Daniel and Jorge Explain the UniverseWe know it exists but what is it and how can we see it?
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Wouldn't it be cool to have the power to see invisible things, like if you had anti invisibility glasses.
Yeah, there's so much of our universe around us that we can't see things that are going on all the time that are invisible to us. It'd be awesome to invent some new technology to reveal that, to peel back that layer of reality and show us all the crazy stuff that's happening.
No.
Yeah, I would definitely love to see that.
Do you have a million dollars to invest in my startup?
I have a million dollars, but maybe not to invest in you, Dadea.
Oh man, somebody already got to you with that idea, didn't they. Somebody already pitched.
You Maybe maybe, but yeah, no, I like this idea that there are invisible things out there in the universe that are really important and are maybe determining my fate and the fate of our planets and our solar system and our galaxy. Hi am hoe, I'm a cartoonist and the creator of PhD comics.
Hi. I'm Daniel. I'm a particle physicist. I've never created a webcomic, but I did co write a book with a webcomic. It's called We Have No Idea, and it's all about the unknowns in the universe.
Oh man, that sounds amazing. I would love to read that.
You should, It's fantastic.
I did actually read it a couple of times as I helped write it.
Yeah, did you read your name on the cover, for example?
But welcome to our podcast Daniel and Jorge Explain the Universe, a production of iHeartRadio.
In which we zoom all around the universe and find cool and fascinating and bizarre stuff to blow your mind. But we don't want to explode your mind. We actually want to take that stuff and insert it into your brain. We want to break it down and make it accessible and reassemble it inside your mind.
That's sorry. We wint to stuff your mind with as much stuff as we can without exploding it.
Critical mental density. That's what we're going for in today's show.
But yeah, all the cool stuff, all the amazing stuff, all the dark stuff in the universe.
All the invisible stuff, all the visible stuff and everything in between.
Because there are invisible things out there in the universe, right There are invisible forces and objects and maybe even matter.
There definitely is. There's a huge amount of stuff going on in the universe that is not directly observable to us. And it's only recently that we've been doun peeling back those layers of invisibility, figuring out ways to subtly detect what's out there that we haven't even noticed.
Right, And we also try to talk about how scientists are trying to discover these things. They're trying to peel back that layer and understand what's going on in the invisible universe.
That's right. Sometimes I think about it like scientists are out there inventing new senses, right, Like your senses are your ways of interacting with the world. You can see, you can smell, you can touch, all these things help you build up a model of what's outside your body. Right. Well, scientists were like trying to create new contraptions that are basically new senses. Things machines that can see things that we our bodies cannot see, and they can translate what they see into something that we can understand.
That would be cool if you can build me like a like a radar helmet. Yeah, like a radar chip I can implant in my brain and have like bat like abilities or their devil like abilities exactly.
Well, if you have a million bucks, you can put that towards the startup I'm going to start after this show inventing the radar helmet. That sounds like an awesome idea.
Man, you're really hunkering for some hankering for some for a million bucks here, Daniel.
But you know, we do this kind of thing a lot, right, We extend the power of our senses, right. Think about like what X rays are, right? X rays are these little invisible rays. You can't see them, but we can use them to see inside of stuff, right, to give us to translate what we couldn't see before into what we can see now.
Wow, Yeah, you're right, physicists did invent X ray vision.
That's right. We literally have literally literally right, yeah, yeah, absolutely, And we do this kind of thing all the time. You know. That's basically what experimental physics is. It's like try to develop a new technology that can discover things that nobody's seen before. Like you know, we've talked on this podcast before about neutrinos. Neutrinos are these weird little particles that are everywhere and they're you know, part of the table of matter as we understand them. But they're very, very hard to see because they mostly just fly through stuff. But physicists figured out a way to spot them. It takes billions of neutrinos to fly through your detector before you see one, but we can see them in that way. We discovered that they're there, that the air is full of them.
And so today we're going to talk about what scientists are doing to see to actually maybe even touch a very important part of the universe, a very big part of the universe, maybe even the biggest part of the universe that's invisible to us.
That's right. It makes up most of the matter at the universe, like eighty percent of the stuff in the universe. It's literally the biggest mystery in the universe.
And so today on the program, we'll be talking about how can we see dark matter, how can we interact with it, how can we finally sort of seed up close touch it maybe to understand what it is, because right now we have no idea what it is, right, Daniel.
