Stuff You Should Know - Seriously, What Is Dark Matter?

Episode Date: September 27, 2018

Chuck and Josh take on astrophysics again and this time it pans out well. It turns out that there simply isn’t enough matter in the universe to account for its mass. Which is super weird. What is this missing matter? Does it even exist? Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

On the podcast, Hey Dude, the 90s called, David Lasher and Christine Taylor, stars of the cult classic show, Hey Dude, bring you back to the days of slip dresses and choker necklaces. We're gonna use Hey Dude as our jumping off point, but we are going to unpack and dive back into the decade of the 90s.

We lived it, and now we're calling on all of our friends to come back and relive it. Listen to Hey Dude, the 90s called on the iHeart radio app, Apple Podcasts, or wherever you get your podcasts. Hey, I'm Lance Bass, host of the new iHeart podcast, Frosted Tips with Lance Bass. Do you ever think to yourself, what advice would Lance Bass

and my favorite boy bands give me in this situation? If you do, you've come to the right place because I'm here to help. And a different hot, sexy teen crush boy bander each week to guide you through life. Tell everybody, ya everybody, about my new podcast and make sure to listen so we'll never, ever have to say. Bye, bye, bye.

Listen to Frosted Tips with Lance Bass on the iHeart radio app, Apple Podcasts, or wherever you listen to podcasts. Welcome to Stuff You Should Know from HowStuffWorks.com. Hey, and welcome to the podcast. I'm Josh Clark, and there's Charles W. Chuck Brown, and there's Jerry, and we're about to try some physics.

Oh yeah, this is Stuff You Should Know. We're about to try some physics. Yeah, this did not break my brain like I thought it would. Yeah, I think it's a pretty surface level explanation, but like it gets the point across, and I don't see any reason for us to try to go any deeper. I think we would very quickly spin out of control, like a up-down quark or something.

Yeah, so dark matter is invisible glue that holds everything together, the end. The end. We just don't know what it is. No, we'll get into it, but you might notice, dear listener, a new thing in your feed popping up next week. Next week, next Wednesday, Wednesday, Wednesday.

Wednesdays, we are debuting a new thing called Short Stuff. Which is just the cutest name. It is. It's Stuff You Should Know, Short Stuff, I guess is the full name? Probably. Or not, who cares? Yeah.

But it's just, it's a Stuff You Should Know episode, it's you, me, and Jerry, but over the years of recording, like we've got these lists of topics we wanna do. So many lists. And this one, like part of the list just kept getting bigger and bigger and bigger, because there are like topics out there

that are really interesting, but they're just not big enough for a full episode. Even with tangent upon tangent. And we could have like, we could have been like, well, we'll put like three of them together randomly. We thought about doing that once. It just didn't feel right.

So what we did was spin off like a new podcast called Short Stuff, which is just a smaller sized episode of Stuff You Should Know, just because the topic wasn't quite big enough to warrant a full episode, or a large size episode. We're doing a small size episode. Yeah.

So look for like 10 to 15 minutes tops. I think we're in the wheelhouse of about 12 minutes. We seem to like magically hit 12 every time. Yeah. And it's like, it's kind of fun. I think it's a great idea. I'm really happy with them. Yeah, same here.

And I think the first four we recorded, we didn't know what we're gonna call it yet. Right. And I don't believe we went to the trouble of going back and changing that. Are we gonna, we might do that. Are we doing that, Jerry? She just shrugged.

No, she said no. She said that sounds like a lot of work. Yeah, it would be just like us to just sort of waddle our way into this thing. Sure. And which is exactly what we did. But hopefully you guys enjoy them. It doesn't cost you anything.

Yeah. So don't complain. Actually do complain. If they're way off base here, they could be better. We want to hear about it. No, I think people will be like, oh, this is just like a little bite-sized stuff

you should know. That's exactly what it is. It's like a Snickers miniature, but of stuff you should know. That's right. And you know our love of small things here. Especially Snickers. Or like tiny Tabasco bottles.

This is the tiny Tabasco bottle version of our show. Those things are priceless. All right, so physics, dark matter, go. Let's do this. All right, so. This wasn't as hard as I thought. No. And it's actually pretty easy to get across.

Yeah. Here's the thing. So astronomers have gotten to the point. It's starting at about 1920 on. Yeah. Astronomers and physicists and astrophysicists and even particle physicists got to the point where all of their combined knowledge was refined enough

that they could look out into the universe and be like, we can figure out how much this weighs. Right. To put it more scientifically, we can figure out what the mass of the universe is. It's gonna take us a really long time, but we are now at the point where our level of observation and our level of understanding of physics

is such that we can do it. We're there now. Yeah, and it's not just like, oh, well that weighs this, the end. Right. Like knowing something's mass tells you a lot about it, the way it behaves. And the nature and future of the universe as we'll see.

