SIO384: Even More Askings of Astrophysicist Bryan!

Transcript

This transcript was generated automatically and may contain errors — the audio is the record.

0:00:17 Thomas: And welcome to Serious Inquiries Only, this is episode 384, I'm your host Thomas Smith, and we are back at it. This is a part two, go back back and listen to part one, although since it's a Q &A, I guess you don't really have to, but definitely go back and listen to part 1 of the Q &a with astrophysicist Dr. Bryan Gillis. So many cool questions, time have even more. And it worked out so brilliantly that we answered all the questions.

It was exactly the right number of questions. Can't believe it. Looking forward to doing this again. And maybe, who knows, maybe I'll do it with different people, people of different specialties, different layers of expertise, because this was fun. So here's part two. Always go to patreon.com/seriouspod if you want to be able to, you know, chime in on these Q &As or get them early, or listen to a show with no annoying ads. All those are great reasons to go to patreon.com/seriouspod. Thanks to all who have pledged. And here we go. Okay, civilpoliticsradio.com, probably at 7 p.m. Eastern on Valley View Radio, asks, also, are there minimum and maximum wavelengths of light? Well, I would think it's got to be yes, right?

0:01:23 Bryan: I'm trying to think about this. It might be some quantum mechanic effects that do it, but it's actually not something I've thought of before. It's something I might have to look up. From a maximum perspective, I'm pretty certain that the answer to that is going to be yes, because, well, the minimum wavelength, Because the smaller the wavelength of light, the more energetic it is. So at the minimum perspective, I think the answer is going to be yes, because at some point, a single photon of light will be energetic enough. And then by E equals mc squared, energy is the same as mass, mass distorts space, that a single full photon would turn into a black hole. So there's going to be a limit there where photons turn into black holes.

0:02:10 Thomas: Well, also, isn't there the plank length anyway? Like stuff can't even be, yeah.

0:02:14 Bryan: Yeah. Yeah. There's a length where, from a quantum mechanics perspective, things just get indistinguishable. Yeah, I think you'll reach limits at the minimum. I'm not sure about the maximum. I would have to look into that to say for sure.

0:02:29 Thomas: Hmm. Guess once again, talking about that red shifting or whatever, that's kind of like that stuff's getting stretched all the way until you can't see it, but is that it's, I guess it's not disappearing per se, it's just we can't detect. Yeah, interesting. Okay, well, I'll tell you, there's definitely a maximum. It's the length of the universe, so So there is a minimum and a a maximum, but at a certain point, I guess, and this might be a dumb question, but does it turn into something other than light? Like if it gets so stretched out or it's so tiny, does it effectively become a different thing, or is it always still the same thing, if that makes sense?

0:02:37 Bryan: Yeah. Yeah. Oh, there you go.

0:03:09 Bryan: Mechanically, it can. Well, it's pair production, basically. Basically, like we before about how an electron and positron can annihilate each other. And all the laws of physics are actually symmetric in time, that you can reverse your perspective of time and all the physics stays the same. So if you take that, okay, so stage one, you have electron, positron. Stage two, they collide. Stage three, you have a burst of light. If you flip that around in time, you could take a burst of light that turns into a collision, which turns into an electron and positron. You do have to balance out conservation of momentum. So it's a bit tricky to turn a single photon of light into multiple particles. I think conservation of momentum prevents that. That, um, if you have multiple photons, then I think it is possible for two photons to hit each other, and on the other side you come out with an electron and positron. Um, yeah, light can turn into other things. Yeah.

0:04:18 Thomas: Fascinating. All right, again, David Back, Spino Breaker, wins the award for most enthusiastic, I think, right now about asking Brian questions, which I love. Oh, well, maybe I could be in that contest too. Are there the most controversial scientific idea you think is right, even though there's minimal evidence to support it? That's a, that's a tricky one.

0:04:38 Bryan: Yeah, for me, um, one I think is right even though I don't like it, which is the multiple universe interpretation of quantum mechanics, because mathematically multiple multiple universes feel almost inevitable with how quantum mechanics works, and you have to step in and add extra laws to prevent multiple universes. But it's controversial because it's such a philosophically horrifying idea if you think too much.

0:04:45 Thomas: Yeah, I know. I still can't wrap my mind around it, to be honest. How does it interact with all this stuff about the universe? Like, are we, is it just, it's all kind of in parallel? Like it's all now

0:05:08 Bryan: Yeah. Yeah, it's like that other time dimension we were talking about. It's just somewhere else on a different dimension. Dimension. Except if you ask a quantum physicist, they'll say it's not a time dimension, it's a different phase, I think, or something like that, that it all exists simultaneously with just different realizations of the wave functions occurring all at the same time. And yeah, from the way the math goes and the physics, if you believe the physics and calculate it out, multiple Multiple universes fall straight out of that. Just horrifying to think it might be true.

0:05:16 Thomas: Yeah.

