Astronomy Cast
#777: The Eddington Limit
How big can a star get? This is a calculation made by one of the original pioneers of modern astronomy, Sir Arthur Eddington. And it’s named after him, the Eddington Limit. Now, astronomers are finding examples of giant black holes early in the Universe, calling into question some of Eddington’s assumptions. Let’s explore this fascinating concept! Why are stars sphere-ish? Why do blackholes not eat everything? Why do pulsating stars pulsate? It all comes down to work done by Eddington at the beginning of the last century, and today we’re going to look back at Eddington’s work and all its applications in modern Astronomy.
Show Notes- What the Eddington Limit is
- Gravity vs radiation pressure in stars
- Why star growth has an upper limit
- How black holes accrete matter
- Quasars and galaxy-scale feedback
- Evidence for super-Eddington growth
- Why modern observations challenge theory
Fraser Cain:
AstronomyCast, Episode 777, The Eddington Limit. Welcome to AstronomyCast, our weekly facts-based journey through the Cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, I’m the publisher of Universe Today.
With me, as always, is Dr. Pamela Gay, a Senior Scientist for the Planetary Science Institute and the Director of Cosmic Quest. Hey Pamela, how are you doing?
Dr. Pamela Gay:
I am doing well. The howling wind is tremendous. If you hear what sounds like ghosts in the background, that is the wind, people.
That is the wind.
Fraser Cain:
Now, as usual, I can’t hear it because we use Zoom to record and the modern technology has made it so, when your dogs are barking, I don’t hear it. And so I’m definitely not going to hear the wind. But yeah, here we are.
Now I’m going to do something kind of mean, but it’s for the best. And that is I’m going to say nice things about you, and you’re just going to have to take it. Which is, you know, I think a lot of people, when they reach out to us about Astronomy Cast and they talk about like our scripts and sort of how we prepare, they don’t realize that there is no script, that this is entirely off of the top of our heads, that I go in and what’s nice is for me, I don’t really even have to prepare at all.
Like I write the intro, which is sort of like my token donation to the cause. And I usually come up with the idea, but, you know, often Pamela has ideas that she wants to express, but then she has to prepare and she doesn’t have to prepare just for whatever is going to be the script. She literally has to prepare for anything that I might ask and I don’t know what I’m going to ask.
So how can she know what I’m going to ask? And so Pamela, you are amazing for being able to gather and prepare so much information. Be ready, sort of on your toes, nimble on your toes to handle whatever comes your way.
And in this case, there’s going to be a lot of information about the Eddington Limit. And I don’t know what I’m going to talk about. You don’t know what I’m going to talk about.
You don’t know what you’re going to talk about. And yet you were always poised and prepared. So amazing job.
Dr. Pamela Gay:
This is a favorite topic. So hopefully I will not disappoint. Great.
Okay.
Fraser Cain:
How big can a star get? This is a calculation made by one of the original pioneers of modern astronomy, Sir Arthur Eddington, and it’s named after him, the Eddington Limit. Now astronomers are finding examples of giant black holes early in the Universe, calling into question some of Eddington’s assumptions.
Let’s explore this fascinating concept. Okay, so the Eddington Limit. What is this calculation that Eddington came up with?
Dr. Pamela Gay:
So back in like circa 1916, that’s when the paper came out. So he’d been working on this. Yeah.
This is fairly modern, but not so modern, because at this point in the history of astronomy, we didn’t actually know how stars worked. Like people had realized they weren’t burning coal, or they hadn’t figured out galaxies existed yet. So yeah, Eddington was trying, like so many other people, to figure out what it was that allowed stars to exist.
And we were at a point in geology and paleontology that we were also realizing, planet is old. And so that meant the star had to be old, that meant stars had to be burning for a long period of time. And they still hadn’t fully figured out all the ins and outs of nuclear fusion.
But Eddington started to propose, okay, so what if we have nuclear something going on in the center of a star?
Fraser Cain:
Not coal.
Dr. Pamela Gay:
Correct.
Fraser Cain:
Correct. As people were perhaps assuming, or would.
Dr. Pamela Gay:
Yeah, it wasn’t any kind of chemical exothermic reaction. They knew that much. It had to be something else.
And we were starting to understand nuclear reactions at this point. And so what he proposed was something was going on, and we were really struggling to figure it out, because electrons were like, no, we won’t allow this. And so they had to figure out electron tunneling and quantum mechanics and stuff like that.
So before we even fully understood the quantum mechanics that would allow the center of a star to do the things it needs to do, Eddington proposed, what if stars are balanced between light pressure pushing outwards and gravity pushing inwards?
Fraser Cain:
And like light pushing?
Dr. Pamela Gay:
Are you mad? It was absolutely amazing. And I mean, it’s more complicated than that.
We have to look at what are the electron pressures involved? What are all the other atomic reactions involved? And we’re still working to figure out the details of stars.
And in coming up with this idea, it was realized, well, shoot, if a star is producing too much light, it’s going to overcome gravity and just blow things apart. If anything is producing too much light, it’s just going to blow things apart. So there is some kind of a limit on how much energy can be presented while at the same time gravity is trying to hold things together.
Fraser Cain:
And this idea, I mean, I think even now, you know, we look at stars, we know they’re in hydrostatic equilibrium and say, well, yeah, it’s the light pressure that is keeping the star from folding in on itself. Explain that idea of just like even the light pressure.
Dr. Pamela Gay:
I love this. And if you ever want to see beautifully, cleanly done maths on this, Chandrasekhar put together a stellar evolution book that was published, I want to say in the 1930s or 40s. And there’s copies of it still floating around.
It’s a little penguin book, Penguin Publishers. And the maths for this is entirely straightforward. It is all algebra.
And so the idea is light has, it doesn’t have mass, but it has energy. And energy in motion has momentum. And so when photons hit things, they transfer momentum.
And so every time you zot something with a photon, it can absorb the photon and it also has a transfer of momentum in the process. And so in the core of a star, we have all of these nuclear reactions taking place. And in the process, photons are being produced.
These photons work their way outwards and they random walk, they’re transferring energy in all directions as they go, which is good because that random walk without any specific direction supports a sphere quite nicely. And because they can escape outwards, you end up with the bulk of the motion on average being outwards balanced against gravity. So in the center, you have this radiation pressure, it goes out, then you have convective zones that are supported through the old fashioned pressure laws and all these different things.
You can just work through the math for each area of the star, figuring out where do these different pressures end up dominating. And this is actually like an undergraduate homework assignment that I still remember both hating doing and really enjoying the fact that I was capable of doing it without getting help.
Fraser Cain:
But that idea, I mean, I think when you think about, say, steam rising or filling up a balloon and you sort of think about the sort of thermodynamic, the movement of the molecules bouncing into each other, that would probably, and people were probably examining this at the time and that was probably their first instinct, well, it’s a giant blob of gas and the gas is hot and here’s how much sort of, you know, entropy is going on. We use that to calculate the star, but no, Eddington said, no, no, it’s the light.
It’s the photons, not just particles bouncing into each other in the way we experience this in steam engines and things like that.
Dr. Pamela Gay:
And what’s wild is it takes all of these things working together. So the light is heating the gas, there’s gas pressure added. So you have light pressure, you have light transferring heat, creating gas pressure.
You have different atomic reactions going on, which are ionizing things and creating an electron pressure. And the classical Eddington didn’t include all the electrons properly. And so we’ve had to modify the equations over the years to better and better represent what’s going on in stars.
It’s super complicated, but Eddington was the first person to really realize what was going on. And this is where having Chandrasekhar coming and being his graduate student made so much sense. Between the two of them, they were able to figure out and Chandrasekhar did surpass his advisor.
And this did lead to a great deal of chaos that we talked about in our episode about Chandrasekhar years ago. But the two of them together were able to explain all the different phases in a star’s life and what keeps stars going the way they’re going.
Fraser Cain:
So, OK, so this is kind of the limit, this hydrostatic equilibrium, but it also sort of defines how quickly a star can accrete mass to grow. Yes. So sort of help me understand this.
Dr. Pamela Gay:
So what you end up with is as stars get more and more massive, it puts more and more pressure on the center of the star, which accelerates the rate at which light is being produced. At a certain point, the light pressure exceeds the gravitational force holding the star together. And so the light pushing outwards starts to push at a rate greater than what gravity can pull inwards.
It’s this balancing of forces that allows a star to start to blow things apart. It’s the slow-mo version of what happens in a supernova. In a supernova, the star’s core stops producing light.
You run out of balance. It collapses violently. In the collapse, you end up with new nuclear reactions going on, releasing energy, and that blasts what’s falling inwards, outwards.
It’s a much slower process or at least a much less violent process that goes on in young stars, in massive stars, as material tries to fall into them. But it’s the exact same physics. And I love the fact that we’re dealing with the same equations, just implemented in different limits for all these different cases.
Fraser Cain:
So then where does this kind of get us in the limits of how big stars can get?
Dr. Pamela Gay:
This is where we keep being like, oh, shoot, our observations don’t match our equations. So we keep finding new ways that stars find to produce things that generate pressure and don’t create pressure. So we think that the limits are somewhere below 200 solar masses.
And I’m going to put it that vaguely because the universe likes to keep going, no, you were wrong. I’m going to make bigger stars. How about this star over here?
Yeah, yeah. And quantum mechanics is incomplete. We know this because particles don’t do what we thought they were supposed to do.
We don’t know the underlying physics to the standard model. We just know the standard model is there may not even be underlying physics, which is super annoying to think about. But at some point below 200 solar masses, you are adding material to a star and it just starts blasting light to the point that it clears the area around it.
Fraser Cain:
And is that sort of separate? Like I sort of I think about the Eddington limit core first, that you’re kind of imagining that you’re you’re adding material to the star. The star is getting hotter both in its core and at its surface.
And like the level of heat is kind of ridiculous. Like say a star like our sun, 15 million at the Kelvin, I think, at the center, while say 5,800 Kelvin at the at the surface. But you take a star like the hottest star, like one of those like 200 times solar masses, and you’re at millions of degrees even on the surface.
I mean, they’re ludicrous. Yeah. And and so if you try to add more material, then this thing is going to you know, it’s going to its age will decrease and it’s going to go through some of its phases of dying almost instantly.
Right. Because it’s just but then I think where you’re getting at next is that not only that, but then you have all of the incredibly intense solar wind that’s coming out, all of the radiation that’s coming off of the star, this is heating up the gas that’s around it. You need cold gas to get a star to form, not hot gas.
But the brightest stars heat up the gas, they make ionized gas. And then that doesn’t want to add to the star. So so in addition to sort of the internal limits of how big a star can get, you also have it sort of interaction with its environment, preventing additional material from falling in.
Dr. Pamela Gay:
And and this is just one of the many super cool things that happens as we we literally live in the realm where we’re looking at the quantum mechanics of how atoms change as a function of temperature, pressure, and everything is balanced between these things. Temperature and pressure defines all these characteristics. And the pressure is coming both from gravity inwards and light outwards.
But some of the energy can go into ionization. And and this starts to lead to really weird things. And and I’m going to take a moment and say variable stars, we have to remember the variable stars.
Because one of the super cool things that Ennikton realized while doing this work is in a star’s atmosphere, you have light going through all these different parts of the star that are at different temperatures, different pressures. And because of this, they have gases at different states. And gases in different states have different optical properties.
And one of the weird ones is helium. So helium one light goes through it. So neutral helium light goes through it.
Helium two, helium with no electrons attached is like I shall not let light pass. And an opacity means that when the photons hit a cloud of fully ionized hydrogen, it is more likely to cause pressure instead of to pass through. It acts like a wall.
So in a star, as it heats up, it hits a point as it’s heating up, heating up, heating up that the helium goes from singly ionized to doubly ionized and it becomes opaque. And it’s like, I’m going to expand instead of getting hotter at this point. And so you have a star’s atmosphere starts expanding instead of heating up the same way.