That's right. We know that it's there, We know that it's stuff. We know it's some kind of matter because it creates gravity, but we don't know what it's made out of. We don't know if it's made out of particles, made out one particle, two particle, seventeen particles, something else that's not a particle. You know, we only have very indirect evidence, very solid, but indirect evidence. It's sort of like you're solving a murder mystery and you have a bunch of circumstantial evidence. You know that Joe Schmoe is the guilty party, but you don't have that smoking gun, you don't have the bloody knife or something. You're not going to rest until you really find all the details that really conclusively demonstrate to you what happened on that fateful night. And that's sort of the situation in the case of dark matter.
I mean, it could turn out to be that it was a physicist in the cloakroom with the wrench, right, I mean, that's what dark matter could be. It could be unicorns, it could be.
It could have been the engineer in the library right with the bag of dark matter.
That's right. Try trying to make things work.
Engineers always have altruistic motives in your mind, right, whereas scientists are out there like trying to take over the world. Right.
Well, you know, I like to think engineers actually know what they're doing and they're not toying with things they don't understand. I'm not trying to create black holes here on earth, you know.
Hey, hey, there's nothing wrong with trying to create black holes on here on Earth. They're tiny, little, cute, very safe black holes. Okay, right right, ped black holes, cozy little black holes, and we got to rebrand them. You know, they sound so dangerous, you know, unicorn, black hole.
Black hole?
Exactly?
Do you feel like they have a PR problem?
Yeah, exactly, black holes have a PR problem exactly. And for those of you hearing that we are trying to create black holes at the Large Adrian Collider and worrying about it, we have a whole episode dedicated to that, you are in no danger whatsoever. Wait.
I just thought of a really nerdy joke. Mm hmmm, Actually black holes have an EPR problems.
That's a pretty nerdy joke, I agree, Impress.
Thank you.
When you have to laugh at your own joke and then rib the other person into into acknowledging it. Then that's how you know it was a good joke.
Those are the best jokes.
Those are the dad jokes. Right, you just made a combination scientist dad joke. It's a whole new subgenre of humor.
A dad scientist joke. Well you, fortunately, you are as bad scientist, so that right to hit you right in the center.
That's right. I am your demographic.
Well, that's that's all. Who's listening to this podcast?
Right? That's right. Hey, give me a million bucks and I'll do a startup company with dad scientist jokes.
All right, but only if you pay your podcast partner all of the million dollars.
Done and done. All right, we did some business today, all right.
So yeah, dark matter, we don't know what it is, and so today we're going to talk a little bit about how we might be able to see it and what scientists are doing to actually see what dark matter is.
That's right, and to tease it a little bit. There are three ways that we're looking for dark matter. You can either shake it, break it, or make it. That's also a recipe for cooking a delicious dark matter soufle.
I feel like that's an infomercial all now, and you'll receive our special offer for shake it, break it, and make it.
And that clever line about shake it, make it or break it is not something that I came up with. I think the first person to say that was Jonathan Fang. He's a dark matter expert at You See Irvine.
All right, well let's see how we can shake, break, or make dark matter. But first we were wondering how many people out there think that we could ever see dark matter? Or if we can see dark matter.
That's right. So I walked around the campus of You See Irvine and asked folks, hey, do you think we could ever see dark matter? And I didn't explain to them what dark matter was or give them much background and just pop this question on them.
And so think about it for a second. If somebody asks you randomly on the street, like, hey, do you think we can ever see dark matter? Think about for a second how would you answer this question?
And would you give that guy a million bucks for his dark matter startup? No?
Well, anyways, here's what people had to say.
Have you heard of dark matter? Yes, but I don't know what it is? Okay, do you have any idea how much see dark matter? Like I would be discovered? It's like energy electrons. Maybe, I'm not really sure. All right, thanks very much. Have you heard of dark matter? Yes? Do you have any idea how we could see or discover dark matter?
No?
Because isn't it just a theory?
Have you heard of dark matter? Yes? Do you know how how might be see dark matter?
I don't know dark I've heard of it, but I can't confidently say what it.
Okay, do you know if it's something we could ever see?
Like?
Can we see or detect dark matter?
Monday?
Probably?
I mean I'm not sure now, but I'm confident that one day we'll all find out what it is and discover many many things.
Okay, I've heard of the term. I'm not exactly sure. I know it's related to like physics in the space.
Do you know if dark matter is something we can ever see? I could we ever be able to see it or detect it?
The name implies that we can't. I'm sure there are methods too, I mean through like radiation, probably can detect if it's there, but I don't know if we can visibly see.
All Right, a little bit of optimism. Some people had never heard of it.
Yeah, some people were a little skeptical. I like the well, it's just a theory. I could have gotten into a whole discussion there about what is a scientific theory, evolution is a theory, what is theory mean? But I just sort of nodded and moved on.