0:05:54 Thomas: Yeah, and they don't ever interact though, never the twain shall meet, right? I mean, it's, yeah. So it's not like because my mind goes to like, how do you have conservation of energy, comes all that stuff, because like, it just feels like you're having a zillion things at all times in a crazy way, but I guess if it's all theoretically just independent, like it, all, you know, then I guess that wouldn't, yeah, crazy.

0:05:59 Bryan: Right. That's, yeah, that's one of the rules. Yeah.

0:06:17 Bryan: It's all independent. And I think the energy also gets split up between the different universes. We don't notice it, but like with every split into two universe, each gets half the energy as each has half the total amplitude of the wave functions. Or actually, no, energy is amplitude squared. Wear it so something like that, yeah.

0:06:17 Thomas: Right.

0:06:36 Thomas: Well, but yeah, yeah, I say, take, take your point. There's also going to be different, different, you have some of these like percentage things, it's like, did this decay or not? You know, that would have different implications for that. I imagine energy and stuff in those different parallel universes. Crazy. Don't get it. Still don't get It. I accept that the math says that, but like I'm with you. I don't fucking get it, but I, isn't exactly the question because they did say, minimal evidence to support it. Is there anything, I'll just, let's just for fun, is there anything in your line of work specifically, or that you can think of where you're like, all right, I don't know for sure. And I don'T, I haven't proven it yet, but I bet this is true about, I dunno, whatever. Or is that not, not bring up anything for you?

0:06:45 Bryan: Oh, Yeah, I

0:07:19 Thomas: I think octopuses can talk.

0:07:20 Bryan: I would have to spend more time thinking about it, yeah.

0:07:21 Thomas: No, I'm just kidding.

0:07:22 Bryan: I would have to spend more time thinking, uh, about it, um, often that's just how hypothesis has come out is just wondering about, about things and then testing it, but yeah, my mind hasn't quite been on those tracks of finding hypothesis, it's been on how to get this telescope to work for quite a while, so I haven't spent much time on that.

0:07:30 Thomas: Sure. Yeah. Yeah, exactly. My scientific belief is telescopes should work. There you go. All Right. Uncle Skid asks, is there any comparison between two high energy events, gamma ray bursts and fast radio bursts? Excuse about it from a conservation of energy point of view, they seem to affect different parts of the EM spectrum in in addition to the other ways the energy of the event is being dispersed, do magnetic fields play a big role in both events? All right, this comes across as pretty technical, so you may have to try to bring us along with you here.

0:07:44 Bryan: Yeah. Yeah, yeah.

0:08:14 Bryan: Well, this is actually another thing that's a bit outside my field of expertise. These are basically weird things that can happen with, uh, rare and exotic stars, um, I think at least in the case of gamma ray bursts, it's a specific type of supernova where magnetic fields align the light from it I'd have to check on that, but that's what I believe. So I think magnetic fields do play a role there. It's basically, we'd have do a whole other episode on just explaining magnetism, and a lot of this is outside my field of expertise. I'd have to look into the details here. Different parts of the electromagnetic spectrum. This means having vastly different wavelengths, which is usually an indication that these have different causes. It could be that one of them is occurring very close to us and something else. But I think these are entirely separate things.

0:08:18 Thomas: Ah, okay. Okay. Yeah, God. Hmm.

0:09:14 Bryan: I'm just not familiar at all with fast radio bursts. I'd have to look into them.

0:09:16 Thomas: Sure. He's not going to know everything. That's fair. All right. Wendy would love a rant on string theory, but that's an episode and a half. I would love to hear his favorite fact. Yeah. String theory, uh, I guess favorite factor, both. We haven't really broached that subject at all.

0:09:19 Bryan: Yeah.

0:09:33 Bryan: So string theory, to basically give you an idea where it comes from. If you go back to the article or we did on Portal, I talked about how the laws of physics are kind of like an inverted pyramid where there's less on the bottom than you think. And the goal is to try to figure out what's the smallest number of theories we can have at the bottom. So at modern physics, when you look just at physics theories, it's basically two-ish, depending on how exactly you count.

There's general relativity, which explains matter and mass. And I think they call it a grand unified theory for the three other fundamental forces, which includes quantum mechanics. And they do have these two theories that are at the bottom. And string theory is saying, okay, but I can take your two and I can make it one theory, but it involves these weird strings and a whole lot of other assumptions.

And I think, yeah, one of the other commenters here made a good point that string theory takes the small oddity. Okay. There seem to be two different theories at the base of this pyramid and says, well, I can make that one. That would be simpler, but we have to live on this 11-dimensional manifold that there's no evidence for. You, it explains some things, but it doesn't make the explanation any simpler. It's a massively more complicated one theory to explain the

0:11:08 Bryan: Observation that we seem to have two theories at the base of the pyramid rather than one. I'm not sure from Occam's Razor it actually explains things any more than just saying, yeah, the universe has these two fundamental theories at the base of it. Not sure there's anything so odd about that, why there needs to be just one theory. Maybe there are hypothetical alternate universes that only have one theory, but maybe those are all too simple and life never occurs there and the universe needs to be complex enough to allow life and that complexity is met here by having these two separate theories. So I don't know.

