WEBVTT - Where is all the missing matter? 0:00:08.440 --> 0:00:11.399 Hey, Daniel, I think we've been using too much toilet humor. 0:00:11.600 --> 0:00:14.319 You mean, all those obvious dark matter jokes we make. 0:00:14.480 --> 0:00:16.000 Yeah, you know, I'm sure it makes all the nine 0:00:16.079 --> 0:00:17.880 year old to google in the audience. But I don't 0:00:17.880 --> 0:00:20.720 think we want to undercut our educational message. 0:00:20.880 --> 0:00:23.120 All right, that's a good point. Let's try that. All right. 0:00:23.160 --> 0:00:24.840 Well, so what are we talking about today today? 0:00:24.840 --> 0:00:26.120 We're talking about hot gas. 0:00:26.400 --> 0:00:44.440 Well, that didn't last very long. Hi. I am joeham Mack, 0:00:44.479 --> 0:00:48.000 cartoonists and the author of Oliver's Great Big Universe. Hi. 0:00:48.159 --> 0:00:51.240 I'm Daniel. I'm a particle physicist and a professor at 0:00:51.360 --> 0:00:53.960 UC Irvine, and I'm often full of hot air. 0:00:55.720 --> 0:00:57.200 Are an all physicists full of hot air? 0:00:57.280 --> 0:00:59.480 I'm just talking about the weather here in southern California. 0:00:59.520 --> 0:01:00.319 I don't know what you mean. 0:01:00.400 --> 0:01:01.880 What do you mean the weather is inside of you. 0:01:02.120 --> 0:01:04.160 I'm breathing in the atmosphere literally. 0:01:05.000 --> 0:01:07.000 I guess if you were breathing out cold there, that 0:01:07.040 --> 0:01:10.559 would be bad news, because we all know physicists aren't 0:01:10.680 --> 0:01:11.160 very cool. 0:01:11.319 --> 0:01:13.440 I'm trying to make physics hot, is what I'm doing. 0:01:13.520 --> 0:01:15.920 But anyways, welcome to our podcast. Daniel and Jorge explain 0:01:16.000 --> 0:01:18.800 the Universe, a production of iHeartRadio. 0:01:18.200 --> 0:01:20.720 In which we try to marinate in all of the 0:01:20.760 --> 0:01:25.000 wonders and mysteries of the universe. We think that everything 0:01:25.040 --> 0:01:27.560 that's out there should make sense to you, can make 0:01:27.640 --> 0:01:30.360 sense to you, will make sense to you if you 0:01:30.480 --> 0:01:33.039 just think about it, ask enough questions and listen to 0:01:33.040 --> 0:01:34.520 this podcast long enough. 0:01:34.680 --> 0:01:36.880 That's why we try to breathe in the universe and 0:01:37.160 --> 0:01:39.960 breathe it out and think about all of the hot 0:01:40.040 --> 0:01:42.360 and cold stuff out there in the universe, even the 0:01:42.400 --> 0:01:43.600 things in toilets. 0:01:44.240 --> 0:01:46.360 I thought we're avoiding the toilet jokes. 0:01:46.640 --> 0:01:48.840 Well that was in the joke. I mean, there is 0:01:48.880 --> 0:01:50.360 physics in toilets, isn't there. 0:01:50.480 --> 0:01:53.640 That's true. You once challenged our listeners to record their 0:01:53.680 --> 0:01:56.720 toilet spinning to see if they flush differently in Australia. 0:01:56.840 --> 0:01:57.600 Oh did they do it. 0:01:57.760 --> 0:01:59.559 I haven't gotten any didy yet, so we're still waiting 0:01:59.560 --> 0:02:02.040 for the rest to those experiments. But that is serious 0:02:02.080 --> 0:02:02.880 toilet science. 0:02:03.080 --> 0:02:03.760 Yeah, there you go. 0:02:04.200 --> 0:02:06.640 But in the non toilet realm of the universe, we 0:02:06.760 --> 0:02:09.800 are very curious about how everything works out there, and 0:02:09.880 --> 0:02:13.600 more specifically, what's out there and where is it all? 0:02:14.080 --> 0:02:16.120 Can we figure out what in the end the universe 0:02:16.240 --> 0:02:18.480 is made out of and where it's all distributed. 0:02:18.600 --> 0:02:21.240 Yeah, because that is a fundamental human quest to figure 0:02:21.240 --> 0:02:23.520 out what's going on out there. What is this universe 0:02:23.560 --> 0:02:26.320 we're in, what's in it? Who else is in it? 0:02:26.480 --> 0:02:27.720 And what is it made out of? 0:02:27.960 --> 0:02:30.200 And where have they been dropping all their trash? 0:02:30.440 --> 0:02:30.680 Wait? 0:02:30.680 --> 0:02:33.200 What well you mentioned who else is in it? Makes 0:02:33.200 --> 0:02:34.639 it sound like, you know, we're trying to figure out 0:02:34.639 --> 0:02:37.079 where all their stuff is, Like did they lose their keys? 0:02:37.480 --> 0:02:39.560 Where did that box go? This kind of stuff? 0:02:40.560 --> 0:02:42.160 I was just wondering, you know, so we could say, hi, 0:02:42.360 --> 0:02:43.800 not find their keys. 0:02:44.880 --> 0:02:46.200 The first thing we want to do when we talk 0:02:46.240 --> 0:02:48.720 to the aliens is ask them where they left their stuff. 0:02:48.800 --> 0:02:50.680 Is this your trash? Did you leave this over here? 0:02:50.720 --> 0:02:51.600 Please pick that up? 0:02:51.680 --> 0:02:54.320 Although if they leave their keys to their spaceship line around, 0:02:54.600 --> 0:02:56.880 I'm not really going to return that one. No one's 0:02:56.919 --> 0:02:57.400 staying with me. 0:02:58.560 --> 0:03:01.320 Well. On this podcast, we are often talking about one 0:03:01.360 --> 0:03:05.200 of the deepest mysteries in modern physics, which is where 0:03:05.320 --> 0:03:08.080 the dark matter is. We know that most of the 0:03:08.120 --> 0:03:11.000 stuff in the universe is an invisible kind of matter 0:03:11.160 --> 0:03:14.640 We've only recently discovered and have very little concrete information 0:03:15.000 --> 0:03:18.399 about what it is. So we're used to the concept 0:03:18.440 --> 0:03:21.120 of not understanding everything that's out there in the universe. 0:03:21.400 --> 0:03:23.359 But it might surprise you to learn that even the 0:03:23.440 --> 0:03:26.399 kind of stuff that we're used to, the hydrogen, the helium, 0:03:26.480 --> 0:03:28.720 the kind of matter where made out of, is still 0:03:28.800 --> 0:03:29.800 something of a mystery. 0:03:30.000 --> 0:03:31.600 Wait what so then, how do we know how much 0:03:31.760 --> 0:03:32.920 of it there is out there? 0:03:32.960 --> 0:03:35.120 We have a bunch of really clever ways of figuring 0:03:35.160 --> 0:03:37.720 out how much normal matter there should be out there 0:03:37.720 --> 0:03:40.960 in the universe, but it's tricky to actually find all 0:03:41.000 --> 0:03:41.240 of it. 0:03:41.880 --> 0:03:43.440 I see, we know how much of there should be, 0:03:43.520 --> 0:03:45.000 but we just haven't found it. 0:03:45.080 --> 0:03:47.840 Is that what you're saying, that's basically it episode done? 0:03:47.920 --> 0:03:50.840 All right, Well, thank you for joining us. I can 0:03:50.880 --> 0:03:53.480 go do something else now. 0:03:53.480 --> 0:03:56.000 Well, maybe the aliens have stolen all that missing matter. 0:03:56.280 --> 0:04:00.680 WHOA, that's a pretty serious allegation or just you know, 0:04:00.720 --> 0:04:04.920 impugning the goodwill of the aliens and their legality. 0:04:05.080 --> 0:04:07.480 Well maybe instead of making a big mess, they've been 0:04:07.520 --> 0:04:10.480 a little bit too aggressive about cleaning up after themselves. 0:04:11.040 --> 0:04:14.480 Maybe it's the physicist mmm who stole all the matter 0:04:14.560 --> 0:04:16.200 on the planet Earth with the wrench. 0:04:17.600 --> 0:04:19.560 In the end, it's not about understanding the universe. It's 0:04:19.600 --> 0:04:21.640 about figuring out who to blame for it. 0:04:21.560 --> 0:04:24.640 Or who do thank for it? Right? Also, right, maybe 0:04:24.680 --> 0:04:27.400 it's good that we live in this universe. I would 0:04:27.440 --> 0:04:30.159 think so. But anyways, it is a big question about 0:04:30.200 --> 0:04:33.320 where all the matter in the universe is that we 0:04:33.400 --> 0:04:35.960 think should be there, and where it all went. So 0:04:36.000 --> 0:04:43.560 today end the podcast, we'll be asking the question where 0:04:43.760 --> 0:04:46.720 is all the missing matter? I guess this is kind 0:04:46.720 --> 0:04:48.760 of a surprising question because because I didn't know there 0:04:48.839 --> 0:04:53.240 was missing matter? Did this happen recently or a long 0:04:53.279 --> 0:04:53.640 time ago? 0:04:53.720 --> 0:04:56.320 I mean, you're making it sound like an Agatha Christie novel, 0:04:56.400 --> 0:04:58.800 like the Case of the Missing Matter, Like we put 0:04:58.839 --> 0:05:00.960 all this hydrogen over here and we came back and 0:05:01.040 --> 0:05:01.720 it was gone. 0:05:01.920 --> 0:05:04.039 Yeah. Yeah, there was a blackout, the lights went out, 0:05:04.279 --> 0:05:06.520 there were some screens, and suddenly there was a missing 0:05:06.560 --> 0:05:08.719 matter and we're all trapped on an island with a 0:05:08.760 --> 0:05:10.200 limited number of suspects. 0:05:10.640 --> 0:05:13.200 That's right. No, it's been a long standing mystery. It's 0:05:13.200 --> 0:05:15.880 gotten a little bit less play and a less attention 0:05:16.400 --> 0:05:19.159 than the grander mystery of dark matter, but it's still 0:05:19.160 --> 0:05:22.320 a very important question in understanding how galaxies form and 0:05:22.360 --> 0:05:24.560 how the universe looks the way that it does, and 0:05:24.600 --> 0:05:25.880 where all this stuff is. 0:05:26.160 --> 0:05:28.760 Now you're saying that this is actually called, or it's 0:05:28.760 --> 0:05:31.000 called physics, the missing baryon problem. 