: was really good electronics, and he happened to have exactly
36:39
Speaker 1: what they needed. So they could plug their telescope into
36:42
Speaker 1: this thing and it would analyze the frequency, like the
36:44
Speaker 1: time between blips and make a little plot from them
36:47
Speaker 1: on a very small screen. So it's sort of like
36:50
Speaker 1: a dedicated computer exactly to do this. They happen to
36:53
Speaker 1: stumble across this guy who had exactly this equipment to
36:56
Speaker 1: do what they needed. So they went out there for
36:58
Speaker 1: their first day. They were very ided, thinking, Wow, maybe
37:01
Speaker 1: we're going to discover something, and they turned it on
37:03
Speaker 1: and they saw nothing. And but they didn't know at
37:05
Speaker 1: the time was that they had made a mistake in
37:07
Speaker 1: their calculations and they had like tweaked the knobs on
37:10
Speaker 1: this thing wrong, so they shouldn't have seen anything because
37:12
Speaker 1: they were looking at the wrong sort of frequency spectrum.
37:15
Speaker 1: The next two nights that they had were both cloudy,
37:18
Speaker 1: and so they lost all of their observing time and
37:21
Speaker 1: they never would have seen this thing that hadn't been
37:23
Speaker 1: for somebody else's bad luck. The person with the telescope
37:26
Speaker 1: next after them, his wife got sick, so he decided
37:29
Speaker 1: he was going to stay home and take care of her,
37:31
Speaker 1: and he gave them his telescope time, so they got
37:35
Speaker 1: an extra bonus of a couple of days of observing
37:37
Speaker 1: time that they didn't expect to get. And the clouds
37:40
Speaker 1: cleared and they had a beautiful night, and they set
37:43
Speaker 1: their thing correctly. And they also had a tape recorder
37:46
Speaker 1: running which recorded their conversation as well as the data
37:50
Speaker 1: coming from the telescope. So this little box not only
37:54
Speaker 1: makes a lit depiction on their screen that shows from
37:56
Speaker 1: the frequency, it also made a little tick for every blip,
37:59
Speaker 1: so you'll hear those ticks. On this tape, you'll also
38:02
Speaker 1: hear them reacting in real time to the discovery they're making. Hey, ah,
38:18
Speaker 1: I was supposed heping ca. So you hear them saying
38:27
Speaker 1: that it's bang in the middle of the period. Remember
38:29
Speaker 1: that they knew what to look for. They knew the
38:32
Speaker 1: period of this pulsar. They knew their frequency of which
38:35
Speaker 1: it should flash, so they were looking for a repeated
38:38
Speaker 1: pattern of flashes with just the right period. They had
38:41
Speaker 1: zoomed in on exactly what they were hoping to see,
38:43
Speaker 1: but of course they never knew whether the universe would
38:46
Speaker 1: show it to them or whether it wouldn't. Hear the
38:48
Speaker 1: rest of their recording really looks something mhm too, Oh yeah,
39:12
Speaker 1: it look so you can hear literally the excitement in
39:17
Speaker 1: their voice. One of them is astonished, look at that
39:20
Speaker 1: bleeding pulse, and the other one is like, I can't
39:22
Speaker 1: believe this is happening right now, it's getting bigger and bigger.
