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

Episode Date: July 22, 2021

Daniel recounts the story of how pulsars were discovered and what they tell us about the death of stars. Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

This is an I-Heart podcast. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, everything changed. There's been a bombing at the TWA terminal. Just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, terrorism. Listen to the new season of Law and Order Criminal Justice System

On the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, luckily, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend's been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now he's insisting we get to know each other, but I just want or gone.

Now, hold up. Isn't that against school policy? That seems inappropriate. Maybe find out how it ends by listening to the OK Storytime podcast and the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. I'm Dr. Scott Barry Kaufman, host of the Psychology Podcast. Here's a clip from an upcoming conversation about how to be a better you. When you think about emotion regulation, you're not going to choose an adaptive strategy,

which is more effortful to use. unless you think there's a good outcome. Avoidance is easier. Ignoring is easier. Denials is easier. Complex problem solving. Takes effort. Listen to the psychology podcast on the Iheart radio app,

Apple Podcasts, or wherever you get your podcasts. Hi, it's Honey German, and I'm back with season two of my podcast. Grazias, come again. We got you when it comes to the latest in music and entertainment with interviews with some of your favorite Latin artists and celebrities. You didn't have to audition? No, I didn't audition. I haven't auditioned in like over 25 years.

Oh, wow. That's a real G-talk right there. Oh, yeah. We'll talk about all that's viral and trending with a little bit of cheesement and a whole lot of laughs. And of course, the great bevras you've come to expect. Listen to the new season of Dresses Come Again on the IHeartRadio app, Apple Podcast,

or wherever you get your podcast. What is the moment of scientific discovery actually like? I mean, in the movies, it always seems so crisp. Scientists find something in her data or an experiment suddenly and dramatically works. We go from ignorance to knowledge in a moment, from failure to success. That kind of drama works for the movie screen, but how does it happen in real life? Is it a slow and steady march rather than a sudden leaf? or are there actually real moments of insight where all of a sudden light penetrates the darkness

and the scientist learns something new about the universe that no human has ever known before? Hi, I'm Daniel. I'm a particle physicist, and I've been doing particle physics experiments for decades, but never discovered a new particle. And welcome to the podcast, Daniel and Jorge Explain the universe, in which we examine. examine everything about the universe, from its origins to its ends, from its biggest things to its smallest things, from all of its mysteries and all of our discoveries. Our goal in this podcast is to open our minds to all of the craziest, biggest, deepest, most important questions, the one that frame the context of being human, the ones that tell us what it means to be in this universe and how this universe works. We tackle all those questions and we go right to the

forefront of scientific knowledge. We take you right to the edge where scientists are currently working and we explain all of it to you in a way that we hope makes sense and maybe even occasionally makes you laugh. My co-host Jorge Cham, the creator of PhD comics can't be here today. So I'm going to share with you one of my favorite stories of scientific discovery. And I mentioned earlier on that I have never discovered a new particle. That's not a hundred percent true. My career in particle physics spans from the mid-1990s till today, and in the mid-1990s was the discovery of the top quark. Jorge and I did a really fun episode about that whole amazing, hilarious, dramatic story, but I sort of joined the field right when that had already happened. So I wasn't around

when the top quark was discovered. I didn't get to participate in that moment of discovery. I was, however, part of the team that discovered the Higgs boson. But you have to understand, this was a really big group of people, thousands of thousands of people who all contributed little bits here and there. And there wasn't really a dramatic moment when we said, aha, the Higgs is there. It slowly emerged out of the data, sort of the way a treasure chest might be revealed in the sand of a beach as a tide pulls out, inch by inch showing you more and more of it. That was sort of the way the Higgs boson discovery went. We saw a little peak. We thought it might be it. It got bigger and bigger and bigger and there was never really a moment other than the official announcement when we could say

now we have discovered the Higgs. But that sort of was a bureaucratic choice, an artificial choice. There was no single aha moment. And part of that is because we knew what we were looking for. We suspected the Higgs was there. We knew how to find it. We knew how to look for it. We knew what to expect. And so when we saw it, it was just sort of this slow creeping realization that we had found what we had been hunting. But that doesn't mean it's always like that. There are moments of discovery in science. Usually they happen when we're more surprised. When we see something we didn't expect, when you go looking for one thing and you find something else. Moments, for example, like the discovery of the cosmic microwave background that we talked about a few

episodes ago. Today we're going to tell the story of one of those moments. When discovery came quickly, when someone went looking for one thing and found something else, something alarming and astonishing, a moment of insight about the universe. Actually, we're going to tell a story of two of those moments because this discovery has multiple parts. And for one of those parts, we happen to have real historical audio of those scientists realizing their discovery in real time as it happens. So you'll get to hear what it actually sounds like when scientists are astonished, when they make a real life discovery. So that's super fun. And for me, it's always really interesting to try to understand what it was like to make that discovery.

