Listener Questions 66

00:00:07
Speaker 1: Hey, Orge, are you preparing your kids for when the end times come?

00:00:12
Speaker 2: Oh?

00:00:12
Speaker 3: You mean when bananas go extinct? Or do you mean when I retire?

00:00:17
Speaker 1: Yeah, I mean the fall of civilization, when we're all listening to podcast in our caves.

00:00:23
Speaker 3: I feel like I've been preparing my whole life. If there's a post apocalyptic movie out there, I probably see it.

00:00:29
Speaker 1: Well, then I hope you're teaching your kids some useful skills, you know, blacksmithing, martial arts, cartooning.

00:00:35
Speaker 3: Oh yeah, cartooning for sure, that's going to come in handy. But you don't think they should learn a particle physics.

00:00:42
Speaker 1: I don't know that anybody's going to be building colliders out of sticks and rocks.

00:00:46
Speaker 3: Isn't it fire? Doesn't it fire evolve particles colliding?

00:00:49
Speaker 1: A fire is kind of a chemical accelerator. I suppose there must be some collisions, or.

00:00:54
Speaker 3: Are you going to be like, you know, freezing out there, and you're gonna be like, oh no, no, sorry, the fire is just not fundamental.

00:01:00
Speaker 1: Enough for me. I think I would be hiding in my cave eating the last of the world's chocolate reserves.

00:01:08
Speaker 3: Who would that be a useful skill? You could be it the world's only chocolate tear. Hopefully the zombies like chocolate.

00:01:15
Speaker 1: Dark chocolate is the world's final currency.

00:01:33
Speaker 3: I am Poorge, my corctoonist and the author of Oliver's Great Big Universe.

00:01:37
Speaker 1: Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine, and I purposely got into particle physics because it was useless.

00:01:45
Speaker 3: You're like, how can I make my time here on Earth less useful?

00:01:50
Speaker 1: I wasn't so much worried about the positive practical benefits as the negative. You know, my parents worked in the weapons programs, and I really really didn't want to do anything that could be used as the basis of a death ray.

00:02:02
Speaker 3: I see, But you could have picked something positively useful, like making a chocolate Yeah, there you go, making people happy.

00:02:11
Speaker 1: Well, you know, my dad did retire from the lab and then became a blacksmith, so he's definitely got useful skills for the end times.

00:02:18
Speaker 3: He became a blacksmith. Wow, was he forging like swords or internal combustion engines in your garage?

00:02:25
Speaker 1: Or what swords? Spears? All kinds of stuff?

00:02:28
Speaker 3: Yes, He's like, I want to wait more weapons.

00:02:35
Speaker 1: I wish I were joking more and.

00:02:37
Speaker 3: More direct, but anyways, Welcome to our podcast. Daniel and Jorge Explain the Universe, a production of iHeartRadio.

00:02:45
Speaker 1: In which our only weapon is our minds. As we tackle the quest of understanding the universe, we go forging through all of the craziness that's out there and try to weave it all together into an explanation that makes sense. We hope that whatever the universe is made out of its time, any little basic bits that somehow they're danced together can explain everything that we experience in the universe, that we can somehow find fundamental laws, and then we can also make sense of it all that's right.

00:03:11
Speaker 3: We try to hone our knowledge of signs here and try to prepare you for the end times when we'll all be looking up at the stars wondering how do we all get here? And how do we avoid those pesky zombies.

00:03:24
Speaker 1: I guess we should all try to sharpen our minds so we can slice our way through these problems.

00:03:28
Speaker 3: Yeah, I'm sure having physics knowledge will be helpful in the apocalypse, right, you can, I guess, try to build a laser gun to fight the zombies.

00:03:40
Speaker 1: If the zombies assigned a lot of homework problems, then I'm definitely there to help.

00:03:45
Speaker 3: Oh, that could be another way to defeat them. You know, you give them physics problems that are so tricky that their brains explode, and that everyone knows that's how you kill zombies.

00:03:54
Speaker 1: Wow. Yes, exactly. Too many into girls.

00:04:01
Speaker 3: Calculus.

00:04:02
Speaker 1: No, you know, Newton definitely believed in zombies. Really, Newton definitely believed in some weird stuff. I don't know about zombies, but you know, he was an alchemist and he definitely was a fan of the arcane.

00:04:17
Speaker 3: Wasn't he really into currencies too?

00:04:20
Speaker 1: Mm hmmm, yeah, exactly.

00:04:21
Speaker 3: At some point became like a coin master or something.

00:04:24
Speaker 1: He was definitely a weird dude.

00:04:25
Speaker 3: Yes, by word, do you mean a genius who basically invented science.

00:04:32
Speaker 1: I think that's actually giving him a little bit too much credit. But yeah, he invented lots of physics and big chunks of math, and I think he would be pretty tickled if we could use calculus against the zombies.

00:04:43
Speaker 3: Oh well, I'm sure a lot of people will be relieved to learn it's useful for something after all that work in high school.

00:04:49
Speaker 1: Yeah, they can integrate it into their lives.

00:04:52
Speaker 3: Oh boy, that was very terrifical joke. But anyways, we do like to think about the universe and we try to explain it here on the podcast, and sometimes that involves answering questions.

00:05:02
Speaker 1: That's right. It's not just Isaac Newton who's thinking about the nature of the universe. It's everybody. The goal of science is to understand the universe, and that means for everybody to figure it out. And that, of course means everybody's got to be out there thinking about the universe, asking questions, wondering how it all works, and we want you to be doing that. We hope that this podcast stimulates your curiosity. You hear on the podcast about the questions we are asking, but we want to hear about the questions you are asking, and then we want to answer them. So if you have questions about the nature of the universe or something you heard about on the podcast, or something you heard about on Gass another podcast, please write to me to questions at Danielanjorge dot com. We'll clear it up for you.

00:05:43
Speaker 3: Yeah, because it's part of human nature to be asking questions, and it's totally fun to ask questions as well, and so here in the podcast we sometimes like to answer questions that listeners send us, and so to be on the podcast, we'll be tackling listener questions number sixty six.