0:05:31.200 --> 0:05:33.360 Yeah, that's right, because the kind of matter that we 0:05:33.400 --> 0:05:36.280 are made out of is made of protons and neutrons, 0:05:36.279 --> 0:05:39.120 and those are things called baryons. A baryon is anything 0:05:39.160 --> 0:05:42.360 made out of three quarks, and protons and neutrons are 0:05:42.360 --> 0:05:44.560 made out of three quarks. So the kind of matter 0:05:44.600 --> 0:05:46.279 that we are made out of, me and you, and 0:05:46.400 --> 0:05:49.080 stars and galaxies and all the dust, all the visible 0:05:49.160 --> 0:05:52.520 matter that's out there, we call that baryonic matter. And 0:05:52.560 --> 0:05:54.840 so scientists have been trying to understand, like, where are 0:05:54.880 --> 0:05:57.800 all the baryons in the universe? Are there as many 0:05:57.839 --> 0:05:59.799 as we think there should be, And when they couldn't 0:05:59.800 --> 0:06:03.040 find them, they call it the missing baryon problem. 0:06:02.600 --> 0:06:05.480 M sounds very mysterious, and you also kind of make 0:06:05.480 --> 0:06:07.360 it sound like it's somebody else's problem. 0:06:07.440 --> 0:06:09.560 Hey, it's all about pre assignment to blame, right. 0:06:10.680 --> 0:06:12.919 Right, Yeah, Like if you say like, yeah, it's a problem, 0:06:13.160 --> 0:06:15.800 I think you're basically saying it's somebody else's problem. 0:06:15.880 --> 0:06:17.520 Mistakes were made, right. 0:06:17.400 --> 0:06:20.880 That's right, Yeah, things went missing. 0:06:21.880 --> 0:06:24.000 Grand funding misallocated, I don't know. 0:06:24.560 --> 0:06:26.960 So as usual, we were wondering how many people out 0:06:26.960 --> 0:06:30.560 there knew or know that there is missing baryonic matter 0:06:30.640 --> 0:06:31.640 out there in the universe. 0:06:31.760 --> 0:06:34.120 So thanks very much to everybody who participates in this 0:06:34.279 --> 0:06:37.159 segment of the podcast. We would love to hear your 0:06:37.279 --> 0:06:40.200 voice among the coorse of listeners, so please don't be 0:06:40.240 --> 0:06:43.719 shy write to me to questions at Danielandjorge dot com. 0:06:43.760 --> 0:06:45.640 So think about it for a second. Do you know 0:06:46.080 --> 0:06:49.680 where the missing baryonic matter in the universe could be? 0:06:49.800 --> 0:06:52.120 What is the missing baryon problem? 0:06:52.160 --> 0:06:54.400 I have never heard of the missing baryon problem, but 0:06:54.520 --> 0:06:57.600 it might be something like the way that we had 0:06:57.680 --> 0:07:01.720 predicted that the Higgs boson exists and we hadn't experimentally 0:07:01.800 --> 0:07:04.320 verified it. So maybe there is a baryon, some form 0:07:04.360 --> 0:07:08.880 of Bearyon particle that we mathematically know must exist, but 0:07:09.160 --> 0:07:09.760 have it found. 0:07:09.920 --> 0:07:12.440 I don't know what the missing baryon is, but I 0:07:12.440 --> 0:07:13.440 hope someone finds it. 0:07:13.760 --> 0:07:15.800 This is the term I've actually heard of before, if 0:07:15.840 --> 0:07:19.440 I remember correctly. It has to do with the fact 0:07:19.480 --> 0:07:23.960 that there is unexplained difference between the matter that existed 0:07:24.680 --> 0:07:27.040 right after the Big Bang and the matter that exists today. 0:07:27.240 --> 0:07:33.080 The baryon sounds like some sort of barrier to a atom, 0:07:33.720 --> 0:07:37.640 So I suppose if it's missing, then it would be 0:07:37.760 --> 0:07:43.120 some sort of other force that we cannot explain, that 0:07:43.160 --> 0:07:46.040 it is holding something like an atom together. 0:07:46.040 --> 0:07:49.480 All right, or interviews here didn't give us a lot 0:07:49.520 --> 0:07:50.000 of clues. 0:07:51.080 --> 0:07:53.760 This has not gotten a lot of press compared to 0:07:53.960 --> 0:07:56.520 dark matter, out of which they've been like dozens and 0:07:56.640 --> 0:07:59.400 dozens of books written, and it's all sorts of podcasts. 0:07:59.480 --> 0:08:02.320 Whatever it's name is problem in physics, but the missing 0:08:02.360 --> 0:08:05.160 baryon problem is sort of like its second cousin that 0:08:05.240 --> 0:08:06.480 doesn't get top building. 0:08:06.800 --> 0:08:09.280 It sounds like maybe it's a branding problem, you know, 0:08:09.360 --> 0:08:11.680 like dark matter. Where's the dark matter in the universe? 0:08:11.680 --> 0:08:15.480 That sounds mysterious and intriguing. Where's the baryonic matter in 0:08:15.480 --> 0:08:19.080 the universe. It's like, I'm not a fan of Barry. 0:08:19.080 --> 0:08:22.800 What they should have called it the dark baryons or something. 0:08:22.920 --> 0:08:27.960 M yeah, or some other name, right, shining matter, super matter. 0:08:28.040 --> 0:08:29.960 Well, you know, dark means a lot of different things. 0:08:30.040 --> 0:08:33.760 As you know, dark can mean mysterious, unknown, not yet understood. 0:08:33.960 --> 0:08:37.000 It can mean literally dark light does not emit light. 0:08:37.600 --> 0:08:39.760 And it's confusing because there are things out there that 0:08:39.880 --> 0:08:42.320 are dark and are made of matter, but are not 0:08:42.640 --> 0:08:46.000 dark matter, right, Like a lump of charcoal is pretty dark, 0:08:46.080 --> 0:08:47.319 but it's not dark matter. 0:08:47.640 --> 0:08:50.439 You might think that physicists name thinks, very confusingly. 0:08:51.400 --> 0:08:53.119 The missing Physics name committee. 0:08:53.200 --> 0:08:55.240 So there's a bunch of matter that's missing that we 0:08:55.280 --> 0:08:57.680 think should be there, but it's missing. That's what we'll 0:08:57.720 --> 0:09:00.680 be talking about here today. And so let's break it down, Daniel. 0:09:00.880 --> 0:09:02.360 What is baryonic matter? 0:09:02.520 --> 0:09:06.720 So baryonic matter is our kind of matter, hydrogen, helium, 0:09:06.800 --> 0:09:10.120 all of the elements are built out of baryons, because again, 0:09:10.120 --> 0:09:13.800 a baryon is a particle made of three quarks. Number. 0:09:13.880 --> 0:09:16.920 Quarks are these little particles that we think are probably fundamental, 0:09:16.960 --> 0:09:20.559 maybe fundamental, but they interact with the strong nuclear force. 0:09:20.800 --> 0:09:23.080 And the way they form stable objects is either you 0:09:23.120 --> 0:09:25.960 get a pair of quarks like quark antiquark that can 0:09:26.000 --> 0:09:28.480 make a pion, or you can get three of them 0:09:28.480 --> 0:09:31.760 together to cancel out a red quark, a green cork, 0:09:31.800 --> 0:09:33.559 and a blue quark, and that gives you a color 0:09:33.679 --> 0:09:36.880 neutral object like a proton or a neutron that has 0:09:36.920 --> 0:09:38.600 no overall strong force. 0:09:38.840 --> 0:09:41.280 Okay, So a baryotic matter is matter made out of 0:09:41.320 --> 0:09:43.880 quarks basically, right, that's the basic definition of it, like 0:09:43.920 --> 0:09:46.079 the things that we're made out of, which are protons 0:09:46.120 --> 0:09:48.839 and neutrons. But it sounds like there are other things 0:09:48.840 --> 0:09:51.360 besides protons and neutrons you can make out of quarks. 0:09:51.559 --> 0:09:54.080 Yeah, you can make all kinds of things out of quarks. 0:09:54.080 --> 0:09:57.840 You can make other hadrons. There's other combinations of quarks 0:09:58.000 --> 0:10:00.040 that you can use to make other hadrons, like you 0:10:00.080 --> 0:10:02.880 put three strange quarks together, or you can make an 0:10:03.160 --> 0:10:05.640 up and down and a strange etc. There's lots of 0:10:05.640 --> 0:10:08.240 different baryons you can make out of three quarks. You 0:10:08.280 --> 0:10:11.040 can also make combinations out of pairs of quarks. It's 0:10:11.040 --> 0:10:14.319 a huge zoo of particles made out of quark pairs. 0:10:14.400 --> 0:10:16.880 The only stable one is the proton. The proton by 0:10:16.960 --> 0:10:19.320 itself we think will last for a long long time, 0:10:19.760 --> 0:10:22.480 and the neutron is stable when combined with the proton 0:10:22.800 --> 0:10:26.040 inside of nucleus. So that's why protons and neutrons are 0:10:26.040 --> 0:10:28.240 the most common kind of baryon out there. 0:10:28.880 --> 0:10:32.000 So today we're talking about which kind specifically all of 0:10:32.040 --> 0:10:34.959 them or mostly protons and neutrons. 0:10:34.640 --> 0:10:37.600 Mostly protons and neutrons, because that's what we expect the 0:10:37.600 --> 0:10:39.400 baryons out there to be made out of. If you 0:10:39.440 --> 0:10:41.960 have other baryons out there, they typically decay down to 0:10:42.360 --> 0:10:45.079 protons and neutrons. Really, though, we're trying to account for 0:10:45.160 --> 0:10:47.000 all the quarks. In the end, we don't really care 0:10:47.040 --> 0:10:49.280 if they're in protons or in neutrons, or in helium 0:10:49.320 --> 0:10:51.760 or in hydrogen. We just want to know how much 0:10:51.800 --> 0:10:54.600 of our kind of matter, quark based matter, is there, 0:10:54.840 --> 0:10:56.520 and how much of the other stuff is there, and 0:10:56.559 --> 0:10:59.120 can we figure out where all the quarks. 0:10:58.720 --> 0:11:03.000 Went saying baryon matter, barry on which kind of matter 0:11:03.040 --> 0:11:03.640 it settles in. 0:11:06.120 --> 0:11:08.560 Yeah, that's right, And it's a fascinating situation to be 0:11:08.600 --> 0:11:11.719 in because we have all these really clever ways of 0:11:11.840 --> 0:11:15.520 knowing how many quarks there should be in the universe. 0:11:15.960 --> 0:11:18.439 That seems sort of crazy, like, how could you possibly 0:11:18.520 --> 0:11:20.839 have an idea of how many quarks they're on the universe. 0:11:20.880 --> 0:11:23.480 They're here, they're there, they're everywhere. How could you possibly 0:11:23.520 --> 0:11:23.959 count them? 0:11:24.080 --> 0:11:26.160 Well, I mean that's kind of basically what you're asking, right, 0:11:26.280 --> 0:11:29.400 is you're asking where are all the quarks in the universe? 