Now, as gas expands, it cools. So as the star is expanding, it eventually hits the point where it’s like, I’m going to become singly ionized again. And then the light can just pass right back through.
And so now you have a star that doesn’t have the same amount of light pressure because it’s now singly ionized helium and it’s also cooler. And so there’s less light pressure in general. And so it begins to collapse as it collapses.
It heats up and it eventually hits the point where it heats up enough where it starts to expand because it’s heating. But it’s also heating faster than it’s expanding until it hits that doubly ionized helium again. This is the Kappa mechanism, and it’s entirely driven by quantum mechanics playing an extra role with the ionization of helium.
So it’s the little physics like this where things decide instead of cooling, expanding, heating, they’re going to ionize and just do something completely different with all that energy. These are the kinds of things that we keep realizing we’ve left something out of our equations. And this is why stars can be bigger and stuff like that.
Fraser Cain:
You just talked a mini episode about variable stars into this episode.
Dr. Pamela Gay:
I did. I hid variable stars in the episode.
Fraser Cain:
That’s amazing. All right. So now I think we need to kind of pull this all together, which is when you take this law, this limit, and use this to calculate how stars grow in the early on in the early universe.
And then you can kind of apply this to the growth of black holes. You get a certain sort of limit for how big a black hole should be.
Dr. Pamela Gay:
And to be clear, the limit is not the feeding of the black hole. The limit is the accretion disk around the black hole, which acts like a star. And so so you can sneak up on bigger and bigger black holes, but it’s trickstery.
So so the situation that we’re looking at is take black hole. This works for stellar mass black holes. This works for supermassive black holes.
It does not matter what size black hole you have. When the black hole is feeding, because angular momentum is a insert naughty word here, as material attempts to fly in towards that black hole, the angular momentum is like, no, you shall go spiraling around.
Fraser Cain:
Right.
Dr. Pamela Gay:
And so material builds up in a disk of spiraling material that is trying to shed its angular momentum through friction and light and other forces.
Fraser Cain:
And how this works is still a bit of a mystery.
Dr. Pamela Gay:
It’s a good homework equation. Another thing I’ve really enjoyed, but this is a graduate school. Right.
Fraser Cain:
Right. But how this.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
Yeah. I mean, just like how you can get material and how you can get, say, black holes to merge is still a bit, you know, this sort of last part of the momentum is is this is where gravity waves you’re now getting rid of energy through gravity, gravitation instead.
Dr. Pamela Gay:
It’s super cool. Yeah, I love this part of physics. So so you have your black hole.
You have an accretion disk around it. And as the material builds up in the accretion disk, it gets thicker and denser and has super high pressure and temperature and pressure are the two things you need to have that are high in order for nuclear reactions to start occurring.
Fraser Cain:
Right.
Dr. Pamela Gay:
And it’s not identical physics to what’s happening in stars other than like it’s nuclear reactions the same way. But you’re not going to get like the CNO cycle that is is working in the same way as in an accretion disk. It’s slightly different, but also the same physics.
Right. Yeah.
Fraser Cain:
But I guess what your point is, is that this disk around the black hole generates gas is being mushed together and the temperature is increasing and is starting to behave like the interior of a star falls under the Eddington limit. Time to calculate how big these accretion disks can be around various black holes before they’re too hot. They start to blow themselves apart.
The same physics is happening in this situation.
Dr. Pamela Gay:
And with supermassive black holes, the ones in the hearts of galaxies that like to be what we call quasars and active galactic nuclei. But once you start hitting the quasar side of that equation, the black holes can have accretion disks so large that they start generating light pressures that empty out the cores of galaxies.
Fraser Cain:
Right.
Dr. Pamela Gay:
At which point there’s nothing there for the black hole to eat anymore. So it chows down on that accretion disk and then sits there going, I am starving. There is nothing I can do about this.
I have done this to myself.
Fraser Cain:
But so then the math, when you sort of think about it, is like you start at the very beginning. You say, OK, we’ve got the primordial hydrogen and helium. Yeah, we know how big a star can get.
So let’s calculate the bit for the first stars. Great. That tells us the stars.
Let’s say those leave behind black holes. Great. Now we know how big those black holes were.
Now the black holes try to pull in mass.
Dr. Pamela Gay:
And I need to put numbers on this because we are starting to realize that these first stars could have been between a thousand and ten thousand solar masses.
Fraser Cain:
Because now you’re long. I’m trying to follow the standard line here.
Dr. Pamela Gay:
And then obviously it’s not the first stars, the second generation of stars.
Fraser Cain:
But even the first, sure. But even the like, even the first stars, like like you’ve got hot cores, they’re going to, you know, you’re going to reach a limit how big the star can get. Yeah.
You know, maybe it can get bigger because it has less metal that’s poisoning it or whatever. But anyway. So then you get those those first stars die. You get black holes, remnants of black holes, feed the black holes, get accretion discs. You’re limited by how big the black holes can get.
But and so that defines how rapidly this these black holes can add on mass. Their accretion discs get bigger, then they can feed faster. There is a limit.
And astronomers have gone back. They’ve made all these calculations, string them together. They’ve reached the sort of the size of the black hole that you should expect at certain ages of the universe.
And the problem is the ones that we see are too big.
Dr. Pamela Gay:
Yes.
Fraser Cain:
Too massive.
Dr. Pamela Gay:
Yes.
Fraser Cain:
That they broke the rules that at some point they either violated the Eddington limit in terms of stars or they violated the Eddington limit in terms of black holes. But now we’re in a we live in a universe with black holes that at some point took Eddington’s careful calculations, tore them up, stomped on them and said, ha.
Dr. Pamela Gay:
Or they just found another process.
Fraser Cain:
Right. And so now, please, let’s hear. Let’s go through where we think the universe has potentially violated the Eddington limit.
Dr. Pamela Gay:
So and the Eddington limit is is limited to this is what happens when gas is doing the infalling. And it’s because light pressure can push on gas, but light pressure pushing on bigger objects is is going than atoms and gas particles and dust particles is going to have a different kind of effect. So when you start looking at two black holes merging together, the Eddington limit plays a different kind of role.
And also with accretion disks, if you look at the situation of supermassive black hole feeding on the gas and dust around it, feeding on the gas and dust around it empties its area. Now, you merge two galaxies together, you rearrange where all the dust, dust and gas is, and you get to start over. Now, where we start running into problems is we expect all of these things to have time scales.
And the time scales are like, nope, you haven’t had enough time in the universe. And we keep finding this over and over and over. So we need to figure out how to reset the time that it takes for things to happen to be different.
And and this is where like new research just in the past few months, I think time has no meaning. It still has no meaning.
Fraser Cain:
Yeah.
Dr. Pamela Gay:
Is starting to point towards the first generation of stars were far more massive than we had envisioned. And they’re actually starting to come out with, well, if you make it this big, you get this chemical ratio. And we actually see nebulae filled with that chemical ratio exactly as expected at less than a billion years of of the universe being in existence.
Fraser Cain:
Right. And so it might be that if you have that first star, just hydrogen, helium, no metals. Right.
They’re able to get much bigger.
Dr. Pamela Gay:
We know that is true. And it’s true because you don’t have all the additional lines that electrons can go into to change how light is held back. You end up with with a lot more of this helium being it’s opaque, self-allowing stars just get big and hot and stuff like that.
Fraser Cain:
And like you mentioned, some recent research and there has been examples of observations that have been made with X-ray observatories and things like that, where they’re literally watching black holes feed at super Eddington rates.
Dr. Pamela Gay:
And that we’re still trying to figure out what what did we miss? And this is where we’re starting to realize, oh, shoot, you have to include electrons in ways that we didn’t originally. You have to include what is the chemical constituency of the accretion disk in ways that we hadn’t thought of before.
Fraser Cain:
Magnetic fields.
Dr. Pamela Gay:
Yeah. So you have to balance every single force. You have to balance every single quantum reaction and trying to figure out what did we forget.
This is where creativity is a part of science that we don’t acknowledge nearly enough because it’s it’s one thing to go through and do our homework where we’re like, let’s just worry about what hydrogen and helium are doing. They’re the bulk of the universe. And then you start realizing, OK, so to explain stars like our sun, you have to start including heavier atoms.
Otherwise, it doesn’t work at the mass it’s at. OK. And so we’re getting more and more complex in a lot of cases.
But the computer power and also the creativity of the person running all of the maths sometimes means we just don’t think of things or our computers aren’t powerful enough for us to include all those things. Both factors are at play. There are a lot of times where you’re like, shoot, if I run this the way I have it written, it’s going to take four months.
So let’s simplify the equations. And then there’s also the human willingness of, well, I could figure out all of those atomic quantum mechanic electrons bouncing around doing their thing. And I do not want to.
So I’m going to simplify. I’m going to do this in one dimension instead of three dimensions. I’m there’s so many ways that we simplify things because that makes the math doable.
And there’s so many ways that we simplify things because we don’t have computational power yet.
Fraser Cain:
Yeah, but you sort of hold that the most complicated field of science is magneto hydrodynamics, plasma dynamics.
Dr. Pamela Gay:
Yeah, yeah. And that’s exactly what this is.
Fraser Cain:
And this is one of those problems that you have. You have magnetic fields. You have magnetic fields, you have plasma, you have moving fluids, charged particles moving like a fluid in this environment, and it is one of the most complicated things. And then it also brings aspects of general relativity and also brings on a whole bunch of quantum mechanics.
What I love about this, though, is that we, it’s kind of like, you know, when you’re like doing homework assignments, you’ve got some complicated problem that you’re trying to do.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
And you do your math, but you know the answer. You go and you look at the answer key, but it just gives you one number. It just says, 45 meters per second.
And you go back in your calculation, you got 31 meters per second. You’re like, how, where did I go wrong? And then you examine every single part of the calculation to get you to go, like, I know what the answer has to be.
And so I have to sort of revisit all of my assumptions and try and figure this out. The universe has told us what the reality is. The Eddington limit works very well most of the time, and yet we live in this universe that is slightly different.
And so it’s those assumptions somewhere that we’re off track and that, but you, but you know, you’re not just like completely moving in an area where you have no idea where you’re going. So it has structure.
Dr. Pamela Gay:
What’s so amazing about this is when Eddington first did this, when Chandrasekhar expanded on this, when I did it as a homework assignment, we were looking at a line through a star from the center to the surface, looking for all of the places where changes in pressure and temperature changed what physics was dominant. So in the core, you have nuclear reactions. At what point as you move away from the core, does the pressure and temperature hit a limit where you switch from one mode to the next?
It’s a straight line calculation through a star and it’s good enough. As we now look at accretion disks around supermassive black holes, we’re still largely trying to figure out how to do it by taking a cut through that disk, looking both up and down and also center outwards. So now it’s two dimensions.
We’re still simplifying and now because of all the rotations and because of everything else, it’s no longer something you can do with pen and paper. We have gone from 1916 working on a chalkboard to 2020s working on a supercomputer and it’s the exact same physics. We’re just changing where we’re applying it.
Fraser Cain:
Yeah. Well, it’s a fascinating concept and, you know, I think we’re going to see a lot of work and thanks to James Webb and other big observatories, we’re making a lot of progress. So stay tuned for maybe someone coming up with the answer.
Thanks, Pamela.
Dr. Pamela Gay:
Thank you, Fraser. And thank you so much to everyone out there on Patreon who allows us to keep the show going. Rich is able to make us sound good.
Aviva is able to keep the website updated. Everything works because of you. This week, I would like to thank the following $10 and up patrons.