00:06:02
Speaker 1: You have a sixty six related snide comment.

00:06:06
Speaker 3: Only a warning, Daniel. If we keep going, we're going to hit listener questions six sixty six.

00:06:11
Speaker 1: Oh, I thought you were going to warn me. But listener question sixty nine, where we turn everything upside down.

00:06:17
Speaker 3: I have warned you repeatedly about that milestone, and you don't seem very concerned.

00:06:24
Speaker 1: I'm mindlessly barreling towards it.

00:06:27
Speaker 3: Well, just maybe we'll record it, but then we'll censor it.

00:06:32
Speaker 1: Maybe we'll just skip it. We'll go straight to seventy.

00:06:34
Speaker 3: Yeah, seventy isn't new sixty nine.

00:06:37
Speaker 1: Nobody says that. Don't make that a thing.

00:06:41
Speaker 3: I don't care if other people say, oh I see, but yeah. We do like to answer questions here on the podcast that listeners said this, and so today we have three awesome questions. They are about galaxies colliding but extreme forces, and about the air we breathe. So let's jump right in. Our first question comes from Pedra from Boston.

00:07:01
Speaker 4: Hi, Daniel and jre I routinely hear not to worry about the impending collision between our galaxy and the Andromeda galaxy, since the space between the stars within each galaxy is so great there won't be any direct collisions. However, on some of the podcast episodes, it seems as though the orbital stability of the planets in our Solar system isn't all that great. For example, some planets may have traded places, while other planets could have been captured or ejected. So, really, which argument wins? Do I need to tell my descendants to start worrying about it in four point five billion years, I really want them to see the Sun become a red giant.

00:07:41
Speaker 1: Thanks for the great podcast.

00:07:43
Speaker 3: All right, interesting question. Basically, should we be worried four and a half billion years from now?

00:07:50
Speaker 1: Yeah, exactly if we're all alive, or should the zombies that have succeeded us, should they be worried about.

00:07:57
Speaker 3: What's going to happen? I think that's the best part of being a zombies is you don't have to worry about anything.

00:08:03
Speaker 1: As long as you've killed off all the people who might assign you homework problems, you're.

00:08:06
Speaker 3: Fine, man, I wou think the best part of being a zombies you can just turn your brain off.

00:08:10
Speaker 1: Don't you need to protect it from exploding? Right? Isn't that the kryptonite of zombies?

00:08:14
Speaker 3: Well, I think fire also kills zombies.

00:08:16
Speaker 1: Oh boy, wow, Yeah, I'm so glad you've been doing this research.

00:08:20
Speaker 3: I'm glad the people I'll be hanging out with know how to make a fire.

00:08:26
Speaker 1: But I think Petra's question is really touching on two things we hear about a lot in science. One that our galaxy is colliding with another galaxy and the other that our solar system is kind of fragile, that the orbits are not really that stable, and so he's worried that even if stars are pretty dilute in the galaxy, would our solar system get upset?

00:08:47
Speaker 3: Basically, what's going to happen when our galaxy collides with Andromeda?

00:08:51
Speaker 1: Like?

00:08:51
Speaker 3: Will be safe?

00:08:52
Speaker 4: Like?

00:08:52
Speaker 3: Is nothing going to happen to us? Or should we be concerned that maybe our plant might get disrupted and thrown out into space?

00:09:00
Speaker 1: Yeah, it's definitely a valid concern, and it touches on a lot of really interesting physics. And the first thing I want to talk about is why Andrama is going to collide with the Milky Way, because I get a lot of questions about exactly this. People hear us talking about how the universe is expanding and space is being created between galaxies, and then they hear us talking about how Andromeda is coming towards us and say, how does that make any sense? Why isn't space expanding between us and Andromeda and pushing it further and further away? And so first we should try to reconcile that apparent contradiction.

00:09:31
Speaker 4: Mm.

00:09:33
Speaker 3: Yeah, because we talked about like how because dark energy is expanding the universe, the galaxies out there getting further and further away from us, But we've also talked about how Drama is in a collision course with our galaxy.

00:09:45
Speaker 1: Yeah, And the answer comes down to distances, and dark energy is something that gets more powerful for distant objects. It's basically like a chunk of space grows a little bit, and so more chunks of space are growing more. So a little tiny chunk of space is hardly growing, but a vast distance between our galaxy cluster and a really distant other galaxy cluster that's kind of growing a lot. And gravity is the opposite. Gravity gets weaker with distance. As things get further apart, gravity fades away. So for stuff that's really close together, like the Earth and the Sun, or even our galaxy in the neighboring galaxy, gravity wins over dark energy. Things that are really really far apart, like clusters of galaxies, not individual galaxies. Dark energy is winning, And most of the universe is far apart from most of the universe, so mostly things are expanding away from each other, but in little neighborhoods like our cluster of galaxy, stuff is still getting pulled together by gravity. So gravity is the reason the Milky Way and Andromeda will collide in a few billion years.

00:10:45
Speaker 3: Is it gravity or is it just that we just happen to be in a course that intercepts the course of Andromeda, Like is Indrameda really being attracted to our galaxy? I mean, obviously it is, But is it really significant to call it the main reason we're going to collide with it?

00:11:01
Speaker 1: It definitely is. I mean, the Milky Way Andromeda are part of a cluster of galaxies, and that cluster exists because of gravity, so it's holding it together and the galaxies are sort of sloshing around. It's not guaranteed at any moment that they're going to hit each other, but it's gravity that holds them together, that's pulling them together. It's sort of like asking if a comet falls towards the Sun and it collides to the Sun, why is that Well, it's definitely because of the gravity. That doesn't mean that every comet does collide with the Sun. Gravity is not omnipotent. Sometimes comets go around the back of the Sun in the same way in the local cluster. Not every galaxy is gonna collide with every other galaxy as soon as possible. Sometimes they pass around each other. But it is gravity that's pulling these two together.