You know, it's easy in hindsight to say, oh, these things exist. Here's how you look for them. They went and did it, bada boom, bada bing, done. But you have to go back to what it was like before we knew it was there to put yourself back in that mental position of ignorance, not knowing whether something is out there, not understanding whether you live in the universe where it's real or where it's just an idea, not knowing which direction human knowledge and science will take. Science is so easy in hindsight and so difficult in foresight. When you stand in the forefront of human ignorance, you don't know necessarily which way to go.

So it's really valuable to revisit these moments when we took a step forward, when we went from ignorance to knowledge and understand what was required, how it happened, and the bravery it took to make that claim to say, I have found something new. I now know something about the universe that no human ever knew before. And so today we're going to be telling one of my favorite stories of discovery,

one about a really weird kind of star, a very fast, very dense, very bizarre kind of star that we've talked about on the podcast before. And so today's episode, we'll be answering the question. How were pulsars discovered? And so as usual, before we dig into the topic and tell you the story today, I wanted to know how much people already knew about this sort of famous story.

So I went out and solicited volunteers from the internet to tell us what they knew about various questions in science, this being one of them. So thank you to all those who participated and give us their speculation without the opportunity to look into any reference material whatsoever on the honor system. Of course, if you'd like to participate and hear your voice on the podcast in the future, please don't be shy, I promise you, it's fun. Send me an email to questions at danielandhorpe.com. But in the meantime, think to yourself, do you know the story of how pulsars were discovered? Here's what people had to say.

I am 80% sure that pulsars were discovered when they stuck a stethoscope onto the Hubble Space Telescope. I'm guessing pulsars were discovered by scientists who observed these stars that were kind of flashing, so dimming and brightening in these regular pulses, hence the name pulsar. I realize I just described what a pulsar is and not how they were discovered. So sorry about that. For what a pulsar is, I would say it was discovered as a rapid. blinking source of light in the sky. They were discovered by, I think she was a graduate student in the 60s, something.

They were, they discovered through listening to some radio signals. And first they thought it was extraterrestrial life because they, called that little green man, that LGM. I always confuse pulsars and quasars. I'm going to guess that someone saw repetition of light in some part of the sky over and over, and that led to an investigation that found the pulsars. Pulsars were discovered by a woman, and I believe it was in the 1970s, but I'm not sure how or why or where even.

There was a woman astronomer, radio astronomer, whose name, unfortunately, I cannot remember, was doing some sort of sky survey when she noticed a set of pulses that were incredibly regularly spaced. She actually annotated them as LGM for Little Green Men that one time they thought it might have been discovery of aliens. but later they discovered that it was actually a rotating neutron star and the magnetic field was exciting the gas molecules around it and giving off radio energy.

All right, so congratulations to our excellently informed listeners. Together, they really do have most of the story there. There's a lot of really insightful stuff and a lot of bits of the story are there in pieces here and there. So let's dig into it. And to really understand how pulsars were discovered, we have to understand, of course, first what a pulsar is, how we came to the idea of it existing in the universe, and that'll help us understand how it was seen and how we knew what we were seeing. All right. So first of all, what is a pulsar? A pulsar is a very, very compact object. Neutron stars and white dwarfs are more famous as the sort of like densest things in the universe.

and a pulsar is a version of these. It's most commonly considered to be a version of a neutron star, but it can also be a white dwarf. But both of them essentially are the endpoints of stars. Stars have these incredible life cycles where you start out as a big molecular cloud, huge blob of gas and dust that somehow shocked to collapse into a hot and dense object, a star,

which burns for billions and billions of years in this incredible, incredible balance, between gravity that's pulling it together, trying to turn it into a black hole or something very, very dense, and fusion, which is erupting and sending radiation out to prevent the collapse of that star. And it always amazes me that these things go on for so long. These two cosmic forces so different, both so powerful, can be so balanced for so many billions of years. Well, at some point, the star gives up because it's burned most of its fuel and its core has become very, very heavy, and it's filled with things that it can no longer fuse.

When the core of the star is filled with iron, for example, fusing iron doesn't generate heat. It actually costs energy, so it cools the star. So now the star no longer has that power from fusion to resist gravity, and it collapses. There's some intermediate stages in there will skip over, such as it becoming a red giant. But depending on the size of the star,

this collapse generally triggers a supernova. So you have this collapse where the materials racing inwards, which then causes a back reaction outwards, a massive explosion where a huge chunk of the stuff that used to be the star is now spread out into a new nebula, like a big sprawling cloud of gas and dust. At the core of it, however, is a very dense, very hot remnant. And that remnant can either be a white dwarf or a neutron star or a black hole depending on the mass of the original star. So smaller stars end up as white dwarfs. which are basically just like huge hot chunks of metal that are resisting, collapsing because

they're fermions and they don't like to overlap too much. Or if they are larger, they become neutron stars where gravity now pushes them together and forces all of the protons and the electrons together into forming new neutrons. And you have this really weird material that's sort of like the nucleus of an atom, but the size of a mountain. So it's incredibly dense, incredibly weird stuff, something we even still today do not understand in detail. And then of course, if the star is more massive, it would become a black hole. So the gravity totally wins and nothing prevents the collapse and it becomes a black hole.

