Listener Questions 61.0158: Black holes, gold asteroids and gravitational waves in time!

00:00:07
Speaker 1: Hey, Daniel, what's the latest news in physics?

00:00:10
Speaker 2: We still don't know how anything works. Newsflash.

00:00:15
Speaker 1: That's not really news, is it.

00:00:16
Speaker 2: It's true every single morning.

00:00:19
Speaker 1: There's been no new discoveries in the last week or so.

00:00:23
Speaker 2: No, we learn stuff every year, but the fraction of all knowledge we have remains approximately zero.

00:00:29
Speaker 1: You mean compared to the infinity of the universe or how much you're already forgetting due to age.

00:00:37
Speaker 2: I think both are true. The denominator is infinite and the numerator is true. It's decaying with time, Yes, exactly. I may have reached my peak smartness a few years ago.

00:00:49
Speaker 1: Oh, I think I reached my peak smartness like when I was five.

00:00:53
Speaker 2: Maybe you should have retired then, man.

00:00:56
Speaker 1: I wish I could have. Yeah, I could have been playing golf for the last fifty years.

00:01:05
Speaker 2: There you go, folks. Advice to all you five year olds out there, what's the advice? Be rich and retire earlier.

00:01:26
Speaker 1: I am Jorge, a cartoonist and the author of Oliver's.

00:01:28
Speaker 2: Great Big Universe. Hi, I'm Daniel. I'm a particle physicist and the professor at UC Irvine, and I don't plan to ever retire.

00:01:35
Speaker 1: What do you mean you'll have to like drag you out of your office at some point, or you plan to die in your office.

00:01:42
Speaker 2: I plan to die in this job, though I haven't actually decided where physically that will be.

00:01:48
Speaker 1: I guess, Yeah, I guess you can work from work and die from home. I guess. But really you don't plan to ever, you know, not do physics.

00:01:57
Speaker 2: As so long as I can keep teaching and thinking, then yeah, I'll keep doing it.

00:02:01
Speaker 3: Mmmm.

00:02:03
Speaker 1: You don't believe in like making room for the next generation of physicists.

00:02:08
Speaker 2: They're all retiring at five. They don't need jobs.

00:02:12
Speaker 1: Well, you need room for the four year olds, you know. But anyways, Welcome to our podcast Daniel and Jorge Explain the Universe, a production of iHeartRadio.

00:02:20
Speaker 2: In which we make the whole universe our problem, to figure it out, to explain it to you, to understand how it all works, to break it down into its tiniest little bits and make it make sense if at all possible.

00:02:33
Speaker 1: That's right. We try to retire the ignorance that we have about our universe and the beautiful cosmos that we all live in, and we try to make headway into your brain to help you understand how it all works and what it all means about our existence.

00:02:49
Speaker 2: And step one to figuring it out is understanding what we don't know is examining the questions we still have in our minds. What is it that we want to figure out? What can the usion do we have about how things are fitting together? What topics remain completely unexplored and unknown. And it's not just professional physicists and five year olds asking questions about the universe. It's everybody. And we want to encourage you, everybody out there who's listening, who is curious about the nature of the universe, to ask questions. Ask them of yourself, and if you can't figure them out, ask them of us. Write them to Questions at Danielandjorge dot com and you'll get an answer.

00:03:28
Speaker 1: Yeah, Because, as we said many times, the process of science, the process of discovery and finding knowledge out there, starts with questions, starts with people being curious about what they see and what they think they don't understand.

00:03:40
Speaker 2: And if you write to us with your questions, you'll get a reply at least even if it's not a complete answer, Because some of these questions nobody knows the answer to, so all we can do is fast forward you to the current forefront of human.

00:03:52
Speaker 1: Ignorance, right, because sometimes asking a question of a scientist helps them come up with new questions, right, or think of questions and new ways in their research. Right. Has anybody ever written you and you're like, WHOA, I never thought about that before.

00:04:07
Speaker 2: People have definitely written to me with questions I've never had myself, ideas I've never thought of all the time, I don't know that any of them have like actually spurred new research.

00:04:19
Speaker 1: Or maybe like a new way to think about what you're doing.

00:04:22
Speaker 2: I think sometimes the way people ask questions forces me to think about things in a new way. Sure, and you know, always the process of teaching and explaining forces you to examine your own understanding and shore it up and make connections you didn't make before. So this whole podcast is like deep in my understanding of physics because I'm forced to go out there and make connections and find explanations for things that I was pretty sure I understood. But when you go to explain it, you can always find holes in your understanding.

00:04:50
Speaker 1: Yeah, it's all the big conversations and we try to make all of you listeners part of the conversation here in our podcast, because sometimes in our episodes we answer questions that we yet from listeners like you.

00:05:01
Speaker 2: As are right. Sometimes the questions that come in through the inbox are fascinating or tricky or complicated, or I just think everybody might enjoy hearing the answer, so we select some to answer here on the podcast. Thank you to everybody who sends in your questions.

00:05:16
Speaker 1: So today on the podcast, we'll be tackling listener questions. Number sixty one, So Daniel, we're back to numbering these sequentially? Or is this still a random number with a secret code in it?

00:05:33
Speaker 2: This is not a random number with secret code.

00:05:35
Speaker 1: No.

00:05:36
Speaker 2: I like to be sequential because when people write in and I tell them we're going to answer it on the podcast, I like to tell them which episode to wait for, So numbers are useful for that, though I suppose I could name them. Also, this could be the elephant episode, or we're going to have a Polka Dot episode or whatever. Those are just as arbitrary as numbers. Yeah, or or like random numbers too?

00:05:55
Speaker 1: Right? This could be sixty one point seven four five three?

00:05:59
Speaker 2: Sure? Why not?

00:06:03
Speaker 1: Aren't extractional names? That's right? Or you give me like Elon Muskin and name things with weird symbols in them. Then we'd have to struggle to pronounce them. Yeah, I guess it is a podcast. We have to read things out loud, so we could.

00:06:15
Speaker 2: Just give them weird sounds then you know.

00:06:18
Speaker 1: Oh, there you go. This is listener questions number and then but then you have to also have to write them, so that might be Yeah, maybe we should just stick the numbers. Wow, it's like numbers are useful integers. Yeah. Yeah, all right, so sixty one. I feel like we've been increasing these numbers because I feel like we just a few weeks ago we were at number forty three.