There was one interesting answer here that said that the answer is no because the name of it implies that we can't see it. That's kind of a pretty metaphysical answer, right, like, if we can't see it one day, do we need to change the name of it?
Oh? I see, Well, I think that's a little bit more thought than this person I had given it. I think they were not sure what dark matter was and just sort of sort of grasping for clues about how to answer this question based on the limited information in the question, and I think that's where they were going. But I like that idea that if we see dark matter, we can't call it dark anymore. We have to rename it. And it probably you're angling to be on that committee to rename it, because I know you have opinions about how physicists have named things.
It's not that I'm angling. I just feel like anyone could do a better job.
Put that on your application to be on the committee. Man, you guys are terrible. Anybody could do a better job than you.
Yeah, for sure, they should put kids in charge of naming things.
You know, then we'd be called squishy rainbow matter.
Yeah, there you go. It would make a lot more sense.
It'd be harder to write grand proposals saying please give us money to see squishy rainbow.
Particles, right, unless it's also children reviewing the proposals.
Sometimes I think it is children reviewing the proposals based on the referee reports.
So Daniell remind us what dark matter is.
Right, So we don't know what dark matter is, but we know that there's something out there. We know that there's a bunch more stuff in the universe than we can see. And we know this in a few ways, but all of them just use gravity. Gravity is our clue that tells us that there's something else out there that has mass, because remember mass is what creates gravity, a mass and energy, And we have a few clues, Like we looked at galaxies and we see that galaxies are spinning really really fast, and there doesn't seem to be enough gravity inside those galaxies just from the stuff we can see, the stars and the dust and stuff to hold those galaxies together. So based on how fast they're spinning, the galaxies should be tearing themselves apart, the stars should be thrown off into interstellar space, but they're not. So people suggested this idea, maybe there's some invisible matter in there that's creating this gravity to hold the galaxies together. And that's the key. It's invisible. We can't see it, hence the name dark, but it creates the missing gravity we need to explain how these galaxies are spinning. So they called it matter because it gives gravit.
So it's like we we can feel it, but we just can't see it. Like we can see it affecting the orbits of things around it, and we can see it affecting how light moves around it and through it, but we can't actually see something there or detect something there through light.
That's right, we can't use light to detect it because it doesn't seem to interact with light at all. It's invisible, you know, the way like the air is. You can tell the air is there because it pushes against you, but you can't see it right. You'd love to be able to see the air. Imagine you had like glasses that you could see different air currents and stuff like that. The world would look like a crazy place. But we can see it only through gravity. We can tell that it's there through gravity, and the reason that's the problem. Yes, we can feel its pull. And you might think, isn't that enough, Like I mean, you're getting greedy, Like you can already tell that dark matter is there, why do you need to see it? The thing is that gravity is really really weak. It's the weakest force by huge amount, by you know, millions and millions and millions, and so we can I can only use gravity to see dark matter when there's a huge amount of it, like galaxy sized blobs of it. So that tells us that it's there, but it doesn't really tell us what's going on where the dark matter is, to see any detail in it, to see if it isn't made out of particles or is it made out of something else really weird. It's like, it's enough to know that it's there and roughly where it is, but nothing else about it, And that's tantalizing. You know because we want to know what this is made out of and how it works and does it interact and is there complicated stuff going on? But we can't. Right, we're blind because gravity is so.
Weak, right, and so it doesn't reflect light, Like if I shine a light into it, the light is just going to go through and it doesn't emit any light. Like, it doesn't glow or it doesn't give off its own energy that we can see. And so that's what makes it invisible.
That's right. Stars give off lights, we can see them. Planets reflect lights, so we can see them. Dark matter doesn't either. It doesn't glow and it doesn't reflect light. Yeah, it's totally invisible to loast, it's like a ghost. It ghosts, yeah, exactly.
I like how sometimes you say that it should have just been called invisible matter, not dark matter.
Yeah.
I think probably there was a meeting somewhere somebody said let's call it invisible matter, and no, dark matter sounds cooler, and I think dark matter does sound cooler. Honestly, dark implies something mysterious, right, something maybe a little sinister. One of my favorite questions I get when we give public lectures is somebody invariably asks, is dark matter like bad matter? Like is it dangerous? You know, because it's an error of like you know, sinister in this or what's the word cynicism? Sinisterism?
You do?
You just call it evil matter? Well, I mean who wouldn't fund that project?
Yeah, it's it's like the dark side of the forest, right, you know, it's just like probably the dark side of matter. There you go, there's my million bucks.
Yeah boom, just like, hey, there's evil matter out there. We need to track it down.
That's something the current administration would probably go for.