0:11:29.480 --> 0:11:31.520 Right, exactly. We are asking that, but we're asking in 0:11:31.559 --> 0:11:35.160 two ways. One way is using information from the very 0:11:35.200 --> 0:11:38.400 early universe, which tells us how many quarks there should be, 0:11:38.800 --> 0:11:40.959 and then another way is more direct, is going out 0:11:40.960 --> 0:11:43.160 there and actually looking for them and saying, can we 0:11:43.280 --> 0:11:46.960 find all the quarks that our early universe theories predict 0:11:47.080 --> 0:11:50.199 are out there? And that's where the discrepancy comes from. 0:11:50.480 --> 0:11:52.400 Hmmm, So I think you're saying that we could have 0:11:52.480 --> 0:11:54.920 just titled the episode where are all the Missing quarks? 0:11:55.320 --> 0:11:57.920 Yeah, where are all the missing quarks? Exactly? But in 0:11:57.960 --> 0:12:01.240 physics it's called the missing barrier problem, and it makes 0:12:01.320 --> 0:12:03.920 up the kind of matter that we're familiar with. Right, 0:12:04.080 --> 0:12:06.520 we think that dark matter is not made of quarks, 0:12:06.760 --> 0:12:10.120 that's made of something else entirely. So this little sliver 0:12:10.200 --> 0:12:12.640 of the universe that we think is about five percent 0:12:12.840 --> 0:12:15.880 of all the energy density of the universe, baryonic matter 0:12:15.960 --> 0:12:18.520 stuff made out of quarks. That's the thing we're still 0:12:18.520 --> 0:12:20.680 trying to understand after all these years. 0:12:21.360 --> 0:12:23.880 Is there an important distinction between asking where all the 0:12:23.920 --> 0:12:27.080 baryonic matter is and asking where all the quarks are? Like, 0:12:27.120 --> 0:12:30.440 are there quarks that are not in baryonic matter? Or 0:12:30.520 --> 0:12:31.880 is it all the same term. 0:12:32.040 --> 0:12:33.680 There are no quarks that are not in some kind 0:12:33.720 --> 0:12:36.600 of particle because quarks can't be by themselves, so they 0:12:36.679 --> 0:12:40.800 always form either masons, which are quark quark pairs, or baryons, 0:12:40.800 --> 0:12:44.760 which are triplets of quarks. Baryonic matter technically probably also 0:12:44.800 --> 0:12:47.320 includes the electrons. So if you have, for example, a 0:12:47.440 --> 0:12:50.720 hydrogen atom that's a proton and an electron that you 0:12:50.720 --> 0:12:53.640 could call baryonic matter because it's based on the baryon 0:12:53.679 --> 0:12:57.960 the proton, that technically includes the electron. So baryonic matter 0:12:57.960 --> 0:13:00.760 is probably more accurate description because it includes the electrons. 0:13:00.760 --> 0:13:02.640 Also they bind with the protons. 0:13:02.840 --> 0:13:04.920 Wait, so what there's electrons missing too? 0:13:05.040 --> 0:13:06.920 Well, electrons are part of the five percent of the 0:13:06.960 --> 0:13:10.440 universe made out of normal matter, basically quarks and leptons. 0:13:11.080 --> 0:13:13.840 Okay, so then there's a certain amount of quarks and 0:13:13.920 --> 0:13:16.520 electrons in the universe that we think should be there. 0:13:16.600 --> 0:13:18.120 And you're saying, we have an idea of how much 0:13:18.280 --> 0:13:21.239 there should be there based on our measurements of the 0:13:21.280 --> 0:13:22.240 origin of the universe. 0:13:22.360 --> 0:13:25.280 Yeah, we have all these really clever ways of looking 0:13:25.360 --> 0:13:28.400 at details from their early universe and using that to 0:13:28.440 --> 0:13:31.880 figure out essentially how many quarks there should be today. 0:13:32.040 --> 0:13:34.160 In order to build stuff up, we should be able 0:13:34.200 --> 0:13:36.319 to predict how much hydrogen and how much helium and 0:13:36.360 --> 0:13:38.839 all sorts of stuff there are from our pictures of 0:13:38.880 --> 0:13:42.600 the early universe. And there's two totally separate ways to 0:13:42.720 --> 0:13:46.199 predict how much baryonic matter there should be left over today. 0:13:46.559 --> 0:13:49.520 One of them comes from the cosmic microwave background radiation, 0:13:49.640 --> 0:13:52.680 this very early light from about three hundred and eighty 0:13:52.720 --> 0:13:55.920 thousand years after the Big Bang, and another comes from 0:13:55.960 --> 0:13:59.160 the ratio of the elements, how much hydrogen, how much helium, 0:13:59.200 --> 0:14:02.080 how much detery there is in the universe. Both of 0:14:02.120 --> 0:14:05.440 those are very sensitive to the quark density in the 0:14:05.480 --> 0:14:08.320 early universe and so can tell us how many quarks 0:14:08.320 --> 0:14:08.960 there should be. 0:14:09.559 --> 0:14:13.040 Meaning like, we maybe start with a guess and see 0:14:13.200 --> 0:14:15.320 if that makes the universe make sense as we see 0:14:15.320 --> 0:14:17.560 it today, and then you adjust that until you get 0:14:17.559 --> 0:14:20.000 an amount that do you think makes what we see 0:14:20.000 --> 0:14:23.960 in the cosmic microwave background and in the amount of 0:14:24.760 --> 0:14:26.240 stuff we see makes sense. 0:14:26.320 --> 0:14:27.680 Yeah, I don't know that we have to start with 0:14:27.720 --> 0:14:30.360 a guess. It's more like there's information in the cosmic 0:14:30.400 --> 0:14:34.560 microwave background radiation that tells us exactly how many baryons 0:14:34.560 --> 0:14:37.400 there should be. And also by measuring the ratios of 0:14:37.440 --> 0:14:40.160 the elements how much hydrogen, how much helium, we can 0:14:40.320 --> 0:14:42.680 use that to make a calculation of how many baryons 0:14:42.680 --> 0:14:44.640 there should be, so we don't have to guess. We 0:14:44.680 --> 0:14:47.680 can just like extract it directly from these measurements. 0:14:48.560 --> 0:14:50.640 Well, maybe break it down for people. How does the 0:14:50.760 --> 0:14:54.040 ratio of hydrogen and helium tells how many quarts the 0:14:54.160 --> 0:14:54.960 universe started with? 0:14:55.120 --> 0:14:57.480 So in the very early universe, things were super duper 0:14:57.560 --> 0:14:59.960 dense and hot, right, the basic story of the universe, 0:15:00.880 --> 0:15:02.920 things were very very hot and dense. We don't know 0:15:02.960 --> 0:15:04.640 how we got to that state, that's sort of a 0:15:04.640 --> 0:15:07.160 big question mark, but we're very certain that things were 0:15:07.280 --> 0:15:09.240 very hot and dense and very compressed. And then the 0:15:09.360 --> 0:15:12.440 universe expanded, and as it expands, it cools. So you 0:15:12.480 --> 0:15:15.320 start out with like crazy high energy, and then things 0:15:15.320 --> 0:15:19.120 cool further and those quarks form protons and neutrons, et cetera. 0:15:19.320 --> 0:15:21.960 And then as things cool even further, those protons and 0:15:22.000 --> 0:15:25.280 neutrons start to form bonds, so you make for example, deuterium, 0:15:25.480 --> 0:15:29.239 which is a combination of protons and neutrons the deuterium 0:15:29.360 --> 0:15:32.080 can then fuse into helium. So what's happening is the 0:15:32.200 --> 0:15:34.600 universe is cooling and things are sort of like settling 0:15:34.640 --> 0:15:37.640 into place. You're like baking bits and pieces of the universe. 0:15:37.720 --> 0:15:40.960 After about twenty minutes, things are then too cold to 0:15:41.040 --> 0:15:44.040 make any more helium or make any more deuterium, so 0:15:44.080 --> 0:15:46.520 you sort of ran out of time to make deterium. 0:15:46.880 --> 0:15:48.920 So in the very early universe you had this little 0:15:48.960 --> 0:15:51.360 window to make deterium and to make helium, and the 0:15:51.400 --> 0:15:53.880 rest of everything is just hydrogen. And the amount of 0:15:53.920 --> 0:15:57.680 deuterium and helium you get depends very very sensitively on 0:15:57.760 --> 0:16:00.680 the density of quarks, Like you have more we're exploding 0:16:00.680 --> 0:16:03.600 around in that window, you get more deterium, you have 0:16:03.680 --> 0:16:06.760 fewer quarks, you get less deterium. So if you measure 0:16:06.840 --> 0:16:11.240 the hydrogen deterium helium ratios, now you can tell the 0:16:11.320 --> 0:16:13.880 quark density back in that first little window in the 0:16:13.880 --> 0:16:15.600 first twenty minutes of the universe. 0:16:16.760 --> 0:16:19.360 And how do you measure that ratio right now? Like 0:16:19.480 --> 0:16:21.920 we can we go out there into space and gather 0:16:22.280 --> 0:16:24.240 hydrogen and helium. How do we determine it? 0:16:24.320 --> 0:16:25.960 Yeah, you can actually just fill up a glass of 0:16:26.000 --> 0:16:29.000 water from your tap, because one out of like every 0:16:29.120 --> 0:16:32.480 six thousand atoms of hydrogen is actually an isotope of 0:16:32.560 --> 0:16:35.520 hydrogen called deuterium, has a little neutron stuck to it, 0:16:35.560 --> 0:16:37.960 and that deuterium is pretty stable. So the amount we 0:16:38.040 --> 0:16:40.240 made back then is still the amount we make now. 0:16:40.360 --> 0:16:44.280 There's like basically no other natural, significant sources of deuterium, 0:16:44.520 --> 0:16:46.480 So the universe is kind of like locked into this 0:16:46.560 --> 0:16:49.200 deterium ratio. When you fill a glass of water at 0:16:49.240 --> 0:16:52.000 the tap, one out of six thousand atoms of those 0:16:52.080 --> 0:16:56.040 waters has a hydrogen in it that's actually deuterium. How 0:16:56.040 --> 0:16:57.440 do you measure that? You can just put it through 0:16:57.440 --> 0:16:59.720 like a mass spectrometer to measure the weight of the 0:16:59.760 --> 0:17:02.600 at and you'll see this little peak of some water 0:17:02.640 --> 0:17:03.560 that's a little heavier. 