00:11:41
Speaker 3: Well, I guess what I mean is like if you have to asteroids, for example, in the Solar System, and they're gonna collide with each other. I mean, sure, they're in the Solar System together because of the gravity well of the Sun, but the fact that they're colliding with each other as opposed to not colliding, it's mostly just kind of look right, Yeah.

00:11:57
Speaker 1: It's gravity plus chance. It's possible a cluster where galaxies like ours and Andromeda don't collide until later on. Eventually everything is going to collide and it's all going to collapse into one supermassive black hole. So it's really just a waiting game.

00:12:12
Speaker 3: But the collision that's going to happen in four and a half billion years, that's basically luck. Right. It's not like it's inevitable. Like if our galaxy was moving a few degrees in another direction, or to the right or to the left, we wouldn't be colliding with Andromeda, would we.

00:12:25
Speaker 1: Yeah, that's right. If you change the initial conditions, that collision might happen later. It also might happen earlier, Right, it could be that we're lucky we got this far without colliding with Andromeda. So yeah, the whole system is very chaotic, but it is gravity. But gravity is really the only force at play here.

00:12:40
Speaker 3: And so the reason we're worried about Andromeda and not other galaxies is because the other galaxies are further away, and those are definitely moving away from us because of dark energy, or are some of them potentially getting closer to us.

00:12:52
Speaker 1: Everything in our galaxy cluster is gravitationally bound, which means it has enough gravity to hold itself together and resist the pull of dark energy, and galaxy clusters are like the biggest thing that have that property. Anything that's larger than that, what we call a supercluster, is probably too big and too spread out for gravity to hold itself together, and dark energy is going to win. So that's sort of the tipping point. So anything that's in our galaxy cluster is eventually going to collapse into one big, super massive black hole. And we're talking very very far in.

00:13:23
Speaker 3: The future unless dark energy changes, right, Yes, like if it accelerates, then it's going to get a little more crowded, but or if it like weekends, things might get a little room hear.

00:13:33
Speaker 1: Yeah, I think it's the opposite. If dark energy accelerates, then even our galaxy cluster is going to get torn apart because it becomes more powerful than gravity. We talked about that once on the podcast. There's even a theory of like phantom dark energy, where dark energy gets so powerful that it tears apart atoms and even protons. And if dark energy weakens, then gravity wins over larger distances and it might gather together even superclusters.

00:13:56
Speaker 3: Right, that's what I meant. I meant the opposite of what.

00:13:58
Speaker 1: I said, But you're definitely right, and the conceptual part, which is that we don't know what dark energy is or what it's going to do, and we can't really predict it. So this is assuming a naive extrapolation of dark energy, which is basically all we can do at this point.

00:14:11
Speaker 3: All Right, so we're in a collision course with Andromeda. What's going to happen when we collide?

00:14:15
Speaker 1: So when we collide with Andromeda, there's a bunch of different components of the galaxy, and you really need to think about each of them individually because they all have different behavior. So, for example, the gas and the dust that are in the two galaxies, those are going to collide and you're going to get all sorts of dramatic stuff. It's going to see the creation of lots of new stars, which would be really exciting. But the stars themselves are very different from the gas and the dust. Right the gas in the dust is very spread out, it's definitely going to smash into the other stuff. But stars are very different from gas and dust. They're not as spread out. They're tiny, and they're clumpy, and they're really really dilute. So when stars approach other stars, it's very hard for them to actually collide because space is really really big, and the stars are really really far apart.

00:14:58
Speaker 3: I guess how far apart are they? Like how far is there our year's neighbor?

00:15:01
Speaker 1: So our nearest neighbor is light years away, right, the closest star to us is almost four light years away, and the Sun is the tiny fraction of a light year wide. I mean, if you shrink, for example, the Sun down to the size of a tennis ball that you could hold in your hand, then the nearest neighbor star would be four or five thousand miles away.

00:15:21
Speaker 3: WHOA, that's like on the other side of the Atlantic kind.

00:15:24
Speaker 1: Of yeah, exactly. So imagine you're throwing a tennis ball and somebody on the other side of the ocean is throwing a tennis ball. What are the chances that they're going to hit each other over the ocean? Like basically zero?

00:15:37
Speaker 3: But I guess how wide is the sphere of influence of something like the sun? Like how close do you need to get to it before you feel it's gravity?

00:15:46
Speaker 1: Yeah? Exactly, good point, because we're not actually just interested in like a collision where like the two stars really touch each other and merge and become one. Stars can pull in each other if they're even near each other. Right, And that's really what Petro's quest is about, is how close does the star need to get to distort our star or distort the orbit of stuff around the star? Right? Because near misses can destabilize things, and we know that already in our galaxy, because other stars are moving relative to the Sun. Sometimes they come closer, sometimes they come further away, and that can distort the orbits of stuff in our Solar system. So it's not a clear, crisp answer. It's not like there's a certain distance within which something happens and out of which nothing happens. It's gradual, Right. The closer it comes, the greater the gravitational distortion.

00:16:32
Speaker 3: But I guess maybe it depends on how unstable our orbit is or how fragile our orbit is. Do you have a sense of how precarious are a path around the Sun is? Like if I bring in another Sun, I don't know, a few million miles away, is it going to affect us and kick us out of the Solar system or maybe cause us to fall into the Sun, or are we going to be Okay?

00:16:57
Speaker 1: Yeah, it's a good question. The Earth is pretty stable, like just the Earth in the Solar System is a pretty stable orbit. There's a lot of stuff going on that's going to influence the Earth's orbit that makes its orbit change. For example, like the Sun is losing mass, so it's gravity shrinks. The Sun is also pushing on the Earth, not just pulling on it with gravity, but its wind pushes on the Earth. There's effects of Jupiter, there's gravitational radiation. But you're right, the biggest wild card are like things from outside the Solar System. And this is something we've thought about, not just in the case of another galaxy, but again just stuff in our Solar system. So, for example, there is a star it's called Glease seven to ten that we've been tracking, and we predict that it's gonna come kind of close to our star. It's gonna come within one twenty fifth of the distance to Proxima Centauri. So Proximus Centauri is four light years away, and so this is gonna come like an eighth of a light year away from our star.