Yeah, yeah, all right, So that's what that's what dark matter is. It's some stuff out there in the universe. There's a lot of it. There's a there's like five times more of it than regular matter. But we can't see it through light or touch it because how we touch things is through electromagnetic forces.
Right, that's right. If you want to push on the wall that's next to you, for example, why doesn't your hand go through the wall. It's because your hand is a bunch of molecules, and those molecules are tied together with chemical bonds, which are mostly bonds from electrons, and so that uses electromagnetism. So your hand is like a it's like a chain link fence, and the walls like a chain link fence, and those links press against each other. So electromagnetism is a dominant force and how you see things and how you feel things, and dark matter just doesn't feel it at all.
So it seems kind of unlikely that we'll ever be able to touch it or see it or know what it is with any kind of resolution. And so let's get into this idea of shaking it, breaking it, and making it. But first let's take a quick break.
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Okay, Daniel, So dark matter with doesn't give off light or reflect light or doesn't even care about light. It just like just goes through it or magnets.
Hey, you don't know that. Maybe it's like feeling left out. It's like, hey, is this light part of the universe and all this fun stuff is happening and we're stuck over here in a dark corner.
Maybe we should call it sad matter then.
Depressed matter exactly.
But yeah, so, but you know, in generally you can't touch it with light, you can't touch up with a magnet, you can't touch it with your finger. But we know it's there because we feel it's gravitational pull. So you're saying that that that gravitational pool is not enough to really study it, to really kind of kind of like run it through your fingers and study what it is and what it's made out of.
That's right. The goal is to get a finer grain sense of where it is, like where on Earth is the dark matter? Is it just a big diffuse blob. Is it clumped up somewhere? Is it all gathered in the sun. You know, we'd like to be able to see it much more in a much finer grain resolution, which requires interacting with it more powerfully than gravity can do. That's one thing. And the other thing is we'd like to know what it's made out of, right, Like, is it made out of particles? Is it made out of multiple particles or something else totally different, And that definitely requires seeing it more up close and interacting with it, and so current the only thing we can do is gravity. And you know, let's start off pessimistically. It might be that dark matter only feels gravity and that's the only force it ever will feel, and that seeing it or touching it or whatever is totally hopeless. We have no concrete evidence that it has to feel another force. We have some indirect clues from the way things happened in the early universe, but nothing really solid.
Well here's a question though, then, I mean, we know that dark matter doesn't feel light or electromagnetic forces, and we know it doesn't feel weak forces or strong forces. I know it's because I listen to our podcast episode about dark matter. But how do we know it doesn't feel Maybe some other forces, some other here to undiscovered forces in the universe.
Yes, in fact, we are hoping that it does. Right, We are resting the entire this entire field of searching for dark matter rests on the hope that there is some new kind of force, some way that dark matter interacts with itself and with our kind of matter. So if it only interacts with via gravity, then we're kind of sunk. All we can never do is do observational astronomy and see galaxy sized blobs. But if there is some new force we haven't discovered yet, then maybe it can mediate the interactions between normal particles like electrons and quarks and these dark matter particles. So that would be awesome because you could make two discoveries at once. You discover some new force which is huge, and you discover that that new force interacts with dark matter particles. So you discover a new force and a new particle and the same day, like two discoveries for the price of one.
Is that possible though? Is it possible that there is another force that we haven't noticed?
Oh? Absolutely, absolutely, it's possible. Yeah. I mean we've only studied a tiny fraction of the universe and the interactions between those particles, so it's certainly possible that there are other kinds of interactions that we haven't noticed because the particles we're familiar with don't interact that way.
Oh, I see, But so then we wouldn't be able to measure.
This force then exactly so. But it could also be that this force is just very very weak, that it's not very powerful, and so it's hard to detect. But if you have enough clever physicists, they can build the device to suss it out and to notice those tiny little hints that give us the clues that it's there, just like we found neutrinos. Neutrinos are very very difficult to interact with. They only feel the weak nuclear force, but we were able to build detectors that can spot them, so we know that they are there. In the same way, if there's another force that dark matter feels, where we're going to talk about in a minute, are all the ways that we're trying to reveal dark matters interaction with normal matter through that new force.
But if it only feels gravity, don't we have some amazing gravitational wave detectors, now, couldn't that maybe help us?
We do have amazing gravitational wave detectors, but as far as I understand, they don't give us much insight into where the dark matter is because gravitational waves come from like huge accelerating masses like black holes and neutron stars circling each other and eating each other. Dark matter, as far as we know, doesn't do that, and so it doesn't create gravitational waves as far as I know. But you know, there could be black holes made of dark matter. I guess that are doing that, but it wouldn't necessarily give us insight into the dark matter itself.