0:17:03.600 --> 0:17:05.600 But how do I know that's just not the water 0:17:05.760 --> 0:17:09.960 in my town that has that level of deuterium, or 0:17:10.000 --> 0:17:12.800 even like in our solar system or even galactic neighborhood. 0:17:12.800 --> 0:17:15.119 How do you do you extrapolate my tap water to 0:17:15.160 --> 0:17:16.000 the entire universe? 0:17:17.119 --> 0:17:20.240 You're right, You've unraveled this entire science. No, we obviously 0:17:20.320 --> 0:17:22.440 don't just base it on the top water in your 0:17:22.480 --> 0:17:24.880 house or in anybody else's house. We make measurements all 0:17:24.920 --> 0:17:26.880 over the place. We can make measurements in the rest 0:17:26.920 --> 0:17:29.439 of the Solar system by looking at like vibrational modes, 0:17:29.440 --> 0:17:33.640 because deuterium has slightly different energy levels than normal hydrogen, 0:17:33.960 --> 0:17:36.520 so you can see evidence for this all over the universe. 0:17:36.600 --> 0:17:38.679 And so we see a pretty well known mixture of 0:17:38.760 --> 0:17:40.600 deuterium inside hydrogen. 0:17:40.680 --> 0:17:42.760 All right, So then that tell us how much quark 0:17:42.800 --> 0:17:45.320 matter there should be in the universe, and how much 0:17:45.359 --> 0:17:46.000 is that amount? 0:17:46.160 --> 0:17:49.960 That's about five percent of the energy density of the universe. 0:17:50.160 --> 0:17:52.199 And this is a number that's easy to misunderstand. What 0:17:52.240 --> 0:17:54.080 we mean by that is like, take a big chunk 0:17:54.119 --> 0:17:56.280 of the universe, like a cubic light year, and out 0:17:56.320 --> 0:17:59.400 of all the energy inside of it, all the photons, 0:17:59.560 --> 0:18:01.960 all the dark matter, all the normal matter, all the 0:18:02.080 --> 0:18:05.440 dark energy, all of that stuff, and the normal matter 0:18:05.480 --> 0:18:08.240 should account for five percent of the energy density of 0:18:08.280 --> 0:18:10.760 that chunk. So we're not saying anything about the size 0:18:10.800 --> 0:18:13.199 of the universe or the total number. We're just saying, like, 0:18:13.200 --> 0:18:15.840 what's the ratio five percent of all the energy in 0:18:15.880 --> 0:18:19.680 any given chunk of space should be due to buryonic matter. 0:18:19.920 --> 0:18:22.960 According to what we know of the Big Bang and 0:18:23.040 --> 0:18:26.800 the cosmic microwave background. But it seems that some of 0:18:26.800 --> 0:18:30.199 that matter is missing. Somebody took it or destroyed it, 0:18:30.359 --> 0:18:33.400 or I don't know, hate it. And so let's get 0:18:33.400 --> 0:18:36.880 into that mystery and who we can blame for that 0:18:37.000 --> 0:18:39.600 in more detail. But first let's take a quick break. 0:18:52.200 --> 0:18:54.880 All right, we're talking about some missing matter in the universe. 0:18:55.000 --> 0:18:58.439 There's a certain amount of quark matter in the universe 0:18:58.440 --> 0:19:01.520 that we think should be there. Five percent of the 0:19:01.640 --> 0:19:03.760 energy and matter in the universe should be quark matter. 0:19:03.920 --> 0:19:06.439 But Daniel, it sounds like that's not what we're seeing. 0:19:06.560 --> 0:19:08.800 Yeah, that's right. We have not yet figured out where 0:19:08.840 --> 0:19:11.360 that five percent of matter is. And if you're skeptical 0:19:11.400 --> 0:19:14.280 about that five percent calculation, know that we have other 0:19:14.320 --> 0:19:17.320 ways to calculate this number that are totally independent. Right. 0:19:17.320 --> 0:19:19.600 The description we gave you about the deterium fraction of 0:19:19.600 --> 0:19:23.840 the universe, that's called Big Bang nucleosynthesis. It's understanding how 0:19:23.960 --> 0:19:26.800 much of various elements were made in the very early universe. 0:19:26.920 --> 0:19:30.000 We have other measurements from the cosmic microwave background radiation 0:19:30.160 --> 0:19:32.160 which come from much later in the universe, like three 0:19:32.280 --> 0:19:36.480 hundred and eighty thousand years that are completely independent, totally 0:19:36.520 --> 0:19:39.840 separate measurements. There, we see the early universe plasma sloshing 0:19:39.920 --> 0:19:42.760 around in a way that's sensitive to the number of 0:19:42.920 --> 0:19:44.960 baryons and the amount of dark matter and the number 0:19:45.000 --> 0:19:48.200 of photons. And that's a very very precise measurement, much 0:19:48.240 --> 0:19:51.840 more precise even than the Big Bang nucleosynthesis, and it degrees. 0:19:51.880 --> 0:19:55.520 It's about five percent of the energy density should be baryons. 0:19:56.280 --> 0:19:59.000 But I wonder are they really that independent? I mean, 0:19:59.040 --> 0:20:01.960 don't they both depend on our model of the universe 0:20:02.000 --> 0:20:04.160 and or at least our model of the Big Bang. 0:20:04.240 --> 0:20:06.359 Absolutely, yeah, there are a lot of assumptions in common, 0:20:06.600 --> 0:20:09.640 but there are independent measurements. Like they have different sources. 0:20:09.680 --> 0:20:12.399 You know, one is measuring the fraction of deterium in 0:20:12.400 --> 0:20:14.680 the universe. The other one is like looking at these 0:20:14.880 --> 0:20:18.320 very cold photons in the night sky. They also come 0:20:18.359 --> 0:20:20.919 from a different age in the universe. So they're absolutely 0:20:20.920 --> 0:20:24.360 they're not completely independent, but they're very useful cross checks. Right, 0:20:24.640 --> 0:20:27.200 we would be surprised and confused if those two numbers 0:20:27.200 --> 0:20:28.480 didn't agree with each other. 0:20:28.680 --> 0:20:30.960 Right, all right, So then those measurements are telling us 0:20:31.000 --> 0:20:33.840 there's missing matter, how much quark matter in the universe 0:20:33.960 --> 0:20:37.879 is missing, so like most of it, five percent of 0:20:37.880 --> 0:20:39.160 the universe is missing. 0:20:39.960 --> 0:20:42.440 More like eighty percent of the universe. If you look 0:20:42.440 --> 0:20:44.560 around for quark matter, you can find loss of it. Right, 0:20:44.600 --> 0:20:47.520 Like I'm made a cork matter, You're made of cork matter, right, 0:20:47.760 --> 0:20:49.919 your lunch is made of cork matter. The Earth, the 0:20:50.080 --> 0:20:52.520 Sun is made out of quark matter. All this stuff 0:20:52.560 --> 0:20:55.400 is pretty easy out of all the galaxies and the 0:20:55.440 --> 0:20:58.679 stars and the gas that glows in the universe, and 0:20:58.720 --> 0:21:00.879 then add the harder bits. Right, Some of the stuff 0:21:00.880 --> 0:21:02.360 that's out there in the universe, like we were talking 0:21:02.359 --> 0:21:05.720 about earlier, is matter that is dark, but it's not 0:21:05.880 --> 0:21:09.560 dark matter. You know, things like black holes or things 0:21:09.600 --> 0:21:12.760 like big massive planets that are not glowing. These things 0:21:12.800 --> 0:21:16.200 are harder to spot and harder to account for. But 0:21:16.240 --> 0:21:18.040 people have done a sort of census of all of 0:21:18.040 --> 0:21:20.919 this stuff. Where is all the stuff that we know about, 0:21:21.240 --> 0:21:23.399 how much is there, and how does it add up? 0:21:23.440 --> 0:21:26.240 And together it comes to, you know, about fifteen twenty 0:21:26.400 --> 0:21:27.720 percent of what we. 0:21:27.680 --> 0:21:30.679 Expect, fifteen to twenty percent of the five percent that 0:21:30.760 --> 0:21:31.600 we think should be there. 0:21:31.720 --> 0:21:34.359 Mm hmm exactly. So most of the buryonic matter in 0:21:34.359 --> 0:21:36.520 the universe is not in the stars and in the 0:21:36.560 --> 0:21:39.399 galaxies and in the gas, or in black holes, or 0:21:39.440 --> 0:21:42.000 in planets, or we think in big chunks of rock 0:21:42.080 --> 0:21:44.479 floating out there in the universe. And again we're not 0:21:44.520 --> 0:21:46.879 talking about dark matter, right. We know dark matter is 0:21:46.880 --> 0:21:49.560 out there and it's another mysterious thing. We're just talking 0:21:49.560 --> 0:21:52.040 about the missing quarks. We just can't find as many 0:21:52.119 --> 0:21:53.280 quarks as we expect. 0:21:54.840 --> 0:21:56.679 I wonder if then you just need to lure your 0:21:56.720 --> 0:22:03.200 expectations anyway, like mactation is wrong. Maybe that's the real problem. 0:22:03.560 --> 0:22:06.800 Yeah, but we have these two fairly independent measurements that 0:22:06.880 --> 0:22:09.639 tell us that the universe should be five percent. And 0:22:09.680 --> 0:22:12.080 this all fits in very nicely with our model of 0:22:12.119 --> 0:22:15.200 the universe, how it expands and how structure has formed. 0:22:15.840 --> 0:22:18.480 We have all these ideas for how the universe comes 0:22:18.480 --> 0:22:21.240 together from the hot gas to forming these very cold 0:22:21.320 --> 0:22:24.360 galaxies later on, and all these things are very sensitive 0:22:24.400 --> 0:22:27.879 to the dark energy, dark matter, and normal matter fraction 0:22:28.080 --> 0:22:30.800 of the universe. So it's the number we feel pretty 0:22:30.800 --> 0:22:34.080 confident in five percent, and it gives us enough confidence 0:22:34.119 --> 0:22:35.919 that we want to go out there and look for 0:22:35.960 --> 0:22:38.600 these missing burials. We're pretty sure they exist, we just 0:22:38.720 --> 0:22:39.760 hadn't seen them yet. 0:22:40.480 --> 0:22:42.120 We Well, just so you know, that is an option 0:22:42.200 --> 0:22:45.400 in life. You can just lower your expectations and then 0:22:45.440 --> 0:22:46.360 you can take a vacationion. 