00:17:56
Speaker 3: Oh wait, wait, wait, so this is a star that's gonna come within one twenty fifth of the nearest star. Yeah, would it become the nearest star if it's coming close to us.

00:18:04
Speaker 1: Yeah, that's just for scale, our current nearest stars for light years away. This one's going to come within one twenty fifth of that distance again in the far far future. How far in the future, in about one and a half million years.

00:18:18
Speaker 3: Oh, that's pretty soon cosmically speaking.

00:18:21
Speaker 1: Yeah, it's a lot of generations to survive between now and then. But yeah, that's not far away, and it's definitely a lot sooner than when the Milky Way collides with Andromeda.

00:18:30
Speaker 3: And this is a star that's like traveling through space relative to us, or are we traveling close to it? You know what I mean? Like, is this an anomaly or in our quiet neighborhood or is it all part of the movement of the stars.

00:18:44
Speaker 1: It's part of all the movement of the stars around the center of the galaxy. You know, all the stars are orbiting the center and they orbit at different velocities. Also, the stars are moving up and down. They're sort of like wiggling through the plane of the galaxy. And so the stars that are in our immediate neighborhood change over millions of years as these stars sort of swim through the lazy river differently. So this is a totally normal thing to happen.

00:19:07
Speaker 3: And what does scientists predict this is going to happen when the start flies close to us? Is it gonna disrupt us? Or are we going to feel it?

00:19:15
Speaker 1: So we are probably not going to feel it directly, in the sense that it's not going to come close enough to perturb the Earth's orbit. So that's already kind of an answer, like you can come fairly close to the Solar System, you know, within an ace of a light year, and really have no effect on the Earth's orbit directly, but it could have serious impacts for life on Earth because it could impact stuff that's in the outer Solar System that could then rain down on the inner Solar System. The very far edges of the Solar System, past Pluto and all the dwarf planets is a theoretical cloud of trillions of icy objects called the Ort cloud. We think it's probably the source of long period comets. These things are really really far away compared to stuff in the inner Solar System or even to Pluto, and so a near passing star could disturb some of these. There's lots of them, and they take just like a little nudge to fall out of their orbit and come barreling into the inner Solar System, where they could become very high speed, very dangerous comets that could impact on the Earth.

00:20:13
Speaker 3: Whoa, but it maybe it might be get lucky not get hit by right, because even the space between us and the Sun is huge.

00:20:21
Speaker 1: Yeah, absolutely, we might get lucky and we could get protected by Jupiter.

00:20:24
Speaker 5: Right.

00:20:24
Speaker 1: Jupiter has a lot of gravity and it tends to shield the Inner Solar System by pulling these things towards it. Like when comet Shoemaker Levey came through the Solar System in the nineties, it impacted on Jupiter and that wasn't an accident. Not only is Jupiter just a much bigger target, but it has that gravity. But it's not a die you want to roll. It's sort of like playing cosmic Russian Roulette.

00:20:44
Speaker 5: You know.

00:20:44
Speaker 1: If a star comes by and dislodges a lot of art cloud objects tens millions even for example, then we're gonna have to get lucky a lot of times to avoid being hit. So that's the most likely scenario for Glease and also for the collision between Andromeda and the Milky Way, that our cloud gets perturbed.

00:21:01
Speaker 3: Well, well, but I guess what is the scenario that's going to happen when we collibe with Andromeda. Are we going to see a lot of these stars flying as close as Gleek or is it going to be worse because I imagine, you know, the nearest star to us is pretty far away, but you know, we're colliding with a cloud of one hundred billion stars. Maybe that increases the chances of something flying closer.

00:21:22
Speaker 1: Yeah. Actually, Andromeda is much bigger than the Milky Way. There's lots more stars in Andromeda than in the Milky Way. It's really a big, fat galaxy. I mean in a very positive way. And so there's no specific answers. There's just chances. Right. The chances of a direct collision are zero, the chances of a near miss are larger. The chances of stars flying sort of within a light year or so is reasonable. I haven't done the actual calculations, don't have numbers, but qualitatively it's extraordinarily unlikely for a direct star star collision. I think it's quite likely for a near miss like Glease seven to ten. But I think the most likely scenario is that no star comes really anywhere near us, though there are a lot of them. There are also very very spread out.

00:22:03
Speaker 3: No, should we just think your word for it, or should maybe one of you guys get on the computer and simulate this to figure it out.

00:22:11
Speaker 1: We've got four and a half billion years to figure it out, so yeah, that's enough computation time.

00:22:16
Speaker 3: I don't know. I like to plan ahead, as you know. No, you gotta get ready.

00:22:20
Speaker 1: The problem with these calculations is that the further in the future you have to extrapolate, the more uncertainty there is. Right Like, NASA can predict the path of these objects for one hundred years very precisely. You ask them to tell you where they're going to be in five billion years, they have no idea because small uncertainties add up over time to make those predictions essentially useless. So our understanding, for example, of the dark matter in the Milky Way will affect this and the dark matter and androma and the dark matter between us and them. So we could do a calculation and give you a number, but it's gonna be different next year, and it's gonna be different in a million years, it's gonna be different in a billion years.

00:22:55
Speaker 3: Well, I mean, you don't need to predict what's going to happen exactly, But could you maybe get us that this sense? Like if I take a cloud of stars like the Andromeda galaxy, and you take a cloud of stars like the Milky Way galaxy, and you smash them into each other at the speed are going, what are the chances or how likely or you know, how often would a star come near as enough to disrupt our orbit?

00:23:16
Speaker 1: That's totally possible, and probably somebody is working on that, but I haven't actually seen that number anywhere.