00:06:40
Speaker 2: Man, We've been doing about one a week for a while now because we got so many more questions coming in.

00:06:45
Speaker 1: MMM. And so our first question comes from Augustine, and his question is about the gravity of black holes.

00:06:54
Speaker 4: Hello, Danny on her head, this is your friend. I have a crazy idea. We know that the gravity and a black hole is so strong that it will reap apart matter or what we call sometimes stagratification. My understanding is that this will happen all the way until even particles are pull apart. My brain now is thinking, okay, what about quarts. If I'm correct, the stronger you pull apart a couple of quarks, the stronger the force. And when we put in a force to pull them apart, we give them force enough to create a new one, and they are always in pairs. So now we have like four age sixteen and close quarts. So it could be possible that inside black holes we have an infinite machine of creating quarts that might even be so many at some point that we create a new universe inside a black hole. Or even more, what if all that energy of the black hole turns into just quarts and making the black hole disappear? Thank you?

00:07:56
Speaker 1: All right? Really fun question. Basically, I think he's asking can he make spaghetti out of quarks?

00:08:03
Speaker 2: Well, you know all spaghetti is made out of quarks and electrons, so yeah, but this is not a cooking show. Now, I think he's asking a really hard question about what happens to particles inside a black hole.

00:08:17
Speaker 1: Now we're talking about black hole, so I suspect the answer will be we have no idea. But Augustine is sort of a friend of the podcast, right.

00:08:24
Speaker 2: Yeah, that's right. Augustine has his own Spanish language podcast, which you should go and check out Kurt Gasidad Scientifica. It's excellent and he and I have been in conversation about physics for several years and I think he wrote this in to try to stump me.

00:08:37
Speaker 1: Cool, So go ahead and check out that podcast, even if you don't speak Spanish. I imagine it's interesting.

00:08:44
Speaker 2: You'll either learn physics or Spanish.

00:08:45
Speaker 1: Yeah, are both?

00:08:47
Speaker 5: Oh my goodness. Yeah, all right, So the question is interesting. I think the question is like what happens to a particle as it goes into a black hole, Because we've talked about before this idea of spa gutification. As you get near a black hole, the intensity of the gravitational feel is so high that it sort of rips you apart.

00:09:09
Speaker 2: Right, Yeah, that's exactly right. Gravity is very very powerful near a black hole. And if you have a physical extent, if you're not just a point particle, like if you're a little blob, then gravity on one side is going to be stronger than gravity on the other side, and that means you're getting pulled harder on one side, and that's equivalent to being pulled apart. So, for example, if you are near a black hole, and your feet are closer than your head, then the black hole is trying to pull you into spaghetti. So it's like trying to pull your head off of your body and your feet off of your ankles, because it's pulling on those things differently. That's where spaghettification comes from. It's the tidal forces of the black hole, not directly the strength of the gravity of the black hole, but the difference in its strength as you get closer or further.

00:09:53
Speaker 1: Right, because gravity depends on distance, right, gravity gets stronger the closer you are to the source, just like gravity stronger here on Earth than it is out there in space. But sometimes the difference can be so big that it can be enough to rip you apart.

00:10:08
Speaker 2: That's right. Technically, the Earth is trying to rip you apart because as you stand on the surface, the gravity on your feet is stronger than the gravity on your head, but that difference is much weaker than the internal strength of your body, and so you're able to hold yourself together. But that's not true near a black hole, because not only is the gravity stronger, but the differences are stronger because gravity gets weaker much faster with distance.

00:10:30
Speaker 1: Right, So it's super intense when you get close to a black hole, and so like if you were to jump in head first, you would get ripped apart. Now, I think Augustine's question is what happens to a particle? Does a particle get pulled apart? And maybe let's start with an atom, like would an atom get pulled apart?

00:10:46
Speaker 2: Yeah, it's a great question, and there's a couple of competing issues here. Like number one, the tile forces depend on you having a physical extent. The further apart you are, the greater the distance between one side of you and the other, the greater the difference and gravitational force will be. So if there's no difference between one side of you and the other, if you're like a point particle, then there's no title forces. So title forces only apply to things that are not point particles. And you're right, an atom, for example, it's not a point particle, and so in principle an atom could get pulled apart. But atoms are so tiny, really really small, that the title forces are going to be super duper tiny compared to like the strength of the nuclear forces holding it together.

00:11:25
Speaker 1: Right, I guess it's not just about how much gravity there is it's about, like you said, the slope of the gravity, or like the intensity of or how quickly gravity is changing, Like the difference between one end of the atom and the other end of the atom has to be large enough to overcome those forces. But is that possible? Though? It is kind of possible, isn't it?

00:11:44
Speaker 2: In principle it is if you take the general relativistic view of black holes a singularity, then as you get closer and closer to the singularity, the curvature is just increasing. And you might argue, well, the curvature has to be crazy high for the title forces to compete with the ternal strength of an atom. But then you can just keep moving closer to the singularity to get arbitra early strong gravity. And so, in principle, somewhere inside a black hole, if there is a singularity there, you can get close enough to it that the tidal forces should overcome the strength of the bonds holding an atom together, and an atom would get spaghetified.

00:12:20
Speaker 1: So it wouldn't happen outside or as it goes in, it would have to happen way in there.

00:12:25
Speaker 2: Yeah, I did the calculation once, and outside the black hole the gravity is not strong enough to spaghetify atoms. But inside Again, if there is a singularity and we don't know that there is, then in principle you could get close enough inside.

00:12:38
Speaker 1: Well, doesn't it depend on the size of the black hole, Like the heavier and more intense the black hole is, the less close you have to get to the center to maybe rip apart an atom. Hmm.

00:12:50
Speaker 2: Although if you can get arbitrary close then it doesn't really matter what the mass of the black hole is because you're decreasing that distance parameter. But yeah, for larger black holes you don't have to get as close.

00:13:00
Speaker 1: Did it even get to the center? Like, doesn't time stop as you get to the edge or the surface of a black hole?

00:13:06
Speaker 2: Yeah, that's a little bit tricky. That depends on who's looking. If you're in the outside of a black hole and you're watching things fall in, then time slows down for those objects according to you, and you never see them fall into the black hole. But for the object itself, time proceeds normally and they just fall in past the event horizon and proceed towards the singularity and reach it in finite time. General relativity is very tricky when it comes to whose time we're talking about.