But it's the first two categories that we're more interested in. And let's focus on the neutron star category because that's the majority of pulsars. So you have this very dense object, right? And the object is a huge chunk of the material that used to be a star. Not all of it. Some of the material is lost in a supernova and some of it remains in this cloud that surrounds the neutron star. But this This neutron star is a very, very dense object and very, very small because gravity's really pulled it together. And what that means is that it's spinning really fast. Why is it spinning fast?

Well, the star itself was spinning because everything in the universe is spinning. And the reason is simple is because angular momentum is conserved. You know how momentum is conserved. If you push on something, it stays in motion until something else pushes on it. Or if you don't push on something, it stays still until something. until something does push on it. That's conservation of momentum. Those are Newton's laws.

Well, there are similar laws for angular momentum. That is, that something spinning tends to keep spinning. And to make something spin, you've got to give it a push. So if you leave something alone, it will keep spinning the way it's always been spinning, right? That's conservation of angular momentum. And so the original gas cloud that formed that star had some spin to it. And that spin can't go away. It needs to stick around.

And as the gas cloud gets smaller and smaller and turns into a star, the star spins faster. Now, that might sound like it violates conservation of angular momentum because it's spinning faster, right? Well, the velocity of the star's spin is not what's conserved. It's the angular momentum, which is the product of the velocity and the radius. So things that are larger, spin slower with the same angular momentum as things that are smaller and spin faster. You know this because if you're a figure skater and you pull your arms in, you spin faster. You have the same angular momentum. You're not pushing against anything to spin faster, but you spin faster because your radius is smaller. So to have the same angular momentum,

you've got to go faster. That's why the star spins faster than the original gas cloud. And that's why the super compact, dense little neutron star that has a huge chunk of the star's mass, but is much, much smaller. We're talking about something only kilometers in size, you know, maybe 10, 15 kilometers has to be spinning really, really fast to have the same angular momentum as most of the original star. So that's why these things are spinning so fast because they are so small, because they are so dense. In addition, some of these things are highly magnetic. There's a magnetic field of these stars, just like every star and most planets have a magnetic field. And that's because of motion of charged particles inside it. A neutron star is mostly neutrons, but there are

protons and there are protons and they are moving around sometimes on the surface. and the flux of the particles on the inside can create these magnetic fields. So you have this object that's spinning really, really fast, and it has a magnetic field. In addition, it's generating a huge amount of radiation. The magnetic field of the thing is rotating, which generates an electric field, which accelerates the protons and the electrons on the surface of the neutron star, and that creates a bunch of radiation, because when you accelerate particles, they radiate photons. So you have this magnetic field on this neutron star,

that's rotating and is generating an electric field, which pushes the electrons and protons on the surface of the star, creating a lot of radiation. And that radiation doesn't go in every direction. Because there's a strong magnetic field, that radiation tends to go along the magnetic north and the magnetic south. Because magnetic fields are really good at bending the path of charged particles. The reason that we don't get a lot of radiation from space is because we have a magnetic field here on Earth. And when particles come from space, they are bent around those magnetic field lines. The magnetic field lines are sort of like the lines on a basketball, right? They run from north to south. If a particle comes from space, it gets bent by those magnetic fields and goes out

in another direction. Or sometimes, they loop around those magnetic field lines all the way up to the north or the south pole, and then they can slip in between the magnetic field lines. And that's, for example, why we have the northern lights and the southern lights, because magnetic fields guide charged particles. In the same way, if you generate radiation on the surface of the planet, it's also bound by those magnetic fields. And so in this case, the magnetic fields are even much more powerful. And essentially, all of the radiation from the neutron star gets guided towards the north

or the south pole of the magnetic field. So you get these beams of radiation shooting off of this crazy, neutron star right like it's not crazy enough it's already super hot super dense super small spinning super fast really magnetized and now on top of that it's shining these two crazy flashlights out into the universe one from its magnetic north pole and the other from its magnetic south pole and these beams don't come for free they are very bright they cost a lot of energy and this energy comes from the spinning of the neutron star because that's what's generating this electric field the rotation of the magnetic field and eventually it's going to slow it down. Like these pulsars, they generate these

beams and they last for maybe 10 or 100 million years, but they don't last for their whole lifetime. At some point, the beams turn off because the neutron star has slowed down and it's not generating that radiation anymore. What that means is that for most of a lifetime, the pulsar is actually quiet. They don't emit these beams. And so something like 99% of the pulsars out there aren't actually emitting any radiation anymore. They are quiet. The universe is filled with dead pulsars, pulsars that have gone quiet. So we've explained what a pulsar is and how it emits these beams, but why do we call it a pulsar? Are these beams themselves like pulsing? Do they turn on and off? Now, the beams don't turn on and off. I mean, they last for millions of years