Alex Cohen, Andrew Palestra, Arctic Fox, Boré Andro-Lovesville, Benjamin Davies, Boogie Net, Brian Kilby, Kami Rassian, Cooper, David, Davius Rosetta, Don Mundus, Elliot Walker, Father Prax, Frank Stewart, Gerhard Schweitzer, Gordon Dewis, Hal McKinney, James Signovich, Jean-Baptiste Lemontier, Jim McGean, Joanne Mulvey, John M, JP Sullivan, Katie Byrne, Kimberly Rake, Larry Dzat, Lou Zeeland, Mark Phillips, Matt Rucker, Michael Prashada, Michelle Cullen, Name, Olga, Paul Jarman, Philip Grant, R.J. Basque, Ron Thorson, Sam Brooks and his mom, Scott Bieber, Subhana, Stephen Coffey, The Big Squish Squash, Tiffany Rogers, Tricor, Wanderer M101, and Zach Coquindal. Thank you all so very much.
Fraser Cain:
All right. Thanks, everyone. And we will see you all next week.
Dr. Pamela Gay:
Bye-bye, everyone.
Live Show#776: The Matter – Antimatter Dichotomy
Shortly after the big bang there were almost exactly the same amounts of matter and antimatter in the Universe, but there was just enough of a difference that we live in a matter-dominated Universe. But it didn’t have to be that way! Explaining this mystery has been one of the great mysteries in astronomy, and today we’ll see if there’s been any progress! Why is the Universe the way it is? Specifically, why is it made mostly of matter? This is the question we’ll look at today!
Show Notes- Why Does Anything Exist? Matter, Antimatter, and the Asymmetric Universe
- The Early Universe
- Symmetry, Violations, and Fundamental Physics
- New Ideas and Radical Theories
- Dark Matter Connections
- How Science Moves Forward
- Matter–antimatter asymmetry as a key to understand the existence of universe
- Future experiments
Fraser Cain:
Astronomy Cast, Episode 776 The Matter-Antimatter Dichotomy. Welcome to Astronomy Cast, our weekly, facts-based journey through the Cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, I’m the publisher of Universe Today.
With me, as always, is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the Director of Cosmoquest. Hello, Pamela. How are you doing?
Dr. Pamela Gay:
I am doing well enough.
Fraser Cain:
Enough. Well enough. Yes.
So, I want to talk about something that is very important, and I think a lot of people are very ashamed to admit it to us, and I think this is a safe space. And that is, it’s okay for you to fall asleep to our Delta Tones.
Dr. Pamela Gay:
It’s true. It’s true. We are aware that you do this.
And honestly, it’s a compliment to know that you’re taking us into such a vulnerable spot where we could potentially give you nightmares, and apparently we don’t.
Fraser Cain:
And that somehow the back and forth between the two of us somehow does not wake you up suddenly when I get into some kind of excited rant, and that’s good. And this is one of those great cycle of life kind of things, where I think we use other people’s audio and video to put ourselves to sleep, and I think this is just one of the great discoveries of the modern internet age, is that you can play audio, it puts you to sleep. How wonderful is that?
And I think, you know, what I consider when you’ve got all of these modern options right now where you can go onto YouTube and you can let an AI read you some kind of sleepy time AI slop. Do not do it. Or you can pick the genuine conversations between two human beings who’ve been doing this for 18 years.
We respect and appreciate the fact that you choose to spend your time going to sleep with us.
Dr. Pamela Gay:
I have one correction, however. It’s been 19 years, my friend.
Fraser Cain:
Whatever. 19 years. You’re such a stickler for the amount of time.
I no longer care. Time isn’t weaning. So yeah, use our material, fall asleep.
Don’t even listen to whole episodes. You have no shame. We appreciate your business, and by that I mean you listening to us.
Dr. Pamela Gay:
See, and I’m required to know how many years this has been because we started two weeks after I got married. And if I forget how long I’ve been married, there are consequences. Therefore, I know how long we’ve been doing this episode.
Fraser Cain:
Yeah. See, so my kid, my eldest, is exactly 30 years younger than me.
Dr. Pamela Gay:
Oh, that’s convenient.
Fraser Cain:
Yeah, exactly. So I’m always to just, I just add 30 or subtract 30, and there will be age. Yep.
Shortly after the Big Bang, there were almost exactly the same amounts of matter and antimatter in the Universe, but there was just enough of a difference that we live in a matter-dominated Universe. But it didn’t have to be that way. Explaining this mystery has been one of the great mysteries in astronomy, and today, we’ll see if there’s been any progress.
So how do we even know that there was matter and antimatter in the early Universe shortly after the Big Bang?
Dr. Pamela Gay:
It’s theory. I have to admit. So the assumption is we know that when things like particle accelerators generate vast amounts of localized energy through collisions that you get both matter and antimatter coming out of that energy.
So the story goes that the Universe came into existence as pure energy, and then that energy divided into matter and antimatter in theoretically equal amounts, and thus the Universe evolved.
Fraser Cain:
Right. And so, sorry, let me just put a, like, I’m going to, we’re going to go through this very slowly and carefully. So when we have a particle accelerator, and we are slamming particles together at enormous velocities that turns into energy, that energy freezes out particles, and what we see in our particle accelerators is this distribution between matter and antimatter.
Dr. Pamela Gay:
Mostly. Mostly. So this is where this whole episode is going to have lots of caveats on it, and that’s where the science is.
The science is in the caveats. So there was some recent research looking at the Large Hadron Collider’s results of lambda particles, and they found that they aren’t actually entirely in equal amounts of particles and antiparticles, which was exciting, because to first order, when you look, they appear to be like you do one or two experiments, and you don’t really see any differences. It’s over the accumulation of data over long periods of time, over lots and lots of, this is why we keep slamming things together, particle accelerators, lots and lots of experiments, they’re starting to see at greater than the three sigma level, not quite to the six sigma level, they’re seeing this asymmetry in matter and antimatter with more matter particles being created.
Fraser Cain:
That’s exciting.
Dr. Pamela Gay:
Yes.
Fraser Cain:
We’ll come back around. But before some of these new experiments with the Large Hadron Collider, originally it was like you either accelerate particles, slam them together, generate energy, energy freezes into particles, particles are balanced between matter and antimatter, boom, or early universe, we are simulating essentially the conditions of the early universe, and so we would get this state where you’d be getting, once things had cooled down, you get matter, antimatter.
Okay.
Dr. Pamela Gay:
And a whole lot of physics depends on this being true. So like the idea of how black holes evaporate is predicated on the idea that energy becomes a particle and an antiparticle. All this stuff is like, it’s just what we breathe.
Fraser Cain:
So then we get all of this, the temperature of the universe cools down, these particles freeze out, you get the particles, the antiparticles, but then they annihilate. Right. And what did that cause?
That annihilation of all of this matter, all this antimatter, did that just get you back to the energy again? Like what happened?
Dr. Pamela Gay:
So it got us to the cosmic microwave background being created. All of the light from the cosmic microwave background came out of this annihilation. And for reasons that make no sense.
Fraser Cain:
Well, hold on a second though. I mean, the cosmic microwave background radiation is the result of all of the protons turning into helium infusion, like the core of the star, and then it cools down and it’s like the surface of the star. And then finally you get to this place of last scattering.
Dr. Pamela Gay:
So the majority of the light is actually from the matter, antimatter.
Fraser Cain:
Whoa.
Dr. Pamela Gay:
Yeah. Yeah. So yes, there is light from when the universe was the inside of a star, sort of.
But also the particle antiparticle, there was a whole lot more of that going on earlier in time.
Fraser Cain:
Right. Yeah. But like in the first like millionth of a second after the universe, right?
Dr. Pamela Gay:
Yeah. But those photons are still going to be there getting absorbed and re-emitted and absorbed and re-emitted.
Fraser Cain:
Right. They’re random walking in the way that we see that random walk inside a star. Okay.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
Yeah. And it starts out as gamma radiation. You know, matter, antimatter gives you gamma radiation and then it’s got to make its way out of the system.
Okay. Understood. Okay.
But like a lot of people ask this question, like did it help drive the expansion in the universe? Like what role, apart from superheating everything, I guess, did this annihilation play in the evolution of the universe?
Dr. Pamela Gay:
It depends on which papers you read, but for the most part, it was a universe that was so energetic that it’s just like one more part of the soup at that point.
Fraser Cain:
Right.
Dr. Pamela Gay:
Got it. So we have what should have been, according to early theories, equal amounts of matter and antimatter should have annihilated and created a universe of pure energy that would then turn into equal amounts of antimatter and matter that would cure. And you get stuck in a cycle of you don’t get us, but there’s somehow us.
Fraser Cain:
Right. I mean, you could still get the expansion and so you would have the energy and the energy would be starting to get farther apart from each other, but it would always be sort of perfectly balanced. It would be a dramatically different universe than the one we experience.
Dr. Pamela Gay:
So somehow, the matter that we are did not get annihilated.
Fraser Cain:
Okay.
Dr. Pamela Gay:
All right. And this gets us to the initial question.
Fraser Cain:
Right. So before we get into the explanation that we’re sort of moving towards, there’s one additional possibility that I want to just sort of take off the table. And that is that, in fact, there were equal amounts of matter and antimatter, they just weren’t evenly distributed.
Right. Could we look out into the universe and see galaxies and so on where they’re all made of antimatter? And in fact, everything is perfectly balanced.
Dr. Pamela Gay:
So that was one of the early explanations for this. Now, the problem is you have our island of matter universe, you have this other island of antimatter universe, and they could be multiple islands. But between the two of them is going to be the place where matter and antimatter are encountering one another.
And that place should be creating a wall of gamma rays.
Fraser Cain:
Right.
Dr. Pamela Gay:
And we don’t see that. So within our ability to look out across the universe for whatever fraction in the universe we see, everything appears to be matter-dominated, and it is now generally accepted that we live in a matter-dominated universe and not in a universe with galaxies made of both matter and antimatter that are separated.
Fraser Cain:
Right. So if that distribution is over the cosmic horizon, not our problem. Exactly.
But we do see examples of places where antimatter is being generated. There seems to be an excess of gamma radiation coming from the center of the Milky Way. But it’s not very much.
And so even where there’s even just like slight amounts of antimatter being generated by, who knows, tons of pulsars that are acting like particle accelerators and they’re producing antimatter, it’s finding its way to matter. It’s producing gamma radiation. We see this excess.
It is subtle. It’s there. If there was whole galaxies of matter and antimatter – Not subtle.
Not subtle. It would just be the universe would be screaming at us that there’s antimatter and matter colliding over here. Take a look at me.
So no. By every measurement that we see, this universe is made of matter and, you know, and then all of the other stuff. It is definitely not equal amounts of matter, antimatter.
Okay. So hopefully everyone was like, oh, that was the one I was thinking of. Okay.
So we, so now we go back and we say, why, why do we have more matter than antimatter?
Dr. Pamela Gay:
So the next big theory that people chased down was this, this idea that maybe there isn’t the parity we think there is. Maybe there isn’t the charge symmetry we think there is. Maybe time isn’t symmetric the way we think it is.
Fraser Cain:
Yeah. You just hit CPT violation. We’re going to have to break that down a bit.
Dr. Pamela Gay:
Yeah. Yeah. So, so the idea is that when, when you take a particle, it has charge, it has parity, and it moves through time.
And ideally every bit of physics that you see that is happening for, for a matter particle should happen in the opposite time direction for the antimatter particle. And, and so everything should be symmetric for all physics interactions.
Fraser Cain:
Right.
Dr. Pamela Gay:
So beta decay, anti-beta decay, the, this, think of the way neutrons decide, I shall become a proton and an electron now. All these reactions that, that are creating positrons and electrons, these all should have symmetries in them. Right.
But, but it was noticed in, in the, I believe it was in the sixties that there are with, with mesons reactions, these, these are particles that are a quirk and an anti-quirk, there, there are reactions that are actually asymmetric. There are reactions that don’t show the, the CP, it’s CP violations is the way they called it. So charge and parity seem to have moments only involving the weak force.