00:13:31
Speaker 1: Right, But to the rest of the universe, it would never happen.

00:13:34
Speaker 2: Right, for the rest of the university, it would never happen if it's the last thing you throw into the black hole. As you approach the black hole, the black holes of vent horizon actually grows out to meet you because the power, the gravitational energy of the black hole increases before the object crosses the event horizon. It's not like it has to physically eat it and then it pops out to be larger. So if you toss something like a banana towards a black hole, it's event horizon grows out or meet the banana, but never reaches it unless you then throw an orange. That orange will pull the event horizon out even further past the banana. So the last thing to get thrown into a black hole never actually reaches it, but earlier stuff will.

00:14:11
Speaker 1: Will it like will the banana actually reach the center of the black hole? Or are things frozen in time inside the black hole?

00:14:18
Speaker 2: Well, you can only answer these questions from the point of view of some observer, and there's no observer on the outside. They can see the inside of the black hole from within the black hole, the banana reaches a singularity. But I feel like Augustine is asking a question about the interplay between the tidal forces and the strong nuclear force inside that atom.

00:14:37
Speaker 1: Right right, Well, we said that it would maybe pull apart an atom and maybe even a cord, but only if it gets close to the singularity. I guess. I mean then now the question sort of hinges like, will it ever get close to that singularity?

00:14:50
Speaker 2: According to general relativity, things will approach the singularity, And Augustine is asking about this interesting question that's trying to balance this power of the black hole to pull basically anything apart if it approaches a singularity, and the strong force, which has this bizarre behavior that if you pull things apart, it pops new particles out of the vacuum. And I think he's wondering whether that's effectively creating an infinite amount of mass.

00:15:13
Speaker 1: Mmm, oh, I see, all right, let's dig into his specific scenario. So now we're imagining it that a quark somehow gets inside of a black hole and it does make it close enough to this singularity that they would get pulled apart, or.

00:15:27
Speaker 2: I think imagine two quarks like you have a quark antiquark pair. They're bound together into something like a pion, or maybe you have three quarks within a proton, and then those get pulled apart by the singularity. And when those get pulled apart, there's now energy in that bond which gets turned into mass in the form of new quarks. Mmm.

00:15:45
Speaker 1: So then what would happen? So now you have a third quark that suddenly appears next to the other two.

00:15:51
Speaker 2: Yeah, actually you're going to get another pair of quarks. So if you start, for example, with a quark antiquark pair, and you pull them apart outside a black hole or inside a black hole, with going to happen is that there's a huge amount of energy stored in the strong force between the two quarks. Because remember the strong force is really weird, and the force between them doesn't decrease with distance. As you increase the distance between the cork and antiquark pair, the amount of energy in that bond becomes enormous, and the universe prefers to convert that energy back into mass, and it creates a new cork anti cork pair, effectively reducing those distances. So you have like cork antiquark now turns into cork antiquork cork antiquark.

00:16:28
Speaker 1: So like they multiplied or they just sort of like divided the energy between two.

00:16:32
Speaker 2: Pairs, because I'm not sure what the difference is. Like, you have one configuration with a lot of energy in the bond. The next configuration, the one the universe prefers, is to have lower energy in the bonds and have more energy in the masses. The reason the universe prefers that is that there's more possible configurations. That way, you have more particles, they can get moved around a lot. In general, the universe prefers to spread energy out because it allows for more options. It's like an effective entropy.

00:16:58
Speaker 1: Okay, so then the black hole would split the cork pair and make four quarks. And now what happens next. Then those four quarks would fall into the black hole. Would they also get split?

00:17:09
Speaker 2: Yep, those get split, and then you get more quarks, and then those get split and you get more quarks.

00:17:13
Speaker 1: But at some point, don't you start to dilute the energy? Isn't each subsequent pair of quarks don't they have less energy in their bonds?

00:17:22
Speaker 2: Yeah? Exactly, And that's what happens in real life, like, we do this at the Large Hadron Collider all the time. We don't have a black hole yet, hopefully that we're aware of. The lawyers require me to say. We create quarks in it at quarks all the time, and we create them in a way that they're flying apart. They have a lot of velocity away from each other, and so what happens is you get new pairs of quarks. That energy is converted into mass, and eventually you got a huge number of quark antiquark pairs and they're flying away from each other, so that energy, that velocity gets turned into mass. Effectively, what's happening here is something similar, except you have gravitational energy. You're using the gravitational energy of the black hole to basically pull the quarks apart. That kinetic energy then gets turned into mass. So you're turning the gravitational energy the black hole into mass.

00:18:09
Speaker 1: So you're just sort of like churning energy around. You're not creating new energy, you're not destroying energy. You know, the energy still stays within the black hole. It's just that, according to your theories, there's going to be a lot of weird slashing around in there.

00:18:23
Speaker 2: Yeah, exactly, and Augustine is wondering, like, does this turn into an infinite amount of energy or where does this energy come from? And the energy really comes from within the black hole. It's just the gravitational energy of the black hole. It's just like asking, hey, if you have a particle near the edge of a black hole, doesn't it accelerate as it gets towards the center of the black hole? Where does that energy come from? That energy just comes from the gravitational energy of the black hole. It's converting the potential energy of the black hole into kinetic energy of this particle. The thing about the black hole is that doesn't change the overall energy of the black hole. It still has the same total energy, which is what in the end controls its gravitational power. So it doesn't really matter what you do within the black hole. Do you have quarks? Did you have the energy in the bonds? You have it in the gravitational potential energy. As you say, it's just sloshing around inside the black hole.

00:19:13
Speaker 1: But do you get like an infinite number of quarks being made or is there at some point does it stop popping off these new quarks or is it that at some point. You know, the courts you create have so little energy to them that there's just not enough to make new quarks.

00:19:26
Speaker 2: It's a great question, and we don't actually know the answer to it. In this simplistic model that I've drawn out, where you have like a pure general relativity black hole with an actual singularity in it, and then you have these particles, you get an infinite number of quarks because as you approach the singularity, there's always a place where the new quarks are going to get rid apart to make new quarks, to make more quarks. But the problem there the infinity in the number of quarks comes from the infinity in the singularity, which we don't think is physical. So the real answer depends on knowing what's actually going on inside a black hole, and the infinity in this answer comes from the infinity and assuming that it's a singularity, which is probably not true.