Yeah, for sure. So it's not just weight. It's more complicated than that and what weight can tell us. Right. The problem is, is you can't just like put a galaxy or star or something on the scale. They tried.

They broke the scale pretty quick. It actually vaporized it. But there are ways you can infer the mass of something. Yeah. One of the ways that you can infer the mass of a star from what I understand is to measure its luminosity, how bright it is. Yeah.

I've also heard that it's a mixed bag because- It seems like it from doing this. They have different sizes in their lifespan. Yeah. I've just heard luminosity in mass is not just straightforward. Sure. Like most things in astrophysics are.

Yeah, that's the word on the street. Right. So when they started getting to the point where they could infer the weight of a star or of a galaxy or of a galaxy cluster, which is basically like a galaxy of galaxies. Yeah. They started to notice something really weird.

All of the matter that they could see, the stars, the gas clouds, the cosmic dust, everything, matter, things that make up you and me, things that everything has a common basic unit in atom that's made up of elementary particles like protons and neutrons and electrons, matter. Every non-living and living thing in the galaxy. You would think, is made of matter.

The problem is, is they started finding that this galaxy over here and this galaxy cluster. And everywhere we're looking, the amount of matter that we're seeing is way too small for the amount of mass that the thing we're looking at appears to have. And a cosmological mystery was launched. What the heck is going on was the question of the day.

Yeah. So all that matter that we know about, they call that baryonic matter. And they were like this, the calculations are off or something, like there's got to be something else there to account for this. Well, that's the two possibilities.

Well, sure. And so way back in, jeez, was it 1932, an astronomer, a Dutch astronomer named Jan-Hendrik Uert, because he's Dutch. Sure. He actually, I believe was the first person to use the term dark matter. Is that right?

That's what I saw. So dark matter is sort of a placeholder name for what they came up with for lack of a better word, this invisible matter that has to be out there, is it sort of like wind, like you can't see wind, but that doesn't mean it's not out there because you can measure it in different ways, see how it reacts on other things.

And so they started calling it dark matter, this invisible, well, we'll talk about what it ends up sort of looking like in a minute. I won't give that away yet. Right. But this invisible matter. That they think is there. Right, but it doesn't emit or absorb light

or electromagnetic energy. So it's way different. It behaves differently such that people were very confused as to what the heck was going on. And they still are. Yeah, sure. So this term dark matter, like you said, it's a placeholder. And it's a placeholder for the current point

we are in our understanding of the universe, which is when we look out at galaxy clusters and galaxies and all this stuff, there's not enough matter to account for the amount of mass that we're seeing. So again, that means one of two things. Either there's something there that we can't detect or our understanding of physics is off.

And the term dark matter stands for both of those. It could be a thing and undiscovered particle or something like that. Or it could be a misunderstanding of physics that we need to eventually correct. Either way, there's a lot of mass that is unaccounted for throughout the universe. And it seems like there's a lot more,

what we call dark matter, than there's regular matter. And the more we look into it, the more it seems like there's something there that we haven't discovered yet. Yeah, so right now, baryonic matter, all the stuff that we know about counts for about four and a half percent, 23% of where they peg dark matter.

Then we have something that I don't even know if I ever want to cover it called dark energy, which makes up the other 72%. But they know it's there because there's something out there that we can't account for that has a significant gravitational force. Right, that's where the whole thing started, where they first detected it.

Right. And so when they first started looking out at galaxies and stuff like that, there's this whole thing that Newton came up with, the second law of motion, where, and this is like a tried and true law, it's a law, this isn't Newton's suggestion of motion, or Newton's second, what about this of motion?

It's a scientific law that's as proven and accepted as a scientific observation can be is to be made a law. And it said that when you're looking at a galaxy far, far away, and the most of the matter is accumulated toward the center of the galaxy, then that means most of the mass is accumulated toward the center, okay? Yes.

Okay, so that means that the stars near the center are going to spin, they're going to rotate around the galaxy a lot faster than the ones on the fringes, because the ones on the fringes are going to go a lot more slowly, because they're further away from that center of mass, so the gravitational pull is going to be weaker. Yeah, I mean, that's the easiest way to say it

is in the center, you have more mass, more mass means things are spinning faster, there's more gravitational pull, so all the astronomers supposed, like you said, the stuff on the outskirts are probably hanging out there spinning a lot slower. Right, well, when they looked, they found that's not the case at all.