00:23:23
Speaker 3: All right, Well, then the answer for Petra is hopefully not nothing bad will happen. Daniel doesn't think.

00:23:29
Speaker 1: Don't worry too much about it, Petra. Zombies are much more likely.

00:23:32
Speaker 3: Yeah, don't collide with any zombies if you can't, especially when with teeth.

00:23:37
Speaker 1: But keep working on those intervals. That's going to save you in the end times.

00:23:40
Speaker 3: That's right. Bring your math book whenever you go out foraging for you know, particle colliders to start in your fire.

00:23:48
Speaker 1: Or do what my dad did. Become a blacksmith and make your own weapons.

00:23:52
Speaker 3: Oh yeah, that's a good suggestion. Or just go to Daniel's garage and you know, steal some of those swords.

00:24:00
Speaker 1: I wouldn't recommend that that's pretty well protected.

00:24:04
Speaker 3: By math. If you come within ten meters, you'll be faced with some physics questions, or you could just blast the podcast out in speakers. They'll keep everyone away. All right, let's get to our other questions here today, and we have some questions about extreme forces in the universe and about what kind of air are we all breathing? So we'll dig into those, but first let's take a quick break.

00:24:41
Speaker 4: Right.

00:24:41
Speaker 3: We're answering listener questions, and our second question comes from Derek, who comes from the planet Earth.

00:24:49
Speaker 1: I guess probably we hope, so, no, we hope not.

00:24:53
Speaker 3: Yeah, Hi Daniel and Jorge.

00:24:57
Speaker 5: So I have a question about extreme forces. Gravity is one of the weakest forces in nature, but it seems like there's no limit to how much gravity there can be, and once you have enough of it, an event horizon is formed and a black hole is made. Even then, more masks can be added and gravity will continue to increase. Can this be done with any of the other forces, Like can a magnetic field become so strong that it forms its own kind of event horizon? Or is there a limit that prevents the other forces from increasing infinitely?

00:25:26
Speaker 3: Thank you all, right, interesting question, I guess The question is how extreme can other forces get? Can you make like a magnetic black hole or a weak black hole?

00:25:37
Speaker 2: Yeah?

00:25:38
Speaker 1: Super fun question, really great to think about, and I love the sort of philosophy behind this question. Trying to make connections between forces and try to understand the differences between ideas. This is really how you make progress in physics. How you build a consistent model in your head, try to understand where that model doesn't work and where the bits don't fit together, and then try to understand how they can possi click together. So kudos to you, Derek for thinking about it this way and for asking this great question.

00:26:06
Speaker 3: All right, The question is Derek is wondering, like, we know that a black hole happens when you gravity gets so intense that it becomes basically a black hole with an event horizon. Can that sort of thing happen with the other forces in nature, like electromagnetism or the weak force or the strong force. Can you get a situation where the magnetic force is so strong it can maybe creates its own kind of event horizon.

00:26:30
Speaker 1: Yeah, so super fun question, and it's tempting to think that there is because Derek probably thinks about gravity as a force in the same way he thinks about magnetism as a force, and that it creates an acceleration on objects. Right, Two objects, as Newton described that have masks will pull on each other the same way two objects with electric charge, the electric force will pull on them or push on them, and the strong force pulls and pushes on things that have color charge. And so it's tempting to think about that, and it's very intuitive, but remember that gravity is not actually a force. It's our understanding of gravity today is that it represents the curvature of space time itself, and in many ways that's equivalent. Like most of the time, you can think about the curvature of space time and from that you can get exactly the same behavior that Newton would have predicted, but it's also crucially different in many respects. There's lots of things that the curvature of space time can do that the simple force of gravity cannot do. And form an event horizon is one of those things. So Einstein's reconception of gravity as a curvature of space time describes all of Newton's physics, but also more than that, it doesn't just reformulate gravity. As another way to think about it, it adds new capacity to gravity, new things that it can do. And so the force description of gravity cannot create an event horizon, but the curvature description of gravity can create event horizons. And so the other forces which can't be described in terms of curvature can't create event horizons. That's not something a force can do. Only spacetime curvature can do that.

00:28:05
Speaker 3: Well, I guess I might ask, are you sure about that? Couldn't you define the event horizon as the point at which the force of gravity is so strong that nothing can escape it.

00:28:16
Speaker 1: I'm definitely not sure about that, because we don't understand gravity right. Gravity is really weird. Einstein's theory is beautiful, but we also know that it's flawed. We don't understand how singularities could form. We don't understand why gravity seems to not be quantum mechanical, or if it is when you zoom in enough, for example. So everything we say here today assumes that GR is correct, but we know that GR is not correct ultimately, and so there's lots of things to be learned, and in the far future this could all be totally wrong. So yeah, absolutely not, But you're right. First, we should define what we mean by an event horizon, right, And the reason a black hole can exist, the reason we have event horizons, the reason that curvature can do this and the forces cannot, is that curvature does something to space. It changes the shape of space, like the relationship between points. So you can think about it as like a region from which even a photon cannot escape, right, And that again is something gravity can do. But you can't do that with magnetism or electric force or the strong force.

00:29:17
Speaker 3: Well, I guess what I mean is, like, you know, for example, you might say that the Earth has an event horizon, right, Like there's a point and a velocity at which you can escape to Earth, and there's a point at which you cannot escape Earth. Right, So maybe you might be able to call that the event horizon of the Earth gravity black holes event horizon. It's just that. But taking to the extreme where you're talking about not even light being able to escape, I wonder if you can do that the same with a magnetic field or electromagnetic force, Like is there a point at which not even like a super fast moving charged particle will escape the attractive force that something has electromagnetically.