00:20:02
Speaker 3: Mmm.

00:20:03
Speaker 1: I see, so you're saying the answer is that we don't know.

00:20:05
Speaker 2: We didn't know.

00:20:09
Speaker 1: We could just skipped the last twenty minutes. Daniel just comes with my answer.

00:20:13
Speaker 2: No, you were totally correct right off the bat, because we don't know how gravity and quantum particles interact we don't even know how to calculate gravity for quantum particles that have uncertain locations. So the right answer depends on figuring out quantum gravity, which we have not yet done.

00:20:27
Speaker 1: Right, We don't even know if it'll make it to the center, right, Like, we don't really know what happens even beyond the event horizon.

00:20:33
Speaker 2: Right, Yeah, exactly right. There are some theories that black holes have no center, have no interiors, all just smeared on this sphericle event horizon, and there is nothing in the bulk. All the information is just encoded on a two D surface, that the black hole is not actually part of our universe.

00:20:48
Speaker 1: Sounds like maybe the next question is not can you make spaghetti out of quarks? Is can you make smir out of quarts?

00:20:57
Speaker 2: All Schmeer has quarts in it, and in fact, the Germans have a kind of spread called quark, which is some kind of yogrity spread.

00:21:05
Speaker 1: It sounds like the Germans know the answer to this question.

00:21:08
Speaker 2: Perhaps the answer is probably one really long German word.

00:21:12
Speaker 1: Are there a German science podcast you've been on that maybe could help us illuminate the topic? Here, you've been on nine of them.

00:21:25
Speaker 2: I'm going to leave you in the quantum superposition of thinking that was nine englishman. I think that was just a bad pun. I think it was a pretty good pun, or a pretty good pun.

00:21:35
Speaker 1: All right, Well, thank you Augustine for what do you do in your podcast and also for sending us this question. So now let's get to our next questions. We have one here about golden asteroids and one about the effects of gravitational waves on time, So let's get to those. But first let's take a quick break where we're answering listener questions here today on podcast number sixty one point zero zero zero zero zero right now? Does a podcast number have those decimals or is it a pure integer?

00:22:17
Speaker 2: I think it gets rounded by our heart processing system.

00:22:22
Speaker 1: I didn't know we had a process for rounding titles. All right. Our next question comes from Mike, who comes from Brooklyn.

00:22:31
Speaker 2: Hi, Daniel, and Jorge.

00:22:33
Speaker 6: Is it possible that somewhere in the universe there are asteroids as big as our moon, made entirely of rare metals such as gold or silver. How large an object or system of such objects could there be? Thanks for considering this question. You guys are the best and Katie and Kelly are awesome co hosts too from Mike and Brooklyn.

00:22:55
Speaker 1: All right, thank you, Mike. Pretty cool question. I guess the question is could you have a giant gold asteroid out there?

00:23:03
Speaker 2: Yeah, and he wants a giant gold moon.

00:23:06
Speaker 1: Moon or a gold planet. Is that possible?

00:23:11
Speaker 2: I love the idea. Well it's a golden idea.

00:23:14
Speaker 1: Well, let's dig into it. What are the chances that pure gold things are out there.

00:23:20
Speaker 2: There's definitely a lot of gold out there in the universe, Like there is a lot of gold in the Earth, and there are big blobs of gold in some sort of like big heavy metallic asteroids. But the process by which gold is made in the universe makes it, I think, pretty unlikely to have like just a huge gold bar floating out there in space.

00:23:39
Speaker 1: Hmmm, what do you mean? How is gold made in the universe?

00:23:42
Speaker 2: Well, gold is a very heavy element, like many very rare valuable elements, and it's so heavy that it can't actually be made inside stars.

00:23:50
Speaker 1: Right.

00:23:50
Speaker 2: The brief history of the universe is that we started out with almost all hydrogen, and then we formed stars after a few hundred million years. Those stars are hot and dense enough to do fusion which can make heavier elements, but only up to about iron. Up to about iron, when you fuse nuclei, you actually gain energy that releases energy. It powers the star above iron. It costs energy to do fusion, so you're cooling the star, you're consuming the star's energy. So stars basically make elements up to about iron. Heavier things than that require more specialized conditions, like the collisions of neutron stars or supernova collapses that briefly create the conditions necessary to consume that energy and make the heavier elements m.

00:24:33
Speaker 1: So you need a star to explode to make anything above iron.

00:24:35
Speaker 2: Anything above iron is made either in supernova so star explosions or in neutron star collisions. And it used to be that we thought it was mostly supernova but then recently observations of neutron star collisions have sort of tilted the balance, and now we think that probably most of the gold in the universe is made in neutron star collisions. How do we do that, Well, some neutron star collisions they've observed in a couple of different ways, Like they've seen the gravitational waves generated by these really intense massive objects orbiting around each other and then eventually colliding, and they also observed them astronomically, like they saw light from the same event, and from that light they can measure like how much gold was created, because gold, like every other element, has a very special atomic fingerprint. It tends to glow in certain wavelengths and give off light in certain wavelengths. So they're able to measure the amount of golden clouds around this neutron star collision by looking at the light that came from it. It's this new era of multi messenger astronomy where you see the same event in two different sort of channels, and our understanding is still pretty fuzzy, but it suggests that like huge amounts of gold were made, like more than the mass of the Earth is made in each of these collisions.

00:25:43
Speaker 1: But I guess maybe a question is is it only gold that gets made or is it all materials above, you know, iron, get made in an equal amount or is it sort of random.

00:25:56
Speaker 2: It's not just gold that gets made. It's all these heavy elements get made these kind of special events in supernova implusions, in neutron star collisions, and it's definitely not equal, right, Some of these things are easier to make because the pathways for them to happen. Some of these things are very very unstable, so even though you make them, they disappear very rapidly and then decay down into other stuff. We had a whole episode recently with Kelly about which elements are more common in the universe, where we dig into the science and the chemistry of that. But basically, you're making everything possible and then only the stable stuff sticks around very long.

00:26:28
Speaker 1: Now, I know that in a supernova, I think what happens is the inside of the star collapses and then it bounces, and there's this huge shockwave. And as the shockwave goes through the rest of the star, the outside of the star, it basically squeezes things so much in this shockwave that the neutrons and protons fuse together to make these heavy elements.