Wow, the way would those be dark black holes or black dark holes?
I don't know that's your responsibility, since you're being nominated to the Physics naming committee, but I'm pretty sure that every black hole has to have some dark matter in it, because remember, eighty percent of the matter in the universe is dark matter. So if you're a black hole, you're just indiscriminately sucking up matter, and you're definitely gonna hoover up some dark matter.
So it seems like a pretty hard problem. And so break it down for us, Daniel, what are some of the different options for studying dark matter?
All right? So number one is shake it. The idea here is, let's build a really big tank of very quiet liquid. By quiet, we mean liquid that doesn't interact very much, mostly just sits there. And we put this tank really far underground so the cosmic rays and other particles from space don't interact with it very much, and then you just wait. You wait for one of those particles to shake. The idea is that maybe a dark matter particle, which should have no trouble penetrating through the ground and getting all the way underground into your vat of liquid, will bump using this new force, will bump into one of these molecules and shake it a little bit, and when you spot that, you can say, ah, maybe that was dark matter.
Oh, I see, so you're not shaking dark matter, you're just waiting for dark matter to shake something else.
That's right. We're hoping that dark matter flies down and then occasionally bumps into one of these it's usually liquid xenon atoms, and then we can see that atom shaking, so we know that that's where the force comes in. Gravity isn't enough for that to happen. But if dark matter has this new force, it could give a little bump to one of these xenon atoms, and by seeing them get bumped, then we could deduce that maybe it's dark matter.
So the theory is that maybe dark matter does feel more than just gravity, Like maybe it feels us some kind of other force, but it's so weak that you really would have to isolate everything else just to maybe every once in a while feel that force from dark matter.
It's like you're listening for the tiniest little whisper. Right, you don't want to do that in a crowded stadium or in a bar. You want to go to a place where there's nothing going on, so you can really crank up the gain on your microphone and listen for that little whisper. So we go deep, deep underground to look for these little particle whispers because they're probably drowned out. I mean, if dark matter is around, then it may be interacting with us all the time, right, giving little shakes, but you can't tell because there's particles everywhere giving shakes. But deep down underground, most of those particles are filtered out. And you put a really quiet liquid there, and then you hope that dark matter hits it, and you know you might be thinking, well, how can you tell it was dark matter not something else? Right, Well, they've come up with really clever ways to just thing wish between dark matter hitting it and like a gamma ray hitting it or nuclear radioactive decay hitting it, because dark matter is probably heavier than like electrons and we've caused different kind of recoil than a gamma ray. So they have all these really clever details about ways to see it, and that make it more likely to tell if it's dark matter or not. But you can never be for sure. You can never be one hundred percent sure that one of these wiggles is exactly dark matter.
Okay, so that's pretty good. Is that an actual like physics position, like particle whisper?
But it should be. It should be again, when you're on the naming committee, you can rename these titles anything you like. You know, throw out professor and come in with particle whisper. But the key is the key is that I don't think anybody would really conclusively accept the discovery of dark matter just from that kind of experiment. And that's why we have three prongs of this search. We have shake it, break it, and make it, because if dark matter does exist and it does feel this new force, we would expect to see it in all three prongs, and that would really be more conclusive.
Why don't you think people would not believe it.
It's a hard experiment to do, and the kind of thing signal we're looking for is like one or two shakes over a year of running. And then you have to really have a lot of confidence that these folks know what other kind of things might shake those molecules at the same level that they've really done everything carefully. You know, it's not as like direct as you'd like. You'd like to like hold the dark matter particle and say here it is, everybody, come and look at it. We found it, right, But instead you're you're noticing it bumps somebody, and that's still a bit indirect. I mean, it's more direct than gravity because you're talking about the interaction with a particle, but you're not left with it. You haven't created it or been able to study it. Well.
I remember our conversation about the sky being blue, that you know, things have to be kind of around the same size or the same frequency for them to interact. Is it possible that maybe dark matter is just like at a different frequency or way.
It certainly is possible, right, It's possible that dark matter feels forces and those forces don't interact with our matter at all. Right, it's certainly possible. And these detectors are sensitive to dark matter of certain masses right usually between like a few giga electron volts and one hundred giga electron volts, And they're sensitive to those masses because those are the masses that are going to make the particles shake the way they're expecting. If the masses are much much smaller or much much heavier, then the shake is going to be different and they might not spot it. So yeah, these have windows where they can see it. And again that's why we have different approaches, so we can try to cover all the blind spots.