0:22:46.400 --> 0:22:48.159 Well, I want to encourage all of our listeners in 0:22:48.200 --> 0:22:51.480 the opposite direction to keep pushing forward until your questions 0:22:51.520 --> 0:22:52.879 are answered. Don't give up. 0:22:52.920 --> 0:22:54.800 All right, Well, let's keep going then. So, there is 0:22:55.000 --> 0:22:57.479 a certain amount of cork matter in universe we think 0:22:57.520 --> 0:23:00.560 should be there, but we can't seem to for it. 0:23:00.600 --> 0:23:02.560 Like we do some accounting of what we can see 0:23:02.560 --> 0:23:04.880 and what we think is there, and it's not enough 0:23:04.960 --> 0:23:06.520 to where could it be and how are we going 0:23:06.600 --> 0:23:07.040 to find it? 0:23:07.080 --> 0:23:10.520 So one obvious place to look is between the galaxies. 0:23:11.080 --> 0:23:13.560 Like we know there's a lot of quark matter in galaxies. 0:23:13.600 --> 0:23:15.960 We can see it. There's gas, this dust, is stars, 0:23:16.040 --> 0:23:17.959 is all that stuff. But we also know that there 0:23:17.960 --> 0:23:20.879 should be a lot of matter between the galaxies, that 0:23:20.920 --> 0:23:24.120 there should be these huge filaments of gas and dark 0:23:24.200 --> 0:23:27.439 matter as well between the galaxies. Because remember, the universe 0:23:27.520 --> 0:23:29.880 is not just like all these little dots of stars 0:23:29.920 --> 0:23:33.600 and dots of galaxies. It's more like a big cosmic web. 0:23:34.240 --> 0:23:36.840 Because as the universe cooled down. It was this hot, 0:23:36.920 --> 0:23:40.440 dense plasma. You have these little dense spots that gather 0:23:40.600 --> 0:23:43.960 together more stuff. The universe is expanding, and then those 0:23:43.960 --> 0:23:47.240 dense spots see the formation of structure, right, they see 0:23:47.320 --> 0:23:50.560 those galaxies, but they don't become isolated. You still have 0:23:50.600 --> 0:23:53.400 these strands between them. And so the place to look, 0:23:53.480 --> 0:23:56.399 the place that our simulations predict there should be a 0:23:56.480 --> 0:23:58.919 lot of quark matter that's sort of hard to spot 0:23:59.080 --> 0:24:00.200 is between the gas. 0:24:00.000 --> 0:24:04.320 Galaxies because they can't be in the galaxies. Because you 0:24:04.359 --> 0:24:06.400 think you can see everything in a galaxy. 0:24:06.520 --> 0:24:08.600 We think we know how much matter there is in 0:24:08.640 --> 0:24:11.679 a galaxy. Yeah, we can see all the luminous stuff 0:24:11.680 --> 0:24:14.679 that's there, all the gas, and all the stars and 0:24:14.720 --> 0:24:17.040 the dark matter, and the motion of those stars tells 0:24:17.080 --> 0:24:21.359 us a lot about the gravitational profile of the galaxy. Remember, 0:24:21.400 --> 0:24:24.840 as the galaxy spins, we can tell how much gravitational 0:24:24.880 --> 0:24:27.000 force there is on those stars by looking at the 0:24:27.080 --> 0:24:30.280 rotation velocity of the stars. That's how we deduce the 0:24:30.359 --> 0:24:33.240 existence of dark matter in the first place. We're pretty 0:24:33.240 --> 0:24:36.760 sure we understand the density profiles of galaxies, which is 0:24:36.800 --> 0:24:39.159 why outside of galaxies is a good target. 0:24:39.359 --> 0:24:41.440 So you're saying that maybe eighty to eighty five percent 0:24:41.480 --> 0:24:43.840 of the missing quark matter in the universe might be 0:24:44.040 --> 0:24:48.119 in between galaxies where we can't see them or what. 0:24:48.400 --> 0:24:50.680 Yeah, that's exactly right. Most of the quarks in the 0:24:50.760 --> 0:24:54.600 universe are not in galaxies. Like you might imagine that. 0:24:54.680 --> 0:24:56.800 You know, matter forms in the Big Bang and then 0:24:56.840 --> 0:24:59.680 things cool and clump together and form galaxies, and that's 0:24:59.720 --> 0:25:01.560 part of the story. But it turns out it's not 0:25:01.800 --> 0:25:05.480 most of the story, that this galaxy formation process is 0:25:05.600 --> 0:25:07.879 kind of inefficient, that most of the normal matter in 0:25:07.920 --> 0:25:11.080 the universe didn't participate it or hasn't. 0:25:10.800 --> 0:25:15.159 Yet, because I guess the stuff that does come together 0:25:15.400 --> 0:25:18.040 is kind of the fancy stuff that everyone pays attention to, 0:25:18.119 --> 0:25:19.560 right the stars and the planets. 0:25:19.960 --> 0:25:22.879 Yeah, it's got the most glitter and glam. 0:25:22.880 --> 0:25:25.320 Okay, So then now is that confirmed? Like if you 0:25:25.480 --> 0:25:27.879 look for things in between galaxies, do you find all 0:25:27.920 --> 0:25:29.120 of this missing quark matter? 0:25:29.320 --> 0:25:31.560 So there's several steps here. The first thing is to 0:25:31.600 --> 0:25:34.879 look for hydrogen, so like, are there huge amounts of 0:25:35.000 --> 0:25:38.440 hydrogen between the galaxies? And you can imagine the galaxies 0:25:38.480 --> 0:25:40.960 is sort of like in these gravitational wells you have 0:25:40.960 --> 0:25:43.720 a blob of dark matter which has gathered together the 0:25:43.760 --> 0:25:46.320 normal matter to form stars and galaxies. And you can 0:25:46.359 --> 0:25:49.840 think about like gravitational filaments like feeding into these wells, 0:25:49.840 --> 0:25:52.639 sort of the way rivers feed into a lake, and 0:25:52.720 --> 0:25:56.160 gas flowing into these galaxies. And we know that gas 0:25:56.200 --> 0:25:58.239 is flowing into these galaxies, we can see like the 0:25:58.280 --> 0:26:01.440 impact of gas flowing to these galaxies. Sometimes it even 0:26:01.440 --> 0:26:04.639 affects star formation in those galaxies. But this gas can 0:26:04.640 --> 0:26:07.399 be tricky to see because it's very, very dilute. Remember, 0:26:07.440 --> 0:26:12.119 there huge space between galaxies, millions and millions of light years, 0:26:12.560 --> 0:26:14.960 and so seeing these things is tricky. One way that 0:26:15.000 --> 0:26:17.320 we have seen them though, is using quasars. 0:26:17.720 --> 0:26:19.879 What do you mean? How do those help us see 0:26:20.040 --> 0:26:22.000 the hydrogen between galaxies? 0:26:22.080 --> 0:26:24.240 They basically light it up for us in this really 0:26:24.240 --> 0:26:27.320 cool way. Remember, a quasar is like a black hole 0:26:27.440 --> 0:26:30.080 at the center of a galaxy that's actively feeding. It's 0:26:30.080 --> 0:26:32.800 like gobbling up a lot of stuff and emitting a 0:26:32.920 --> 0:26:36.000 huge amount of radiation. Now it's confusing for people sometimes 0:26:36.000 --> 0:26:37.840 when you say a black hole is emitting a lot 0:26:37.840 --> 0:26:41.000 of radiation, the black hole itself is not emitting the radiation. 0:26:41.119 --> 0:26:44.080 But if there's a very intense disk of matter near 0:26:44.160 --> 0:26:46.440 the black hole. It's going to be very hot because 0:26:46.480 --> 0:26:49.320 of all the gravitational tidal forces glowing, and a lot 0:26:49.359 --> 0:26:51.560 of that radiation gets funneled up because of the magnetic 0:26:51.640 --> 0:26:54.560 field of the black hole, and you get these extraordinarily 0:26:54.600 --> 0:26:57.480 powerful beams of light that sort of like pencil raised 0:26:57.480 --> 0:27:00.600 through the universe. Some of them hit the Earth. So 0:27:00.640 --> 0:27:03.160 if there's this very powerful beam of light that passes 0:27:03.160 --> 0:27:05.159 all the way through the universe, it's also going to 0:27:05.200 --> 0:27:07.680 pass through some of these filaments of gas. And when 0:27:07.680 --> 0:27:10.760 it does so, it changes the spectrum of light because 0:27:10.760 --> 0:27:13.000 that gas likes to absorb some light. So if this 0:27:13.119 --> 0:27:15.520 hydrogen there, it's going to absorb the light that likes 0:27:15.520 --> 0:27:19.119 to interact with hydrogen, it's sort of deleted from the spectrum. 0:27:19.359 --> 0:27:22.440 So by looking at the spectrum of light from these quasars, 0:27:22.680 --> 0:27:25.440 we can tell how much hydrogen there is between us 0:27:25.720 --> 0:27:26.880 and the source of the light. 0:27:27.160 --> 0:27:29.639 You mean, like all of this quark matter that's floating 0:27:29.640 --> 0:27:32.320 out there between galaxies X kind of like a filter. 0:27:32.840 --> 0:27:35.440 So you have something bright like a quasar is shining 0:27:35.680 --> 0:27:38.760 just directly at us and it filters through this gas. 0:27:38.840 --> 0:27:40.919 You can sort of tell how much of the gas there. 0:27:40.800 --> 0:27:44.080 Is exactly, and it's even more detailed and powerful than that, 0:27:44.480 --> 0:27:48.040 because the hydrogen between us and this distant quasar is 0:27:48.119 --> 0:27:50.840 all going to be moving at different velocities relative to us, 0:27:51.119 --> 0:27:53.359 Like the further away it is, the faster it's going 0:27:53.400 --> 0:27:54.840 to be moving away from us, it's going to be 0:27:54.840 --> 0:27:58.120 red shifted, and that actually changes the frequency of light 0:27:58.160 --> 0:28:00.959 that it interacts with. So if you look at the 0:28:01.000 --> 0:28:03.480 spectrum of life from a quasar, you don't just see 0:28:03.520 --> 0:28:05.560 one dip that tells you how much hydrogen there is. 0:28:05.800 --> 0:28:07.920 You see a lot of dips. You see a forest 0:28:08.080 --> 0:28:11.920 of these dips, each one corresponding to absorption of hydrogen 0:28:12.040 --> 0:28:15.080 at a different red shift. And so not only does 0:28:15.119 --> 0:28:17.240 it tell you how much hydrogen there is between you 0:28:17.280 --> 0:28:19.720 and the quasar, it's like a one d map that 0:28:19.760 --> 0:28:23.160 tells you where that hydrogen was between you and the quasar. 