0:11:07 Thomas: Boy, that's interesting.

0:11:50 Bryan: I'm not really an expert on string theory, but that's kind of my rant on it is that I feel like it adds more complexity than it takes away and it doesn't serve to explain anything extra.

0:12:03 Thomas: Interesting. Yeah... More than one... I... That's... Okay. That's I'm trying to think, you know, philosophically, of my favorite things to try to think about, although it's so difficult to even conceptualize is like, what is a law of physics? You know, like what is, it's just, it's a description, but it's like, why, you know, you can get to such a baseline level where you're like, okay, but why? And I figured that it was just like taken for a given that there must be some some way to describe everything that that is only one theory just because I I didn't know a theory, you know, like I so I guess to say you would need two theories would be to say what, like there's some emergent property that you can't you one set of things with the other because it's just fundamentally a different thing.

0:12:39 Bryan: Yeah.

0:12:50 Bryan: Yeah, there are two different sets of laws. Or maybe here's another way to look at it. Like, mathematics is one case where this is kind of solved to an extent, is that there's been a lot of work of mathematicians to try to break down all the theorems of mathematics and get it ordered. So using math definitions, there's a theorem, which is something that's provably true based on other theorems or axioms. And what's an axiom? That's something that we assume to be true, but doesn't depend on anything else. Like basically axiomes are the things that are at the fundamental level of math, and you can build theorems on it. And the theorems are the thing that say all the interesting things, And the axioms are things that seem so simple and obvious that you're surprised you even have to it. The current best agreed upon formulation of math has something like nine fundamental axioms. And they're ridiculously trivial things like sets exist.

0:13:34 Thomas: Oh, wow.

0:13:58 Bryan: Exist.

0:13:54 Thomas: The part is less than the whole or something

0:14:00 Bryan: Yeah, like you can create a new set from an old set by adding something else to it or things like that. And they come up with, okay, we've got this full formulation of math and it's based on like these nine axioms that we've been able to get it down to. So for what happens in the universe, we can maybe get it done to two theories. Or maybe if If you say math has to count as its own theory, then you could add math or the nine axioms that make it up as the fundamental layer of the universe.

But I think kind of this goes into the anthropic principle, which states that life will only exist where it's possible for life to exist. And you can extend this to the universe as a whole. Life will only exists in a universe if it's possible for life to exist. And maybe life is such a complex thing that the universe needs a certain minimum level of complexity for life to evolve in it. So maybe there are other universes out there that are much simpler.

There's like one universe, this universe just has nothing. That's the universe. It's a whole bunch of nothing. This universe has only mass and gravity, but that's not enough to really create life. This one has a few different things. We've got gravity and we've got these other forces. This gives us enough complexity that we can have life and then people evolve. They look at the universe and say, why is this universe so complex? But they're only there because it's complex.

0:14:00 Thomas: Right yeah that's Interesting. I mean, I'm not sure how much time to spend on this, but you say, I would have assumed, or I would have thought that it's not necessarily a complexity issue. Like, isn't it possible that this grand unified theory could be something very simple that we're missing that would actually make it seem simpler, like make the universe seem like, oh, duh. Okay. Like that's, this explains all of this, and that wouldn't necessarily lead to a more or less complex. Actually, okay. Here's the, here's what I'm getting at that I, that I don't totally understand. I have thought that our explaining universe in the form of these theories, how many it takes us, is sort of independent of how complicated the universe is. Like the axioms are the axioms, and us putting language to those and explanations to those. And we're, it seems like we're missing something about how all that works together, and whether or not we could figure that out doesn't really affect the underlying axiom. Does that not make sense?

0:16:36 Bryan: Yeah, that's the way to look at it. And on your earlier point, Yeah, sometimes the underlying theories are simpler, but they don't necessarily have to be Like the simplicity is just a guise over complexity, like general relativity, you can break down to a single equation, but that one equation has ridiculously complicated tensor math in it. And it takes like lots of studies universal to understand what that one occasion means. And so sometimes you, you can say this all fits together nicely, nicely, but sometimes it's taking a lot of complexity and demonstrating for the satisfaction of the rest of us that that complexity is actually well ordered, and I think that's the real genius behind general relativity, is showing that all of this weird stuff is actually a well-ordered set of things that make sense together. Yeah.

0:16:45 Thomas: Right.

0:17:35 Thomas: Anti patriotism. Hatch asks, I have heard that the universe is expanding and And the rate of its expansion is growing. So, the universe is accelerating apart. Is that acceleration constant or variable? If it's constant, does that rule out an eventual big crunch scenario where the universe eventually contracts?