and they eventually fade, but they don't like flicker on and off. The reason we call it a pulsar is because we only see those beams as they pass by the earth because the beam is shooting up and down along the magnetic field lines, but that's not necessarily the same as the axis that the pulsar is spinning around. So if it were, if the magnetic north and the magnetic south were the same as the north and south of the actual star, so spinning around the north pole, then it would always be shooting the beam north and the beam south. However, if instead the magnetic field is tilted so that it's like spinning along one axis, but its beams are shooting off a little bit skewed, then when it spins around, the direction of that beam changes, right? It's like if you're holding a flashlight and you

point it straight up and then spin, the direction of the flashlight doesn't change. But if you hold a flashlight straight out and then spin, right, then what happens? Then your flashlight's going to sweep around 360 degrees every time you rotate. And what does somebody see if they are standing in front of you watching you spin, they see a flash, they see a pulse of light only when the flashlight is pointed in your direction. So it's this difference between the direction of the pulsar's magnetic field and its actual spin axis, which makes it a pulsar, right? That's what makes it appear to pulse. They don't actually pulse. They're sending bright streams of light continuously out into the universe until they fade. But we see them pulsing because that beam

sweeps across Earth, and that's what we see. So that's what a Pulsar is, an introduction to these weird things in the universe. Next, we're going to talk about why we suspected they might exist and how they were actually found. But first, let's take a quick break. December 29th, 1975, LaGuardia Airport. The holiday rush. Parents hauling luggage, kids gripping their new Christmas toys.

Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal. Apparently, the explosion actually impelled metal glass. The injured were being loaded into ambulances. Just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism. Law and order criminal justice system is back.

In season two, we're turning our focus to a threat that hides in plain sight that's harder to predict and even harder to stop. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Well, wait a minute, Sam, maybe her boyfriend's just looking for extra credit. Well, Dakota, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other, but I just want her gone.

Now, hold up. Isn't that against school policy? That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professor, and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him

because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. Hola, it's Honey German, and my podcast, Grasasas Come Again, is back. This season, we're going even deeper into the world of music and entertainment, with raw and honest conversations with some of your favorite Latin artists and celebrities. You didn't have to audition.

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injury because I landed on my head. Welcome to Season 2 of the Good Stuff. Listen to the Good Stuff podcast on the Iheart Radio app, Apple Podcasts, or wherever you get your podcast. All right, we're back and we're talking about the incredible story of the discovery of pulsars. And we reminded ourselves that pulsars are tiny, very hot, very dense, very quickly spinning stars, the leftover heart of a supernova. They're shooting a beam of light out into the universe and they are also spinning. And so that beam of light passes over the earth and looks like pulsations. It looks like pulses from something out there in the universe. And before we discovered these things, we had a suspicion that they existed.

People have been thinking about the life cycle of stars. And in 1934, people suggested that when you had a supernova, it might not all blow out into the universe, that you might get this small, dense core left over. And if so, it would have this really weird state of matter. These neutrons would form that would be in a really dense state. This thing that is sort of like nuclear matter, the things in the heart of atoms. but now on the size of like a mountain, something kilometers wide. Imagine that the nucleus of an atom, but kilometers wide. So this was a novelty, but nobody had ever seen one before.

We didn't know if neutron stars existed in 1934. And they would be difficult to detect because these things don't have fusion anymore. They don't glow the same way that very bright stars do. So to see neutron stars seem like a puzzle. But then decades later, people said, well, you know, they might have very strong magnetic fields. and if so they might be rotating and if so then they might be pulsing and so this idea sort of came into existence in the 60s the idea that pulsars as weird spinning magnetized beaming light neutron stars might be out there but you have to remember that there are lots of crazy ideas for what might be

out there the astronomy literature is filled with people speculating maybe these things exist maybe boson stars exist. Maybe these other things exist. Now with the hindsight of history, we can go back and trace the development of this one thread of an idea that turned out to describe something in the actual universe. But don't forget, it was buried at the time in a forest of other crazy wrong ideas about what might be out there in the universe. You know pulsars exist. And if you took a time machine back to the 60s, you might say, I know these things exist and I know how to find them. It's not actually that hard. But without the hindsight of that history, of course, it's hard to pick the wheat from the chaff. So let's get to the story of how they were actually discovered.

They were found by a graduate student at the University of Cambridge, a woman named Jocelyn Bell, and she was not looking for pulsars. In fact, she wasn't looking for stars at all. She was trying to study quasars. Quasars are at the heart of really large galaxies. They are the accretion disks around black holes. The stuff that has not yet fallen into the black hole, but is swirling around. And because of the tidal forces and the incredible gravity, these things get really hot and they radiate a lot of light. And we had seen these things and we knew that they were very, very far away because these quasars have existed for a long time. They were formed in the very early universe, like a billion years after the Big Bang. But they're still super duper bright. And for a long