00:29:54
Speaker 1: I mean, you can definitely form bound states, right, Like the Moon is bound to the Earth gravitation, but it can still escape, right, Or photons from the Moon can definitely escape the gravitational system. And that's not just like a difference in degree, it's a difference in kind. Right. The inside of an event horizon really is cut off from the rest of the universe. Nothing that happens there can influence anything that happens outside the universe, whereas things that happen on Earth can always influence things far away. It just takes some time. So it's a question of like causality, like are these things linked or not? Can one area of space affect another? You can definitely attract things together, and they can even be stuck together, and they can be stable, and they can even last for millions or billions of years or configurations, Like the proton might last forever, but you know, the quarks inside the proton could still potentially escape you give them enough energy. It's a bound stay. That's not the same thing as an event horizon.

00:30:50
Speaker 3: But could you say that, like a charge ball of electricity has an escape velocity to it and a point at which no charge particle can escape it.

00:30:58
Speaker 1: A charge ball, for example, definitely has an escape velocity, like there's a minimum energy you would need to escape the potential well created by that ball, and things below that energy are bound to it, but there is still always an escape velocity. And that's why photons are a useful way to think about event horizons, because there's no force that can bound a photon. Like photons always move at the speed of light locally, and there's no force that can prevent them from doing that. But changing the direction of space, right, changing the configuration of space the way gravity does, that can trap a photon because it can change space from flat to curve. You can make the photon move in a circle forever, which is sort of amazing. And so that's why gravity can do this, which no other force can do.

00:31:39
Speaker 3: But I guess light is an electrically neutral right, Yeah, So I wonder if you can envision, like, is there a ball of charge that can be so intense that not even a core going at the speed of light can escape it? Do you maybe call that the event horizon of an electromagnetic force.

00:31:57
Speaker 1: So you take a ball of charge has a very strong electric force, right, and now imagine some electron near it, and you're wondering, like, is it possible to have that ball be so electrically charged that even an electron moving at the speed of light couldn't escape it. Yeah, yeah, it's a great question. The problem is that electrons can't move at the speed of light because they have mass.

00:32:17
Speaker 3: Right, Well, of course I know this, but like, if it was moving at the speed of light, is there a point we're closing on nin point nine nine nine percent? Yeah, the speed of light. Is there an event horizon for that ball of positive charge?

00:32:29
Speaker 1: Right? And I bring up the velocity not just to be like actually, but because velocity is the wrong way to think about it, because for a massive object, energy is the right way to think about it. As you say, it can't get to the speed of light. You can get arbitrarily close, but there's no limit to the amount of energy that an electron can have, and so you can just keep putting energy into that electron and eventually it will escape that ball of charge. So no, there's no way you can trap an electron forever. You can't create an event horizon using electric charge. You could always just give that electron more energy and it would escape your ball of charge no matter how big it is.

00:33:03
Speaker 3: All right, So then the answer for Derek is no, you can't make an electromagnetic black hole.

00:33:08
Speaker 1: Yeah, and I think there's another wrinkle there, which is something you brought up, which is photons are neutral electromagnetically, right, And I think that's really cool. I'm kind of weird that photons, even though they carry electromagnetic information, they don't feel the force themselves. And that's something true about all of the forces, electromagnetism, the weak force, a strong force, there are always some particles that are neutral to it, right, So, like the strong force can create really really strong bound states, but then neutrinos ignore it, right, they would just fly right through it. So in that sense, an event horizon for like electromagnetism wouldn't really be an event horizon even if you could make one, because some particles ignore it. The amazing, awesome thing about gravity is that nothing can ignore it. Gravity is just linked to energy. So anything that has energy, which is basically anything in the way we conceive of it, is affected by gravity. It's inescapable.

00:33:58
Speaker 3: Oh all right, hmm I'm still wondering, like, could you make that calculation? Like, what did you take an electron, give it the speed of light? Could you use that to compute a positive ball of charge strong enough for which that's the escape velocity.

00:34:14
Speaker 1: Well, if you have an electron and you effectively give it velocity the speed of light, you're giving it infinite energy. And of course that's impossible. But what that means is that there is no ball of charge that's powerful enough to bound it because there's infinite energy, so has more energy than any energy level in that bound state unless you make that ball infinite. Right, So now it's like infinity versus infinity.

00:34:37
Speaker 3: Well, I guess what I mean is like, when you compute the escape velocity of something escaping Earth, you're not actually using the relativistic equations, right, You're just kind of using more basic math. You're ignoring relativist effects.

00:34:49
Speaker 1: Right, Yeah, the simplest calculations ignore relativistic effects. But I don't think relativistic effects are really relevant for the Earth.

00:34:56
Speaker 3: Right, But so let's say I do that for an electron, give it the speed of light. Could I compute an event horizon, even though maybe it's not realistic, but it is there. One.

00:35:08
Speaker 1: So you're saying, if I ignore the fact that electrons can't go the speed of light and I ignore relativity, can we make an event horizon for an electron.

00:35:16
Speaker 3: Yeah, just like when we compute the escape velocity of a satellite or a spacecraft, we sort of ignore that too.

00:35:22
Speaker 1: You can definitely calculate and escape velocity right or effectively an energy beyond which the electron is free and below which the electron is bound. So you can definitely calculate that. You can ignore relativity, you can include relativity or whatever. But in order to trap that electron forever so that there's no chance that ever leaves, then you essentially need an infinitely powerful electric force. You need an infinite amount of charge to trap an electron that could effectively have infinite energy.

00:35:49
Speaker 3: So would that mean that my electric black hole is infinitely big or infinitely small?

00:35:57
Speaker 1: It would be infinitely charged.

00:35:59
Speaker 3: Oh does it have to be in constily charged or could it just be a charge but infinitely dense.

00:36:05
Speaker 1: You might imagine bringing the electron like really really close to that charge so that the electric force gets really powerful, because the electric force also gets powerful as things get really close together. But again, these are quantum objects. There's always like a minimum effective radius. It's not really an orbit, but this is like a mean distance from the center for the ground state, and so that effectively limits how powerful these things can get. Like there's a reason the hydrogen atom has a ground state and the electron is not closer to it. It can't settle any closer, and that effectively bounds like how strong the force can get.

00:36:37
Speaker 3: Oh Man, So you're seeing quantum mechanics ruins all the time.