00:26:47
Speaker 2: Right mm hmm, yeah, that's right. You need very high pressure and very high temperature in order to create these heavy elements, and you need a lot of energy because these processes absorb energy rather than creating it.

00:26:59
Speaker 1: Now, is there a sort of a a propensity or a tendency as the shockwave goes out to have phases where it's making a lot of gold and then suddenly it's making a ton of other elements and then suddenly or is it all random all the time?

00:27:13
Speaker 2: Yeah, that's a great question. It's not something we understand. It's an area of current research exactly how that's happening. This shockwave physics is very complicated because it's very sensitive to a lot of the details. It's not like, on average it ends up doing the same thing a little bit hotter, a little bit colder, or the shockwave starts here or starts there, and the conditions of the shockwave change. So that's something people are working on right now. They have these really complicated models of what's going on inside supernova.

00:27:38
Speaker 1: So we don't know yet, but I imagine maybe the conditions to make gold are maybe different than the conditions to make lead or titanium, right, And so I imagine that it's not just all random all the time. Maybe you know, as the explosion goes out, maybe you get the conditions for gold, and then suddenly the conditions change for something else, etc.

00:27:58
Speaker 2: But it's also not clear that the condition are the same across the whole star. The explosion might start in one spot and then end in another. Spot, and so you might simultaneously have different conditions across different parts of the surface.

00:28:10
Speaker 1: But I imagine there has to be a reason that you find gold nuggets on Earth, right, like all those atoms, those trillions of atoms in a gold nugget must have been made at the same time. Or do you think they were made separately in different phases and somehow they got together at some point.

00:28:26
Speaker 2: I think the formation of the gold that we find here on Earth doesn't reflect how it is actually made in the star. I think it more reflects the differentiation process and the geology, the rock formation of what's happening here on Earth. As the Earth cools. I think likely anyway, gold made in these neutron stars comes out as a huge fine spray, a mist, which then gets mixed out into the universe, and you know these little granules that then spread out. I don't think gold nuggets are formed and then survive in that shape to be dug up.

00:28:56
Speaker 1: You're saying, maybe it all gets made as dust, gold dust, and then when the Earth was like a big ball of lava, maybe gold doest sprinkle throughout it. The gold doest somehow, you know, settled in the same spot and then stuck together.

00:29:11
Speaker 2: Yeah, that's exactly right. The Earth is formed from a huge blob of gas and dust. Some of that is little flecks of gold or heavier elements, and then as that gets squeezed together into a planet, it gets hot, right, and it gets molten, and then you have all sorts of processes that happen. Like some of these elements are called iron loving elements. They like to mix with iron and they flow with the iron. So then as the Earth is cooling, it differentiates and some of the heavy things sink and some of the lighter things rise. And the flow of those molten rocks and elements and oxides and all sorts of complicated stuff determines where things end up. And the big blobs that's why, like you get veins of heavy metals or veins of copper here and there comes from those molten flows, which then cool.

00:29:52
Speaker 1: But you're saying that out there in space in the supernova, we're not sure if these things get made as dust or as layer chunks.

00:30:00
Speaker 2: Yeah, we're not sure. I mean, I think it's most likely because it's just the chaos and they energy this process that it's spread out in terms of tiny granules, But I don't know what the maximum size would be. It's certainly possible that you get big ingots or even enormous blobs. I mean, you can't rule out the possibility that you're making like a blob the size of the Los Angeles of pure gold. You know, quantum mechanically, anything as possible.

00:30:22
Speaker 1: So in principle it could be What about these neutron star collisions. Is the mechanism the same like a shockwave or do things it made from the soup of neutrons and quarts that make up the stars.

00:30:34
Speaker 2: Well, there definitely is a collision there and that creates a shockwave through both neutron stars. Then they settle down to form one bigger neutron star or a black hole more likely if they're over the threshold now for a neutron star to be stable, but we really don't understand what's inside a neutron star and how that all works. So we know that there's a process there that's capable of creating these heavy elements, but we do not have a detailed understanding of it. We don't even understand a single stable neutron star, not to mention like two of them smashing into each other, having complex shock waves bouncing around inside.

00:31:05
Speaker 1: Because I think neutron stars are basically like a giant ball of soup of neutrons and quarks, right, So, I mean it seems possible you could just scoop up some neutrons or quarks and then damn you certainly get a giant gold planet.

00:31:19
Speaker 2: Well, neutron star is a little bit more complicated than that, Like near the outside, they actually have a crust which you can have some protons and electrons in it. Then then we think there's probably a layer there's pure neutrons, and below that we just don't really know, Like below that probably doesn't even make sense to call it neutrons, As you say, it's just like a soup of quarks, like a quark gluon plasma, where the energy and the density are so high that the whole idea of a neutron doesn't really make sense. It's like a drop in an ocean, right, you don't really call it a drop anymore. And then below that we think probably there are new states of matter, nuclear pasta or other weird exotic forms of matter that only exist under these very high pressure and temperature situations. So it's not just a ball of neutrons, though there's plenty of neutrons there to play with.

00:32:00
Speaker 1: H all right, So it sounds sort of unlikely that in our universe there have foreign moons or big asteroids of just pure gold. Right. Although there aren't there giant asteroids of pure iron out there.

00:32:12
Speaker 2: There are giant asteroids out there which are very metallic. Like in our Solar system. We have a bunch of different kinds of asteroids. There's like C type that have a lot of water and ice in them, but there is a kind called S type, which is a lot of metal. For example, like a ten meters wide asteroid might have like six hundred thousand kilograms of metal, including like fifty kilograms of platinum and gold. And then there's the M type, which are more rare, but they have like ten times as much metal. So yes, these asteroids do have a lot of metal in them, but they start from the same basic materials as the Earth, and so roughly they have like a random scoop of the Solar system. It's just on the Earth, a lot of this stuff is sunk down into the core and so it's not as prevalent in the crust.

00:32:57
Speaker 1: So you're saying that there are metal asteroids out there, but there are sort of a mix of metals.

00:33:01
Speaker 2: Yeah, exactly. It's not a pure gold asteroid, very unlikely, or pure platinum. Most of these things are rocks with a lot of metals mixed in and so, yes, they are rich in gold and platinum. It's definitely out there. But a pure gold asteroid or a silver asteroid, especially when the size of the moon seems very unlikely.