time, there were a big mystery because people thought, well, what could it be that? It's so incredibly bright and so far away. So at its source, it's got to be like mind-bogglingly bright. What could that even be? People thought for a long time this was a mistake. It's not even really a thing. We must be misunderstanding how these things work. And Jocelyn Bell was trying to understand these quasars. She was trying to understand how these quasars twinkle, how they scintillate. You know that when you look at a star in the sky, you see a twinkling. And that's mostly because the stuff between you and the star is interfering with the star light. That's why planets, for example, don't twinkle, but stars do because the light from the star has to go really, really far. So Quasars kind

of twinkle as well. They do this thing called scintillation. And it's due to fluctuations in the densities of particles in the solar wind. So the way we see quasars is not by looking usually at visible light, but by looking at radio waves. These things come from really, really far away and where they're best seen in the radio spectrum. And in the radio spectrum, and in the radio spectrum, an obstacle is the solar wind. Remember that the sun doesn't just shoot out photons. It also shoots out a bunch of charged particles, protons and electrons and other crazy stuff. And this is what we call the solar wind. And when a radio photon enters our solar system from somewhere really, really far away, it hits this barrage of radiation coming from the sun and interacts with it.

This radio signal made of light and electromagnetic radiation, essentially photons, comes from these quasars billions of years away, they sometimes get deflected or interfered with by these particles in the solar wind. And so that's what makes these quasars scintillate. So she wanted to study this because she wanted to understand quasars. People at that time didn't know that black holes were real. So they didn't know what was powering these quasars. What could possibly be generating so much radiation from so far away?

So she built a radio telescope. And a radio telescope is just a bunch of antennas. But the thing about radio waves is that their wavelength is very, very long. They can be meters or hundreds of meters. So to capture a radio photon, you need a big antenna. You need something large. So she built something which was four and a half acres. Like this thing is big.

She spent two years and for her doing astronomy meant every day pounding fence posts into the ground and stringing wire among them. Imagine one of those old-fashioned TV antennas. It was like a grid of metal that could capture a signal. That's essentially what she built. And she strung 120 miles of wire over two years to build her radio telescope to capture the signal from these quasars, to look at them scintillating. She wanted to see the fluctuations in these signals. And that's really key because what she did is get these radio signals and look at them

and develop her own personal sense for what this data should look like. She was looking for characteristic wiggles, changes. in this data as they studied a pulsar. And this is back in the day before they had computers and before people could just like, you know, dump the data onto the screen and analyze it. Bump, bump, bump. Her data came out directly onto a printer.

Like her radio telescope, captured this, turned it into an electrical signal, which was directly sent to a printer, which dumped it onto paper. So her output from her telescope was stored on 100 feet per day of printer paper, which just like came out steadily. And she would stand there and look at it.

She would get to know it. She was like a natural neural network where she learned, oh, if I'm looking over here, then I'm going to see this thing. If we're pointing at the sun, then I'm going to see this kind of radio waves. And this isn't the kind of thing that she could easily point, right? This thing is just something you build in the ground. But the earth turns. And as the earth turns, this thing is essentially pointed in a new direction.

She herself is like sweeping her instrument across the sky, examining different parts of the universe. And you can get some directional information from a radio antenna based on like when the signal arrives. Does it arrive first on the eastern part of the antenna or first on the western part of the antenna? But it's not great at telling where something is coming from exactly. So she became really good analyzing these signals. And then one day, November 28, 1967, she saw the signal that she did not understand something she had never seen before. What she saw were pulses separated by one and the third seconds.

So it was like, boop, boop, boop, and she would get these pulses of radio waves. And the regularity of it, the exact distance between the pulses, is what made it seem really weird. And at first she thought, oh, this must be a signal from something here on Earth. Because, of course, there are lots of sources of radio waves here on Earth. Almost everything we do with our electronics generates radio noise. Every time you turn on your television, certainly every time you use your cell phone. And of course, there are radio transmitters all over the planet. And so first you have to rule out various sources of human interference like other radio astronomers,

people sending pulses off the moon to measure the distance to the moon, television signals, beeps from orbiting satellites, even like, you know, possible effects from large corrugated metal buildings near the telescopes. She went through this whole list. And you got to do that when you see something weird in your data. You got to first look for the boring explanation. Like, oh, well, maybe I'm just measuring what happens when somebody turns on the microwave in the break room or something like that. You don't go straight to, I've discovered something new in the universe. So she very carefully went through all these different explanations and eventually even borrowed somebody else's radio telescope to confirm her observations. She wanted to make sure it wasn't just like some weird

blip in her telescope. So she knew it wasn't just her telescope. She ruled out all sources of human earthbound interference, and she saw that it tracked it with a particular location in the sky. And that's a great clue that tells you that it's not from Earth. Because if it's from Earth, then it doesn't matter which direction the Earth is pointed. If it's not from Earth, then you will only see it when the Earth is pointed in a certain direction, only when the message itself sweeped across your radio telescope. So where do their minds go? The strange regularity of it,

the fact that it came like every one and a third seconds made them think not of some new astrophysical object because nature is not often that precise, right? Nature is messy. When you go out into the world, you don't see like rocks that are exactly square. You don't see like 10 rocks exactly the same size. You don't see this sort of regular patterns.