00:36:42
Speaker 1: Like usual, But you also have another question about like why can't we describe the other forces in terms of curvature? And there are people working on that, people wondering like, well, what if electromagnetism actually is curvature but not in our three D space? What if it's curvature in like additional spatial dimensions. And nobody's really made that theory work, but it's really fun to think about how electromagnetism might be like curvature in other ways that we can't see it yet. And even in that theory, you might be able to describe electromagnetism as curvature, and you might wonder like can I make event horizons in those other dimensions, but then you wouldn't be making event horizons in our three D space, which I think is really what the question was.

00:37:21
Speaker 3: So then it would be sort of like a black hole. But the inn other dimensions.

00:37:24
Speaker 1: It's pretty hard to think about, but it would be curvature in other dimensions, and you might have event horizons in those dimensions, but not in our dimensions, So pretty wonky stuff.

00:37:33
Speaker 3: There'd be holes in our black hole, is basically.

00:37:35
Speaker 1: What you're saying.

00:37:36
Speaker 3: Yeah, exactly, all right, Well that's an interesting answer for Derek. Now let's get to our last question of today, and it's about the air we breathe and where does part of it come from? So let's dig into that question, but first let's take a quick break. We're answering listener questions here today and our last question comes from Steve paren from Quebec.

00:38:10
Speaker 2: Hi, Daniel and Jorge, this is Steve Pargan from Quebec, Canada. My question is where is all the nitrogen in our atmosphere coming from? And what role does it play? Amazing podcast, guys, I love it, Thank you.

00:38:26
Speaker 3: All right, A pretty straightforward question here, Where does all the nitrogen in our atmosphere come from and what role does it play?

00:38:34
Speaker 1: Yeah, nitrogen is a big deal on Earth. Like, most of the atmosphere is nitrogen. You take a deep breath, you think yourself as a gulping oxygen, but it's mostly nitrogen that you're breathing in, which is kind of weird.

00:38:47
Speaker 3: Well, what do you mean mostly? What are the percentages?

00:38:50
Speaker 1: It's almost eighty percent of the air is nitrogen.

00:38:53
Speaker 3: Eighty percent by like a volume mass or adams.

00:38:57
Speaker 1: It's seventy eight percent by mass.

00:39:00
Speaker 3: And how much of it is oxygen? So it's like most of the air is nitrogen.

00:39:04
Speaker 1: It's seventy eight percent by quantity.

00:39:07
Speaker 3: You mean by volume or what do you mean by quantity like number of atoms?

00:39:11
Speaker 1: Yeah, like number of molecules. Actually, if you count it up, if you take like a cubic meter of air and you count all the molecules in it, seventy eight percent of those are nitrogen and twenty one percent of those are oxygen.

00:39:22
Speaker 3: Oh, no, hydrogen.

00:39:24
Speaker 1: There's almost no hydrogen in the atmosphere because it's very volatile. Any hydrogen will react with the oxygen and make water.

00:39:30
Speaker 3: So where did all this nigrogen come from?

00:39:32
Speaker 1: Yeah, it's a really fun question. It goes back to the whole origin of like why we have an atmosphere in the first place, because it's kind of weird. You know that we have enough gravity to like hold this little super thin envelope of gas around the planet. And if you think about how the planet came to be, it's not clear, like why we have an atmosphere that survived the formation of the Solar System, because as things were condensing very early in the Solar System, it was a very volatile place. Like first of all, we're in the Inner Solar System, which means we're pretty close to the Sun, and so most of the hydrogen in the Inner Solar System was gobbled up by the Sun. Like the Sun has huge gravity. The reason that Earth was formed is because it's not hydrogen. It's because it's rocky, had like enough gravity to form its own little gravitational well and cluster stuff together before it all got gobbled up by the Sun. But that tends to gather together heavy things like rocks and metal, right, chunks of iron floating in space, not clouds of gas, most of which fell into the Sun. Some of it did form with the Earth. But then when the Sun started fusing, it created all this intense radiation and blasted away our atmosphere. So we might have had like a very thin hydrogen atmosphere to begin with, but then most of that got lost due to the solar radiation and then also collisions by heavy stuff, like the formation of the Moon was due to this collision with a protoplanet and that probably destroyed all the atmosphere we had initially.

00:40:57
Speaker 3: But I guess a deeper question is where it did all come from originally, Like it just got form inside the Sun like all the other heavy elements in previous iterations of the Sun or supernova or what.

00:41:10
Speaker 1: All the nitrogen and everything in our Solar system that isn't hydrogen was not made by our star, right, All that was made by previous stars. So like the deeper history is that we have mostly hydrogen formed in very very early universe, tiny tiny trace amounts of helium, and then you have to wait for stars to be born hundreds of millions of years later to turn that hydrogen into heavier stuff. And so that nitrogen that you're breathing right now was made at the heart of stars previous generations which burned created that nitrogen inside them and then blew up and spread those heavier elements, including nitrogen and iron and copper and on carbon and all that good stuff throughout the galaxy, and then that re coalesced into our solar system. So all the nitrogen and the iron and all that stuff in our bodies and in the air and in the Earth was made by a different star that no longer exists.

00:42:00
Speaker 3: And it was made at the core of that previous star, or when it exploded.

00:42:04
Speaker 1: The stuff that's iron or lighter was made to the core of that stars made by fusion, because when you fuse two lighter elements together, you release energy. But that's only true up to making iron beyond iron, When you fuse stuff together, it costs energy. So if a star starts to do that, it begins to dim and like steals away the energy. And stars need that energy to survive because they're fighting against gravity. Gravity is trying to compress them down into a black hole. And the only reason the star survives for millions or billions of years is that radiation pressure outwards that's created by the energy released by fusion. If that goes away, then the star starts to collapse, and so stars can't make a lot of the heavier elements above iron. For that, you need either the death of the star, the supernova which has super dense conditions capable of creating those heavier elements, or things later on like collisions of neutron stars to create the heaviest elements. But nitrogen is made in the heart of those stars during normal fusion.