00:33:19
Speaker 1: What about gold plated, I mean it is, you know, sometimes that's just as violable.

00:33:27
Speaker 2: Well, you know, maybe we've been fooled and they actually aren't filled with gold.

00:33:31
Speaker 1: They just covered it's a pure gold inside. It's just a mix of metals on the outside.

00:33:36
Speaker 2: Well, you might wonder, like, how do we know the composition of these things. It's mostly by looking at their gravitational behavior. We can deduce their mass, and by looking at their size, we deduce their volume, and that gives us a sense of their density, and so we estimate from the density of these things what they might be made out of. For example, NASA is planning a mission to an asteroid called Psyche, which is a big M type asteroid. It's like two hundred kilometers across, and it's so heavy, so dense that it has one percent of the mass of the entire asteroid belt in this one very metallic, very dense asteroid.

00:34:10
Speaker 1: WHOA. Well, I wonder if maybe Mike was also asking the question, like could you make a giant moon out of gold? Like would it hold?

00:34:24
Speaker 2: I don't think Mike was asking that. I think you're asking that. I'm wondering what sort of like astro geoengineering projects you have in mind over there.

00:34:31
Speaker 1: Well, he's asking how large an object there or such an object could there be?

00:34:35
Speaker 2: Hmm, Yeah, that's a good question. In principle, you can make an object about the size of the Earth, any rocky object, anything primarily made out of heavier elements. You can't really make it much bigger than the Earth because then it's gravity just makes it denser and denser. You can make about an earth sized blob of gold and have it floating out there in the solar system.

00:34:55
Speaker 1: Whoa, it's a lot of bling for the solar system.

00:35:01
Speaker 2: That'd be a pretty cool engineering project. Like if you come to an alien solar system and you find that it's filled with like huge diamonds and Earth sized blobs of gold. You might think like, Wow, these aliens know what they're doing.

00:35:12
Speaker 1: Or maybe gold is so cheap that they can make a whole planet out of them.

00:35:18
Speaker 2: Or maybe they've transcended the Kardashev scale and into the Kardashian scale as you joked about it.

00:35:24
Speaker 1: Yeah, there you go. All right, Well, thanks Mike for that question. I guess the answer is that it's not likely, but still possible. In the end, we don't really know.

00:35:36
Speaker 2: In the end, almost anything is possible, but it seems very unlikely for the universe to arrange for a gold moon in our sky.

00:35:43
Speaker 1: Unless Mike is secretly a super trillionaire or something.

00:35:47
Speaker 2: If he finds that gold moon, he'll definitely be one.

00:35:49
Speaker 1: Yeah. Other then you have to wonder why he lives in New Jersey.

00:35:52
Speaker 2: Oh he said, Brooklyn.

00:35:54
Speaker 1: Oh, Brooklyn, Brooklyn. Oh, well that makes more sense. All right. Well, let's get to our last question of the day, and this one is the effects of gravitational waves on time. So let's get to that. But first let's take another quick break where we're asking listener questions here today, and our third question comes from Max.

00:36:25
Speaker 3: Hi, Daniel Dan JORGEV. This is Max calling from Stockholm, Sweden. I have a question about gravitational waves, as they affect the space, which has been proven in Bligo and Virgo, do they also affect time the same way? Being compressed and stressed as space, time is basically just one unit?

00:36:58
Speaker 1: All right? Pretty cool? Can you get wavy with time? Is basically the question.

00:37:04
Speaker 2: Yeah. I love this kind of question because here again he's bringing together two ideas we talk about all the time, space and time are related. Gravitational waves or ripples in space and time? Do they also affect time? Great question, Max.

00:37:18
Speaker 1: Right, because I guess we know from relativity that gravity is not just about making things come together. It's about distorting space, and it's not just about distorting space but also distorting time. Right, Like a black hole not just bends space around it, but it also bends time around it.

00:37:35
Speaker 2: Right. Yeah, that's exactly right. And there's a really important progression of subtle ideas here as we go from like Newton's idea of space and time to Einstein's special relativity view of space and time where he brings space and time together to one coherent object where they affect each other. But we still have a clear sense of what time is and what space is, and then into general relativity, where concepts of space and time are much harder to enter crprit out of our sort of generalized coordinates that people use.

00:38:03
Speaker 1: So maybe Tarrika for our listeners. What is a gravitational wave?

00:38:07
Speaker 2: So gravitational wave is a wave in space time itself. General relativity says we don't know what space time is, but effectively, all we can do is measure the distances between two points, Like we have this point here and that point there. We can measure the distance between them, and we can also measure the curvature of space, which is how those relative distances change. So in space is curved, things get closer together or further apart, depending on exactly the nature of the curvature, and so ripples in that curvature are gravitational waves because everything with energy creates curvature in the universe. According to general relativity, if I have a big massive object, then it's curving space and that's what controls how things move around it. If I then wiggle that object, then how I'm curving space is changing with time because that information takes time to propagate out from the wiggling object. So take a big black hole. It's bending space. Now wiggle it, and you're making gravitational waves from that black hole, waves in that curvature of space.

00:39:07
Speaker 1: Right. It's kind of like about the propagation or how it spreads the effects and how the group's effects of gravity spread out basically.

00:39:15
Speaker 2: Right, Yeah, if you wiggle a black hole, if the curvature at a distant point doesn't instantly wiggle, right because it doesn't know that you wiggle that, it takes time for that information to propagate. And that's what the gravitational wave is, is the propagation of that information.

00:39:29
Speaker 4: Right.

00:39:30
Speaker 1: Like, for example, if the Sun for some reason started moving back and forth or wiggling or rocking back and forth, like, we would feel that gravitational effect here on Earth, right, we would feel that wiggling of the Sun gravitationally, like the Earth would start to wobble too. But since it takes some time for that gravitational effect to come from the Sun to the Earth, that's kind of what we call the wave, right, Like those wiggles as they propagate out into the universe and then reach us, those are the waves exactly.

00:39:58
Speaker 2: It's very similar to other kinds of waves. You take an electron has an electric field. Now you wiggle that electron, you're making wiggles in that electric field. Those wiggles are photons. Those ripples are updating you about where the electron is now. So the same way you can create ripples in the electromagnetic field by wiggling an electron, you can create ripples in space time by wiggling anything that has mass.