I mean, sometimes you do, in crystals and other places, but nature is more often messy than precise and regular. So their immediate thought was like, wow, maybe this is alien intelligence. You know, she says, quote, we did not really believe that we had picked up signals from another civilization, but obviously the idea had crossed our minds and we had no proof that it was an entirely natural radio emission. It is an interesting problem. If one thinks one may have detected life elsewhere in the universe, how does one

announce the results responsibly. So they really didn't know what they had. They were wondering, is this something weird and new? Are these aliens? Or is this some natural source of radio emission that's weirdly regular? So in their internal notes, they called this thing LGM1 for Little Green Men. And so here you can see the process of discovery in motion. Like there existed in the literature, the speculation that these things might be out there, that spinning neutron stars might generate pulses and here they are discovering pulses in the radio spectrum essentially exactly what was predicted but they couldn't put it together because as we mentioned before there are lots of predictions out there in the literature only in hindsight you know exactly who to listen to it's like picking

one of nostradamus's predictions right most of them are nonsense and if you look back through all them you can always find one that seems to make sense so what they did was they kept looking And pretty soon they found another pulsar somewhere else in the sky. And that told them, hmm, it's probably not aliens because there are signals coming from two very different, very distant locations in the universe. So probably it's a natural source. And then by Christmas of 1967, right, just like weeks after the first discovery, they had found four of these things. So four pulsars. And early the next year, they publicized their results and they wrote a nice paper.

and this was a huge discovery. And then everybody with a radio telescope started looking for these things. Like, wow, oh my gosh, these things are out there. The incredible thing is that once you know to look for them, they're not that hard to find. Pulsars are pretty bright. Radio telescopes were kind of new. Optical astronomy was dominant at the time. But there were a lot of radio telescopes out there.

And by the end of 1968, dozens of these things had been found. And it was another scientist, a guy named Thomas Gold, that put the story together, who said, ah, these pulsars are the rotating neutron stars that we've been thinking about. What these folks have seen out there in the universe is exactly what we thought might happen in some circumstances at the end of a supernova. So that was a really incredible moment to see like, wow, these things, these crazy, weird little blobs that we predicted might be there as like the tombstone at the end of a supernova actually are out there. And they do this weird thing that lets us find them.

I think the discovery that really put a pin in it was the discovery of a pulsar at the heart of the crab nebula. Crab nebula is a huge cloud of gas and dust. It's the remnant of an old supernova, a star that blew up and spread most of its stuff out there in the universe.

So then when we looked with the radio and we saw that at the heart of a crab nebula was a pulsar, we thought, that's what this is and that completes the story. That tells us that at the heart of many nebula, there may be these neutron stars. Not all of them become pulsars, but pulsars tell us that the neutron stars are there, that this supernova remnant has this hard little nub at the core of it. But remember that we're

using radio waves so far to find these pulsars, and radio waves are not very good at telling the direction of a signal. It's not like an optical telescope where the photons of very short frequencies, nanometers, and you can capture them with a telescope pointed in one specific direction, and you could tell exactly where on the lens it hit. These things are captured by very large antenna, and it's hard to tell what direction they're coming from. So while we say we saw a pulsar in the direction of the Crab Nebula, it's not like we could really pin down its location exactly.

So there's a second part of this discovery story, a part that was caught on audio tape that I want to share with you. But first, let's take another break. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal. Apparently, the explosion actually impelled metal glass.

The injured were being loaded into ambulances, just a chaotic. chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism. Law and Order Criminal Justice System is back. In Season 2, we're turning our focus to a threat that hides in plain sight. That's harder to predict and even harder to stop. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app,

Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Well, wait a minute, Sam, maybe her boyfriend's just looking for extra credit. Well, Dakota, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other, but I just want her gone. Now, hold up.

Isn't that against school policy? That sounds totally inappropriate. Well, according to this person, this is her. boyfriend's former professor and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him

because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. Hola, it's HoneyGerman. And my podcast, Grasasas Come Again, is back. This season, we're going even deeper into the

World of Music and Entertainment, with raw and honest conversations with some of your favorite Latin artists and celebrities. You didn't have to audition? No, I didn't audition. I haven't auditioned in, like, over 25 years. Oh, wow. That's a real G-talk right there. Oh, yeah. We've got some of the biggest actors, musicians, content creators, and culture shifters, sharing their real stories of failure and success.

You were destined to be a start. We talk all about what's viral and trending with a little. little bit of chisement, a lot of laughs, and those amazing vibras you've come to expect. And, of course, we'll explore deeper topics dealing with identity, struggles, and all the issues affecting our Latin community. You feel like you get a little whitewash because you have to do the code switching? I won't say whitewash because at the end of the day, you know, I'm me. Yeah. But the whole pretending and code, you know, it takes a toll on you.

