Seriously, What Is Dark Matter?

reason for us to try to go any deeper. I think we're very quickly spin out of control, like a up down cork 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, but it's just it's a stuff you should know episode.

It's you, Me and Jerry but over the years of of recording, like we've got these lists of topics we want to do, and this one, like part of the list is kept getting bigger and bigger and bigger because they're 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 one. 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 warn a full episode or a large size episode, we're doing a small size episode. Yeah, so look for like ten to fifteen minutes tops. I think we're in the wheelhouse of about twelve minutes. We seem to like magically hit twelve every time. Yeah, and it's like it's kind of fun.

I think it's it's a great idea. I'm really happy with him. Yeah, same here. And I think the first four we recorded, we didn't know what we're gonna call it yet, 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, now, 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, and which is exactly what we did. But

hopefully you guys enjoy them. It didn't cost you anything. Um, so don't complain. Actually do complain if they're way off base or 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 size stuff you should know. So that's exactly what it is. It's like a Snicker's 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 over 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. Here's the thing.

So astronomers have gotten to the point it's starting in about on astronomers and physicists and astrophysicists and even particle physicists guys 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 ways, to put it more scientifically, we can

figure out what the mass of the universe is. It's going to 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, Like knowing something's mass tells you a lot about it, the way it behaves and the nature and future of

the universes we'll see, yeah for sure. So it's not just weight, it's it's more complicated than that, and what weight can tell us, right. The problem is that you can't just like put a galaxy or star or something on the scale. They have to broke the scale pretty quick. Uh, it actually vaporized it. But the the there are ways you can infer the mass of something. Yeah. Um. One of the ways that you can infer the mass of a star from what I understand is to measure it's luminosity,

how bright it is. Yeah, I've also heard that's a mixed bag because they have different um different sizes in their lifespan. Um, I've just heard luminosity and mass is not is not just straightforward like like most things in

astro physics are. Yeah, that's the word on the street right. So. Um. When they started getting to the point where 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, they started to notice something really weird.

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

would think is made of matter. The problem is is they started finding that, you know, this galaxy over here, in 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 barrionic matter. Uh. 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 to the two possibilities. Well. Uh, and so way back in uh geez was at nineteen thirty two an astronomer, a Dutch astronomer named Jan hendrik Ert because he's Dutch, 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 a is a sort of a placeholder name for what they came up with for this, for lack of a better word, this invisible uh matter that has to be out there is it's 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 called started calling it dark matter. This in sable. Well we'll talk about what it ends up sort of looking like in a minute. I want give

that away yet. But this invisible matter that they think is there, right, but it doesn't. It doesn't emit or absorb light or electromagnetic magnetic energy. So it's 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 there's 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 our understanding of physics is off, and the term dark matter stands for both of those. It could be a thing, an underscovered 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 then 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, barrionic matter, all the stuff that we know about counts for about four and a half percent. Uh, where they peg dark matter. Then we have something that I don't even know if I ever want to cover, called dark energy, which makes up the other SEV. But they know it's there because there's something out there that

we can account for that has a significant gravitational force. Right, that's where the whole the whole thing started where they first detected it. Right, so, um, 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 how that's has 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 towards the center of the galaxy, then that means most of the mass is accumulated towards 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 easy ist 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, if you look at this um 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. We're circling just as fast as the ones towards the center, and it just must have knocked their socks off. I can't imagine how many times they went over the same

thing to make sure that they had gotten it. This is for uh clarity. This was the nineteen fifties and nineteen sixties when the 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. 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, that that 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, uh, measuring the rotational velocity of things, like how fast something was spinning in relation to where it was like towards the center, it, 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 um angular rotation was or acceleration of

the outer stars was clue number two. So now we've got to 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 they're aligning in that there's something missing here um. And I think that's a pretty good cliffhanger for a breakdown too. I think people are going to 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.