00:43:00
Speaker 3: So we're basically breathing dead stars. Every time you take a.

00:43:04
Speaker 1: Breath, it's a gift from those stars.

00:43:08
Speaker 3: You're basically breathing zombie star.

00:43:11
Speaker 1: Yes, exactly, zombie star brains. Take a deep breath.

00:43:16
Speaker 3: Yeah, h smells delicious, smells like brains. So the previous star made the It was floating around just like all the hydrogen and carbon and dust and rocks that was made by previous stars when our Sun started burning. And then how did it end up on Earth or is it spread out all around the Solar System?

00:43:36
Speaker 1: It's all over the Solar System. Nitrogen is everywhere, It's not just on Earth. And the nitrogen in our atmosphere ended up on Earth in an interesting way. Number One, it came from the bombardment of the Earth by like comets and asteroids that had like frozen nitrogen in them, and so we think, like a lot of the water on Earth may have come from comets, the same thing is true of nitrogen. The early Earth was blasted clean. Essentially, it was just a bare rock because of the solar radiation. But then it got a second atmosphere due to collisions and also because of nitrogen and other gases trapped inside the Earth which escaped out due to like volcanoes. You know, you have a lot of these gases in the early Earth, and as the Earth is settling, the heavy stuff goes down to the core and the lighter stuff rises in the mantle, and then some of that escapes through cracks in the Earth. So volcanoes and the bombardment of asteroids created our second atmosphere, which was mostly nitrogen and carbon dioxide. So that's where the nitrogen comes.

00:44:35
Speaker 3: From, and then eventually we got oxygen. But I guess the second part of these question is what a role does nitrogen play? Like do our bodies need a nitrogen or do we just ignore it?

00:44:49
Speaker 1: Mostly? Yeah, it's definitely not inert. Nitrogen plays a really important role in the life cycle here on Earth, Like plants need nitrogen. It's a crucial part of a lot of the you know acids, and so in order for plants to grow, you need nitrogen in the soil, a big component of like fertilizer that people are constantly putting onto their plants, farmers and pour huge amounts of it. The reason you put manure on fields is that it has nitrogen in it and other stuff. So plants need this nitrogen in order to grow. And there are these bacteria that will breathe the nitrogen from the atmosphere and then basically make it available for the plants. So there's a whole complicated nitrogen cycle that involves like these nitrogen fixing bacteria and then plants using it to grow, and animals eating it and then pooping it back out into the ground. And it's a very complex cycle, but it's definitely not inert It's a huge part of life on Earth right right.

00:45:41
Speaker 3: And I just want to take a quick moment here to note that you were the first one to bring up poop in this episode, not me.

00:45:48
Speaker 1: Is that something you keep track of who says poop first?

00:45:53
Speaker 3: I'm just saying sometimes they get you know, accused of.

00:45:57
Speaker 1: Cultural language is down. Yeah, Well you know that's the conversation we have at my house all the time because my wife works on the gut microbiome, like literally, what's happening inside your guts? And so the kids are always timing like how long till mom brings up poop at the dinner table? Oh boy? And it's never very long.

00:46:15
Speaker 3: May should you just call it nigrogen instead of poop nigrogen rich content. They'll spare your appetites.

00:46:25
Speaker 1: We're just fertilizing the conversation.

00:46:27
Speaker 3: Yeah, you just want to make it more fregrant. But I guess why is nigrogen important and biological processes? Is it something There's something special about that molecule, you know, because carbon has some special things about it that make it kind of crucial to life. Is nudigen similar?

00:46:42
Speaker 1: Well, I think you're getting pretty deep into the chemistry here. You know, the amino acids are the basic building blocks of life, and having different kinds of atoms there, it gives you different options, different things you can build. But yeah, dot dot dot chemistry. I guess.

00:47:00
Speaker 3: To be a Wikipedia later.

00:47:04
Speaker 1: I mean, nitigen is already at the edge of my ability to think about things. There's so many protons there, it's crazy and then you have it connected.

00:47:12
Speaker 3: With another your brain would explode.

00:47:15
Speaker 1: Yeah, exactly, too many integrals from me.

00:47:18
Speaker 3: For as a physicist zombie. You just have to throw some chemistry questions at them, absolutely, and then their brains will explode.

00:47:24
Speaker 1: Yes, chemistry is our kryptonite for sure. And they don't even have to be that hard, just like my high schoolers ap chemistry questions. Whoa headache? Time?

00:47:33
Speaker 2: Right?

00:47:34
Speaker 4: Right?

00:47:34
Speaker 3: Hey Daniel, what's up? Regardless number big Welcome to Jorge explains the universe. All right, Well that's the answer for Steve, which is that the nigogen we're all breathing, eighty percent of the air we're breathing, came from a debt previous star in our solar system. Then it got formed with the rest of the Earth and the rocks and the other elements, and that's how we're breathing it today, that's right, possibly from comments, possibly from the earth burping.

00:48:06
Speaker 1: Yeah, exactly. And there's been some people doing really interesting studies to try to understand exactly where this nitrogen came from, because not all nitrogen is the same. Some of them have different isotope ratios, and you can tell like, was it formed in the Outer Solar System or the Inner Solar System, the molecules, not the pure nitrogen which was made in the stars. And so there are these studies that tell us that some of the nitrogen on Earth came from the Inner Solar System and some definitely came from the Outer Solar System. So it's a similar question to like where did our water come from?

00:48:35
Speaker 3: All right, well, three awesome questions here today. Thanks to all of our listeners who sent in their questions.

00:48:40
Speaker 1: And thanks to everybody who asks questions. Please don't be shy. Write to us two questions at Daniel and Jorge dot com. You'll definitely hear back from us.

00:48:48
Speaker 3: We hope you enjoyed that. Thanks for listening, See you next time.

00:48:56
Speaker 1: For more science and curiosity, come find us on social media where we answer questions and post videos. We're on Twitter, Discord, Insta, 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.