So electrostatic, fine, strong, fine. Weak force, nope, not going to do it.
Fraser Cain:
Yeah. Which is kind of fascinating, right? That you, you know, you take a bunch of particles, you take a, a dock, you, you, you flip the charge on every single particle in the dock.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
You’ve now made yourself an antimatter dock.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
Right. Don’t do this. Don’t do this.
Meet, meet, meet a regular dog, you get annihilation. But, but the point is, is that the antimatter dog is going to behave exactly like the regular matter dog, just that everything is going to be, you know, that, that you’re going to get the same outcome because you’re going to get this, this symmetry. And that, but they found that when you have the charge and the parity, the antimatter dog does not behave like the matter dog in these really subtle ways, but only for the weak force.
Dr. Pamela Gay:
And, and this leads to a small amount of more matter.
Fraser Cain:
Oh, there’s a hint.
Dr. Pamela Gay:
So, so then.
Fraser Cain:
So, so sort of like, sorry, I just got to believe this point. You take dog, you let it decay, I guess you take an anti-dog, you let it decay. Okay.
I shouldn’t be using, I should be using radioactive elements.
Dr. Pamela Gay:
No, we’re not going to decay them.
Fraser Cain:
You take, you take a little bit of radioactive element, you let it decay. You take a little bit of, of anti-radioactive element, you let it decay and, you know, both sort of run by the weak force and they, you don’t get the version and the anti-version. You get a slight difference with this hinting that, okay, maybe there are these forces that are involved in this somehow, something to do with this sort of asymmetry when you, when you, when you flip everything over.
Dr. Pamela Gay:
So, so the question became, does normal baryonic matter that is made of trios of quarks have, have the same CP violation and decades pass, generations pass until finally enough data was, was accumulated by the Large Hadron Collider’s instruments looking at, at baryonic particles that they were able to go, yes, occasionally there is at the five sigma level, which is enough to say it is real. We are seeing baryons, but the problem is they’re seeing them, but the violation isn’t enough to explain the universe we’re in. We have, we have too much matter for this violation.
So, so while yes, CP violation is real, yes, we can start to understand how, how there’s more matter than antimatter. This is not a complete solution.
Fraser Cain:
Okay. So now that does not solve the whole problem.
Dr. Pamela Gay:
No, no. And, and this brings us to a fairly new theory. This is not something I learned in grad school.
It is something that actually came out of the Perimeter Institute fairly recently by, have you interviewed him? Do you know how to actually say his last name? Niall Turok?
Turok?
Fraser Cain:
Niall Turok?
Dr. Pamela Gay:
Niall Turok.
Fraser Cain:
I would say, I would say Turok. Have I interviewed Niall Turok? I have not interviewed Niall Turok.
You should. You should.
Dr. Pamela Gay:
I want you to.
Fraser Cain:
Okay. Yeah. He’s one of those maverick thinkers.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
Tons of crazy ideas coming out of, out of him. Yeah. I have not.
Dr. Pamela Gay:
That are science-based and make predictions. So.
Fraser Cain:
Yes. Uh, yes, but also are seen skeptically by large amounts of the particle physics community, which is fine, you know?
Dr. Pamela Gay:
And that is okay.
Fraser Cain:
Like this is the way it’s supposed to be done.
Dr. Pamela Gay:
If it’s disprovable, it’s still science.
Fraser Cain:
Yes. Yeah. As long as you don’t hold onto it after it’s been disproved.
Dr. Pamela Gay:
Yes.
Fraser Cain:
There, there is that part too. Yeah. Let it go when it’s been disproved.
I’m not saying that, that, that Turok isn’t doing this. I’m just saying like, in general, there are people who are making statements that are disprovable and yet when they’re disproved, they’re not releasing the idea. They are continuing to hold onto it and it’s switched from science to marketing, to self-promotion, just saying, just laying that out there, not naming any names, not pointing any fingers.
Dr. Pamela Gay:
And they do not work for the Perimeter Institute.
Fraser Cain:
No, they do not. We are not casting any aspersions.
Dr. Pamela Gay:
No.
Fraser Cain:
We are casting a wide net. Yes. A general how-to, as it, as it were.
Dr. Pamela Gay:
So, so Turok, uh, there’s, there’s this really cool suite of papers that have come out that look at the idea. Well, what if the way to look at CPT violation is…
Fraser Cain:
You’ve got to choose the charge. You’ve got to include the parody and you’ve got to include the time.
Dr. Pamela Gay:
What if the universe at the moment of its creation sent matter in one direction and anti-matter in the other direction through time?
Fraser Cain:
Whoa.
Dr. Pamela Gay:
Yeah. So, so now you have one side that’s matter dominated, another side that’s anti-matter dominated. The way this works out, it actually doesn’t require inflation.
It explains dark matters being, uh, a, a plethora of sterile neutrinos being required. It works out gracefully, except it’s, it’s so novel and weird that there’s a whole lot of people going, no, no.
Fraser Cain:
And hard to detect.
Dr. Pamela Gay:
And hard to detect. It does, it does make predictions about sterile neutrinos. Um, it also makes, uh, there should be a neutrino with no mass.
Um, right.
Fraser Cain:
And so, so this is one example. And so like the point here is, is that, is that if you go all the way to charge parody and time, you flip them all. Yeah.
That you theoretically get that violation. That you get more matter in one direction and more anti-matter in the other other direction. While the sort of expectation is no.
If you, if you take the universe and you flip all the charges and you flip all the parody and you flip all the, the time and you run the universe backwards with that you would not be able to tell.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
Right. That you can run a universe backwards, all the charges reverse, all the parodies reverse, you know, up quarks become down quarks, down quarks become up quarks, uh, positive becomes negative. You look at that universe and then you’re like, I can’t tell the difference.
Everything is perfect. And in fact, what you’re saying is maybe there’s like a little difference.
Dr. Pamela Gay:
And it’s super uncomfortable to think that out of the moment of creation, you get two universes that are one universe, but matter anti-matter time for time backwards, parody swaps. And, and because chaos theory is a thing, this doesn’t mean that there’s an anti astronomy cast that is a 13.8 billion years in the before times, um, before Big Bang, so BBB, um, it, it is to say that there were matter and anti-matter created and then chaos theory and everything else allowed perturbations to exist between the two. It’s just cool.
And it’s also not perfect, right? So we have all these different concepts. None of them are complete solutions.
And I, I am of the thinking that someday, just like with dark matter, it’s, it’s a multiple solution. Perhaps with this, it’s going to be a multiple solution of CP, CP violations.
Fraser Cain:
And, and we’re looking for the, and, and you are like, just describing a theory that was presented by one researcher, three researchers. He was, yeah, yeah. Yeah.
I reported about three weeks ago and Dr. Brian Koberlein wrote this up on universe today. Another theory that proposes that in fact, sort of early on in the universe, there were these kind of knots in space-time called a soliton field and that the sort of, while the particles themselves all behave, they were the way they were expected, these soliton fields, uh, sort of were the source of neutrinos, either axions or sterile neutrinos. And that those would, would sort of get in there and mess up the, the matter antimatter sort of side and, and, and they would only be matter.
And so you would get, yeah. And so you would get not only an explanation for dark matter, but you’d also get an explanation for the matter antimatter symmetry problem. And, and that again, like the math, but how do you observe it?
And so I think, you know, like we sat down and really researched, we could probably come up with dozens, if not hundreds of papers that are proposing novel ideas for how to explain this. And, and I think that makes it really exciting. There is this field where everybody acknowledges that this is a problem and everybody sort of is mapping out the parameters of what the solution has got to look like.
And then it’s up to the creativity of the individual researchers, the ingenuity of the people who are making the science experiments to actually perform observations, and this is how science works.
Dr. Pamela Gay:
And, and what I’m really appreciating about this is there’s a chance that they’re going to come up with something that has a single solution to explain dark matter, why it’s a majority matter universe, the expansion of the universe, and potentially inflation or lack thereof, all in one, still not grand unified theory, but one particle physics set of theories.
Fraser Cain:
I mean, that would be delightful, but come on.
Dr. Pamela Gay:
I can’t hope, a girl can’t hope.
Fraser Cain:
Right. You know, it’s going to be this horrible mishmash, inelegant collection of things that slowly, when you do the math, they all add up together to provide the explanation, but it’s a nightmare and, you know, and nobody deeply understands it and that’s just the universe is messier than we expected.
Dr. Pamela Gay:
And, and that is excellent too. And, and this is where, so, so I don’t know if you have one of these, but I have this Patreon Yeti mug that is my favorite thing and it says creativity over everything and like that describes science as well as art and, and this concept that you have to be massively, I’m not creative enough to be a particle physicist. It’s just that simple.
I am designed to be a photometrist. I have a good degree of creativity, not enough to be a particle physicist. And, and this, this is just the universe we live in and this is why we science.
We don’t understand everything. And so we keep exploring on the pursuit of it.
Fraser Cain:
Yeah. Like, you know, that feeling when you’re trying to solve a math equation and like there’s an answer in the back of the book and yet, and yet it’s not just a simple like punch in the numbers. Like it’s literally like prove this mathematical theorem.
And we did this a bit in, in my computer science mathematics class in linear algebra and we did some, some math proofs and it’s next level. Like normally you’re like factored this polynomial and you’re like, no problem. And then you’re like, prove this theorem.
And you’re like, eh, where do I even start?
Dr. Pamela Gay:
I loved that part.
Fraser Cain:
Can I disprove it? Yes. Okay, great.
Done.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
Right. No, I can’t. Okay. So how do I, and so like things like, like there are other people who prove one plus one equals two and that, that there is this whole class of mathematics equations which are, which are literally unproven and it’s just this, I can’t even imagine.
My brain would nope out so hard trying to just blank, clean slate, solve a mathematical problem like this. And you’d, and you have these creative ideas. You’re like, oh, maybe I do this.
And then you spend the next three years of your life filling up one piece of paper with equations. You’re like, nope, that didn’t work. No, that just sounds like hell to me.
But yeah, but there are people out there who love it.
Dr. Pamela Gay:
So I, I particle physics, like kinematics, physics, that kind of like relativity. I’m down with all of that.
Fraser Cain:
Um, but just blue sky, no pure math. No, no, no. But mad respect.
Thanks, Pamela.
Dr. Pamela Gay:
Thank you, Fraser. And thank you so much to all the patrons out there who allow us to put the show together week after week. This show is made possible by our community on patreon.com slash astronomycast. This week, we’d like to thank the following $10 and up patrons, Alan Gross, Andrew Allen, Antisor, Aster Setz, Benjamin Carrier, Bob Krell, Brian Breed, Buzz Parsec, Conrad Howling, Daniel Schechter, David Green, Dr. Whoa, Ed, Fairchild, just as it sounds. Frederick Salvo, Jeff McDonald, Gold, Gregory Singleton, J Alex Anderson, Jason Kwong, Jeremy Kerwin, J O, John Herman, Jordan Turner, Kate Sindretto, Kim Barron, Lab Rat Matt, Les Howard, Mark, Masa Herleu, MHW1961, Super Symmetrical, Michael Regan, Naila, Noah Albertson, Paul Esposito, Peter, Red Bar Is Watching, Robert Plasma, Sachi Takeba, Scone, Sergey Manalov, Steven Rutley, TC Starboy, Thomas Gazzetta, Travis C. Porco, Vitaly, William Andrews.
Thank you all so very much.
Fraser Cain:
Thanks everyone. And we will see you next week.
Dr. Pamela Gay:
Bye bye everyone.
