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