Okay, so that's option number one in our infomercial offering is listening to dark matter whispers. Listening to dark whispers, that's right, and see if it maybe bumps a particle in a really, really really quiet environment. But that one is a little suspicious because it's so hard. But you're saying there's a second option, which is to break it, break dark matter.
That's right. If you imagine is the interaction we talked about a moment ago shaking it. That's one dark matter particle comes in and a normal matter particle comes in like xenon, and then both those come out, Xenon comes out and dark matter comes out. You can sort of rotate that ninety degrees in your head and say, well, if that can happen, then maybe it's possible for two dark matter particles to bump into each other, annihilate using the same force, and turn into normal matter particles quarks for example, which is what makes up xenon. And so it's the same interaction, right, it's dark matter interacting with quarks, but instead of dark matter bouncing off of quarks, it's dark matter annihilates itself and turns into quarks.
Oh, because dark matter, if it's in our universe, it's stuff. And if it's stuff, then it can turn into energy, which can then turn into other things.
That's right, And only if there's this particular force, this force that can that can touch normal matter and can touch dark matter, then dark matter can annihilate. It turns into the particle that mediates this new force, and that particle that mediates this new force can also touch normal matter, right, and so we can turn into normal matter. That's the idea.
It would have to be a new kind of force, or it could like the weak force or one of these forces.
Do that we thought for a while a weak force might be able to do that. Maybe dark matter felt the weak force like Neutrino's. But we've pretty much ruled that out because if that had happened, we would have seen it already. Our detectors are powerful enough to see dark matter interacting via the weak force, and it hasn't, so it'd have to be a new force.
But you're saying, but we don't really know what dark matter is, So how can we be so confident that we haven't seen it this way?
We don't know what dark matter is, and so we are not confident and basically anything but all we can do is what we can do, and we can say, well, what if dark matter is a particle, and what if it interacts with normal matter? What would that look like? Okay, let's go look for that, and if we find it, awesome. If we don't find it, then there's a lot of things that we might wonder about, like, well, maybe it's not a particle, or maybe it doesn't interact with via this new force, or maybe we built this thing wrong. Right, So negative results are less powerful than positive results, for sure, But you can only do what you can do, right, and in science, we do this a lot. We say, we don't know how to solve this problem. Let's start simple and see if that works.
It's imagine it's a unicorn and see if we see any rainbows.
That's right. And so you might be wondering, like, well, how do you make dark matter collide into other dark matter? And the way you do it is that you just look for places where there's a lot of dark matter. And we think that dark matter is clumped at the center of the galaxy, like close to that black hole that's the biggest blob of dark matter. So what we do is we point our space telescopes at the center of the galaxy and we wait and we hope to see like a flash of light from the center of the galaxy that's of a particular energy that would tell us that dark matter collided and created normal matter. It's a really hard thing to do.
Yeah, it seems like a really wishful thinking, or you know, like you're reaching a little bit.
It is, but you know, there was a moment when we thought we saw a signal a few years ago. We had the data from this telescope, and if dark matter exists and it can do this and it happens, then you would expect that all the particles that come from the center of the galaxy would have a particular energy, and that energy would tell you what the mass of the particle was. So you'd be looking for like a peak over a spectrum. And there was a guy in Germany who looked at the data and he saw this big peak in the spectrum and everybody thought, oh my gosh, maybe he discovered dark matter. Then it turned out no.
Really, so it would happen in a big flash. That's brighten us for us to see.
It's not one big flash. It's a slow accumulation of data. It's how great you build up years and years of information. And then maybe you see a bunch of You see a bunch of these things all the same energy, and that tells you that maybe there's something else going on here, some process that's happening in the center of the galaxy that's producing these partsarticles at all the same energy, and that gives you clue as to what the dark matter is. And again, on its own, not that convincing. But if you see that and you see something in these underground detectors, and the two are consistent you're like, oh, look, maybe these two things are telling us the same story from a different point of view. Then you start to build up a credible story.
All right. But then now there's even a third option to study dark matter, right.
That's right, And this is my favorite because it's the one that I personally work on, and that's making dark matter. I feel like, if we're going to believe that dark matter is a paricle, we got to be able to create it. We got to be able to like make it in the lab and play with it and study it. So that's what we're trying to do at the Large hair gen Collider. You laugh, you think that's ridiculous.
Well, we just talked a little bit earlier about scientists making things and playing with things that they don't fully understand.
Yeah, exactly, that's how we understand them. Right, you know, what is this thing? I don't know? Let's make a pile of it and poke it and see what happens. That's not a grand plan to take over the world. It's not like here, I'm going to become the dictator of the Earth by making dark matter. Right, dark matter is not dangerous. It's like it's even difficulty to spot to interact with. Right, it's not going to hurt anybody. We just like want to create some of it so we can see what it's like. Is that so wrong?