00:40:20
Speaker 1: All right, Now we've been able to measure those from really incredible events that are happening out there in space.

00:40:26
Speaker 2: Yeah, it's really sort of amazing. Einstein predicted these things, but he also said we may never see them because these are very very small. We're talking about tiny changes in the distances between objects. Like you hold two mirrors a couple of miles apart. The distance between them might change by less than the width of a proton as the gravitational wave passes by. So these things are very difficult to measure. But we actually have been able to. They have these very sensitive interferometers. We shoot laser beams between these mirrors that are very carefully isolated from everything. Credible triumph of experimental physics. And they've seen them a few years ago, and now we've seen dozens and dozens of these things.

00:41:06
Speaker 1: Right, Well, as we've mentioned before, like everything moving, any mass moving makes a gravitation wave. If I wave my arm, I'm creating gravitational waves. They're just so small that nobody can ever really feel them, although I have been working out on my arm is pretty pretty massive lately.

00:41:23
Speaker 2: Technically requires acceleration, not just motion. But yes, any accelerating mass will create gravitational.

00:41:29
Speaker 1: Waves, right right, Like if I wave my arm, right.

00:41:31
Speaker 2: Yeah, if you move it back and forth, that's acceleration, and that will create gravitational waves. Those are so tiny we'll never see them. Gravitational waves we have been able to see are from super incredibly massive objects black holes or neutron stars swirling around each other as they collide.

00:41:47
Speaker 1: Now, does it have to be acceleration, Like if let's say an asteroid is moving in a straight line through space, doesn't it create a ripple as it goes along too? Because I like, I'm going to feel differently it's gravitation attraction as it goes past me.

00:42:02
Speaker 2: Well, velocity is relative, right, and so the gravitational field there doesn't depend on relative quantities. It only depends on absolute quantities. Acceleration is absolute, and so you don't create gravitational waves. Just by having a velocity. You can experience a changing gravitational field, but that's not necessarily a gravitational wave. Like if you're near the Earth and you're moving away from the Earth, you're measuring a change in your local gravity because you're moving away from the Earth. So time dependence in your position and in your velocity. But there's no gravitational wave created unless you have acceleration, which is an absolute quantity.

00:42:38
Speaker 1: It's sort of a wave, right, Like if an asteroid flies past me, I'm going to feel no gravity from it, and then I'm going to feel a lot of gravity as it's near me, and then I'm going to feel les gravity as it flies away from me. Then I sort of experience kind of a wave of gravity.

00:42:51
Speaker 2: Well, again, you experience a change in how much local gravity you measure, Like if you get closer to an electron, you're going to measure a stronger electric field, and if you move away, you're gonna measure a weaker electric field. But there's no electromagnetic wave there. It's just your motion relative to the electron that's changing your local measurement.

00:43:08
Speaker 1: The effect is the same, though, don't I feel changing my gravitational field over time?

00:43:15
Speaker 2: If you wanted to create exactly the same set of local measurements, you wanted an oscillating gravitational field that you need to move back and forth, and that's acceleration. So you can't do it without acceleration.

00:43:25
Speaker 1: M Well, let's get to the question here. Now, we know that a gravitational wave affects space. That's how we measure them, right, Like we have giant rulers made out of lasers very deep underground, and as they contract and expand we know that a gravitational wave has passed by us.

00:43:44
Speaker 2: Yeah.

00:43:45
Speaker 1: Now the question is does it also affect time?

00:43:47
Speaker 2: Yeah? And the answer is pretty unsatisfying. The answer is you can't really say yes or no because it depends on what time means in general relativity, which is very fuzzy and unclear. That's the short version of the unsatisfying answer. The longer version of the unsatisfying answer. It takes a bit of a tour through special relativity. Right, Like Newton says, space and time are totally separate things. Things move through space there obviously, time moves forward. Space and time are unrelated, Einstein tells us in special relativity, No, no, space and time are two parts of the same thing. It's a beautiful realization that together they make a lot more sense than a part. It's like electricity and magnetism fused together into one idea makes much more sense than two separate ideas. This is not to say that they're the same thing. Two things can be two parts of the same thing without being equivalent. Like you say the front and the back of the elephant are two parts of an elephant. Doesn't mean the front and back are the same thing. So space and time are closely related in special relativity, and space affects time and time effects space. But you can always still say what is time and what is space? Now we get to general relativity. In general relativity, the coordinates you choose, like which direction things we're moving in, are not so physical. They're just sort of like abstract, and you can choose lots of different sort of systems in order to do your calculations, like are using polar coordinates or using xyz or lots of much more complicated abstract coordinate systems, And some of those coordinates it's impossible to say, like which direction is time and which direction is space, they're all sort of mixed together. For example, as you were saying earlier, what happens as you're going inside a black hole, Well, time and space sort of reverse. Right now, your future is the singularity. Every path into your future ends at the singularity. Time and space have sort of reversed roles there. That's just sort of shorthand way of saying that we have a new interpretation for the coordinates.

00:45:45
Speaker 1: Now I imagine this is super complicated, but I feel like we're getting a little bit abstract here. Like I wonder if Max is asking, you know, how in these experiments where we can measure gravitation of ways, you can see that the length of something changes as the wave goes past. Does I wonder if he's asking, you know, if I had a clog, would I see my clock suddenly take a little faster and then take a little slower as the wave goes past me.

00:46:10
Speaker 2: The answer is, you can't really separate it out into the effects of space and the effects of time, and the details of it dependent a little bit on exactly how you've built your clock. Like let's say, instead of having lego or you have lasers, and you're shooting lasers back and forth to measure distance. You have like two people far apart from each other, and they're constantly sending each other little laser pings. Right like, I'm going to send you a pulse of lasers every one nanosecond or something, and then you're going to observe those We're going to try to see if the time between the pulses changes as the gravitational wave goes by. Right, Well, what's going to happen as the gravitational wave goes by is that those pings are going to get either red shifted or blue shifted by the gravitational wave. But whether you interpret that as like space expanding or time slowing down depends in general relativity, on these coordinate systems that you've chosen. So somebody could come along and say, look, I interpret this as space bending. Somebody else come along and say, no, I interpret that as time bending. In general relativity, most people tend to work in what's called a synchronous gauge, where you basically put all the bending into the space part and you say time doesn't bend at all, And that's just sort of like our interpretation. But it's totally valid to say no, actually, time is doing the bending. So the answer is sort of like, yeah, space time as a whole is bending. Whether you call that space bending or time bending is a little bit arbitrary.