39:25
Speaker 1: You can see them discovering it. You can hear in
39:28
Speaker 1: their voices that they're realizing that they've caught it, that
39:32
Speaker 1: they've seen this pulsar flickering invisible light, that they've pointed
39:36
Speaker 1: this telescope at this weird, far away object and they've
39:39
Speaker 1: caught it doing its thing. So that's a super fun
39:42
Speaker 1: little follow up discovery. They published that paper, and this
39:45
Speaker 1: must have been a really fun moment for these guys,
39:48
Speaker 1: because again, this is the first time they ever went
39:50
Speaker 1: to a telescope. This is the first time they ever
39:52
Speaker 1: like looked out into the universe. Most of their science
39:55
Speaker 1: was done with pencil and paper and just sort of
39:57
Speaker 1: thinking about what might be out there. And so I'm
39:59
Speaker 1: glad they got to go out there and actually experienced
40:02
Speaker 1: this moment of discovery. And it also really helped us
40:05
Speaker 1: understand what these pulsars were because with the optical telescope
40:08
Speaker 1: with a visible light, you could really pin down exactly
40:11
Speaker 1: where this thing was, and we knew then that really
40:14
Speaker 1: was at the heart of the crab nebula and it
40:16
Speaker 1: really was a pulsar. So very exciting discovery and very
40:20
Speaker 1: quickly appreciated, of course by the scientific community. And in
40:24
Speaker 1: nineteen seventy four, just a few years later, Jocelyn Bell's
40:28
Speaker 1: advisor is the first astronomer to ever win the Nobel
40:32
Speaker 1: Prize in physics. That's right, her advisor won the Nobel
40:36
Speaker 1: Prize now, of course he was involved, right, You know,
40:39
Speaker 1: a graduate student never works alone. He gave lots of guidance,
40:42
Speaker 1: lots of ideas, probably provided the funding. But it's clear
40:46
Speaker 1: that she's the one who made the discovery. She built
40:48
Speaker 1: that thing, She was out there day to day, she
40:50
Speaker 1: saw it in the data. And there's a lot of
40:53
Speaker 1: discussion these days about why she was left out of it.
40:56
Speaker 1: It's because she was a student. While there are lots
40:59
Speaker 1: of other cases when a student participated in discovery and
41:02
Speaker 1: was included in the Nobel Prize. Discovery. Wholes and Taylor,
41:06
Speaker 1: for example, was a graduate student advisor pair that discovered
41:10
Speaker 1: binary pulsars just a couple of decades later, and they
41:13
Speaker 1: were both given the Nobel Prize even though one of
41:16
Speaker 1: them was a graduate student. Of course, there's the question
41:19
Speaker 1: of whether or not it was sexism. In the history
41:21
Speaker 1: of the Nobel Prizes, very few women have been given
41:24
Speaker 1: the prize and many have been qualified, so it seems
41:27
Speaker 1: like an obvious case of injustice. Burnell herself is very
41:30
Speaker 1: gracious about it. She recently was given the Breakthrough Prize
41:33
Speaker 1: and Fundamental Physics, which comes with millions of dollars, which
41:36
Speaker 1: she then donated to advancing the cause of having more
41:39
Speaker 1: women in physics. But of course she didn't know that.
41:41
Speaker 1: The journalists didn't ask her science questions. They tended to
41:44
Speaker 1: ask her questions about like how many boyfriends she had.
41:47
Speaker 1: But this kicked off a whole really exciting era of astronomy,
41:50
Speaker 1: because every time you discover something new out there in
41:53
Speaker 1: the universe, it gives you another handle, it gives you
41:55
Speaker 1: a way to learn things. It reveals new things about
41:58
Speaker 1: the universe that you didn't know before. And just a
42:01
Speaker 1: few years after that, we discovered things like millisecond pulsars.
42:05
Speaker 1: These are things that's been around so fast that we
42:08
Speaker 1: see a pulse from them, not every second, but every
42:11
Speaker 1: mill a second. So these stars are spending a thousand
42:14
Speaker 1: times faster than the original pulsar spun right every one
42:19
Speaker 1: point six seconds. This incredible, enormous dense object spins around.
42:24
Speaker 1: These things are moving really really fast, spinning like tens
42:27
Speaker 1: of thousands of times per minute. The fastest pulsar we've
42:30
Speaker 1: ever seen, we talked about on our episode about the
42:32
Speaker 1: fastest spinning things in the universe is sixteen kilometers in
42:36
Speaker 1: radius and the surface of it is moving at a
42:39
Speaker 1: quarter of the speed of light. That's how fastest thing spenning.
42:43
Speaker 1: I won't tell you the name because it's a ridiculous
42:45
Speaker 1: series of letters and numbers, but it's spinning at seven
42:49
Speaker 1: hundred and sixteen hurts. That means every second, this entire
42:53
Speaker 1: mountain sized blob of nuclear matter spins seven hundred times
42:58
Speaker 1: around and it's eighteen thousand years from Earth in the
43:01
Speaker 1: constellation Sagittarius and is sending us pulses very very regularly.