Live Show#775: The Hydrogen 21-cm Line
Atomic hydrogen is the raw material for stars, but there’s a problem. It’s cold & dark, but it can do a very rare trick, releasing a photon in a very specific wavelength, known as the 21 centimeter line. And thanks to this wavelength astronomers have mapped out star forming regions across the Milky Way, the Universe and into the Dark Ages! This forbidden transition of Hydrogen has led to the mapping of galaxy rotation, a cool classroom application of quantum mechanics, and weirdly no Nobel prize. In this episode, Fraser and Pamela take a look at this line’s out-of-proportion awesomeness!
Show Notes- The Power of the 21-Centimeter Line
- Why the 21-Centimeter Line Matters
- Seeing the Invisible Universe
- Galaxies, Dark Matter, and Hidden Mass
- Learning and Discovery
- Looking Back in Time
- Challenges and Future Solutions
- Beyond Astronomy
[Fraser Cain]
Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, I’m the publisher of Universe Today. With me, as always, is Dr. Pamela Gay, Senior Scientist for the Planetary Science Institute and the Director of CosmoQuest.
[Dr. Pamela Gay]
Hey, Pamela, how you doing? I am doing well enough. I am currently finding, I have new technology, which is absolutely amazing, but nothing works.
So everyone, thank you for your patience as there is ludicrous hacking that went into putting together this episode.
[Fraser Cain]
Now, normally, after the amount of time that I’ve been gone, I would say like, hey, it’s great to be back. And did you all miss me? But because you, in your infinite wisdom, said, let’s just record all these shows, get them in the can, and then you don’t have to think about this anymore.
We record all the shows, we got them in the can, and then I didn’t have to think about them anymore. And I am so glad you were so smart. You were so right, because I, because it is, you know, being on the road, it’s a gum show.
And trying to then set up internet of different time zones. It was so nice to go, oh, yeah, all those astronomy casts are done. So and now we continue uninterrupted, which was just great.
And so I’m back.
[Dr. Pamela Gay]
And you escaped, you escaped the CosmoQuest hangout-a-thon this year. There was no live recording of astronomy cast. You did not have to be part of our wild fundraising.
By the way, if anyone wants to donate money, please join both Fraser’s Patreon and my Patreon. We both need your support to keep doing what we do as independent journalists. All right, that’s done.
[Fraser Cain]
Yeah. Yeah. I mean, this will turn into a rant, so I don’t want.
But anyway, I’m finding that journalists are reaching out to me and saying, do you have any work?
[Dr. Pamela Gay]
Yeah, it’s really bad right now.
[Fraser Cain]
And that is telling me that the sort of copywriting apocalypse is starting to roll out. And fortunately, because we’re Patreon funded and we don’t use AI for our writing, we are going to be this island of stability as as the rest of this industry erodes all around us. So thank you, everybody, who supports us financially.
You are allowing me to pay everybody salaries. All right, let’s get into this week’s episode. Atomic hydrogen is the raw material for stars, but there’s a problem.
It’s cold and dark, but can do a very rare trick, releasing a photon in a very specific wavelength known as the 21 centimeter line. And thanks to this wavelength, astronomers have mapped out star forming regions across the Milky Way, the universe and into the dark ages. All right.
21 centimeter line. It’s a very obscure sounding topic. Yeah, very, very nerdy topic.
But it is like just one of the most useful tools that astronomers have at their disposal. And it’s kind of weird that we haven’t talked about this up until now. I mean, we’ve mentioned it, but I think, you know, let’s give it the the, you know, the appropriate amount of conversation.
[Dr. Pamela Gay]
And I have to admit, I had to go back and rewrite the show promo I initially wrote because I was quite certain that not only had we recorded an episode about this, which I determined we hadn’t, I was also quite certain that a Nobel Prize had been given to the 21 centimeter discovery humans, which it hadn’t. This is a line that’s like super, super important and just doesn’t seem to get the love it deserves.
[Fraser Cain]
Right. It will. It will.
[Dr. Pamela Gay]
It will.
[Fraser Cain]
Maybe after the show, we’re giving it the astronomy cast bump.
[Dr. Pamela Gay]
It’s true.
[Fraser Cain]
OK, so I guess let’s talk about. I’m trying to think. Let’s talk about molecular hydrogen, I guess, the raw material for stars.
[Dr. Pamela Gay]
So so molecular hydrogen. And just to be clear, the the 21 centimeter hydrogen line comes from atomic hydrogen. It comes from the atom of hydrogen.
[Fraser Cain]
Yeah.
[Dr. Pamela Gay]
So so molecular hydrogen take two hydrogen atoms. They each have one electron going around them in normal cases. And it turns out that that the electron shells and atoms really are completionists.
And I understand this is someone who is a completionist. You and hydrogen. Get all your tasks done.
Yes, exactly. And and so the S shell wants to have two electrons in it. So two hydrogens, they get close enough together like we can complete our shell if only we share our electrons.
And so they come together, they share their electrons, they complete their shell and they’re much happier this way. So this is the stuff of the cold, dark universe.
[Fraser Cain]
Right. Right. And and I think it’s really important to sort of understand, like when hydrogen receives a lot of radiation, then it starts to warm up.
It glows. Those are nebulae, right? We see them, but they don’t want to turn into stars.
They’re too hot.
[Dr. Pamela Gay]
Right. And so with 21 centimeter line, this is something that you don’t encounter in anything vaguely warm. So you’re now taking me in a direction I was not prepared for.
Where are we going?
[Fraser Cain]
Well, right. So I guess the point here is that that if you want to find clouds of hydrogen, clouds of hot hydrogen.
[Dr. Pamela Gay]
Yes.
[Fraser Cain]
All you have to do is look out there with a telescope.
[Dr. Pamela Gay]
Yeah. Hydrogen alpha. So so there’s there’s two major series of hydrogen lines that we look for, depending on what redshift we’re looking at.
So in the local universe, we have the bomber series, which is electrons jumping from higher energy levels down to the second energy level. Then at the ultraviolet locally, we have the Lyman series where Lyman alpha is two to one. And so it’s higher energy level into the first energy level.
And as things get redshifted further and further, that Lyman alpha eventually migrates into the visible wavelengths. And it allows us to see hydrogen at the highest redshifts out there up until the point when there’s no light going through the universe, when we have this foggy period before the universe reionized.
[Fraser Cain]
Right. And like I can look, I have nice dark skies here. I can look towards Orion and I can see the Orion Nebula.
[Dr. Pamela Gay]
Yes.
[Fraser Cain]
With my eyes.
[Dr. Pamela Gay]
Yes.
[Fraser Cain]
Right. There is this little glowy spot in Orion scabbard. And if you look in pair binoculars or telescope, then you definitely can see it.
And then you take a picture and you can absolutely see it. And so to see where the clouds of hydrogen are that are ionized, that are bright, glowing, you can it’s it’s not that challenging a problem. The what is the challenging problem is to find the hydrogen that is cold, the hydrogen that is that is has not been ionized is pumping out radiation that is cold.
And yet it is that cold hydrogen, which is the raw material for stars. And that’s where I’m going, is that astronomers need a technique to find the cold hydrogen.
[Dr. Pamela Gay]
Yeah. And and so what we’re looking for is the stuff that isn’t so dense that it’s blocking the light behind it. So it’s fairly easy to spot molecular clouds of super dense hydrogen.
They are great walls of blocking the rest of the galaxy.
[Fraser Cain]
Yeah.
[Dr. Pamela Gay]
So these are things like the Bach globules to see warm stuff. You have all these wonderful transitions and hydrogen that are quite happy to transition for you. So if you have hydrogen atoms that are not getting collisionally excited, that are not getting heated up by surrounding light, that are just cold, non-interacting, so diffuse, this this is like collisions are not a thing that an atom can expect to experience.
This is where you start to be able to imagine. And it turns out that it’s actually there that you can start to see what are called forbidden transitions. These are transitions that statistically we just should never have a chance of seeing.
[Fraser Cain]
Right.
[Dr. Pamela Gay]
And the specific forbidden line that we’re looking for is if you have a proton that has a spin up and you have an electron that has a spin up, that has a higher energy in that alignment than if you have them anti-aligned. So if the electron flips from spin up to spin down, or if you had the proton down, electron down and it flips to up, that flip between being aligned and being anti-aligned gives off a tiny amount of energy. And the smaller the amount of energy, the longer the wavelength of light.
[Fraser Cain]
Right.
[Dr. Pamela Gay]
And in this case, that length of light is is 21 centimeters is is your wavelength. So you’re going from something that is is like hair’s breadth to can measure it with your hands.
[Fraser Cain]
Yeah. Yeah. I mean, like when we talk about wavelengths of light, we’re talking, you know, often it’s like, oh, it’s 500 nanometers.
Are you thinking about visible light? And it is like we don’t have any practical experience to understand how small that is.
[Dr. Pamela Gay]
Yeah.
[Fraser Cain]
We talk about even infrared light. We’re looking at things that are in the micrometers to sub millimeter.
[Dr. Pamela Gay]
Yeah.
[Fraser Cain]
But but the you know, this thing, the 21 centimeter line, you know, it’s like about that.
[Dr. Pamela Gay]
Yeah.
[Fraser Cain]
And podcast listeners, I’m holding my hands out, you know, about two thirds of a foot. Right. Twenty twenty centimeters.
What what wavelength like what regime is that in? Is that in the microwave?
[Dr. Pamela Gay]
It’s it’s it’s part of the L band of microwave radio is where my brain puts it, because all of that is is something that you can measure with basically a radio dish. It’s just what is the horn you’re using? So this is part of a atmospheric hole that there’s there’s various wavelengths that are atmospheres like, no, you’re not allowed to observe that.
And this luckily falls into one of the bands that we can completely see from the surface of our world. And so when folks were starting to get a handle on quantum mechanics, we’re starting to get a handle on on these are all the different ways that energy can get released as protons and electrons flip and interact. It was predicted in nineteen forty four.
This this is a fairly new realization. It was predicted in nineteen forty four that this could be something that might be observable. And then in fifty one, they finally put together the set of observations to detect this super faint line.
And and the reason it’s faint is the the alignment that we’re looking for with with the aligned proton and electron that flipped to be anti aligned. That atomic situation is stable for eleven million years.
[Fraser Cain]
Right. So hold on. So so so I take a proton with its electron and I leave it.
And then if I wait eleven million years, that’s about how long it’s going to take for it to do that spin flip.
[Dr. Pamela Gay]
That that’s half life is the wrong word for this. But yeah, the probability of it flipping is probabilistically eleven million years.
[Fraser Cain]
Right. Probably it’ll probably happen.
[Dr. Pamela Gay]
Yeah.
[Fraser Cain]
In eleven million years. Right. And so if you have any one individual proton of hydrogen.
Yeah. It’s not going to do this in, you know, a thousand lifetimes, but you get a cloud that is large enough, then some number of them is is giving off this signal.
[Dr. Pamela Gay]
So you need to have a cloud that is excessively cold. So things aren’t moving around very much, excessively diffuse. So what little motion you’re going to have just because of the base temperature of our universe isn’t going to let these things collide with each other on timescales of tens of millions of years.
And then you need enough atoms that enough of these flips are occurring that we’re receiving enough light in our direction that it’s detectable.
[Fraser Cain]
OK, why? Why is this important? Why is this this this weird behavior of of atomic hydrogen?
Why does this matter?
[Dr. Pamela Gay]
I there’s a variety of different reasons. The first is it allows us to map out the least dense corners of our galaxy, the outer parts of the disk. It’s it’s like the line that we can catch from diffuse clouds of hydrogen.
I that are just barely gravitationally held on to. And it’s from these 21 centimeter measurements of our galaxy and other galaxies that folks like Vera Rubin were able to start saying, wait, these motions don’t what’s going on here.
[Fraser Cain]
And this is the person, not the telescope.
[Dr. Pamela Gay]
Right, right. The human being, the human being. Sorry.