Well, I'll let you know if you guys destroy the earth, I'll let you know if that was a good idea or not.
Yeah, drop me a line. Put that on my tombstone. Was that so wrong?
On your twobstone? Inside the dark matter black hole?
Okay, that sounds good. Dark matter black holes. There's a startup idea one million bucks please.
Well, this is a perfect point to take a break.
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You're saying that another way to study dark matter is to make it, to like create it out of nothing.
Yes, not out of nothing. So imagine think about the process we just talked about in the Galactic Center. We're talking about dark matter annihilating into some particle and that particle turning into quarks. Well, if that can happen, then the reverse can happen. That is, quarks should be able to annihilate turn into some new force particle, and that new force particles should be able to turn into dark matter. So we should be able to smash quarks together and create dark matter. And that's coincidentally exactly what we're doing at the Large Hadron Collider. We smash quarks in the form of bags that we call protons together at super high speeds and try to create new kinds of matter.
But again, that assumes that you have this magical force that helps you go between the two worlds kind of right.
Yes, exactly. We have to assume that it's it's there to look for it, right. It's like you're saying, like, well, you went hunting for unicorns in the forest, aren't you assuming the unicorns exist? Well, you know we're out there looking for them, like we'll see.
Yeah. Right, it is that kind of similar, right, like.
Yeah, yeah, sure. But you know, if you go out looking for unicorns and you find something else crazy instead, you still call it a success. Right, But you have to have something to look for, and this in particular, like you know, we believe dark matter is there. Have all the crazy things we look for at the Large Hadront most of them. We have no clue that exists. Supersymmetry and large extra dimensions and all this other crazy stuff. We have no real clue that it's even real. Dark matter, we know is a thing. It's out there. It's part of the universe. Man, It's like it's an important element in the matter pie. So at the Large Hadron Collider, when we smash particles together, we make everything that can be made. So if dark matter exists and it can be made, then eventually we'll make it, and we should be able to find it in the remnants of some of those collisions.
Right. And the interesting thing is that it's not like you make it and then you hold it in your hand and say, hey, see, I made it. It's more like you made it.
That is my particular fantasy.
But you're right, well, technically you do have some dark matter in your hand already.
Right, that's right, but you can't hold it because it passes through you because it doesn't interact with you. But you're right, go ahead, Well, you can't just make it and hold it.
Yeah, yeah, I think the idea is that you make it and you know that you made it because some energy disappeared and you can't account for it.
Exactly. The problem with making dark matter is that we can't then see the dark matter. It's like, hey, look, I here's my science for a project. I made an invisible man. You can't touch. Where is he? I don't know. It's not that.
Convinced, honey, but it disappeared after I made it. So but hey, the effort is what counts, right, honey.
Here's your invisible Mother's Day present exactly. I didn't forget. It's just invisible. It's extra impressive. That's exactly the problem. But as you say, we can deduce the presence of invisible things because we know some things about how these collisions work, and in particular, we know that momentum is conserved, meaning you have a momentum coming into the collision. All that same momentum has to come out of the collision. So if you add up all the stuff that you saw come out of the collision, and we're pretty good at capturing things, and something is missing, it doesn't add up. Then you know something disappear at something invisible. So we can tell when we make invisible stuff at the colliders, and in fact we do this all the time. We can't see neutrinos either, and all the time we do this interaction where quarks annihilate and then they turn into a pair of neutrinos, which just basically look invisible. So we can do this, we've measured this, we can see it happening. The question is is it also making dark matter? So that's what we're doing. We're trying to tell like is it just making neutrinos or is it making neutrinos and dark matter?
All right, so those are the three ways in which we might see dark matter again, just to recap. One of them is to listen for it really, really quietly. The other one is to try to look for places where it's crashing into itself. And the other one is to try to make it here on Earth.
That's right with a million dollars, that's right exactly. So we have those three ways, and you know, we've been doing this for a while, and at first we were sort of just playing around with like could we even see dark matter in the collider? Couldn't you look at the center of the galaxy. And people spend a lot of time refining these techniques and making them more and more powerful. And then at the same time we have predictions. We have like clues from the early universe that say dark matter is definitely there, And these clues from the early universe tell us that probably dark matter came into equilibrium with normal matter. That means that it's like the energy has sort of like smoothed doubt, and for that to happen, it has to be able to interact. So we suspect that there's some way for dark matter to interact with normal matter, but it's very indirect clue, and we just don't know what that is. So we're hoping that we'll be able to see in one of these experiments, and that indirect clue suggests that the experiments that we're doing now in the next few years should be able to see dark matter interact with interacting with normal matter at the level necessary to explain that equilibrium. So it's an exciting moment in the search for dark matter.