0:17:55 Bryan: So the acceleration is variable, the acceleration itself is accelerating, but the rate at which the acceleration is accelerating is decelerating. Does that answer your question?

0:18:09 Thomas: I didn't know that last part.

0:18:11 Bryan: Well, I said that in the deliberately most confusing way possible, but yes. So it keeps accelerating more and more. Basically, what happens is that how fast the universe accelerates depends on what type of energy dominates it, like whether it's regular regular matter, light, or dark energy. And we're kind of going through a transition period right now where it went from regular matter dominating it, which if you calculate it out says, okay, that should be the expansion is decelerating, to a phase where dark energy is dominating. And in the dark energy dominated scenario, the expansion should be accelerating. So we're going from a phase where it should be decelerating to one where it should be accelerating. So as you go through that phase, the rate of expansion is going to accelerate more and more. So the acceleration is accelerating. Now eventually you can think, well, once we're fully in the dark energy phase, we're going to basically level out at that phase, that we just get eventually constant acceleration at the dark energy phase. So, eventually, that acceleration of the acceleration will stop and we'll get to a level out phase of the expansion accelerating.

0:19:42 Thomas: That was too many acceleratings. Now I've lost. So, you got a car. And you got your foot on the gas.

0:19:44 Bryan: Yeah. Yeah. Well, physicists actually have terms for that. Yeah, there's actually physical terms. So, yeah, speed is rate of change of position, acceleration is rate of change of speed, jerk is rate of change of acceleration, then snap is rate of change of jerk, and I am not, yeah not making this up, the next is crackle and then pop, and no, I am not making this up Yes

0:19:52 Thomas: Yeah.

0:20:05 Thomas: You're making this up. What? Wait, I thought so, I- oh, I didn't know you could have a- so can you go forever on that? How many iterations? Yeah, more?

0:20:19 Bryan: Yeah, theoretically, it's just it's just taking more and more derivatives What's the rate of change of the last thing? And it goes So it was position, speed, acceleration, jerk, snap, crackle, pop. And I assume after that, it's just more, yeah, yeah. Captain Crunch.

0:20:22 Thomas: Derivatives? Yeah. So Some Captain Crunch? After That? Yeah, It's More cereals. Yeah, oh Man, I didn't think about that, yeah, the rate- because it is just- right, so if you- yeah, you just got to have enough exponents to where the derivative doesn't just- okay, you're at zero. Eventually, you run out of exponents, and you've gotten zero in your calculus.

0:20:36 Bryan: Yeah. Yeah. Well, with some functions you do, but if it's a function like the exponential function, E to the X, you never run out.

0:20:59 Thomas: That's crazy. Okay.

0:21:00 Bryan: Yeah? Does that rule out a big crunch? Yes. Yes, for what we know, the universe will just expand forever until it eventually, we get what's called a heat death, which is a misleading term because it doesn't become heated. It means it's the death of heat, that there is no more heat. Nothing interesting else happens. So no, we won't get a big crunch.

0:21:18 Thomas: Yeah. It would be weird if it just expanded, expanded, and expanded. There's nothing, nothing. And then all of a sudden, at the end, it's like, and then someone pops on the microwave, and we all heat to death. That would be funny. No, it is just there's no more heat. It's just so, yeah.

0:21:31 Bryan: Yeah, yeah, that's where the snap, crackle, and pop come in. Okay,

0:21:38 Thomas: All right, now it's time for the general contact, you know, problem child iteration of the show. All the, all the, uh, got a lot of these questions. Let's go through them. In one of my favorite sci-fi books, Look to Windward, there's a war between two type two civilizations. Okay, I don't know what that is. What's the type two civilization? Should start there. What?

0:21:58 Bryan: So this goes back to kind of a sci -fi way of classifying civilizations. I think a 0 civilization is like what we have, that we can't fully harness the energy of our planet. A type 1 civilization can harness the full energy of a planet, and a type 2 can harness the full of energy of the solar system, then type 3 is a galaxy, or something like that. I might be off by one, but read the rest of the question.

0:22:26 Thomas: Are we using all this energy for? Oh, okay, you're right. One point, one of them makes two stars explode. The stars are said to have habitable planets, so they're probably yellow dwarfs like our sun. Can you think of a way that you could theoretically make a star that's too small to naturally go nova explode if you had near unlimited control over matter and energy? Oh, interesting.

0:22:52 Bryan: So I like the response this got from another commenter, ADHD Programmer, who said, well, with unlimited control, just add a large outward velocity vector to every proton and neutron and boom, which is, yeah, basically, yeah, that's kind of the brute force scenario. So, okay, that's covered, so I've got to think of a more elegant way to do it, and I, I think it is possible. Um, so to make a star explode, you basically need to have a nuclear fusion reaction that goes, um, the ones that happen even in hypergiants, that gets into the fusing heavier elements together all the way up to iron phase. And to get to that, you need the moderately heavy elements to already exist in a great enough concentration. So yellow dwarfs, like our sun, are mostly hydrogen fusing into helium.