That’s now a requirement to say, yes. Yeah. So so the human being who studied dark matter, right, along with other human beings who studied dark matter, were able to spot this flattening of the rotation curve of our galaxy, which isn’t something anyone expected.
It was expected that as the visible material dropped off, we we’d see the velocities decreasing with distance. Right. And they’re not, which says there’s a whole lot of stuff out there that that isn’t gassy enough to have forbidden lines.
[Fraser Cain]
Right. So that we look out in space and we see a galaxy and we see all of the stars, we see all the star forming regions, we see all the bright stuff.
[Dr. Pamela Gay]
Yeah.
[Fraser Cain]
But that is not the galaxy. There is more galaxy around that galaxy. There is also surrounded by clouds of hydrogen that will maybe eventually get pulled into stars or maybe get spun out or be sucked away through tidal tails, through interactions with other galaxies.
How big is that galaxy really? By mapping out this cold hydrogen, which is, I guess, more dense than just the than just intergalactic space.
[Dr. Pamela Gay]
Yes.
[Fraser Cain]
Right. There’s more stuff in that than there is just an intergalactic space. You can map out the real shape of the of the actual galaxy and all of the clouds of hydrogen that are surrounding it.
[Dr. Pamela Gay]
And this is something that we can do locally and a standard homework assignment at many universities that have small radio telescopes is to just assign a senior lab where you go out and you measure the 21 centimeter line in clouds of gas around the Milky Way and you do your own rotation curve repeating this historic work.
[Fraser Cain]
That’s amazing.
[Dr. Pamela Gay]
Yeah. It’s one of those things of it’s fundamental, but it’s repeatable in a way that you can’t deny that there’s unseen stuff that is out there when you see the data for yourself as a student.
[Fraser Cain]
But I think it’s important to like qualify that’s not dark matter like that’s that’s right. Dark comma matter. Right.
It is regular matter, regular hydrogen. You’re you know, you’re yeah, whatever. Seventy five percent made of the stuff.
[Dr. Pamela Gay]
Yeah.
[Fraser Cain]
Right. Or whatever. Right.
[Dr. Pamela Gay]
But dark matter is different stuff.
[Fraser Cain]
Different stuff. Yeah. React with the electromagnetic force.
So but and so like as an astronomer, you might be able to ask questions like how much gas is left in that galaxy that can form more stars? Where are the where are the reserves of gas in that galaxy? Do they line up with the spiral arms?
How do they transition between just clouds of gas to star forming regions? What is the potential of that galaxy? That’s where you’re you’re you’re mapping out using the 21 centimeter line.
[Dr. Pamela Gay]
And that that is the next place to go with this is so first you have, for me, the most interesting part, which is the discovering that not all the stuff that makes up a galaxy can be detected through through gravity allows us to see that that other stuff is out there. And then what is the potential for star formation? What is the potential for continued life?
What is the stuff available to feed supermassive black holes? There’s amazing maps of our own galaxy that allow you to see all throughout the disk of the Milky Way, the presence of 21 centimeter emission. And that’s telling us there is still gas and dust out there.
Not so dark that it blocks all the light, not so hot that it glows in bomber or Lyman lines of hydrogen transitions. It’s just out there being diffused and not colliding.
[Fraser Cain]
It’s it’s our war chest. It’s our it’s our gas reserves that the Milky Way can draw on for trillions of years into the future to make new stars. And the question, you know, the astronomers will ask this question, how many stars can this galaxy make?
It comes from the the cold. Sort of inert hydrogen that’s just sitting there, not glowing, not interacting, not blocking light, just being all right, so you take your microwave telescope, you tune it to 21 centimeters, you point it in the sky, thanks to the atmosphere, allowing that wavelength to get through. And then you just move around and you map out blobs here, blobs there and so on.
How does that then change as we want to look out into the cosmos, which, of course, is looking back in time?
[Dr. Pamela Gay]
So we have two ways to see the cold blobs of gas that haven’t bothered to get themselves into galaxies as we look out. So one of those is we see what are called the Lyman-alpha forest, where the light from background galaxies passes through clouds of gas that are between us and those galaxies. And at the redshift of those galaxies, we see the hydrogen lines of absorption.
Now, the other side of that is sometimes we are lucky enough to see the ever lengthening hydrogen 21 centimeter emission from those gas clouds. And once you start getting out to around 50 centimeters, you’re starting to look at cosmological distances where there really isn’t much light to give us a clue as to what’s going on. The only way we’re ever going to be able to detect light from the dark ages of our universe is to look for this extremely, extremely faint background light.
[Fraser Cain]
And you mentioned sort of 50 centimeters. So in other words, that the universe has been expanding, the wavelengths have been redshifting in the same way that what was once red light after the cosmic microwave background has turned into microwave. This light started out in the microwave and has now been redshifted to much longer wavelengths.
[Dr. Pamela Gay]
And there’s two different effects that does this. One is just as the universe expands, it expands the light with it. And the other is just the cosmological expansion of the universe adds its own redshift.
So it’s a really ugly calculation. But it means that while interesting things like Lyman Alpha, land in the visible, things that started out long ended up even longer.
[Fraser Cain]
Right. And so that takes a very special kind of telescope to see redshifted 21 centimeter long.
[Dr. Pamela Gay]
And and we haven’t gotten to the point yet that we’re starting to detect this this age before reionization from this light. It is something that we dream of doing, that we plan on doing.
[Fraser Cain]
Right.
[Dr. Pamela Gay]
But yeah, yeah, yeah.
[Fraser Cain]
And like I think it’s really important for people to understand, right? Like you, you had the beginning of the universe, you have the cosmic microwave background, the whole universe is kind of red and then it becomes transparent for the first time and then it cools down. But the first stars haven’t formed yet.
And so now we talked about those clouds of gas that are in the Milky Way. Imagine if the whole universe was that. Right.
Where is the stuff? Right. Well, you need the 21 centimeter line to show you where the stuff is.
So so that is the key to us understanding how those first galaxies, those first stars came together at a time when everything is obscured and you can’t see it. Wasn’t until all of those galaxies got going, the stars got going, they cleared out all the rest of that material and we could see them again. That’s the reionization you’re mentioning.
So so what are the sort of best ideas to do this? You mentioned we’re kind of at the cusp, like we really are at this point in the history of astronomy where this is a technique that is just within reach for us to be able to try and observe the first, you know, to map out this initial cold hydrogen. So, you know, what can we sort of count on, do you think?
[Dr. Pamela Gay]
Well, first of all, we need to get more detectors off our planet. That’s one of the big frustrations is as we get to this particular set of wavelengths, we’re fighting tooth and nail against the atmosphere, right? There there are atmospheric poles short word of this.
There are atmospheric poles long word of this. Right. This is a cursed wavelength.
[Fraser Cain]
Right. So you mentioned that if it was just a regular 21 centimeter line, then it gets to go through the atmosphere. But now it’s been redshifted.
So now the atmosphere is not playing nice with it anymore. Correct.
[Dr. Pamela Gay]
So building radio telescopes in space is something we have the capacity to do. But there’s other things that are a whole lot more interesting that like the James Webb Space Telescope is capable of looking at myriad different problems. A long wavelength radio telescope is going to be difficult to build.
You have to have really big dishes to get any kind of resolution or you have to have an interferometric system to get any sort of resolution because your resolution is dependent on the diameter divided by the wavelength. Your wavelength goes up. You need a bigger diameter to get the same wavelength to get the same resolution.
[Fraser Cain]
Right. But it’s also faint, right? Like it’s it’s faint, too.
So so an interferometer doesn’t get only gets you so far because you also need a telescope that can handle you need a lot of just antenna space. So you need something that is that has a large amount of resolving area and has a large baseline. Ideally, right.
So so have you like looked at some of the cool lunar telescopes to try and solve this problem?
[Dr. Pamela Gay]
They’re dead to me until they’re funded.
[Fraser Cain]
Right. Of course. Yes.
All right. Well, then I am going to explain this to you. Yes.
Which is that there are a bunch of teams that are working on ideas for moon based telescopes that would be on the far side of the moon. So we’ll be blocked by the by the the moon. And so you wouldn’t get the radiation coming from the earth.
All of our stupid, you know, radio traffic, you’d have this pristine, dark radio environment. And then they could build really big telescopes. And so the idea is where you would say land a spacecraft on the moon, you have a rover on board and it would reel out an antenna because you need to have you need to have like a big dish.
You can actually just have wire that you put down on the surface of the moon in a shape that that you need. And so you could have this sort of central lander and then rovers that are crawling out in all directions from it, laying down antenna onto the regolith that would form this gigantic antenna that’s blocked from the surface of the earth. There’s one called Far Side.
There’s one that NASA is working on. The Europeans are working on some ideas. The Chinese are actually going to be doing a test in a couple of years.
They’re going to send a radio telescope to the far side, but orbital of the moon and try to make some detections of the 21 centimeter line at the dark ages of the universe.
[Dr. Pamela Gay]
It’s super important to put this stuff on the far side of the moon because our atmosphere does leak these radio frequencies because we are literally using radio and television in this frequency band.
[Fraser Cain]
Yeah, we’re yelling in this frequency band and we would corrupt the results from radio telescope.
[Dr. Pamela Gay]
Right. So we have to block our own shouting. Yeah.
As as we look for this.
[Fraser Cain]
And there are enough plans now that one of these is going to happen. Like there are there was a prototype experiment that was on one of the lunar landers that toppled over.
[Dr. Pamela Gay]
Yeah.
[Fraser Cain]
And so they were going to try and make those observations. You’ve got like some tentative observations with things like the Murchison Array, which is the precursor to the Square Kilometer Array. You’re probably going to get some some detections using the Square Kilometer Array, but it’s sort of not its main job.
So it’s really going to be let’s put a telescope on the far side of the moon, a big, giant antenna or like a wire spooled out across the moon that will get us these observations. Because like the other ideas are like little Christmas trees, like what they’ve got with the Murchison Array. There’s been a lot of like really cool ideas.
Like it doesn’t have to look like a telescope, doesn’t even have to look like a big radio dish. It can be this very, very simple, very robust telescope. And yet it will do this job and detect.
And then there could be this time when astronomers are able to start to just get a sense of the density mapping out.
[Dr. Pamela Gay]
Yeah
[Fraser Cain]
You know how thick was this hydrogen early on when what was the separation between the clouds of hydrogen and the initial galaxies that were forming do we see the supermassive black holes forming first pulling in material from around them so there’s a lot of yeah yeah I mean it’s it’s called the dark ages for a reason
[Dr. Pamela Gay]
Right and and there’s one other obscure usage of this line that we haven’t talked about and and that’s the idea that lots of different space observing civilizations would probably want to protect just as we’ve protect protected this line from being used for everyday transmission so we don’t have radio stations or television stations using this wavelength because it’s reserved for astronomy now you can start to imagine that if that is a common habit preserving wave bands for science that there could be civilizations out there that decide they’re going to transmit purposefully making their existence known at this particular wavelength so it’s been proposed that the 21 centimeter line also works for SETI potentially
[Fraser Cain]
I love that
[Dr. Pamela Gay]
yeah so I I particularly love the idea that wanting to do science is something we should expect to be a universal idea of civilizations and I really hope it’s true I really hope that’s all wonderful
[Fraser Cain]
thanks Pamela
[Dr. Pamela Gay]
thank you Fraser and thank you to everyone out there in our patreon audience you are all amazing this show is made possible by our community on patreon.com slash astronomy cast this week we’d like to thank the following $10 and up patrons Adam Anise Brown Alexis Andy Moore Astrobop Bebop Apocalypse Bob Zatzke Brett Moorman Burry Gowman Cody Rose Daniel Loosley David Gates Dizastrina Dwight Ilk Evil Melky Flower Guy Galactic President Scooper Star McScoopsalot Glenn McDavid Greg Vylde Helge Bjorkhog Jarvis Earl Jeff Wilson Jim of Everett John Drake Jonathan H Staver Justin S Kenneth Ryan Kinsella Panflenko Lee Harbourn Marco Iorassi Mark Steven Raznak Matthias Hayden Michael Wichman Mike Hizzi Nick Boyd Paul D Disney Pauline Middleink Randall Robert Cordova Sergio Sanchevier Sergio San Severo Shersom Semyon Torfason Slug Taz Tully The Lonely Sandperson Time Lord Iroh Van Ruckman Will Hamilton thank you all so very much
[Fraser Cain]
great all right thanks everyone and we will see you next week
[Dr. Pamela Gay]
bye-bye everyone
Live Show#774: How Does Bad Science Happen?