As a matter of fact, the stars on the outside are spinning around the center of the galaxy just as fast as the stars near the center of the galaxy, which makes zero sense. Yeah, it's almost as if there's some invisible force out there. Right, like if you look at this galaxy, the situation that they started to find, and it wasn't just one galaxy,

they found it in this galaxy too, in this galaxy too, and even stranger than that, they found it in those clusters, those galactic clusters, so rather than stars that make up a galaxy, this is galaxies making up a huge giant mega galaxy, the same thing happened, the galaxies on the outer edge of the cluster were circling just as fast as the ones toward the center,

and it just must have knocked their socks off. I can't imagine how many times they went over the same formula to make sure that they had gotten it right. For clarity, this was the 1950s and 1960s, is when they discovered. When they first noticed this. Yeah. Okay, so what they figured out

was that either there was something really wrong or there was something that they hadn't picked up yet, because those stars on the outer edges of the galaxy, or those galaxies on the outer edges of the cluster, for as fast as they were flying, they should have spun off into space. Yeah. There was something missing that explained

what was holding that galaxy or that cluster together as fast as the stars of the galaxies were spinning around on the outside. That was the first clue that something was way up with, that astronomy was missing something big. Right, and they knew this was off because they had been using luminosity, like you said, to take measurements for years, and it was pretty good.

But then when they started measuring the rotational velocity of things, like how fast something was spinning in relation to where it was, like toward the center, like you said, there was a missing ingredient there that didn't match whatever these luminosity readings were showing. So you're right, luminosity was clue one.

The angular rotation was, or acceleration of the outer stars was clue number two. So now we've got two different ways of measuring the mass and gravity of remote bodies in the universe. And they don't align. Our point, well, they're aligning in that there's something missing here.

Right. And I think that's a pretty good cliffhanger for a breakdown too. I think people are gonna be like, what? Yeah, well, why don't you guys go listen to the first half of this podcast, or first part again, and we'll see you after these messages.

On the podcast, HeyDude, the 90s called David Lasher and Christine Taylor, stars of the cult classic show, HeyDude, bring you back to the days of slip dresses and choker necklaces. We're gonna use HeyDude as our jumping off point, but we are going to unpack and dive back into the decade of the 90s. We lived it, and now we're calling on all of our friends

to come back and relive it. It's a podcast packed with interviews, co-stars, friends, and nonstop references to the best decade ever. Do you remember going to Blockbuster? Do you remember Nintendo 64? Do you remember getting Frosted Tips? Was that a cereal? No, it was hair.

Do you remember AOL Instant Messenger and the dial-up sound like poltergeist? So leave a code on your best friend's beeper, because you'll want to be there when the nostalgia starts flowing. Each episode will rival the feeling of taking out the cartridge from your Game Boy, blowing on it and popping it back in

as we take you back to the 90s. Listen to HeyDude, the 90s, called on the iHeart radio app, Apple Podcasts, or wherever you get your podcasts. Hey, I'm Lance Bass, host of the new iHeart podcast, Frosted Tips with Lance Bass. The hardest thing can be knowing who to turn to when questions arise or times get tough,

or you're at the end of the road. Ah, okay, I see what you're doing. Do you ever think to yourself, what advice would Lance Bass and my favorite boy bands give me in this situation? If you do, you've come to the right place, because I'm here to help. This, I promise you.

Oh, God. Seriously, I swear. And you won't have to send an SOS, because I'll be there for you. Oh, man. And so, my husband, Michael. Um, hey, that's me. Yep, we know that, Michael.

And a different hot, sexy, teen crush boy bander each week to guide you through life, step by step. Oh, not another one. Kids, relationships, life in general can get messy. You may be thinking, this is the story of my life. Just stop now. If so, tell everybody, yeah, everybody, about my new podcast, and make sure to listen,

so we'll never, ever have to say, bye, bye, bye. Listen to Frosted Tips with Lance Bass on the iHeart Radio app, Apple Podcasts, or wherever you listen to podcasts. I really hope we're putting this, like, well. I feel like we are, but sometimes, you know, you just can't tell. No, this isn't the sun redux.

I hope not. No, no, no. This is much more simple. Okay. So, like you said, they not only studied regular galaxies, but they started to study what you refer to as, and you didn't make it up, but galactic clusters, these knots of galaxies, could be thousands of them,

could be hundreds of them, but they are bound together by gravity, and they were like, you know what, let's study these, because maybe what we can find, or, you know, this is what we suppose at least, is there might be these big giant pools of hot gas that we never could detect before, and that would account for all of this mass.

Right. And they did find these superheated gas clouds, and were like, great, that's it. But they're like, no, that still doesn't account for everything. That's like a small percentage of what needs to be accounted for. Right, so it was a breakthrough,

but it wasn't the solution solver that they were looking for. It was, because so if you can find, you know, something that we know has mass, like huge clouds of gas, that again, you know, a particle has mass, and if you put enough particles together, it has a lot of mass.