So if you're a ridiculously advanced civilization and you have unlimited, limited control, then okay, we'll just, we'll speed run that process. We'll take all of that hydrogen, turn into helium, then we have to go a step further, turn the helium into heavier elements like carbon and up, and then we'll, uh, take all, all of the hydrogen and then get it to right before the one phase, before it's ready to diffuse into iron, and then leave it there, let it go, keep it dense enough that it can interact with each other, and you'll get a supernova explosion. So,

0:23:12 Thomas: Yeah.

0:24:22 Thomas: How are we doing any of this? Is it just magic?

0:24:24 Bryan: Basically.

0:24:25 Thomas: Okay. There's no like plausible Yeah.

0:24:25 Bryan: Yeah, sci- -fi magic. Yeah.

0:24:28 Thomas: Like, okay.

0:24:29 Bryan: Yeah, if it were me, I'd just say, okay, um, let's just wait, let it happen naturally, or I guess if it's too small, then you just add a lot of mass to it. Okay, it's too small now, but let's add, uh, more stars to it, then it'll be massive of enough. Yeah.

0:24:34 Thomas: You need Get a big rope, take another star, get it over there, let, introduce them, and then they, they're very volatile. Okay, also GCU Problem Child asks, in the movie Age of Ultron, Ultron's plan. Altron.

0:24:48 Bryan: Yep.

0:24:58 Bryan: Of Altron, we, we this is a different movie yeah they they said Age of Altron, and we have to go with what they said, yeah.

0:25:04 Thomas: Oh, yeah. You could, look, you make me believe this. Like, be that hard to be like, no, they made another one, Age of Ultron.

0:25:13 Thomas: Ultron's plan to wipe out humanity to levitate a chunk of land into space and then drop it to create an asteroid-like impact event. Oh, I love it. You take a chunk of dirt, let's say about 5 km in diameter, and just dropped it from about 5 km up, how much damage would that do compared to an actual asteroid of equivalent size? Okay, so the question is, just how much of this destruction is our Earth's gravity pulling it in at that rate, versus it already has that insane speed relative to Earth because of whatever else it was doing out there in the galaxy?

0:25:45 Bryan: So, This kind of goes back to the Armageddon episode where he talked about this, so when asteroids come into it Earth, they usually come in at around, I think, 20 kilometers per second is a typical speed. Um, this, I did some back of the napkin math on this for five kilometers up, and this just assuming constant gravity, it will be a bit less. But my calculation was about three kilometers per second. So it's going slower than an asteroid coming from space. But yeah, a chunk of Earth five kilometers in diameter is still decently bigger than the asteroid which wiped out the dinosaurs, which I think they expected to be around like 1.6 kilometers. I'd have to look it up again. So it's about three times the diameter, which is going to be, you 27 times the mass. Yeah, even at a smaller velocity, it's going to have comparable energy. So, you Know, for my rough calculations, I'd say, yeah, that would indeed be an extinction -level event.

0:25:46 Thomas: Right, okay, yeah. Sure.

0:26:18 Thomas: That's Still pretty freaking Fast.

0:26:52 Thomas: Wow, okay, no one do that, I guess. So, Just, yeah, I mean, you think about it, three kilometers per second is still pretty fucking fast, that's, that's gonna do a lot, but

0:26:55 Bryan: Yeah. Assume that it doesn't lose any energy to air resistance, which, yeah.

0:27:05 Thomas: Oh, it Would Definitely would, yeah.

0:27:06 Bryan: It would. That's going to reduce it. I mean, it's going be bad. Maybe some people will survive in underground caves if they get enough warning, but it's not going to be good.

0:27:07 Thomas: Not Gonna be good. It, it, like, break up though, or something? Is there any, you know, like, yeah, right.

0:27:23 Bryan: Quite Probably, particularly around The edges, a lot of the edges will be blown off, it'll shrink in size, so the severity of it will be reduced. Happens to any asteroid that enters the Earth's atmosphere, or well, not just asteroids, but meteoroids, which they're the same thing but smaller, basically.

0:27:46 Thomas: Well, not to split hairs, but like an asteroid is much different than taking a chunk of the top soil of earth, right? There's going to be, yeah.

0:27:47 Bryan: If Yeah. Asteroid Is, is rockier versus a topsoil. But yeah, if you dig down enough into the Earth's crust, it's on average a mostly iron. But the way it's held together, it can be held together more loosely. But actually, there are a lot of asteroids which are described as flying rubble piles, which is they have enough gravity to be held altogether, but they don't merge together. They aren't part part of the same body, like they're just a bunch of rocks that the mutual gravity holds them together. And one of the worries about like, if an asteroid comes to us, and it is a flying rubble pile, you could say, you to push it out of the way, but you push on some of the rocks, push some ofthe rocks out ofthe way, but the rest

0:28:04 Thomas: Ah, oh, wow. Yeah. Well

0:28:41 Bryan: Of the asteroid is still coming at us. So that'sone of the biggest unsolved problems for how we would defend against an asteroid is how to handle the rubble pile asteroids.