Listen to the new season of Grasasas Come Again as part of my Cultura podcast network on the IHartRadio app, Apple Podcast, or wherever you get your podcast. Hey, sis, what if I could promise you you never had to listen to a condescending finance, bro? Tell you how to manage your money again. Welcome to Brown Ambition. This is the hard part when you pay down those credit cards. If you haven't gotten to the bottom of why you were racking up credit or turning to credit cards, you may just recreate the same problem a year from now. When you do feel like you are bleeding from these high interest rates,

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All right, so we are in the late 60s, and the field of astronomy was very excited because people had been discovering pulsars. But these pulsars had been seen in the radio frequency, which means they were hard to pin down exactly where they were. And people were wondering, are there pulsars out there where the beams of light that they are shooting are visible light, not just radio noise,

but like actual visible beams that our eyes and our telescopes could see. Well, most pulsars, we think, are brightest in the radio or the x-ray. But the idea was that there might be some optical pulsars. So there were a couple of theorists named John Cook and Mike Disney. And these were not experienced astronomers. But they were curious about whether or not you could see one of these pulsars in the optical. So they decided, hey, let's give this thing a shot. Let's sign up for some telescope time, pointed at one of these pulsars and see if we can see any

flashes. So these guys, not experimentalists, right? They didn't really know how to use a telescope. This is their first time using like real serious astronomical scientific equipment. And they went down to Kid Peak near Tucson and they signed up for a couple of days of observing time. And what they had going for them was that they were going to point this thing at the Crab Nebula. And they already knew the frequency of the pulsar. So they knew like what frequency of light flashes to look for. So what they did is they pointed this telescope at the Crab Nebula and then they looked at the light that came in. Remember that this again was before like dedicated computers where you could rapidly and flexibly analyze your data. What they needed was some sort of like dedicated electronics

that could turn their flashes of light into blips that they could study. So there was a guy there who was really good at electronics and he happened to have exactly what they needed so they could plug their telescope into this thing and it would analyze the frequency like the time between blips and make a little plot for them on a very small screen. So it's sort of like a dedicated computer exactly to do this, they happened to stumble across this guy who had exactly this equipment to do what they needed. So they went out there for their first day. They were very excited thinking, wow, maybe we're going to discover something. And they turned it on and they saw nothing. And what they didn't know at the time was that they had made a mistake in their calculations

and they had like tweaked the knobs on this thing wrong. So they shouldn't have seen anything because they were looking at the wrong sort of frequency spectrum. The next two nights that they had were both cloudy. And so they lost all of their observing time. And they didn't never would have seen this thing that hadn't been for somebody else's bad luck. The person with the telescope next after them, his wife got sick, so he decided he was going to stay home and take care of her and he gave them his telescope time. So they got an extra bonus of a couple of days of observing time that they didn't expect to get. And the clouds cleared and they had a beautiful night and they set their thing correctly. And they also had a tape recorder

running, which recorded their conversation as well as the data coming from the telescope. So this little box not only makes a little depiction on their screen that shows from the frequency, it also made a little tick for every blip. So you'll hear those ticks on this tape, and you'll also hear them reacting in real time to the discovery they are making. You've got a bleeding pulse, yeah? Hey. Wow.

You don't suppose that's really like that. Can they? She's not banging in the middle of the period. But maybe not banging in the middle of the scale. So you hear them saying that it's bang in the middle of the period. Remember that they knew what to look for. They knew the period of this pulsar. They knew the frequency at which it should flash.

So they were looking for a repeated pattern of flashes with just the right period. They had zoomed in on exactly what they were hoping to see. But of course, they never knew whether the universe would show to them or whether it wouldn't. Here's the rest of their recording. It really looks on it from here at the moment. It's growing, too. It's been at the side of it too.

I don't know. Yeah. It could be, you know. It's a great, John. It is. Look. It is. So you can hear literally the excitement in their voice.

One of them is astonished. Look at that bleeding pulse. And the other one is like, I can't believe this is happening right now. It's getting bigger and bigger. You can see them discovering it. You can hear in their voices that they're realizing that they've caught it, that they've seen this pulsar flickering invisible light, that they've pointed this telescope at this weird faraway object,

and they've caught it doing its thing. So that's a super fun little follow-up discovery. They published that paper. And this must have been a really fun moment for these guys because, again, this is the first time they ever went to a telescope. This is the first time they ever, like, looked out into the universe. Most of their science was done with pencil and paper and just sort of thinking about what might be out there. And so I'm glad they got to go out there and actually experience this moment of discovery. And it also really helped us understand what these pulsars were, because with the optical telescope, with a visible light, you could really pin down exactly where this thing was.

And we knew then that it really was at the heart of the crab nebula and it really was a pulsar. So a very exciting discovery and very quickly appreciated, of course, by the scientific community. And in 1974, just a few years later, Jocelyn Bell's advisor is the first astronomer to ever win the Nobel Prize in Physics. That's right. Her advisor won the Nobel Prize. Now, of course, he was involved, right? You know, a graduate student never works alone. He gave lots of guidance, lots of ideas, probably provided the funding. But it's clear that she's the one who made the discovery.