If you could fill in the blanks of the missing matter that explains the mass of this thing you're looking at, great, especially if it's something we already know about like hot gas, and they did find some hot gas, but say that that explained 5% of the missing mass. The missing mass, it did explain everything. And what that did do also was, okay, we've gotten that much more sophisticated,

and it still hasn't answered this dark matter thing. It's pointing to the idea that there's something we haven't discovered yet that is accounting for all of this. It's very foreboding. It is, but it's also, I think, very exciting. Sure, yeah, for them and us. So the other thing that happened

when they started studying these galactic clusters was that they found out that these clusters and superclusters can, and this is really neat, you can look up images of this, it can distort space time because their mass is so great. So if you're on planet Earth, and there is a light, so you're looking from like a telescope on Earth, you're looking at a distant light,

like who knows how far away. Like a star three billion light years away. Sounds great. In between you and that is a galactic cluster, let's say, that will act as a lens and depending on where it's situated to where you are relative on Earth, it will distort that light into one of several things. If you're in perfect alignment in it,

it's gonna form what's known as an Einstein ring. And if you look it up on the internet, it's like this beautiful circle of light. It's really cool looking. It could be elliptical or oblong, they call it the Einstein cross, basically splits it into four. That's amazing.

Those look like four little stars all like perfectly aligned. Four copies of the same image. Yeah. Yeah, and like a cross. Yeah, perfect cross. Or it could be a cluster and this one is sort of cool just cause it's like kind of scattered. It looks like a bunch of like arcs

and banana shaped arcs and arclets. But it's all different versions of the same image that you're seeing. And what you're seeing is that far away star, but you're seeing it through that galaxy cluster. That is a distortion of space time. Right, the mass of these clusters are so big and so huge that the gravity in them bends light.

Just like a mound of glass can bend light. Yeah, like a magnifying glass. Same thing. Now, we've gotten to the point where we are so good at math and physics that we can look at that reflection, that bend and say this galaxy has that much gravity. And since this galaxy has this much gravity,

it must have this much mass. Yeah. Now, if you take that number, this much mass and you examine the luminosity of the galaxy. There's that difference. Yeah, you're like, this is like not off by you know, like the luminosity is 10, but the mass is 10 and a half. Right.

There's like factors, sometimes factors of like times a hundred, sometimes like there's just no way that your math is off. There's a huge discrepancy. So there's a third clue that there's something missing. Yeah, I mean, that's basically all these are are little hints along the way that we're still not able to account

for something with our calculation. Yeah, and rather than the better and more sophisticated our observations and exploration of space in the universe becomes, it doesn't become like this, this blank is not getting filled in. It's just becoming clear and clear that that blank is really there.

Yeah, exactly. There's a void and either our understanding or our discovery. So then computers started getting better and better and more advanced. I love how this article puts it. They turned to the computer. It sounds like they turned to the bottle or something.

Yeah, to compute. So computers started getting so good and our knowledge of what was out there and our measurements of matter and mass was so great that we could take a pretty good guess on how much baryonic matter there was out there, maybe how much dark matter there might be, design a program and a model

that you could feed this information into to spit out what it might, quote, look like, end quote. Yeah, they basically said, this is how much baryonic matter we think there is. This is how much dark matter we think there is. Like map it out. Go, go computer. And they hit start on the Whopper machine

and it spit out what was sort of like a, it turns out that it wasn't on the edges. It was everywhere. It was like a web that wound through everything invisible to us that sort of acted like this cosmic glue. Yeah, and so in some places it clumped. In other places there were long filaments and it kind of looked like it had galaxies

or galactic clusters trapped in a spider's web. So cool. It permeated everywhere and like you said, it seemed to be like this cosmic glue or cosmic connective tissue. And it was pretty surprising. So they said, okay, well, that's the computer's take. Let's see if we can replicate that.

And that kicked off a series of projects that are still going on today to map dark matter in the universe. Which I want everybody to stop for a second because this is about as nuts as it gets. They have gotten to the level of sophistication where astrophysicists are mapping in 3D models stuff that isn't there.

Well. They're mapping 3D models of voids based on how much light bends around a galaxy three billion miles light years away. Yeah, nine miles light years. Right, and then using that to infer the gravity and then the mass. And then they're using that information

to create a 3D map of something that may not exist. Yeah, and the coolest thing about all this to me is it's based on stuff that Isaac Newton and Einstein came up with. Right, yeah. And well, we won't spoil it, but they weren't wrong. But that is nuts. This is either physics has gone totally insane.

Yeah. Or this is the pinnacle of human ingenuity thus far. Well thus far for sure, I'm glad you added that. So let's talk about a couple of these. About seven years ago in 2011, there were a couple of teams using data from Chandra's x-ray observatory. And what they're trying to do here, like you said,

is take these, create this real map based on direct observation instead of this speculative computer map. Right. What they found out is the computer map was pretty on, which was great. Yeah. But they needed the real thing.