0:28:51 Thomas: Shoot. Now I had a whole new fear unlocked. So, uh, GCU problem child also asks, uh the asteroid in Armageddon be round? Like given it's the size of a small dwarf planet.

0:29:03 Bryan: Yeah, basically, yes. As GCU Problem Shell says, the asteroid they describe, half the size of Texas, is pretty close in size to the dwarf planet Ceres, which is an asteroid in the asteroid belt, which is indeed round. It has enough gravity to, over enough time, smooth itself out. Like, you know, solid objects aren't easily deformable, but if you apply enough force over a long enough time, they will indeed deform.

0:29:32 Thomas: Sure.

0:29:33 Bryan: Now, this depends on exactly what it's made of. Some materials are easier to shape than others. So if this asteroid is made of some material that's particularly hard to deform, then maybe it wouldn't. But yeah, as we said, when looking at it, the asteroid looks like Mordor. It doesn't look like a body.

0:29:53 Thomas: Yeah, I was going to say, it won't look like mortar. We can all agree it won'T have death spikes going into the upper atmosphere of it. There's no atmosphere, but you know what I mean. Okay. Right. And one more from GCU here. This is kind of a history of physics question. I saw Oppenheimer recently. There's a bit in the movie where Oppenheim meets with President Truman to talk about nuclear proliferation. And Truman just asserts that the Russians will never develop nuclear weapons of their own. Wait, the period between the end of the war, Russia Russia testing their first nuke in 49, was the U.S. government that naive about the plausibility of keeping nuclear weapons tech to themselves? Like even if Russia didn't have the spies in the U S's nuclear program, which they did, they have their own scientists, massive resources, and it's not like the laws of physics are different here. You'd have to assume they'd figure out on their own eventually. Yeah. I don't. So I saw Oppenheimer.

I'm not, I don'T have a firm, I thought some people were of the opinion that like, yeah, no, they're gonna figure it out one way or the other. Um, I, I DON'T even think in the movie they were that naive. Now I, you know, who knows, uh, who KNOWS what presidents believed, but, uh yeah. Do you have any thoughts on this? Not exactly astrophysics

0:29:56 Bryan: Yeah. Yeah.

0:31:04 Thomas: Question. Question?

0:31:03 Bryan: Yeah, it's history of science. But I think the best response I can give is that maybe Truman believed that, but that doesn't mean the government as a whole did. And this is the reason that presidents have advisors and theoretically listen to those advisors is because he can't trust one person to know and be right about anything. So you get the expert. So yeah, maybe Truman thought that but was wrong, or he briefly thought it until the advisors talked him down. Yeah, I'd say the government as a whole, you had to know it was a my vague memories of this is that I know there was definite fear about Germany Germany coming up with nuclear weapons. I'm not sure if there was as much fear of Russia doing it, as at least in World

0:31:19 Thomas: Oh, Definitely.

0:31:53 Bryan: War...

0:31:53 Thomas: There were, it just, it depended on when in the war we were, you know, but yeah.

0:31:53 Bryan: Yeah, World World War II, the U.S. and Russia were theoretically allies, so Russia getting the nuclear bomb wasn't as immediate a threat as Germany, who they were at war with at the time, getting the nuke.

0:31:57 Thomas: Right.

0:32:08 Thomas: But this conversation takes place after the war, and I think that I Like I'm pretty sure they, even in the movie, different people used, I think this is more a political question than anything, I think different people use different views of that to accomplish different things, I think some people wanted Like, Okay, let's build up, we need to build the shit out of our nuclear arsenal because any minute other, you know, Russia and others are going to have it. And then, then other people were like, well, no, we should not. We have the bomb. We're safe. We don't need to develop a bunch of other nukes. That's just dangerous for everybody. So, you know, I think, I bet you if you were to ask scientists at the time, I'm sure they would have thought like, yeah, I mean, scientists are going to scientist. And something that I think is unambiguously true is once you know something's possible, it's much easier to figure it out. Once you know for sure

0:32:11 Bryan: Yeah, yeah, yeah. Yeah. Yeah. Yeah, definitely.

0:32:54 Thomas: This is possible, that it's only a matter of time either way, you you know?

0:32:57 Bryan: Yeah, like, I bet if the Americans hadn't figured out the nuke in, like 44, 45, the Russians would have figured it out later, but it wouldn't have been as early as they did. Because, yeah, once you know it's possible, you can focus resources on it. Because if you don't know it'S possible, You're going to split up your resources among many different things you can do. But once you know, oh, that super weapon can actually exist, we're going to put all our resources towards that one.