0:28:23.280 --> 0:28:24.919 You can use these quasars to sort of like X 0:28:25.000 --> 0:28:27.919 ray the universe and tell you where the hydrogen is. 0:28:28.200 --> 0:28:31.080 WHOA, but how often do we get signals like this? 0:28:31.160 --> 0:28:33.439 How many quasars are pointing directly at us? 0:28:33.520 --> 0:28:35.800 Yeah, not as many as we'd like, of course, lots 0:28:35.800 --> 0:28:37.879 of them, because there's lots of galaxies out there, and 0:28:38.320 --> 0:28:41.360 in the early universe, quasars were very active. It's a 0:28:41.360 --> 0:28:44.280 whole other mystery like why the quasars mostly get formed 0:28:44.320 --> 0:28:46.720 in the early universe and not so much now. But 0:28:46.760 --> 0:28:49.320 there are a lot of very distant, very bright quasars 0:28:49.320 --> 0:28:51.920 that sort of like shine these lights through the universe, 0:28:51.960 --> 0:28:53.680 and we'd like to see more of them. It's tricky, 0:28:53.840 --> 0:28:55.720 but there's enough that we could have an estimate for 0:28:55.800 --> 0:28:59.960 how much hydrogen gas there is in these filaments between galaxies. 0:28:59.560 --> 0:29:04.120 And these quasars basically like illuminate the hidden matter between galaxies. 0:29:04.320 --> 0:29:06.920 They do. They illuminate the hydrogen. Right. That's when you 0:29:06.920 --> 0:29:09.920 have a proton and an electron together, because that's what's 0:29:09.960 --> 0:29:13.120 going to interact with these photons. The neutral hydrogen will 0:29:13.120 --> 0:29:14.959 do this. So when you look at this information from 0:29:15.000 --> 0:29:16.640 the quasars, you can add it all up and you 0:29:16.680 --> 0:29:20.680 can guess how much neutral hydrogen gas there is between galaxies, 0:29:21.000 --> 0:29:23.400 and that brings you to about half of the five 0:29:23.480 --> 0:29:26.520 percent that we expected. So just stars and galaxies and 0:29:26.560 --> 0:29:29.680 all that stuff gives you like fifteen percent. Adding the 0:29:29.720 --> 0:29:32.920 neutral hydrogen between galaxies and you're up to about fifty percent. 0:29:33.080 --> 0:29:34.320 That we can account for. 0:29:34.480 --> 0:29:36.320 That, we can account for exactly Well. 0:29:36.200 --> 0:29:38.160 You're saying it's not missing, then that we know where 0:29:38.160 --> 0:29:38.440 it is. 0:29:38.640 --> 0:29:41.000 Well, even this very clever technique only brings us to 0:29:41.040 --> 0:29:44.280 fifty percent. The other half is still not explained. 0:29:44.640 --> 0:29:47.760 Mm so only half of that five percent is missing. 0:29:47.520 --> 0:29:50.320 Then, Yeah, so like fifteen percent of it is stars 0:29:50.320 --> 0:29:53.400 and galaxies and black holes and the obvious easy stuff. 0:29:53.640 --> 0:29:56.400 Another like thirty five percent turns out to be this 0:29:56.560 --> 0:30:00.959 neutral hydrogen between galaxies. Until very re we've had no 0:30:01.120 --> 0:30:04.840 explanation for the other fifty percent that part was still missing. 0:30:05.040 --> 0:30:08.080 Could it be some other kinds of gases in between galaxies? 0:30:08.360 --> 0:30:11.520 So the crucial thing is that this quasar method will 0:30:11.560 --> 0:30:14.720 tell us about neutral hydrogen, because you know, the photons 0:30:14.800 --> 0:30:18.200 passing through these filaments will excite. Neutral hygrogen has these 0:30:18.280 --> 0:30:21.280 very particular energy levels. The rest of a popular theory 0:30:21.680 --> 0:30:25.040 is that it's a low density plasma that it's ionized. 0:30:25.320 --> 0:30:27.600 It's not like a proton or electron hanging out in 0:30:27.600 --> 0:30:29.760 a hydrogen atom. It might just be like a bunch 0:30:29.760 --> 0:30:32.120 of protons and a bunch of electrons that are too 0:30:32.240 --> 0:30:34.480 hot to settle down into a hygrogen atom. They're like 0:30:34.520 --> 0:30:37.840 flying around free and they wouldn't interact with equasars in 0:30:37.880 --> 0:30:40.560 the same way. And people argue about whether it's warm 0:30:40.720 --> 0:30:43.080 or whether it's hot, and so they give this stuff 0:30:43.120 --> 0:30:48.160 the name warm hot Intergalactic medium WHIM or. 0:30:48.240 --> 0:30:54.600 WHIM interesting acronym there. So you're saying that light doesn't 0:30:54.960 --> 0:30:58.720 interact with cork matter unless there's an electron attached to it, 0:30:58.800 --> 0:31:02.120 and that's because light only interacts with electrons. 0:31:02.240 --> 0:31:05.280 Light will interact with any charged particle. But this particular 0:31:05.320 --> 0:31:08.640 signature that we can see relies on a feature of 0:31:08.840 --> 0:31:12.640 neutral hydrogen. So photons will interact with protons when electrons 0:31:12.640 --> 0:31:15.080 and scatter and do all sorts of stuff. But this 0:31:15.120 --> 0:31:17.800 particular method only lets us see the neutral hydrogen. 0:31:17.880 --> 0:31:20.000 Why doesn't it let us see the protons. 0:31:20.160 --> 0:31:22.120 Well, what happens when the life from the quasar hits 0:31:22.120 --> 0:31:24.240 a proton or hits an electron is it just basically 0:31:24.240 --> 0:31:26.560 gives it a boost. It makes it glow a little bit. 0:31:26.640 --> 0:31:28.360 But it's hard to know how to interpret that. We 0:31:28.400 --> 0:31:30.720 can't see very well the glow from these protons and 0:31:30.720 --> 0:31:34.120 these electrons because they're very very hot, so we think 0:31:34.160 --> 0:31:37.640 they might emit some X rays or some UV rays 0:31:37.760 --> 0:31:40.480 but it's very hard to detect those here on Earth. 0:31:40.240 --> 0:31:43.160 So we wouldn't see it in the signature from the quasars. 0:31:42.720 --> 0:31:45.360 Exactly, because these free protons and these free electrons can 0:31:45.400 --> 0:31:48.040 interact with any kind of photon, so they generally would 0:31:48.080 --> 0:31:51.280 just like overall, reduce the signature from the quasars neutral 0:31:51.360 --> 0:31:53.480 hydrogen because it's a bound state of the proton, and 0:31:53.520 --> 0:31:56.360 the electron is very rigid about which photons it will 0:31:56.360 --> 0:31:59.000 interact with, and so it makes this very particular measurable 0:31:59.040 --> 0:32:02.320 signature on the quasars. A free proton or free electron 0:32:02.360 --> 0:32:04.720 can interact with any kind of photon, and so it 0:32:04.760 --> 0:32:08.000 doesn't create this like obvious signature in the quasar beam. 0:32:08.240 --> 0:32:11.400 We need another method to see these protons and electrons. 0:32:11.800 --> 0:32:14.320 I see the light from the quasar is maybe getting 0:32:14.360 --> 0:32:18.160 absorbed by these free quarks floating out there, but it 0:32:18.200 --> 0:32:20.000 would just look like it's a little dimmer to us, 0:32:20.040 --> 0:32:22.120 which we can tell if it's because of that or 0:32:22.320 --> 0:32:24.320 maybe because the quasar is not as bright as we 0:32:24.320 --> 0:32:26.520 thought it is. All right, well, let's get into some 0:32:26.640 --> 0:32:29.320 of the ways that we maybe could measure this missing 0:32:29.480 --> 0:32:32.680 quark matter and what it all means about our understanding 0:32:32.760 --> 0:32:35.880 of the universe. But first, let's take another quick break. 0:32:48.480 --> 0:32:52.360 All right, we are slowly piecing together this problem, this 0:32:52.480 --> 0:32:55.280 missing matter in the universe. Apparently there's a lot of 0:32:55.360 --> 0:32:57.400 quark matter that we think should be there, but it's not. 0:32:57.640 --> 0:32:59.480 Although I feel like we've already a kount of for 0:32:59.560 --> 0:33:01.960 fifty percent of it. We started with only being able 0:33:01.960 --> 0:33:04.719 to count fifteen percent of it, but now we're up 0:33:04.720 --> 0:33:05.640 to fifty percent of it. 0:33:05.800 --> 0:33:07.680 Yeah, and you know, I guess fifty percent is like 0:33:07.840 --> 0:33:10.320 on the edge of a passing grade. So you might 0:33:10.360 --> 0:33:12.400 be tempted to call it a day move on, But 0:33:12.640 --> 0:33:14.320 you know, some of us are curious. We want to 0:33:14.360 --> 0:33:16.720 know where is the other half of all the matter in. 0:33:16.680 --> 0:33:19.000 The universe, don't Some of these measurements have like a 0:33:19.040 --> 0:33:23.480 plus or minus fifty percent uncertainty or error bar on them. 0:33:23.480 --> 0:33:25.760 Anyway, I guess that's one way to resolve the mystery. 0:33:25.920 --> 0:33:28.200 Just be like, well, let's just inflate the aerror and 0:33:28.280 --> 0:33:29.680 it's no longer a mystery. 0:33:29.880 --> 0:33:30.520 There you go. 0:33:31.640 --> 0:33:34.120 Yeah, there are big uncertainties on some of these measurements, 0:33:34.160 --> 0:33:36.560 but they're smaller than the discrepancy. And that's how you 0:33:36.680 --> 0:33:39.040 know when you have an interesting scientific puzzle that you 0:33:39.080 --> 0:33:41.280 think you have measured things well and yet you still 0:33:41.360 --> 0:33:44.040 can't explain it. Things are not adding up. The error 0:33:44.160 --> 0:33:46.720 is smaller than the size of the effect you're looking for. 0:33:47.440 --> 0:33:49.680 All right. So now we've accounted for fifty percent of 0:33:49.720 --> 0:33:52.720 the quark matter in the universe. There's still fifty percent missing. 