So they are looking at a cluster or have been called Abel 383, 2.3 billion light years from Earth. And what they saw was what looks like sort of a football, an American football, or an Aussie football for that matter. Oh, are they similar? I just got one in the mail, I bought one. You need to get Simon to sign it.

Go Melbourne, I should. But it would cost so much to ship it there and back. Maybe I'll just see Simon again one day. Is Melbourne your team now? Yeah, that's who I got on. That's good city. Yeah, I like it. So it looks like a football with one end

pointing toward us or we're on Earth. So we're the observer in this case. And here's the one thing they didn't agree on though, was the density of the dark matter on Abel 383. In the center. Yeah, which is weird because some people calculated it was more dense in the center and matter increased and other people said it was the opposite.

Not like, well, we're not sure, but they thought it was less dark matter at the center, which is a big deal. But they both came up with virtually the same shape and same orientation separately and independently, which showed we're onto something or else again, we're all collectively out of our minds. Based on some shared delusion that we're all working under.

Right, then there was another one. This one is super cool. In January, 2012, any time I see international team of researchers, I get excited. But the Canada, France, Hawaii telescope has a 340 megapixel camera. So you can actually take pictures of stuff that far away. It's like the iPhone XS camera.

Is that one of the new ones? Yeah. Yeah, okay. Is it good? I think it's pretty good camera. It's not 340 megapixel. No, it's not. But I have to say, I've been to this observatory before.

Oh, really? It's really cool. Did you look at like the photos on display and stuff? No, no, they had like telescopes that you walked around and looked out into the universe on. It's amazing. Did they let you take pictures? Yeah, I guess so with your phone.

Oh, I thought you meant, I mean, with the 340 megapixel camera, no. I'm probably, I'm sure they were taking pictures. They didn't give them to us or anything. But what's crazy is it's on Hawaii, so it's just hot and muggy and humid. And then you drive up this mountain and you're like freezing in a north-face coat

with like a hat on. Yeah. And then you just go back down the mountain and it's Hawaii again. That's great. It's a very, very cool experience. So what they did here was basically stitched all these photos together.

It was like photos of 10 million galaxies in four different regions over five years, stitched it all together. And what they finished up with was basically saying that computer model was pretty on target. Cause what this looks like is what it spit out so many years ago. Yeah.

So they're definitely onto something it seems like. Should we take another break? Yes. All right, we'll talk about what dark matter is. Hint, we don't know. I don't know, we're living ours until tomorrow. the decade of the 90s. We lived it and now we're calling on all of our friends

to come back and relive it. It's a podcast packed with interviews, co-stars, friends, and non-stop references to the best decade ever. Do you remember going to Blockbuster? Do you remember Nintendo 64? Do you remember getting Frosted Tips? Was that a cereal?

No, it was hair. Do you remember AOL Instant Messenger and the dial-up sound like poltergeist? So leave a code on your best friend's beeper because you'll want to be there when the nostalgia starts flowing. Each episode will rival the feeling of taking out the cartridge from your Game Boy,

blowing on it and popping it back in as we take you back to the 90s. Listen to, Hey Dude, the 90s called on the iHeart radio app, Apple Podcasts, or wherever you get your podcasts. Hey, I'm Lance Bass, host of the new iHeart podcast, Frosted Tips with Lance Bass. The hardest thing can be knowing who to turn to

when questions arise or times get tough or you're at the end of the road. Ah, okay, I see what you're doing. Do you ever think to yourself, what advice would Lance Bass and my favorite boy bands give me in this situation? If you do, you've come to the right place because I'm here to help.

This, I promise you. Oh God. Seriously, I swear. And you won't have to send an SOS because I'll be there for you. Oh man. And so my husband, Michael. Um, hey, that's me.

Yep, we know that, Michael. And a different hot, sexy, teen crush boy bander each week to guide you through life step by step. Oh, not another one. Kids, relationships, life in general can get messy. You may be thinking, this is the story of my life. Just stop now. If so, tell everybody, yeah, everybody

about my new podcast and make sure to listen. So we'll never, ever have to say bye, bye, bye. Listen to Frosted Tips with Lance Bass on the iHeart Radio app, Apple podcast or wherever you listen to podcasts. All right, Chuck, we're back. This is where I start to get a little like brain breaky. I understood all that stuff,

but this stuff is where I was like, what? Well, we're transferring from astrophysics to particle physics. Maybe that's my hang up. And particle physics is hard. I actually had to teach myself particle physics to write one episode of The End of the World. Maybe that's my problem.

And even still, I'm like, wait, what? It's really hard to understand. Yeah, I've always been an astrophysicist, though, at heart, I think. So that just goes against my nature. Okay, I'm with you. But they're very much tied together. Like you need particle physics

to explain these larger cosmic structures. Right, so the big question here is, at the end of the day, is it the fact that we just can't really observe this stuff and it's just like all the other matter, or is it some new matter that we don't even know about yet? That's the question. That's the big question.