0:33:12 Thomas: Right.

0:33:27 Thomas: Yep. Right. Elias Armando Garcia Guevara asks, hello, any advice for starting in STEM as a second career later in life? I'll been in my late thirties, early forties when I graduate with a bachelor's in mechanical engineering. Oh, congrats.

0:33:41 Bryan: Okay. Yeah. So my personal experience is different from that. I went on the traditional path into university straight out of high school. The traditional pathway to almost no one actually does. It's, you know almost everybody goes into a career outside of what they They study in university, but I did. So I don't really have much personal experience with that. But mechanical engineering is a very good degree to have with broad application. Like, well, even just having a degree in a useful STEM field can get you jobs in other related or somewhat related fields. Like my father has a degree in mechanical engineering, but spent his entire career working in chemical engineering because he got an internship in that. He did well on the job and stayed in from there on what he learned in the job and references. So I guess from that perspective, the best advice I can give is don't limit yourself to exactly what the degree says. Use it as a springboard to use the skills you brought up, you built up in getting the degree to look at other things you can do. Yeah.

0:34:02 Thomas: Yeah.

0:34:53 Thomas: Great advice. I think about this all the time. I'm like, fucking, I want to go back to school, man. Someday I'll figure out if I can do that. I just love it so much, but who knows?

0:34:59 Bryan: Yeah. Well, if you're not in school right now, the question of whether or not to go back is a bit different, as you have to weigh in the financial costs of it, which in the U.S. are huge.

0:35:10 Thomas: Oh yeah. It would be not at all about the money. I'm not knowing. I wouldn't be going back to make more money or anything. It'd be like, okay, I have the time and maybe I can go to a cheap enough school that I don't have to, you know, worry about it that much.

0:35:12 Bryan: Yeah. Yeah. Yeah. The time cost, or the opportunity cost, as they call it. Like, you could go to school, or you could do independent study on something that doesn't require specifically going to school. Uh, yeah, it's what you want to do with your time in that case. Oh,

0:35:24 Thomas: Um, Right. Collective asks, is the universe infinite in size and how can we know one way or the other? We've talked a little bit about this, but, uh, no reason not to tackle it again. Yeah.

0:35:45 Bryan: I Yeah, I think the previous questions kind of went into it, and that, um, it's bigger than everything we can see, and we don't really know for sure if it's infinite. It might be. Now, there are some ways we can get some indications. One is by looking at the curvature of the universe, which is basically a mathematical way of expressing if you go far out, how much closer together are things than they would be on a flat surface. So just like, think the surface of the earth is what we call positively curved. So imagine you're on the North Pole and you go halfway the South Pole, ending up on the equator. If you draw a circle at that distance, that circle wraps around the equator, and then if you go to your old early oh, diameter equals, or sorry, circumference equals pi times diameter, or 2 pi times radius. Radius.

But in this circle you've drawn around the Earth, the circumference of the circle actually ends up being lower than 2 pi times the radius because of the curvature of the Earth. So when that happens, we call it positively curved. If it's exactly what we expect, we called it flat. And if we get the opposite, that the circumference is larger than 2pi times the radius, we call it negatively curved.

Now, if we were to measure the curvature of the universe, which we've done a lot of attempting, and as far as we can tell, it's pretty close to flat. It might not

0:36:18 Thomas: Hmm. Right.

0:37:23 Bryan: Be exactly flat. We might find out later it's a bit positive or a bit negative, but so far it looks pretty flat. Now, if we did find out the universe looks positively curved, that might indicate the universe is finite in size and wraps around at a certain size. It doesn't necessarily, when you get to higher dimensions and stuff, it's not a guarantee that the universe does wrap around. But that's basically the only way we could even maybe know it would not be infinite. Or, well, actually not the only way. If you go back to what we talked about before, if we saw that the universe was repeating, like we saw the same stuff on one side as the other, um, if we found that, we would know, okay, it's not repeating, we're seeing the other side of it here, so it's this big. Oh,

0:38:03 Thomas: Yeah. Yeah.

0:38:13 Thomas: It about if we came up with a model that but was so seemingly accurate and had so much good predictive power that, and then the model inferred like one way or the other. I mean, that would be a way we could probably know with some certainty.

0:38:24 Bryan: Yeah. Oh, Yes. That that That's a very good point. Like, let's say we were trying to solve our, uh, theory of everything, and we find, oh, this fits all of the things perfect. And it also predicts these other phenomena which we could detect. We go out, we detect, oh, those are right. Okay, so this theory is probably pretty good. And we look at the theory more. Oh, it says the universe should be exactly this big. Well, this theory ist so good that, you know, okay, okay. Maybe it is.

0:38:50 Thomas: Yeah. You couldn't couldn't be certain, but it would be, you know, certain as some things in science. Cool. All right. Unlikable Internet Goblin asks, I like you.

0:38:58 Bryan: Yeah. Oh, I like you.