She built that thing. She was out there day to day. She saw it in the data. And there's a lot of discussion these days about why she was left out of it. It's because she was a student. Well, there are lots of other cases when a student participated in discovery and was included in the Nobel Prize discovery. Hulse and Taylor, for example, was a graduate student.

advisor pair that discovered binary pulsars just a couple of decades later and they were both given the Nobel Prize, even though one of them was a graduate student. Of course, there's the question of whether or not it was sexism. In the history of the Nobel Prize's very few women have been given the prize and many have been qualified. So it seems like an obvious case of injustice. Bernal herself is very gracious about it. She recently was given the breakthrough prize in fundamental physics, which comes with millions of dollars, which she then donated to advancing the cause of having more women in physics. But of course, she did note that the journalist didn't ask her science questions, they

tended to ask her questions about, like, how many boyfriends she had. But this kicked off a whole really exciting era of astronomy, because every time you discover something new out there in the universe, it gives you another handle, it gives you a way to learn things. It reveals new things about the universe that you didn't know before. And just a few years after that, we discovered things like millisecond pulsars. These are things that spin around so fast that we see a pulse from them not every second, but every millisecond. So these stars are spinning a thousand times faster than the original pulsar spun, right?

Every 1.6 seconds, this incredible, enormous, dense object spins around. These things are moving really, really fast, spinning like tens of thousands of times per minute. The fastest pulsar we've ever seen, we talked about on our episode about the fastest spinning things in the universe. is 16 kilometers in radius and the surface of it is moving at a quarter of the speed of light. That's how fast this thing is spinning. I won't tell you the name because it's a ridiculous series of letters and numbers, but it's spinning at 716 hertz. That means every second this entire mountain-sized blob of nuclear matter spins 700 times around.

And it's 18,000 light years from Earth in the constellation Sagittarius and is sending us pulses very, very regularly. The other amazing thing about these pulsars is that they are precisely timed. It's not just like roughly 716 hertz. It's like exactly. And every second, it's the same. These things do not change. And it's astounding when you see something in nature that is so regular.

These things have the regularity to consistency that rivals that of atomic clocks. You can use them as a probe of the rest of the universe because they send out these very, very regular pulses. For example, a pulsar was actually the first way that we had evidence of a planet around another star. Because when a pulsar has a planet around it, that planet is tugging on it gravitationally as it orbits. And it means the pulsar moves towards us sometimes and away from us other times. And this velocity changes the frequency of the pulsar by a very small amount. But because the pulsars are so precise and so accurate, we can detect that. And if it's a regular shift in the frequency of the pulsar, you can deduce the presence

of a planet around the pulsar. How do you have a planet around a pulsar? It's crazy, right? Because a pulsar comes from when a sun was destroyed. So probably some chunk of that nebula has now reformed some planet, which is orbiting the pulsar. Or some planet happened to amazingly survive the supernova explosion that created the pulsar. And you can also use them to navigate around the galaxy because every pulsar is different. Each one has like its own unique fingerprint.

You can tell which one you are listening to. And you can also tell where you are in its cycle. Is it pointing towards me or away from me? And if you look at multiple of these things, you can tell like how many cycles you are away from multiple pulsars lets you triangulate exactly where you are in the galaxy. I've had a whole fun podcast episode about navigating deep space using pulsars. And people have crazy plans for how to use pulsars.

For example, they want to use them as gravitational wave detectors. Remember that we have seen. ripples in the fabric of space by seeing how these gravitational waves stretch and shrink the distances here on Earth. Well, there might be really massive ones that we can measure their stretching and shrinking the entire galaxy. And those would affect the pulses from these pulsars. And so a bunch of really precise clocks sending us dings from all around the galaxy can be used to detect gravitational waves. So there's a bright future for the signs of pulsars as well as a fascinating story that tells us exactly how they were discovered.

So thanks for coming along with me on this ride of historical exploration to understand how we actually make these breakthroughs, how people actually win Nobel prizes, or are sometimes cut out of it by their advisor, but how scientific knowledge is very slowly, very painstakingly, but very excitingly accumulated. Thanks for joining us. Tune in next time. Thanks for listening and remember that Daniel and Jorge Explain the Universe is a production of IHeartRadio. For more podcasts from IHeartRadio, visit the IHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.

LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, everything changed. There's been a bombing at the TWA terminal. Just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, terrorism. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious.

Wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, luckily, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend's been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now he's insisting we get to know each other, but I just want her gone. Hold up. Isn't that against school policy? That seems inappropriate. Maybe. Find out how it ends by listening to the OK Storytime podcast. podcast and the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts.

Every case that is a cold case that has DNA. Right now in a backlog will be identified in our lifetime. On the new podcast, America's Crime Lab, every case has a story to tell. And the DNA holds the truth. He never thought he was going to get caught. And I just looked at my computer screen. I was just like, ah, got you. This technology's already solving so many cases.

Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. This is an IHeart podcast.