I really hope we're putting this like well, I feel like we are, but sometimes you know, you just can't tell. Now, this isn't the sun re ducks. Oh god, no, no, no, this is much more simple. So, uh, like you said, they not only studied regular galaxies, but they started to study what what you referred 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 were 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 be these big giant pools of hot gas that we never could detect before and that would account for all of this mass. And they did find these superheated gas clouds and we're like, great, that's it. But they're like, it still doesn't account for everything. That's like a small percentage of of the of what's

what is needs to be accounted for. Right, So it was a it was a breakthrough, but it wasn't the solution solver that they were looking for. It was because so if you can find, um, you know, something that we know has mass, like huge clouds of gas. That again, you know, 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, um, 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 guests. But say that that explained five of the missing of the missing mass. It didn't 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, yeah for them, uh 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, uh, 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 mean you and that is a

galactic cluster. Let's say that will just 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 uh into one of several things. If you're in perfect alignment in it, uh, 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 like circle of light. Yeah, it's really cool looking. Uh. It could be elliptical or oblong.

They call it the Einstein cross basically splits it into four so it just looks like four little stars, all like perfectly lined 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 because it's like kind of scattered. It looks like a bunch of like arcs and banana shaped arcs and arklets. But it's all different versions of the same image that

we'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 spacetime that the 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. 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, this galaxy has that much gravity, and since this galaxy um has this much gravity, it must have this much mass. Now if you take that number, this much mass, and you examine the luminosity of the galaxy, yeah, you're like, this is like not off by you know, like the luminosity is ten, but the mass is ten

and a half. There's like factors sometimes factors of of like times a hundred. Sometimes like there's just no way that your math is off. It's it's 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 there. Yeah, exactly, there's a void in either our understanding or our discovery. So then computers started getting better and better and more advanced. I love how this, uh this article puts it. They turned to the computer. It sounds like they turned to

the bottle or something to compute. Uh. So computer 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 barionic matter we

think there's. This is how much dark matter we think there is. 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. But it just permeated everywhere. And like you said, it seemed to be like this cosmic glue or cosmic connective tissue um, and it was pretty so prizing. So they said, okay, well that's that's the computers take 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 three D models stuff that isn't there. They're mapping three D models avoids based on how how much light bends around a galaxy three billion miles light years away 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 three D map of something that may

not exist. And the coolest thing about all this to me is it's based on stuff that Isaac Newton and Einstein came up with, and well, well we won't spoil it, but they weren't wrong. But that is nuts. This is either 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 two thousand and eleven, there were a couple of

teams using data from uh Schandra'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. What they found out is the computer map was pretty on, which was great, um,

but they needed the real things. So they are looking at a cluster or have been called a bell three three two point three billion light years from Earth, and what they saw was what looks like sort of a football and American football, we're a n Ausi football for that matter. 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 coust so much to ship it there and back maybe

able to see Simon again one day. Is Melbourne your team? Now? Yeah, that's what I got on. That's that's a good city. Yeah. I like it so. Uh it looks like a football with one end pointing towards us or you know, we're we're on Earth, so we're the observer in this case. And uh they Here's the one thing they didn't agree on though, was the density of the dark matter on

able three in the center. Yeah, which is weird because some people calculated it was more dense in the center and matter increase, and other people said it was the opposite, not like, well, we're not sure, but they thought it was uh less dark matter at the center, which is a big deal. But they yes, but they both came up with virtually the same shape and same orientation. Yeah,

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. Uh in January two thousand twelve. Uh, anytime I see international team of researchers, I get excited. But the Canada, France Hawaii telescope has a three forty megapixel camera, so you can actually take pictures of stuff that far away. It's like

the iPhone Excess camera. Is that one of the new ones? Yeah? Okay, is it good. I think it's pretty good camera. It's not three forty megapixel. No, it's not. 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 and it's amazing. Did they let you take pictures? Uh? Yeah, I guess so with your phone? Oh I thought you meant,

I mean with the me I'm probably. I'm sure they were taking picture the 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 another face coat with like a hat on, and then you just go back down the mountain and in Hawaii. Again, it's very very cool experience. So what they did here was basically stitched all these

photos together. It was like photos of ten million galaxies and 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 because what this looks like is what it's spit out so many years ago. Yeah, so they're they're 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. Alright, Chuck, we're back, which is where I start to get a little like brain breaking. 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 UM write one episode of UM

The End of the World. Maybe that's my problem. It's it's and even still I'm like, wait, what there's it's really hard to understand. Yeah, I've always been an astrophysicist, though at heart I think so that's just goes against

my nature. Okay, I'm with you. But they're 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, Uh, 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 are understanding of physics is wrong, right, which means, well, we'll see some people go back in tamper with things. Newton said he didn't like that much

to the dismay of brain. So, um, if if it's just stuff that we already know exists but we just can't observe yet, those fall under the umbrella of Macho's massive compact halo objects, which are huge massive structures that we already know about Neutron stars, black holes, round dwarf stars that are huge massive it have a tremendous amount of mass and thus exert a lot of gravity around them, um, but are too dim to show up clearly when we're looking at say a galaxy or galactic cluster. Yeah, like

we talked about luminositi, 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. No exists, we just can't see them in these particular things.