Or the third option is that our physics, our understanding of physics is wrong. Right, which means, well, we'll see. Some people go back and tamper with things Newton said. He doesn't like that. Much to the dismay of a- Newton, kill, brain. So if it's just stuff that we already know exists,

but we just can't observe yet, those fall under the umbrella of machos, massive compact halo objects, which are huge, massive structures that we already know about, neutron stars, black holes, brown dwarf stars, that are huge and massive and have a tremendous amount of mass,

and thus exert a lot of gravity around them, but are too dim to show up clearly when we're looking at, say, a galaxy or a galactic cluster. Yeah, like we talked about luminosity. They have low luminosity. We know they're there, but they're not shining. But we don't know that that's them. That is one proposal for what dark matter is.

They're just things that we already have identified know exists, we just can't see them in these particular things. That actually doesn't have, for as Occam's razor-y as that is, that actually does not have as much support in the physics community as the other idea that dark matter is made up of some particle that we have not discovered yet.

Yeah, so that's where I got a little confused with the WIMPs and the SIMPs. WIMPs stands for Weekly Interacting Massive Particles, huge amounts of mass, but difficult to detect because they just interact weekly with ordinary matter. Right, here's why they're difficult to attack. They interact weekly with matter that's not stating it very well.

The weak nuclear force is one of the four fundamental forces and it's found almost exclusively in the nucleus of an atom. What these WIMP particles, weak interactive massive particles are, they're hypothetical. We don't know that they exist, right? Mathematically, they fit the bill of dark matter. The fact that they interact with gravity

and with the weak force only means that, no, we can't detect them. We don't have weak force detectors. We have detectors along the electromagnetic spectrum. So everything we do when we look out in the universe, we use x-rays or microwaves or radio waves. All of those are electromagnetic. If these particles don't interact

with the electromagnetic force that has no effect on them whatsoever, we have no way of detecting them. Right, right, right. All we can do is, since they have a gravitational pull because they have so much mass, we can just sense their gravity and be like, what the heck is going on?

Which is exactly the position we're in now. WIMPs were a big, they were promoted as the particle, I think starting in the 80s. It seems like an 80s thing. Because they're, yeah, it does, doesn't it? A little bit. Because there was something called the WIMP miracle and this breaks my brain.

Yeah. But apparently if you take the relic density, which is really unimportant for getting into here, but say the density of a WIMP, like how dense the universe would have to be for a WIMP to exist, it corresponds with the weak force number. And that made everybody say,

oh, well, there are particles that don't interact with the electromagnetic force, they just interact with the weak force. Nowadays, they've kind of moved to the strong nuclear force. Simps. Simps. And the strong nuclear force also was found just basically in the nucleus of an atom.

It's the thing that holds an atom together, super tightly. It holds the quarks into the proton and it holds the proton and the, what's the neutral charge one? Neutron? Yeah, the neutron and the proton together and it keeps them together. That's the strong nuclear force.

And they think that that is probably the particle now. So same thing though, doesn't interact with the electromagnetic spectrum. So we have no way of detecting it, but it would still have mass and hence exert a lot of gravity. So that's sort of the takeaway. Right.

Gotcha. Well, not everyone is on board with this period. Like some people, there are some astronomers out there who say they dare say maybe Newton got it wrong. Newton got it wrong. And maybe we should crack open the Bible and rewrite it like Thomas Jefferson. That's a good episode.

In the 80s, there was a dude, physicist named Mortahai Milgrom. Great name. He suggested that Newton's second law of motion, which is force equals mass times acceleration. Which I got wrong in the board breaking episode. That's right, but we're not physicists. We just play them on the air.

He said, maybe we should look at that again. And maybe he was wrong. And maybe we should modify this. And he called this modification Mond, the modified Newton, Newtonian dynamics. And the way that I read this was it almost sounded like, it's probably not quite right, but almost sounded like he had some answer.

So he was sort of rewriting the question to fit. Yeah, it was ad hoc. Yeah. That's what he was called out on. That it wasn't like, oh, here is a new understanding of a physical law around the universe. This just applied to those galaxies in their rotational momentum or rotational acceleration.

His whole position was that, that breaks down at very small accelerations. Like a planet on the outside, or a star on the outside of a galaxy. But over a long distance. Right. And so a lot of people were like, that's ad hoc. It doesn't hold any water.

Anyone can do that. Get out of here, yeah. And then apparently there was a study in 2007 that showed that even down to accelerations as slow as 500 trillions of a meter per second squared, which is really low acceleration, Newton's second law of motion still held fast. That is so awesome.