0:33:52.800 --> 0:33:53.720 How are we looking for it? 0:33:53.840 --> 0:33:55.800 So we're using all sorts of clever techniques to look 0:33:55.840 --> 0:33:58.280 for this stuff the whim. And this stuff is hard 0:33:58.320 --> 0:34:00.720 to see because even though it could be pretty hot, 0:34:00.760 --> 0:34:04.120 we're talking about like a million calvin right ten to six, 0:34:04.240 --> 0:34:08.360 ten to seven calvin, it's also very very dilute, you know, 0:34:08.400 --> 0:34:11.840 it's like one atom per cubic meter. It's like a 0:34:11.920 --> 0:34:15.480 billionth of a billionth of the density of our atmosphere. 0:34:15.719 --> 0:34:17.760 So this stuff is not very easy to see, especially 0:34:17.760 --> 0:34:20.440 if it's very far away. And so we're looking for 0:34:20.560 --> 0:34:22.480 a way to excite it. We're looking for something that's 0:34:22.520 --> 0:34:24.960 going to pass through it and get interacted with it 0:34:25.000 --> 0:34:27.480 in a characteristic way that can tell us about the 0:34:27.480 --> 0:34:30.120 density of this plasma. And one really cool way is 0:34:30.160 --> 0:34:34.960 to use another cosmic mystery, these things called fast radio bursts. 0:34:35.520 --> 0:34:38.560 Something out there in the universe is generating these very 0:34:38.600 --> 0:34:42.319 intense pulses of radio waves. Remember, radio waves are just 0:34:42.360 --> 0:34:46.319 photons with very very long frequency. We call it radio waves. 0:34:46.360 --> 0:34:48.279 If it's in a certain frequency regime, we call them 0:34:48.400 --> 0:34:51.440 X rays, and another frequency regime, and visible light in another. 0:34:51.800 --> 0:34:54.719 It's all just photons of different energies. But these very 0:34:54.800 --> 0:34:58.000 very bright pulses of radio waves are created somewhere out 0:34:58.000 --> 0:35:01.200 there in the universe, passing through all the matter between 0:35:01.320 --> 0:35:03.720 us and them, And as we study them here on Earth, 0:35:03.760 --> 0:35:05.920 we can look at the details of those radio waves 0:35:06.120 --> 0:35:08.640 as a way to sort of like X ray, this whim, 0:35:08.800 --> 0:35:10.800 this warm, hot intergalactic medium. 0:35:10.960 --> 0:35:13.960 So how do these bursts of radio waves tell us 0:35:14.000 --> 0:35:17.640 about this plasma that might be hiding all of the 0:35:17.640 --> 0:35:18.480 missing cord matter. 0:35:18.640 --> 0:35:21.160 Yeah, so you had the basic idea earlier when you're saying, like, 0:35:21.520 --> 0:35:25.240 wooden photons interact with this whim. The protons, they're electrons, 0:35:25.280 --> 0:35:27.799 they're charged particles, and you're absolutely right they do. But 0:35:27.880 --> 0:35:30.040 you need the right kind of photon in order to 0:35:30.080 --> 0:35:32.400 tell you what you need to know. As light passes 0:35:32.440 --> 0:35:35.080 through matter, it slows down like the speed of light 0:35:35.160 --> 0:35:37.520 through a vacuum. Is the famous speed that we all know, 0:35:37.800 --> 0:35:40.359 but light passing through glass or through air will move 0:35:40.440 --> 0:35:43.600 slower than light through a vacuum, and that effect actually 0:35:43.600 --> 0:35:47.680 depends on the energy of the photon. So longer wavelengths 0:35:47.680 --> 0:35:51.399 of light are slowed more than shorter wavelengths of light. 0:35:51.480 --> 0:35:53.200 So if you start with the pulsive light of several 0:35:53.239 --> 0:35:56.160 frequencies and then you measure the arrival time of that 0:35:56.280 --> 0:35:59.200 light here on Earth, you can actually measure the density 0:35:59.200 --> 0:36:03.120 of stuff between you and the pulse, because the higher 0:36:03.120 --> 0:36:05.640 the density, the more the difference in the arrival times 0:36:05.680 --> 0:36:08.240 between the long wavelengths and the short wavelengths. 0:36:08.560 --> 0:36:10.840 I see, But don't you need to know what that 0:36:10.920 --> 0:36:13.319 bursts looked like before it went through the filter of 0:36:13.440 --> 0:36:16.560 this plasma between galaxies? How do we know that if 0:36:16.600 --> 0:36:18.680 these are of unknown origin? 0:36:18.760 --> 0:36:20.680 You're right, we do need to know something, But essentially 0:36:20.719 --> 0:36:23.400 all we need to know is that they're all produced 0:36:23.440 --> 0:36:25.600 at the same moment, or very very close to the 0:36:25.600 --> 0:36:28.120 same time. We don't need to know something about the 0:36:28.160 --> 0:36:30.560 spectrum because we're looking for it's just the difference in 0:36:30.640 --> 0:36:32.960 arrival times. If you shoot a long wavelength and a 0:36:33.000 --> 0:36:36.200 short wavelength photon at me at the same time, then 0:36:36.239 --> 0:36:38.640 I can tell you the density of matter between us 0:36:38.880 --> 0:36:41.200 by looking at the difference in the arrival times between 0:36:41.239 --> 0:36:44.359 the short and the long wavelength photon, because the long 0:36:44.400 --> 0:36:47.600 wave looking photon will be slowed down more by higher 0:36:47.640 --> 0:36:49.879 density material. So I don't need to know anything else. 0:36:49.920 --> 0:36:51.480 I just need to know that there's like a pulse 0:36:51.560 --> 0:36:54.160 created and these two photons were made of basically the 0:36:54.200 --> 0:36:56.920 same moment. And that's what these fast radio bursts do. 0:36:57.040 --> 0:36:59.800 We don't know what's actually making them. That's a big mystery, 0:37:00.360 --> 0:37:02.160 but we suspect that they're being made in a very 0:37:02.200 --> 0:37:04.560 short amount of time, like a one millisecond pulse. 0:37:05.320 --> 0:37:07.480 But how do you know they weren't made at different times. 0:37:07.600 --> 0:37:09.680 Yeah, we're not exactly sure. That's an assumption. When they 0:37:09.760 --> 0:37:11.680 arrive here on Earth, they're spread out over a few 0:37:11.719 --> 0:37:14.040 seconds or sometimes tens of seconds. But because of the 0:37:14.160 --> 0:37:17.160 enormous amount of energy overall, we suspect that it was 0:37:17.200 --> 0:37:19.960 a very fast event, though we still don't understand it. 0:37:20.000 --> 0:37:21.319 I think I know what you're saying. You're saying like 0:37:21.640 --> 0:37:24.320 there's a burst of radio waves, like a bright flash 0:37:24.360 --> 0:37:26.920 of light that we see that was made out there 0:37:27.120 --> 0:37:30.239 in the universe, and we measure that burst of light 0:37:30.280 --> 0:37:33.319 when it gets here on Earth at different frequencies. You're saying, like, 0:37:33.480 --> 0:37:37.160 the bursts at one frequency is going to arrive earlier 0:37:37.200 --> 0:37:40.440 than the burst from another frequency, and that difference in 0:37:40.480 --> 0:37:42.560 the arrival time tells you like, oh, there must have 0:37:42.600 --> 0:37:47.080 been some quark matter in plasma form between us and 0:37:47.160 --> 0:37:51.239 that burst that absorb or slowed down some of that 0:37:51.400 --> 0:37:53.320 second frequency exactly. 0:37:53.440 --> 0:37:57.360 This effect is called dispersion, you know, wavelength dependent effect 0:37:57.520 --> 0:37:59.640 on the speed of light essentially, and by measuring this 0:37:59.680 --> 0:38:03.200 dip you can infer the density of the plasma between 0:38:03.239 --> 0:38:05.600 you and the source. But you're right, we're making some 0:38:05.680 --> 0:38:08.600 assumptions about the nature of the source. We're assuming, essentially 0:38:08.920 --> 0:38:11.720 that the length of time over which those radio waves 0:38:11.719 --> 0:38:14.239 were produced is negligible compared to the length of time 0:38:14.280 --> 0:38:15.200 over which they arrive. 0:38:15.560 --> 0:38:17.640 You also have to know where that burst came from, 0:38:17.680 --> 0:38:18.080 don't you. 0:38:18.160 --> 0:38:20.560 Yeah, you do. You have to know the direction. And 0:38:20.600 --> 0:38:23.600 so we've been seeing these fast radio bursts over the 0:38:23.680 --> 0:38:26.600 last few decades. They were discovered sort of accidentally. We 0:38:26.680 --> 0:38:29.600 have a whole fun podcast episode about that, but only 0:38:29.640 --> 0:38:32.000 recently have we been able to locate them, to tell 0:38:32.040 --> 0:38:34.600 where in the sky they come from, and to do 0:38:34.640 --> 0:38:37.400 that you need like larger instruments, or you need coordination 0:38:37.520 --> 0:38:40.400 between various instruments so you can tell about their arrival 0:38:40.440 --> 0:38:42.480 time at various parts on Earth. But in the last 0:38:42.480 --> 0:38:44.360 couple of decades they've been able to do that and 0:38:44.440 --> 0:38:47.920 gather enough information to estimate the mass of the WHIM 0:38:48.120 --> 0:38:49.600 from these fast radio. 0:38:49.360 --> 0:38:53.000 Bursts, at least the part of that quark plasma that's 0:38:53.040 --> 0:38:56.320 hiding that we can tell using this method. 0:38:56.440 --> 0:38:59.719 Yeah, exactly. And you always want to have like multiple 0:38:59.719 --> 0:39:02.440 ways to measure things, especially if it's very uncertain, and 0:39:02.520 --> 0:39:04.759 if you're talking about half of all the stuff in 0:39:04.800 --> 0:39:07.719 the universe or the normal matter. So there actually is 0:39:07.760 --> 0:39:12.080 a second, completely independent way to measure this WIM to 0:39:12.120 --> 0:39:14.719 see where it is and how much stuff there is. 0:39:15.160 --> 0:39:17.840 And this one is more sensitive to the electrons in 0:39:17.840 --> 0:39:19.880 the wim. Remember we think the WIM is a plasma. 