That's actually doesn't have for as as Acam's razory as that is, that actually does not have as much support in the physics community as the other idea that 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 whimps and the scimpse. WHIMPS stands for weakly interacting massive particles, uh, huge amounts of mass, but difficult to detect because they just interact weekly with

ordinary manner. Right, Here's why they're difficult to attack. To detect that they interact weekly with matter. That's not stating it very well. There's the weak nuclear force is one of the four fundamental forces, and it's found almost exclusively in the nucleus of an atom. What what these WIMP particles weak interactive um massive particles are. They're hypothetical. We

don't know that they exist. Mathematically, they fit the bill of dark matter um 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. 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. Whimps were a big um They were promoted as as the particle I think starting in the eighties because there does because there was something called the

whimp miracle. And this breaks my brain. But apparently if you take the the relic density, which is really unimportant for getting into here, but say the density of a whimp, like how how dense the universe would have to be for a whimp to exist, it corresponds with the weak um force number. And that made everybody say, oh, well, they're particles that don't interact with the elect a magnetic force, they disinteract with the weak force. Nowadays they've kind of

moved to the strong nuclear force simps. And the strong nuclear force also has found just basically in the nucleus of an atom. It's the thing that holds an atom together super tightly, holds the corks into the proton and hold the holds the proton and the and the um the what's the what's the neutral charge one neutron. Yeah, the neutron and the proton together and keeps them together. That's the strong nuclear force. And they think that that

that is probably the particle. Now so the same thing though doesn't interact with the electro magnetic 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. Well, not everyone is on board with this UH period, Like some people, there are some astronomers out there who say they dare say maybe Newton got it wrong and maybe we should crack open the Bible and rewrite it, like Thomas Jefferson and UH.

In the eighties, there was a dude physicist name Mordecaig mill Grom. 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 physicist. We just played them on the air. Uh. 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 mind modified Newton Newtonian dynamics.

And Uh, 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 it was at hawk. Yeah, that is what he was called out on that. It wasn't like, oh, here is a new understanding of a physical law around the Uni verse. This just applied to

those galaxies in the 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. Yeah. 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. Um. And then apparently there was a study in two thousand seven that showed that even down to accelerations as slow as five hundred trillions of a meter per second squared, which is really low acceleration, Newton's second law of motion still held fast. So mind is pretty much out out the window. From what I understand, Newton is giving the finger from the grave to see what you get. He very famously liked to say, bite it. It's on his tombstone. I think, Uh, what else do

we have here? Um? Alternative wise, this guy, I love this dude's name. I looked it up, Dragon H. Kovic. Oh he is he one of the guys at CERN. Yeah. I can do better than that, Dragon, Hey Dukevich, hy Dukevich, Sorry, draw on, but yeah, he said that there's such things as um gravit pollar gravitational polar opposites to particles and anti particles have not only opposite electrical charges, but opposite

gravitational charges. Yeah. So if those are near a galaxy, then it would strenk sort of like a magnet almost, they'd form pull a dipole. Yeah, so it would strengthen the gravitational field. So that's what's accounting for. Uh. In fact, I guess he's saying there is no dark matter, right, Yeah, he's saying that that's dark matters 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 they have it would have an opposite gravitational energy. Yeah, that's pretty neat. It's pretty neat. I would love to have like a pencil made of any particles used to be like, watch this right, just knock everyone sucks right off. So, uh, should we talk about that? That's what I would do if I had a whole bunch of anti particles. That's 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 want to 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 tin part series, The End of the World. The End of the World. Yeah, it's um slated to come out in November seven, and it's this and more