So Mond is pretty much out the window from what I understand. And Newton is giving the finger from the grave. Like to see what you get. He very famously like to say, bite it. That's on his tombstone, I think. What else do we have here? Alternative wise.

This guy, I love this dude's name. I looked it up. Dragan Hjudkovich. Oh, is he one of the guys at CERN? Yeah, I can do better than that. Dragan Hjudkovich. Hjudkovich. Sorry, Dragan.

But yeah, he said that there's such things as gravitational polar opposites. Right. That particles and antiparticles have not only opposite electrical charges, but opposite gravitational charges. Yeah, so if those are near a galaxy, then it would sort of like a magnet almost.

Yeah, they'd form a dipole. Yeah, so it would strengthen the gravitational field. So that's what's accounting for. In fact, I guess he's saying there is no dark matter, right? Yeah, he's saying that that's dark matter is dipoles, gravitational dipoles, which is interesting because that means if that's correct,

then if you got your hands on an antiparticle, it would fall upward because it would have an opposite gravitational energy. Yeah. That's pretty neat. That is pretty neat. I would love to have like a pencil made of antiparticles. You'd just be like, watch this.

Right. Just knock everyone's socks right off. So should we talk about them? That's what I would do if I had a whole bunch of antiparticles. That's where my imagination ends. Should we talk about the big bang a little bit? Yeah, because this is the thing, like if you've been sitting here going like,

come on, why does this matter at all? It actually does matter if we wanna figure out how the universe can possibly end. Right, which is your specialty these days. Man, I'm so excited about this coming out. Yeah, we're talking again, Josh's upcoming 10-part series. The end of the world.

The end of the world. It's Josh Clark. Yeah, it's slated to come out November 7th. Yeah. And it's this and more. Time's 10. Literally, time's 10. Yeah.

What other stuff you talk about? AI, I know that's in there. AI, reckless experiments with viruses. Oh, geez. The Fermi Paradox, the Great Filter, the whole things about existential risks. Man. You're getting smarter.

I'm just talking about the old movies. It's a downer. Yeah, but you're like getting in there with people, you know, like getting into the heart of people. It's just different. It's not better. Well, you got interviews and stuff though with like leading experts, right?

Yeah, but I kind of use them as like a Greek chorus to kind of chime in and help like explain it or be like, yeah, Josh is actually right here. You know, that kind of thing. Sure. Like it's not just me saying this, you know. All right, so look for that everyone. But with the Big Bang, the idea is that

the universe is expanding. And the big question is, what's the end game there? Are we gonna expand forever? All right. And what does that mean in relation to dark matter? So again, this is the point that we're at. We've actually figured out what the density of the universe has to be.

There's something called the critical density and it's 10 to the negative 29th grams per cubic centimeter which this article says is equivalent to a few hydrogen atoms in a foam booth. That density of matter. Yeah. And if the, that is the critical density of matter in the universe.

If it's more than that equal to that or less than that, there are three different possible outcomes for the universe depending on how dense the universe is with matter. Right. In a phone booth, everyone is a thing, a box that used to hold public telephones that you would step into to make a call.

Yeah. What's a good movie you can go watch to see. There's one called phone booth. Oh yeah. I said a good movie though. Oh right. Superman changes his clothes in a phone booth. There you go. Go watch the original Christopher Reeve Superman.

Right. Or imagine if you were laying dead in a casket and someone sat you up and you were on your cell phone. But you were only three hydrogen atoms. And your cell phone was connected to a machine by a cord. Right. Exactly. All right. So where were we?

We were talking about the critical density of the universe. Right. So there are a few different outcomes here that they've come up with. Right. As far as where we're headed. Yeah. So if the universe has a density of matter, all the matter in the universe, if you could just slice the universe up into phone booths

and equally spread out all of the matter in the universe across all those phone booths, if that equals just a few hydrogen atoms per phone booth, again, that's the critical mass density. And if that is actually the same as the density of matter in the universe, then what we have is a universe that keeps expanding forever.

Because the universe started inflating at some point after the Big Bang. Yes. And this is a huge discovery in and of itself. Sure. Right? Everybody thought the universe was just kind of there and unchanging. No, the universe is actually expanding in size.

It's inflating. And the matter in the universe is actually spreading away from it. So everybody's like, like you said, what's the end game about that? If the universal mass is the same as the critical mass density, it's gonna just keep expanding forever.

But eventually it'll get kind of cool and everything's gonna die and stop. I think it's called the heat depth of the universe. Yeah, and that's called the critical or flat universe. If the actual mass density is greater than the critical mass density, they call that the big crunch. That's not good.