00:47:30
Speaker 1: I wonder if what do you mean is like, let's say a measuring time using a Grandfather clock, right with like a swinging pendulum, and that's how measuring time. Now, if the wave is coming let's say from directly at me, and I face the Grandfather clock in one direction, then maybe it's not going to fec how it takes. But if I turn in ninety degrees, maybe it is going to efac how it takes. And in which case you might say in one instance that it did slow down time, But in the other instance you might say, no, it doesn't slow that time. It just stretched space.

00:48:08
Speaker 2: Yeah, that's right. And even in the case where it did slow down time, you could argue it did it slow down time because time actually went slower or because increase the distance that the pendulum had to swing, Right, You can interpret it both ways. Sort of how even in special relativity you can interpret like contraction of distances and stretching of time to be two sides of the same coin, Like when I travel to a nearby star at nearer the speed of light, I see the distance to the star contracted, so it only takes me a minute to get there. Somebody else sees me flying for light years, but my time is slowed down, which is why it only seems like a minute for me. So I see length contracted, somebody else sees time dilated. In many cases, it just depends on your perspective whether you're calling it a space effect or a time effect.

00:48:53
Speaker 1: Well as it is super complicated. But I feel like maybe in the past we've talked about or you've mentioned there are separate effects in terms of the bending of space and the slowing down of time, Like if you swing by a black hole, then time will move slower for you. Right, that's not up for interpretation, is it.

00:49:12
Speaker 2: You're exactly right that there are two separate effects we're talking about here. One is like velocity dependent time dilation or length contraction, which is a different effect than gravitational based time dilation, which is just due to the curvature of space. You're totally right, those are two separate effects, and you're right that the gravitational one is an absolute effect. It's not like I see your time slowed down and you see my time slowed down and the gravitational one. Everybody agrees, like the person close to the black hole agrees that their time is going slower than the person further from the black hole.

00:49:43
Speaker 1: So then what's happening as a gravitational wave goes past me? Is it more like a black hole, like we're getting far from a black hole, or is it more like we're speeding up and slowing that.

00:49:53
Speaker 2: The gravitational wave is a curvature effects, so it's definitely more like being close to a black hole. But I was going to say that even the story with being close to a black hole, we're interpreting that as an effect on time. You can also change your gauge. They call it in general relativity, redefine the axes and pretend that it's only happening in space coordinates. So in general relativity you can basically interpret these things as space or time, because the distinction between the two becomes much more fuzzy.

00:50:19
Speaker 1: Even the case of going near a black hole. I me, you just say that everyone can agree that time slow.

00:50:24
Speaker 2: Down, everyone agrees about the magnitude of the effect, and if both of you agree on the co ordinates, then we interpret that in terms of time. So, yeah, everybody agrees that the person close to the black hole has a stronger effect. If you're using a certain gauge, then we interpret that as a time effect. If we choose a different gauge, then we interpret that as a space effect. The thing we agree on is the magnitude of the effect. Whether it's space or time is up to interpretation.

00:50:49
Speaker 1: Wait, so then you already saying that when I go near a black hole, I could interpret that not as a change in time.

00:50:55
Speaker 2: Yes, you could choose some weird coordinates in general relativity to interpret that as just a bend of space, because it is a bending of space, right, that's curvature, And so if you redefine your time, then you could choose time to be invariant.

00:51:07
Speaker 1: Yeah, but it isn't the case. I mean, I know this because I saw the movie Interstellar that if you go near a black hole and then come back, you'll be younger than me. That's not That doesn't seem like it depends on a coordinate system. That's like, I'm gonna see you're you're gonna be younger than me. There's no way that I cannot see that.

00:51:24
Speaker 2: If one of us takes a trip to the black hole and comes back, then you completed a loop. You're back to the same location in space, and that makes those calculations invariant. It actually doesn't depend in that case on the choice of coordinates or gauges. So yeah, in that case, like in Interstellar, everyone also agrees.

00:51:42
Speaker 1: All right, well, then let's mee just close it out then, and what would say is the answer then? For Max's question, does time get dilated as a gravitation away comes through or can you just ignore it?

00:51:55
Speaker 2: I would say that space time does get dilated absolutely, which part of space time? Saying gets stretched out is a little bit arbitrary. Most people tend to work in a choice of gauges where only space is getting stretched. It's just sort of simpler, and it's more natural for people to choose. But in the end it is a little arbitrary because it really is all of space time getting squeezed.

00:52:16
Speaker 1: All right, And if Matthew McConaughey were to serve a gravitational wave, would he look come back younger or older? Let he makes it too sure.

00:52:25
Speaker 2: I think he's frozen in time. He doesn't look like he's aging at all.

00:52:28
Speaker 1: Right, right, that's what I mean that maybe that's a secret he's serving gravitational waves up there.

00:52:33
Speaker 2: Yeah, we should all be in the Matthew McConaughey gauge.

00:52:35
Speaker 1: There you go, and then maybe we can all retire. All right. Well, we tried, Max, Sorry, but it sounds like the answer is that it's really complicated and you need a degree in gravitational relativity to figure it out.

00:52:51
Speaker 2: But you're right that space and time are deeply, deeply connected.

00:52:54
Speaker 1: All right. Well, thanks to everyone who sent them their questions here today. It's always fun to take a deep dive into people's curiosity and to think about these scenarios that we don't think about it every day.

00:53:07
Speaker 2: Absolutely, we love your curiosity, not just because it tells us that our passion for wanting to understand the universe is shared by so many other people, but because it actually literally powers us. Your support for science and your curiosity is what makes science possible. Thank you very much.

00:53:23
Speaker 1: Yeah, and if anyone ever makes a gold asteroid out there, hey, how about you sent me a chunk of it, because you know more about forty two years late on retiring.

00:53:32
Speaker 2: Yeah, so please donate a chunk of your next gold asteroid to Jorge's retirement.

00:53:37
Speaker 1: Yeah, there you go. All right, Well, we hope you enjoyed that. Thanks for joining us, See you next time.

00:53:47
Speaker 2: For more science and curiosity, come find us on social media, where we answer questions and post videos. We're on Twitter, disporg, Instant, and now TikTok. Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.