time Sten literally Timesten. Yeah, what other stuff you talk about ai I know that's in there, ai UM, reckless experiments with viruses, FAMI paradox, the Great filter, um, the whole things about existential risks. Man, it's you're getting smarter. I'm just talking about the old movies. It's down. Yeah, but you're like getting in there with people, you know,

like the heart of people. It's just different. It's not better. Well, you've got interviews and stuff though, with like like leading experts, right, yeah, but I kind of used them as like a Greek course to kind of chime in and help like explain it or be like, yeah, Josh is actually right here, you know that kind of like it's not just me saying it's 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 where what's the endgame? There? Are we gonna expand forever? 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 a critical density, and it's tend to the negative twenty nine grams per cubic centimeter, which this article says is equivalent to a few hydrogen atoms in a phone booth.

That density of matter, and if the unit that is the critical density of of matter in the universe, if it's more than that, equal to that, are less than that, there are three different possible outcomes for the universe depending on how dense the universes with matter. Right, and 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 booth. Oh yeah,

I said a good movie the right. Uh, Superman changes his clothes in a phone booth. There you go go watch the original Christo Reef Christopher reef um Superman. Right. Or imagine if you were laying dead in a casket and someone set you up, and you were on your cell phone, but you were only three hydrogen atoms and your cell phone is connected to a machine chord r exactly.

Oh all right, So where we were talking about the critical density of the universe, right, So there are a few different uh outcomes here that they've they've come up with as far as where we're headed. Yeah, So if if the universe has a density of matter, all the matter in the universe, if you could, 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. And this is a huge discovery in and of itself. Right, everybody thought the universe is just kind of there and unchanging. No,

the universe is actually expanding inside. 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 endgame that if it's if the universe, if the universal mass is the same as the critical mass density, it's gonna just keep expanding forever. But eventually it'll it'll get kind of cool, and everything's gonna die and stop. I think it's called the heat death of the universe. Yeah, and that's called

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 to close the universe. That means it'll expand and then eventually slow down, stop expanding, and then collapse on itself. Right like you you know those a bungee uh um swings. Yeah, my daughter was just on one of those. Okay, So they launched up in the air, right, yep, Well they she she she went that way, and then she came back this way,

she did. So when you come back this way. When when you came back this way is 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. Uh. 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. Doesn't 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 Waterson universe, right, alright, alright, alright, or specifically the coasting or open universe. I like that, ak Waterson.

So the only way to figure this out for Shure is to live until the end of the universe, and we're talking billions, possibly trillions of years into the future, 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 truly how much matters in the universe, and then we can predict how it's gonna end. Yeah, it's not just uh folly and like, hey, this would be neat. I mean part of it is. Yeah, there's a part of sandwich and a glass of milk at the end of that calculation. That's true. Uh, And I want to 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. Uh. If you want to more about dark matter, type that word into the search bar. Of those words in the search bar. And since I said that it's time for listening to mail, I'm gonna call this uh something on game shows, Hey, guys, always um 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 that wasn't a Select podcast, that was just a live show. Oh yeah, right, and they fooled me. I love all your episodes, but I found this one particularly fascinating. Last forwarded. 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 Guess her fiance to just pick something

to watch. He puts on quiz show, Oh Emil, not realizing it was based on the real life of it. So I started telling Peter about your podcast. And now quiz shows like this one on the movie were rigged in the fifties 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. Awesome.

It's a Mandela effect, right, syncretism. Anyway, thank you for what you do for keeping me company as a drive around d C on the belt Way every day. Oh you poor person. I know when one of your episodes cueues up, I know my drive will go so much faster. Lots of love, Kristen, Thanks a lot, Kristin. I was a greed email. We're glad we could help you out. Make it look pretty good in front of Peter. Yeah. Good luck with the upcoming wedding, yeah, which we assume

is impending. Okay, um, well, if you want to let us know you're getting married, let us know, we'll say best wishes. Every once while, somebody will send an invitation in. We're not taking 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 exactly. Uh so maybe

make it twelve o'clock. Uh. 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 dot com. That's right, um, and you'll find all the links there and um. You can also send us an email. Just wrap it up, spank it on the bottom, and send it off to Stuff podcast at how stuff works dot com. For more on this and thousands of other topics. Does it how stuff works dot com.