A closed universe, that means it'll expand and then eventually slow down, stop expanding, and then collapse on itself. Right, like you know those bungee swings? Yeah, my daughter was just on one of those. Okay, so you know. Once you're up in the air? Right, yep. Well, she went that way

and then she came back this way. She did. So when you come back this way, when she came back this way, it was because the universe is closed and the gravity because of the mass was greater than the critical mass density. And so gravity overcame it and brought it back together

in what was called the big crunch, which I'm assuming she did not undergo. I tried to explain that to her and all she said was again, again. I don't blame her. And then finally we have another outcome. If actual mass density is less than critical mass density, then we keep expanding,

but there's no change in the rate of expansion. We don't start expanding faster and faster. Right, and I think nothing really cools off. It just keeps going forever, which is kind of the all good one really. That's called the Wooderson universe. Right, yeah. All right, all right, all right.

Or specifically the coasting or open universe. I like that. AKA Wooderson. So the only way to figure this out for sure is to live until the end of the universe and we're talking billions, possibly trillions of years into the future. Right.

Or we could just figure out how much matter there really is. The problem is, even if we can account for all the regular matter, every bit of things that makes up you, me and everything we can see in the universe, we still have to account for dark matter. Hence the reason why people are mapping dark matter. So we can figure out truly how much matters in the universe.

And then we can predict how it's gonna end. Yeah, it's not just folly and like, hey, this would be neat. Right. I mean, part of it is, there's a peanut butter sandwich and a glass of milk at the end of that calculation. That's true. And I wanna say you got anything else,

but I'm not going to say that. I got nothing else. All right, well, that's dark matter. Don't even get us started on dark energy, please. Please God, don't get us started on dark energy. If you wanna know more about dark matter, type that word into the search bar or those words in the search bar

and since I said that, it's time for Listener Mail. I'm gonna call this something on game shows. Hey guys, always wonder what it was like to have a moment where they say, I have to write into stuff you should know for Listener Mail. Well, I just had that moment. Yesterday I listened to the Select podcast on game shows.

It wasn't a Select podcast, it was just a live show. Oh yeah. Right? Yeah, they fooled me. I love all your episodes, but I found this one particularly fascinating. Flash forward to this evening, my fiance and I were sitting down to watch a movie.

I'm not much of a movie person. Sorry, Chuck. So I told Peter, I guess her fiance, to just pick something to watch. He puts on quiz show. Oh, I saw this email. Not realizing it was based on the real life event. So I started telling Peter about your podcast

and how quiz shows like this one on the movie were rigged in the 50s and it almost killed game shows. I was like a sponge releasing all the information I had heard yesterday. The chance that he selects that movie the day after I listened to your podcast just blows my mind. It's pretty awesome.

It's a Mandela effect, right? Syncretism. Anyway, thank you for what you do for keeping me company as a driver on DC on the Beltway every day. Oh, you poor person. I know. When one of your episodes queues up

and then my drive will go so much faster, lots of love, Kristen. Thanks a lot, Kristen. That was a great email. We're glad we could help you out, make you look pretty good in front of Peter. Yeah, good luck with the upcoming wedding. Yeah, which we assume is impending.

Sure. Okay, well, if you want to let us know you're getting married, let us know. We'll say best wishes. Every once in a while somebody will send an invitation in. It's always nice. We've not taken them up, but we usually sign it and send it back at least.

Yeah, I mean, if someone was getting married here in the studio on a Tuesday at one o'clock, we'd be there. And we'd also be like, we need the studio. Yeah, exactly. So maybe make it 12 o'clock. Agreed. If you want to get in touch with us,

you can hang out with us on social media. Just go to, what's our website? Stuffinchenote.com, that's right. And you'll find all the links there. And you can also send us an email. Just wrap it up, spank it on the bottom and send it off to StuffPodcast at howstuffworks.com. For more on this and thousands of other topics, visit howstuffworks.com.

On the podcast, Hey Dude, the 90s called, David Lasher and Christine Taylor, stars of the cult classic show, Hey Dude, bring you back to the days of slip dresses and choker necklaces. We're going to use Hey Dude as our jumping off point, but we are going to unpack and dive back into the decade of the 90s. We lived it, and now we're calling on all of our friends

to come back and relive it. Listen to Hey Dude, the 90s called on the iHeart radio app, Apple Podcasts, or wherever you get your podcasts. Hey, I'm Lance Bass, host of the new iHeart podcast, Frosted Tips with Lance Bass. Do you ever think to yourself, what advice would Lance Bass and my favorite boy bands give me in this situation? If you do, you've come to the right place

because I'm here to help. And a different hot, sexy teen crush boy bander each week to guide you through life. Tell everybody, ya everybody, about my new podcast and make sure to listen so we'll never, ever have to say. Bye, bye, bye. Listen to Frosted Tips with Lance Bass on the iHeart radio app, Apple Podcasts,

or wherever you listen to podcasts.