0:39:19.880 --> 0:39:22.880 It's protons and its electrons, and those are separated, and 0:39:22.880 --> 0:39:26.759 the electrons themselves can get like jazzed up by interacting 0:39:26.800 --> 0:39:29.799 with the old cosmic microwave background light in a way 0:39:29.840 --> 0:39:32.319 that some people can see and can use that to 0:39:32.520 --> 0:39:34.759 estimate where the WIM is and how much there is. 0:39:35.520 --> 0:39:38.520 And so using these measurements what is our estimate of 0:39:38.640 --> 0:39:41.799 orre all this missing quark matter up to. 0:39:41.920 --> 0:39:44.400 So it comes out pretty close to one hundred percent. 0:39:44.840 --> 0:39:47.719 So the current idea is that this WIM fills in 0:39:47.760 --> 0:39:50.040 the gap that when you add in the WHIM and 0:39:50.080 --> 0:39:53.040 the neutral hydrogen between galaxies and then all the stuff 0:39:53.040 --> 0:39:56.560 inside the galaxies, it all adds up to explain the 0:39:56.600 --> 0:40:00.279 amount of baryonic matter we predicted from the CMB and 0:40:00.320 --> 0:40:03.080 from Big Bang nucleosynthesis. So it all sort of like 0:40:03.120 --> 0:40:04.520 clicks into place amazingly. 0:40:04.680 --> 0:40:07.000 So then we think we found all the missing matter. 0:40:07.040 --> 0:40:09.320 Then we have cracked the case of the missing matter 0:40:09.400 --> 0:40:12.839 in the universe, which is like sort of exciting and 0:40:12.880 --> 0:40:14.319 also sort of disappointing. 0:40:14.480 --> 0:40:17.200 So wait, using these radio burss, we think we've seen 0:40:17.560 --> 0:40:18.520 all of the missing matter. 0:40:18.680 --> 0:40:20.799 Yeah, the current thinking is that this WHIM is that 0:40:20.880 --> 0:40:23.680 missing piece, that fifty percent that we couldn't account for 0:40:23.800 --> 0:40:26.560 after we figured out the neutral hydrogen component is probably 0:40:26.600 --> 0:40:28.960 all the WHIM, which means that like half of all 0:40:29.000 --> 0:40:31.840 the quarks in the universe are in the WHIM. 0:40:31.880 --> 0:40:34.680 Are in hot gas in between in the middle of nowhere. 0:40:34.719 --> 0:40:38.360 Basically, yeah, the universe is half hot gas. 0:40:38.480 --> 0:40:42.520 It's incredible sort of like the US. I guess, so 0:40:42.600 --> 0:40:44.360 the population lives in the middle of nowhere. 0:40:44.520 --> 0:40:46.920 Yeah, exactly. And so if you want to like make 0:40:46.960 --> 0:40:48.640 a ranked list of all the stuff that's out there 0:40:48.640 --> 0:40:50.920 in the universe, it's mostly, you know, stuff that's very 0:40:50.920 --> 0:40:54.080 susceptible to toilet humor. It's dark matter is a lot 0:40:54.120 --> 0:40:56.759 of the universe, and then of the five percent that 0:40:56.800 --> 0:40:59.080 makes up our kind of stuff, half of it is 0:40:59.160 --> 0:41:02.480 hot gas floating out there in the universe between galaxies. 0:41:02.680 --> 0:41:04.960 Well, it's only toilet humor if you like, if your 0:41:05.200 --> 0:41:06.399 head is in the toilet. 0:41:08.760 --> 0:41:10.680 Maybe it's good or humor then. But you know, it's 0:41:10.719 --> 0:41:13.239 exciting to have these confirmation to be like, wow, we 0:41:13.280 --> 0:41:15.600 do really understand what's going on out there in the universe. 0:41:15.719 --> 0:41:18.799 These incredible calculations from the early universe that make these 0:41:18.800 --> 0:41:21.920 predictions about how many baryons should be floating out there 0:41:21.960 --> 0:41:25.640 billions of years later are kind of accurate. And we've 0:41:25.680 --> 0:41:28.160 been able to like X ray and pinpoint the universe 0:41:28.239 --> 0:41:30.520 using all these clever techniques to figure out where the 0:41:30.600 --> 0:41:33.920 stuff actually is. And it tells us this amazing story 0:41:33.920 --> 0:41:36.840 that galaxies are not the most important thing in the universe. 0:41:36.880 --> 0:41:39.520 They're not even the most important part of the normal matter. 0:41:39.880 --> 0:41:43.440 There are these massive halos of gas surrounding the galaxies 0:41:43.440 --> 0:41:47.279 and then between the galaxies, So that's super exciting, but 0:41:47.360 --> 0:41:49.680 it's also kind of a letdown because when you do 0:41:49.680 --> 0:41:52.560 these kind of calculations, which you're hoping for is some 0:41:52.840 --> 0:41:55.760 great new discovery. Right the way we discover dark matter 0:41:55.960 --> 0:41:58.920 by finding a discrepancy in our calculations, this could have 0:41:58.960 --> 0:42:02.000 been the discovery of something else, totally weird and new. 0:42:02.280 --> 0:42:05.000 Well, you're disappointed that you solve the problem. You wanted 0:42:05.040 --> 0:42:05.760 more problems. 0:42:05.840 --> 0:42:07.880 Yes, I wanted more problems exactly. 0:42:07.920 --> 0:42:09.959 You want it more, more of a job. 0:42:11.160 --> 0:42:13.200 It would be fascinating, right, Like finding out that it's 0:42:13.200 --> 0:42:16.160 the whim is cool, it makes sense, But it would 0:42:16.160 --> 0:42:18.479 have been more exciting if it was some new kind 0:42:18.480 --> 0:42:21.320 of matter, something else that we didn't expect, quarks forming 0:42:21.400 --> 0:42:24.680 some new kind of stuff that we hadn't anticipated, or 0:42:24.719 --> 0:42:27.959 maybe discovering something was wrong in our early universe calculations. 0:42:28.239 --> 0:42:30.759 That would have been I think a bigger discovery because 0:42:30.800 --> 0:42:32.880 we would have learned more about the universe. 0:42:33.120 --> 0:42:35.160 Well, maybe that's why this problem didn't get a lot 0:42:35.160 --> 0:42:37.200 of press, because you guys sold it as like, Eh, 0:42:37.480 --> 0:42:41.040 we found it. Whatever, it's not that exciting. Now you're 0:42:41.040 --> 0:42:43.560 complaining that it doesn't get any uh. 0:42:43.400 --> 0:42:45.600 Press, Well, here we are trying to get it some 0:42:45.640 --> 0:42:48.319 more attention. Right, So I'm out here trumpeting the case 0:42:48.360 --> 0:42:50.680 of the missing matter and its whimsical solution. 0:42:50.960 --> 0:42:52.879 Well, I think maybe the other reason is that it's 0:42:52.920 --> 0:42:54.480 not really a problem anymore, exactly. 0:42:55.239 --> 0:42:58.480 Yeah, Unfortunately we've mostly figured it out. I unfortunately or 0:42:58.560 --> 0:43:01.160 unfortunately fortunately because it means our theories of physics are 0:43:01.160 --> 0:43:04.520 mostly working and our techniques are clever and effective. Unfortunately, 0:43:04.560 --> 0:43:06.160 because it means now we've got to move on to 0:43:06.239 --> 0:43:07.000 something else. 0:43:07.480 --> 0:43:10.000 So maybe you just need to rename it. Right, It's 0:43:10.000 --> 0:43:12.560 no longer the missing baryon problem is just the found 0:43:12.600 --> 0:43:13.360 barian flat. 0:43:16.200 --> 0:43:19.440 Yeah, the once missing baryon. The Baryon's formerly known as 0:43:19.480 --> 0:43:20.399 missing all right. 0:43:20.440 --> 0:43:24.640 Well, another interesting reminder that the universe keeps surprising us, 0:43:24.719 --> 0:43:28.200 even in I guess not so surprising ways. It's surprising 0:43:28.239 --> 0:43:31.360 that you can sort of make these models and figure 0:43:31.360 --> 0:43:34.680 out where everything should be and where it needs to be. 0:43:34.880 --> 0:43:37.759 Yeah, asking questions in several different ways, trying to do 0:43:37.840 --> 0:43:40.720 calculations from this and from that, piecing it all together 0:43:40.840 --> 0:43:42.759 is a great way to figure out what's actually out 0:43:42.800 --> 0:43:45.480 there in the universe, and sometimes actually leads you to 0:43:45.520 --> 0:43:46.000 an answer. 0:43:46.080 --> 0:43:47.439 Well, I kind of wish we had read the last 0:43:47.480 --> 0:43:49.960 chapter of this mystery. I had to save this a 0:43:49.960 --> 0:43:50.759 lot of time here. 0:43:50.960 --> 0:43:54.360 This was decades of work and lots of careful energy, 0:43:54.480 --> 0:43:57.160 and like lots of people's peachdtcs. You know, we're like 0:43:57.239 --> 0:44:00.840 taking tiny steps in this direction. So you can summarize 0:44:00.840 --> 0:44:02.960 it all in about five seconds, but you know, it 0:44:03.000 --> 0:44:03.239 was a. 0:44:03.239 --> 0:44:06.439 Journey, and also it's kind of a still a work 0:44:06.440 --> 0:44:08.919 in progress, I imagine. I mean, you have some measurements, 0:44:08.960 --> 0:44:12.080 but you can always refine those or somebody might find 0:44:12.120 --> 0:44:13.960 something that disproved those measurements. 0:44:13.600 --> 0:44:16.480 Right, yeah, precisely. Now we fold these things into our 0:44:16.480 --> 0:44:19.600 models of galaxy formation. Because we have a better understanding 0:44:19.640 --> 0:44:22.440 of the density and the temperature of this whim. We 0:44:22.480 --> 0:44:25.160 can make sure that it describes the kinds of galaxies 0:44:25.160 --> 0:44:27.480 that we see, the sizes of galaxies, the rate of 0:44:27.520 --> 0:44:31.400 galaxy formation, how often galaxies merge. It all gets folded 0:44:31.440 --> 0:44:34.680 into a more precise description of our universe, which we 0:44:34.760 --> 0:44:38.960 hope will reveal more discrepancies and more surprises in the future. 0:44:39.160 --> 0:44:43.239 And more toilet humor inevitable. All right, well it's time 0:44:43.280 --> 0:44:46.799 to flush. I guess we hope you enjoyed that. Thanks 0:44:46.800 --> 0:44:49.080 for joining us, see you next time. 0:44:57.000 --> 0:44:59.880 Thanks for listening, and remember that. Daniel and Jorge Explaining 0:44:59.880 --> 0:45:03.879 You Universe is a production of iHeartRadio. For more podcasts 0:45:03.880 --> 0:45:08.560 from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever 0:45:08.600 --> 0:45:10.320 you listen to your favorite shows.