Can you explain what that equiliary means? So you're saying that you have some sort of feeling that it does feel a special force that we haven't discovered yet because there's evidence that it has interacted with matter in this way.
That's right, can sort of trace back the history of the universe and the very beginning of the universe, just after the Big Bang. There's a bunch of matter created, some matter, some normal matter, some dark matter, right, and then the universe expanded and cooled. Right at some point, the universe cools enough that certain kind of interactions can't happen anymore. So that's what we call that freeze out because it's not hot enough to like make certain things happen anymore. Since the freeze out moment is less interaction between normal matter and dark matter, we think, right, so we think that before that they were sort of mixing and playing along and interacting, and then the universe cooled down and is less interaction, And we can do those calculations, and we could say if there was interaction and things were, you know, getting into equilibrium and bouncing off each other, that changes how much dark matter is left in the universe. So we call this a relic density. So the amount of dark matter in the universe now depends on how much it was interacting with normal matter in the early universe, because that changes like how much is made when when normal matter turns into dark matter, or how much disappears when dark matter interacts with itself and turns into normal matter. And so the amount of dark matter we see in the universe now tells us that there was very likely interactions in the early universe.
I think what you're saying is that you know, the universe right now only makes sense from what we know of it if there is some sort of interaction between dark matter regular matter. Yes, yes, exactly, Okay, But if it turns out that there isn't this special magical unicorn force, then we're sort of toast. Right, then there's really no way for us to really study dark matter.
It would be much much harder, and all we can do in that case is lean on gravity, and we're pressing that pretty hard. You know. We're looking at galaxies and how they rotate, but we're also looking at gravitational lensing, we're looking at collisions. We're doing everything we can to try to use the gravitational information, but it's pretty limited. Yeah, gravity is a weak forced and it doesn't capture a lot of information. So it would be a bit of a tragedy if dark matter doesn't feel anything but gravity, it would make it really hard to ever discover. Is it made of particles? Is it made of something else? Is it made of little unicorns? You know, it would be it would be a sad day if we discovered that.
So that that's amazing. It could be that will never ever in the history of humanity until the end of the universe know what this thing is.
You sort of sound like you're rooting for that outcome.
I'm not ready for either outcome.
Are you playing the playing on the tragic arc here?
I'm not taking size between the dark side and the light side. I'm just saying that that is a distinct possibility, and it's interesting to think about, isn't it to know that maybe there are mysteries we'll never know the answer to.
I'm sure there are mysteries we never know the answer to, and probably the greatest mysteries we don't even know to ask, right, We're that clueless when it comes to the nature of the universe. This is a mystery that we've recently stumbled on, that we discovered that these huge parts of the universe we don't understand. In fact, most of it the biggest slice of the pie. So we should even be grateful that we know it exists. And now we're getting greedy. We don't want to know everything about it, right, But you're right, it could be that we never know anything more than that it's there and that it has gravity and it plays a role in how things clump.
All right.
So that's the answer to the question can we ever see dark matter? And the answer is stay tuned, right, maybe we'll see it, maybe we won't.
The answer is keep funding particle physics.
The answer is send Daniel a million dollars.
That's the answer to every question, isn't it sure? Yeah?
What did you have for breakfast? What do you a million dollars?
I don't know. I send Dannel million bucks and I'm still waiting for my ex Benedict. Hey, startups don't offer a quick return, okay, right?
Right?
Or breakfast?
Right?
Or breakfast? Not usually?
All right?
Well, thanks for joining us. I hope you enjoyed that discussion. And next time you look out there into the universe, know that there you are bathing in dark matter, but that we may never or possibly soon be able to see it.
That's right, Mysteries the Universe potentially.
Revealed tomorrow on our net next podcast. Stay tuned, all right, see you next time.
Thanks for tuning in. If you still have a question after listening to all these explanations, please drop us a line. We'd love to hear from you. You can find us at Facebook, Twitter, and Instagram at Daniel and Jorge That's one word, or email us at Feedback at Danielandjorge dot com. Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. When you pop a piece of cheese into your mouth, you're probably not thinking about the environmental impact. But the people in the dairy industry are. That's why they're working hard every day to find new ways to reduce waste, conserve natural resources, and drive down greenhouse gas emissions. House US dairy tackling greenhouse gases. Many farms use anaerobic digestors to turn the methane from manure into renewable energy that can power farms, towns, and electric cars. Visit you as dairy dot COM's Last Sustainability to learn more.
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