Scientific expertise is under attack on all fronts with concerns coming from politicians and the public. While most of this is unwarranted and politically motivated, there can be germ of truth. Bad science does happen, but how? How is it that papers that very few believe still make it through peer review and to publication? Why do professors at prominent universities get quoted saying things that seem to be fiction? In this episode, we consider the case for letting potentially impossible things make it to publication.
Show Notes- What is “bad science”?
- Bias and the scientific method
- P-values and “p-hacking”
- Breakthroughs that challenged consensus
- Academic pressure and “publish or perish”
- Competition and bad behavior in academia
- Institutions, media, and incentives
- Filters for real breakthroughs
- Careers, communication, and risk
[Fraser Cain]
Astronomy Cast, episode 774. How does bad science happen? Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos.
We’re helping you understand not only what we know, but how we know what we know. I’m Fraser Cain. I’m the publisher of Universe Today.
With me, as always, is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute, and the director of Cosmic Quest. Hey, Pamela, how are you doing?
[Dr. Pamela Gay]
I am thinking right now that we need to say that this episode is not how we know what we know, but it’s how what we know gets confused by bad publications.
[Fraser Cain]
How we know what we know, how we know what we don’t know, how we don’t know what we don’t know, how we don’t know what we know.
[Dr. Pamela Gay]
How noise gets added to the system, basically.
[Fraser Cain]
Yeah.
[Dr. Pamela Gay]
Yeah, mistakes get made.
[Fraser Cain]
Scientific expertise is under attack on all fronts, with concerns coming from politicians and the public. While most of this is unwarranted and politically motivated, there could be a germ of truth. Bad science does happen, but how?
So, do you have an example in your mind of perhaps some bad science that you want to share?
[Dr. Pamela Gay]
So, lately the two big ones in my life have been all of the attempts by non-planetary scientists to publish about 3i Atlas. And there have been some fascinating cherry picking of supernova data that is attempting to get rid of dark energy until you realize they’re cherry picking the data and what they’re saying doesn’t actually make sense if you look at stellar evolution.
[Fraser Cain]
So, specifically, you’re talking about examples where people who do have scientific training are cherry picking results to tell a certain scientific narrative that is not necessarily shared by the scientific consensus and the scientific mainstream.
[Dr. Pamela Gay]
Yes.
[Fraser Cain]
Right. And, like, this is a spectrum because, you know, there are even, you know, you could almost describe them as scandals that are happening, the reproducibility crisis that’s going on in biology, psychology, this concept of p-hacking that scientists will sometimes do.
[Dr. Pamela Gay]
We have to back up on that one because said out loud, that’s deeply confusing. There is a value in statistics, it is the lowercase letter p equals value that is used to define how likely your output fits to a given situation. And it’s called the p-value.
Luckily, I never have to deal with it in my life, but there are statisticians and stats is largely black magic as far as I’m concerned because you’re dealing with what is the noise in your system, what is the noise in the universe, what is the distribution that should occur due to things like chaos theory, what is the distribution that should happen because of motion and thermal statistics, all of these different things layer up to affect what the population should look like for a given system because of just noise.
[Fraser Cain]
Right. Well, we’ll get into this a bit more as we talk about this. So I want to approach this from a couple of perspectives.
The first perspective is how good scientists can delude themselves. And, you know, really focusing on this idea of confirmation bias, that we are looking for evidence that matches our preexisting conclusion. Yeah.
So give me a sense as a scientist, how do you approach a problem or approach a scientific question without biasing yourself on what is the outcome that you’re hoping to accomplish?
[Dr. Pamela Gay]
The best examples I’ve seen and what I try to do is you take the data and then you brainstorm every single possible thing that could fit that data and you work through and you’re like, if it is this, we expect to see all of these things. Do we see all of those things? No.
Well, what parts of them do we or don’t we see and what could explain that? All right. So let’s look at the next thing.
What of these things would we expect to see? What do we actually see? What could explain the difference?
A brilliant paper I once saw that also made me die laughing was trying to figure out data that had dimming in an object. And they said, eagle flies in front of telescope as one of the things that they had to figure out what would that do to the light curve.
[Fraser Cain]
What would that look like to the light curve?
[Dr. Pamela Gay]
And so you have to take into account all the different things that could be at play and what are all the different things that could explain what you see.
[Fraser Cain]
Yeah. And this idea of confirmation bias is pernicious. It is baked in to our brains.
And this is a thing that we are always going to be having to double check and double check. And the best amongst us will fall for this confirmation bias, that there is an outcome that you are expecting, an outcome that you think is most likely, most logical, and that then you are looking for the evidence that matches that outcome and you are ignoring the evidence that is less evidence for that outcome. You talk about this, you brainstorm this gigantic list, but even just how do you resist?
How do you notice when you are potentially going down this confirmation bias pathway?
[Dr. Pamela Gay]
It’s really hard. And quite often, human beings simply aren’t as creative as the universe is, which is a really weird thing to say. But there’s different things that occur in science where I look at the results and I’m like, how did they ever figure that out?
Who came up with that explanation? It’s brilliant, but how did you get from here to here? And you have to be super creative.
And this is part of where you hear people saying that it’s young scientists who make the amazing breakthroughs because they’re still not as influenced in a way by having to cynically keep saying to people, no, no, that actually doesn’t work. No, no, no, that doesn’t work. And you reach a certain point in your life where your gut response to everything is going to be no.
[Fraser Cain]
Right, that won’t work.
[Dr. Pamela Gay]
Right. So it’s when you’re young and not as, I don’t know, embittered, something, that you’re willing to go there and take in all the different ideas. And sometimes your data doesn’t give you a choice.
The 1998 supernova results, there was two different research teams that both saw a trend in the typical luminosity of supernova as a function of their velocity. And this indicated that either something is screwy with supernovae as a function of when they went off in the universe or our universe is actually accelerating over time and how it expands. That was undeniable.
And since then, people have been going through trying to find every possible way to explain that supernovae were actually just intrinsically fainter in the past. And nothing works if you look at an unbiased sample of galaxies.
[Fraser Cain]
Right, yeah. So confirmation bias is, I think, the strongest one. Yes.
But there are a bunch of other biases. Recency bias is another one. You can go and look up cognitive biases, and I think there’s like 80?
I forget how many there are. There are a lot, easily in the 30s, of biases that can influence our thinking. And often you have to go through this process and say, okay, I learned about this, I don’t know, kind of car, and now I’m seeing this car everywhere.
Is it a conspiracy? Oh, no, that’s recency bias. Man, confirmation bias is that experience you have when you’re on autopilot and you’re expecting something to go one way and then it doesn’t go that way.
Like you take a jar out of the fridge, you take a drink, you’re expecting it to be cold coffee and it’s apple juice.
[Dr. Pamela Gay]
Yeah.
[Fraser Cain]
And suddenly, the moment you realize that it’s apple juice is the moment that you’re drinking it, and you’re like, wait a minute.
[Dr. Pamela Gay]
Yeah.
[Fraser Cain]
Okay, of course it’s apple juice. I’ve grabbed the apple juice container. But my brain was so certain that I was going to be grabbing the coffee that I drank the coffee, and then it’s that moment when reality informs you that you’ve made this mistake.
But that’s just, you know, those are a couple of examples. There are so many different biases that we can fall for that are constantly, and really the scientific method has been about let’s learn all of the different ways that the human brain can go wrong and try to account for those. And so what are the kinds of techniques that a scientist will use to try and hit the gold standard of good science?
[Dr. Pamela Gay]
Literally the best that I see in the literature are just where you’re like, okay, I’ve gone to a bunch of conferences, I’ve presented this research, I’ve listened to the question and answers, I’ve heard everyone saying, well, could it be this? Could it be this?
[Fraser Cain]
Right, yeah.
[Dr. Pamela Gay]
And here’s me going through and addressing every single one of them. Now, that’s the gold standard. The problem that you run into though is sometimes people, and this can occur at any point in your career, are so shaped by I wrote a proposal for my dissertation to do X, I got a grant funded to do X, and the data is actually consistent with three.
Not X. It’s not even a letter. It’s something over here somewhere.
And it’s really hard to get your brain, especially when you’re only talking to rooms full of people that are in your subdiscipline, it’s really hard to get your brain to open up all the way like that person whose paper said, this is what an eagle would do if it flew in front of our data. It was brilliant. Big bear observatory for the win.
You have to sometimes sit down and talk to people in other fields. You have to hopefully work somewhere that if your results don’t match what you proposed, it gets celebrated. You hopefully are working on a dissertation where you will still get it if you prove something very different from what you set out to prove.
And so being, this is going to sound so dumb, but being in a place where you are safe to talk to people outside of your discipline to get input and you’re allowed to have unexpected results are both necessary.
[Fraser Cain]
So we’ve talked about how the researcher can kind of fool themselves. How does, and you sort of touched on this a little bit, but how does the environment of the scientific community, the expectations and the demands of how science works, how can that potentially cause bad science?
[Dr. Pamela Gay]
People end up working on the same idea year after year after year, trying to prove what I’m doing is right. You get into a rut. You get your old grants renewed.
You keep going down the same rabbit hole. And once you start down that path, you have to say I was wrong or this isn’t going where I was hoping it was going, which isn’t the same thing as I was wrong. It’s just the I am bored now.
This is just not what I was hoping for. And human beings really aren’t good at doing either of those things. And so we will see people that start on a project as a graduate student and it’s cool and they get attention and they get their PhD and they get their first job to continue working on that work.
And so they continue building on the same data set, getting a very similar data set. And they don’t make the necessary leap to broaden even their own horizons. And by siloing themselves and following the easy dopamine hit of incremental breakthroughs, they can end up doing things where they are working with deeply biased data sets.
We’re seeing this in cosmology right now. They can end up being influenced by if I come out and say it’s not alien spacecraft, my books are going to stop selling and I’m going to lose a major part of my income.
[Fraser Cain]
Right, right. We’re going to talk about that later on. But I guess for me, my question was more about the environment of the academic system.
So for example, Publish or Perish, right?
[Dr. Pamela Gay]
Yeah.
[Fraser Cain]
That your worth as a scientist depends on you publishing on a regular basis. Yeah, it’s constant. It’s constant.
And you are either trying to fundraise or you are trying to write up the results of your work. Or both. And null results are not interesting, right?
People want results. And so if you go and do this enormous amount of work and you’re like, yeah, we didn’t find it, right? That is considered a waste of your time.
Even though null results are equally as important as positive results. And so it just shows you where to not look or constrains the boundaries or whatever, right? That it’s a mill, it’s a grind that scientists are in this position.
And instead of being able to take the time to really come up with a result that they’re very proud of, the pressure is hurry up and get out your results. Publish, publish, publish. And we are swimming in papers.
[Dr. Pamela Gay]
Yeah. Half-baked papers.
[Fraser Cain]
Yeah, yeah. Millions of papers. I think a million papers a year.
Paul Sutter wrote a book on this. And there’s just so many papers coming out. And he identified a whole bunch of these ideas that the environment is very much working in a direction that makes it very hard to be a really good scientist.