43:05
Speaker 1: The other amazing thing about these pulsars is that they
43:08
Speaker 1: are precisely timed. It's not just like roughly seven sixteen hurts,
43:13
Speaker 1: it's like exactly and every second it's the same. These
43:17
Speaker 1: things do not change. It's astounding when you see something
43:20
Speaker 1: in nature that is so regular. These things have the
43:23
Speaker 1: regularity the consistency that rivals that of atomic clocks. You
43:27
Speaker 1: can use them as a probe of the rest of
43:29
Speaker 1: the universe because they send out these very very regular pulses.
43:33
Speaker 1: For example, a pulsar was actually the first way that
43:35
Speaker 1: we had evidence of a planet around another star. Because
43:39
Speaker 1: when a pulsar has a planet around it, that planet
43:42
Speaker 1: is tugging on it gravitationally as it orbits, and it
43:45
Speaker 1: means the pulsar moves towards us sometimes and away from
43:48
Speaker 1: us other times, and this velocity changes the frequency of
43:51
Speaker 1: the pulse are by a very small amount. Because the
43:54
Speaker 1: pulsars are so precise and so accurate, we can detect that.
43:57
Speaker 1: And if it's a regular shift in the free and
44:00
Speaker 1: see the pulsar, you can deduce the presence of a
44:02
Speaker 1: planet around the pulsar. How do you have a planet
44:05
Speaker 1: around a pulsar? It's crazy, right, because a pulsar comes
44:09
Speaker 1: from when the Sun was destroyed, So probably some chunk
44:12
Speaker 1: of that nebula has now reformed, some planet which is
44:16
Speaker 1: orbiting the pulsar, or some planet happened to amazingly survive
44:20
Speaker 1: of the supernova explosion that created the pulsar. And you
44:23
Speaker 1: can also use them to navigate around the galaxy. Because
44:27
Speaker 1: every pulsar is different, each one has like its own
44:30
Speaker 1: unique fingerprint. You can tell which one you are listening to,
44:34
Speaker 1: and you can also tell where you are in its cycle.
44:37
Speaker 1: Is that pointing towards me or away from me? And
44:39
Speaker 1: if you look at multiple of these things, you can
44:41
Speaker 1: tell like how many cycles you are away from multiple pulsars.
44:45
Speaker 1: Lets you triangulate exactly where you are in the galaxy.
44:48
Speaker 1: But a whole fund podcast episode about navigating deep space
44:51
Speaker 1: using pulsars, and people have crazy plans for how to
44:55
Speaker 1: use pulsars. For example, they want to use them as
44:58
Speaker 1: gravitational wave detector. Remember that we have seen ripples in
45:02
Speaker 1: the fabric of space by seeing how these gravitational waves
45:06
Speaker 1: stretch and shrink the distances here on Earth. Well, there
45:10
Speaker 1: might be really massive ones that we can measure their
45:12
Speaker 1: stretching and shrinking the entire galaxy, and those would affect
45:16
Speaker 1: the pulses from these pulsars. And so a bunch of
45:19
Speaker 1: really precise clocks sending us dings from all around the
45:23
Speaker 1: galaxy can be used to detect gravitational waves. So there's
45:27
Speaker 1: a bright future for the signs of pulsars, as well
45:29
Speaker 1: as a fascinating story that tells us exactly how they
45:32
Speaker 1: were discovered. So thanks for coming along with me on
45:35
Speaker 1: this ride of historical exploration to understand how we actually
45:39
Speaker 1: make these breakthroughs, how people actually win Nobel prizes or
45:43
Speaker 1: are sometimes cut out of it by their advisor, but
45:45
Speaker 1: how scientific knowledge is very slowly, very painstakingly, but very
45:49
Speaker 1: excitingly accumulated. Thanks for joining us tune in next time.
46:01
Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain
46:04
Speaker 1: the Universe is a production of I Heart Radio. For
46:07
Speaker 1: more podcast for my heart Radio, visit the I heart
46:10
Speaker 1: Radio app, Apple Podcasts, or wherever you listen to your
46:13
Speaker 1: favorite shows. Yeah.