There’s a lot of changes they could make that would allow science to move more smoothly. All right. So the beginning of this episode has all been about how scientists can fool themselves and either end up in a dead end or even publish a result that is incorrect just through confirmation bias, through whatever.
How the system really encourages you to publish quickly, to cut corners, to get by on trying to do more with less. That there’s a lot of institutional and sort of larger architectural issues with the scientific community. But let’s talk about individuals.
What if you know how the scientific system works and you want to do bad science because it makes your life better? Either you have courses you want to sell, you have positions that you want to gain, you have books you want to sell, you have TV appearances you want to do, blogs, you want to gain tenure. There’s stuff that you can do.
How can you sort of work this system?
[Dr. Pamela Gay]
One of the easiest ways is to have a friend group of prominent individuals that will both suppress the papers of your competition and support your papers. Befriending, it’s at the end of the day, an old boys network. And I mean that in every adjective I used.
Right, yeah.
[Fraser Cain]
So does this come like there are people who are on the journals who are reviewing these things, people who are doing the peer review?
[Dr. Pamela Gay]
So you send it to a journal that’s friendly. You suggest people to review your paper that you know will approve it. And you get the word out, hey, I heard this group is about to come out with this paper.
You’re going to want to turn it down. And you say this to all the people who might be reviewing it. And you get the word out.
And you give your list of reasons that it shouldn’t review well. And one of the most eye-opening moments I had in undergraduate was we had a prominent solar scientist at our institute. And he took two or three of the graduate students with him to a conference.
And we were all hanging out talking. And the grad students were like, it was wild this other prominent solar scientist put a slide down on it. This was the days of the overhead projectors.
That was literally a gravestone of prominent person at my institute. And then just spent their talk shredding. Wow.
Yeah, it gets that brutal. It gets that mean. You and I have been at conferences where we’ve seen one person give a presentation.
And then their competitor went around the room saying, no, no, no, no, that’s wrong to all the journalists. Yes. And it’s insane.
[Fraser Cain]
Yeah, right. So this sort of like the politics and the sort of because the benefits are like if you are successful, if you discover something important, if you get meaningful papers published in distinguished journals, you get funding, you get tenure, you get all of these benefits. And so the tendency, the natural human tendencies to try to play to the humans factor of what you’re doing is really hard to resist for a lot of people.
[Dr. Pamela Gay]
And it goes as deep as it’s common for a while. I don’t know if it’s still true, but for a while there was this like chain between Michigan State University and the University of Texas where there is a bunch of people between both institutions. There was between Harvard and Stanford.
There’s just these various institutes where it’s fairly common for someone to do undergrad at one, grad at the other, grad at one, postdoc at the other. And people just flow back and forth. And you end up with entire networks of people that just like, oh, this team does good work.
I approve their paper. And at the same time, you know, this institute and this institute are both going up for funding for the same thing, are both competing for the same thing. Your buddies on this team, your students can get jobs on this team.
You’re going to support this team. And on this team’s paper, like the comment that caused me to throw things was, why did you not explain why we shouldn’t fund your competitor with this grant? Well, my competitor didn’t ask for funding to do this work.
I did. But it’s at that level of comments going back and forth.
[Fraser Cain]
Right, right. And the reality is just that what you have to gain is that you get to do your science. What you have to lose is that you don’t have a job.
Right. And so you’re going to, you know, unfortunately try to adapt what you’re saying, what you’re proposing, what you’re planning so that it will be more acceptable to the people who make those kinds of decisions. And, you know, I mean, I think we’ve got a current climate that’s happening in the U.S. where, you know, up until a certain point, there was real value in proposing topics that deal with people with, you know, diversity, people who come from less advantaged backgrounds. You know, think about things in psychology and economy. And now suddenly, boom, everything’s switched around. And so now, you know, if you were before trying to say why it’s important to educate disadvantaged youths, it just blah, blah, blah, blah, blah, blah.
Now that’s a very difficult sell. And the universities are on tenterhooks. And you need to be very, very careful about how you do that.
And that, like, how can that not affect the science?
[Dr. Pamela Gay]
And people are going to work even harder to protect their friends. And we work with the same people our entire life. There are people in this profession that have known me since I was in eighth grade, and that’s horrifying.
No one in their midlife wants anyone to remember what they were like when they were in middle school. And because it’s such a small community, there are so few jobs, the number of jobs are decreasing. People are just going to want to look much more favorably upon the work of the people, the institute, the research teams that they hope to see survive.
[Fraser Cain]
So one thing that I’ve noticed, and especially as a journalist, you know, people reach out to me directly to promote their work. And I will always respond to them, you know, I’m just a journalist. I’m not a scientist.
I have no way of knowing whether what you are doing is science or not. You know, I am unqualified to judge. So I need some kind of filter, such as archive or a journal article or a press release coming from NASA for me to know whether or not it is the actual breakthrough discovery that you are suggesting.
So we’ve seen, you know, we’ve seen a bunch of examples. There was like a superconductor, a room temperature superconductor. There was cold fusion back in the 80s.
There’s, you know, there’s claims, as you said, about supernova, claims about alien spacecraft moving through the solar system, that there’s a kind of a turn to the public. Going on the, you know, making the rounds on the podcasts. What is the kind of the end goal for that?
Because from my perspective as a journalist, that’s a one-way street that you don’t come back along. You know, if you’re going to go on the podcast and you’re going to say stuff that your scientific colleagues will go, well, that’s just nonsense. Will you ever be able to exist in this, in the realm of academia again?
[Dr. Pamela Gay]
The trick that I’ve seen is you get tenure. Once you have tenure, it’s almost impossible to fire you. You can say anything you want.
Yeah. Then you start the press releases that will get you the speaking gigs that pay large amounts of money. Then you get the agent who will sell your books.
Then you go on the podcast circuit to sell your books. Then you launch the substack, the ghost, the beehive, whatever. Don’t use substack.
It has Nazis. All of these things generate revenue and clicks. It turns out that nowadays, universities and institutes want their researchers to accomplish four different things basically.
One, do not get them in trouble. Now, certain institutes, bad press is still good press. Just don’t touch anyone inappropriately.
Then they want you to be a source of revenue.
[Fraser Cain]
Raise money.
[Dr. Pamela Gay]
That can take the form of grants or donations. Saying wild stuff can often attract donations.
[Fraser Cain]
From the people who this meets their political objectives.
[Dr. Pamela Gay]
Yes.
[Fraser Cain]
We don’t see it so much in astronomy, but in other fields for sure that there are climate things you can say. There are political things, sociological things, biological things you can say, science you can do that will bring in the donations.
[Dr. Pamela Gay]
Then in addition to that, they want to raise attention for the institute. This can be name recognition. This can be news articles.
I make so many universities sad because I cite the name of the researchers and the name of the publication. Because the publication goes with the researcher forever, the researcher doesn’t go with the institute forever. Words are short and time is short.
Quite often, institutes don’t count news coverage that doesn’t cite the institute by name.
[Fraser Cain]
I purposefully cite the institution by name. I do that to literally make the press officer happier. I do this on purpose. I want to be able to dig through their Rolodex and come back again and again and again. And so for me, the press officer is my point of contact that I’m trying to impress. And so I’m trying to get, I want them to come to me with stories and scoops and interesting research that’s happening in their institution.
And then I will also reach out directly to the researcher and then I will want to connect back up so that the press officer is like, oh, I didn’t know that we were doing that, you know, that you were on this podcast. That’s great news. Oh, and hi, Fraser.
Nice to meet you. Yeah. So that’s, you know, I’m working that system.
I have a totally different, I have totally different incentives than you do.
[Dr. Pamela Gay]
And my point of perspective is I want to call attention to the new ideas and get the paper into the hands of whoever’s reading that wants to get more information. So, so-and-so did such and such, you can find the paper in, is the phrase that I would normally, and I’m saying it. And like I said, I’m going to mispronounce all of it anyways.
[Fraser Cain]
So- There was a fourth thing that universities want?
[Dr. Pamela Gay]
So the fourth thing that universities want is they want opportunities for students. So if you publish enough papers and you put your students as first author, that totally makes the institute happy. So what we’re currently seeing is institutes often having students as first author on some of these slightly squirrely papers, at least on round one of squirrely paper.
Like I said, these people, once they started in grad school, will often continue down the same route for their career. And so once you have the student doing the work, it’s getting lots of clicks, you’re bringing in money, and you haven’t actually done anything that causes the university to get the kinds of bad press that they have to put out statements about, they’re good.
[Fraser Cain]
Yeah. Yeah. Yeah.
And so, I mean, you can enrich yourself personally, you can get the book sales, you can get the television appearances, you can get your own television show, and so on and so forth. Being able to walk back to academia, like I said, from my perspective as a journalist, watching this process happen, I have not seen it work. I’ve seen people who have done what I consider to be the honorable step to say, I’m going to detach myself from the academic system so that I can become a science communicator.
I think about Phil Plait, I think about Ethan Siegel, I think about even Paul Sutter, right? That they have the academics, they have the credentials, but they understand that they can’t both be a communicator to the public and a person who is attempting to also fundraise and so on. And then you can see the people who are clearly doing everything they can to maintain a level of balance while keeping a foot in both realms.
And I’m not even going to name names here. And then you can see people who I feel have… They’ve gone to the dark side.
They’ve gone to the dark side. There is no path back that when they come back to academia, academia is going to go, oh, I don’t think we have room for you here anymore. Yeah.
And that’s a really tricky thing because I think it’s heartbreaking for the people who, you know, they wanted to be scientists, but the siren song of publicity and revenue pulls them in other directions.
[Dr. Pamela Gay]
And what I think has been very interesting is watching people who essentially grew up in the age of blogging and Twitter. Dr. Katie Mack, I think, is someone who’s managing to do excellent science communications and excellent science. And I will name that name.
[Fraser Cain]
Yeah. And I think David Kipping is another example of someone who I think is doing a good job of that. But they are, I think, rare.
And I think are at great risk if they make a misstep of getting high on their own supply. And, you know, for them, I would be very, very careful because there’s a, you know, it’s the, you know, what is it? Hate leads to anger.
Anger leads to whatever. You end up in the dark side, right? And then there’s those who’ve gone all the way.
So. And now we’ve reached the end of our episode. So there you go.
It’s true. Thanks, Pamela.
[Dr. Pamela Gay]
Thank you, Fraser. And thank you so much to all of our $10 a month and higher patrons. You allow us to do everything we do.
This show is made possible by our community on patreon.com slash astronomycast. This week, we’d like to thank the following $10 and up patrons. Abraham Cottrell, Alex Rain, Andrew Stevenson, Arno DeGroot, Bart Flaherty, Benjamin Mueller, Bresnik, Bruce Amazine, Claudia Mastriani, Dale Alexander, David Bogarty, Diane Philippon, Dr. Jeff Collins, Iran Zegev, Felix Gut, Frodo Tanimba, Glenn Phelps, Greg Davis, Hannah Tackery, Janelle, Jeanette Wink, Jim Schooler, Joe Holstein, John Thays, Justin Proctor, Katie and Ulyssa, Christian Golding, Laura Kettleson, Lana Spencer, Mark Schneidler, Matthew Horstman, Michael Purcell, Mike Dog, Nate Detweiler, Papa Hot Dog, Paul L.
Hayden, Philip Walker, Robbie the Dog with the Dot, Ruben McCarthy, Sandra Stanz, Scott Briggs, Zege Kemmler, Stephen Miller, The Brain, Tim Girish, Tushar Nakini, Will Feld, and Zero Chill. Thank you all so very much.
[Fraser Cain]
All right. Thanks, Pamela. And we will see you all next week.
[Dr. Pamela Gay]
Bye-bye, everyone.
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