0:39:04 Thomas: Yeah.

0:39:04 Bryan: Don't worry.

0:39:05 Thomas: The wife and I were watching a quote unquote documentary the other night on Max about photons being generated in the center of the sun and then bouncing around for a long time before finally escaping. They had interviews with actual astrophysicists, but the narrator sounded like he was doing a voiceover for a 90s reality program about an awful disaster. Anyway, one astrophysisist, can't remember the name, said it can take a photon around 100,000 years to escape the sun. But right after that, another astrophysics was quoted saying something like hundreds of thousands to a million years. And after that the narration seemed to cling to a million years, but that's a full order of magnitude difference. Seems a lot to be off by, so my question is, what's the right number, and is there really disagreement among astrophysicists on this topic, or did the show just do a horrible job of expressing the data?

0:39:49 Bryan: So, first of all, I'll give credit to another commenters here. Chris Conley, who said, it like expressing a cumulative probability as a single number, which is basically saying that for any one photon, there's a range of amounts of time it can take to escape the sun. It might take 100 ,000 years. It Might take a million. It could take longer. It Could go straight out. It just happens to come straight out we've just, it's just just on average.

0:40:14 Thomas: Boy, imagine that Photon, I packed for a million year journey and then uh, right, wow, 10 minutes, holy crap. Yeah.

0:40:16 Bryan: Yeah. We're out in like 30 seconds. Wow.

0:40:23 Thomas: What do I do with the rest of my life? Okay, yeah.

0:40:23 Bryan: Okay, that was quick. Yeah. So what's going on here is this is what we call a random walk. If you take like a computer programming course or something, or a lot of these, you'll set these up. It's basically just imagine you have a photon, like let's say it's just one dimensional. You have a proton at the the center and any given amount of time it can go right or it can go left.

And it's 50 -50 each way and you just wait and then when it gets 100 meters away it's out. You count that as done. So for each photon, you let it do its random walk. Some will go right every single time and get out as soon as possible. Some won't go right then left then right then right then take forever to get out. You know, every one of them, eventually, you give it enough time, it's going to get out.

But it's gonna be a lot of variation in how long they take to get up. And so, physically, what's happening in the sun is that there's a lot of atoms and, you know, free electrons and stuff in the, in the sun. Actually, not so many atoms. It's probably, um, uh, cores of atoms. But there's lot of stuff it can hit. So, it goes, get, uh—gets absorbed by something gets re -emitted, bounces off, gets close to something, gets deflected.

So it's taking an essentially random walk and, you know, some will get out relatively quickly, others will take a while. And so you've got this broad probability distribution and you can assign numbers to it, like what's the mean time it takes to get out, but there will be an appreciable number, which which take much longer than that. So maybe what's going on is 100 ,000 years is the mean.

But if you look into like the standard deviations or you set your 95 percentile there, that, okay, 95 % of them will be out by a million years. And on average, it's about 100 ,00 years. But there are going to be like 5 % still trapped in after a million years.

0:42:29 Thomas: Boy, those pour one out for them. Yeah, pour out a glass of photons for that. Yeah, it sounds like the documentary didn't do a great job, I guess, is the answer.

0:42:38 Bryan: Well, one of the things about astrophysics is in order of magnitude in astrophysics terms often isn't a lot to be off by.

0:42:46 Thomas: Yeah, that's a good point.

0:42:47 Bryan: The universe is so ridiculously large that often if you're right within the order of magnitude, that's pretty good.

0:42:48 Thomas: Yeah. What's an order of magnitude between friends? Yeah, close enough. All right, final question. Holy crap, Brian, this is amazing. We're perfect timing getting through all of them. We'll have to do this again. Matthew Williams asks, something I've never heard a good explanation of is generations of stars. I hear our star is third generation. What kind of, I mean, it just means it's great -grandparents immigrated to this solar system, I think is what it means. What kindof elements are in a second or nth generation star versus, I assume, only hydrogen in the first? What would be a good assumption for requirements for life? Which generation of stars would work? Can we tell what generation a star is from looking at it with telescopes?

0:43:34 Bryan: So as before, star isn't my thing. So this is kind of a broad strokes explanation. But the generation of stars are determined by how much metal they have. And when you hear an astrophysicist talk about metal, they mean any type of element other than hydrogen or helium, not what other physicists say for metal.

When you have these heavier elements, these affect how the star ages, and they tend to slow things down that the star will take longer to burn through the different phases of its light. So back in the early universe, where you just have, you coming into existence outside of stars in a process we call Big Bang Nucleosynthesis, how they initially get up. You get mostly hydrogen and helium, a very small amount of, I think, lithium and beryllium and basically nothing of anything else.

And so all the stars are going to be almost pure hydrogen helium. And this means they'll burn through that very quickly, go through the life cycle, explode. And when they go through that, they create lots of heavier elements, the metals as we call them. And then those metals are then floating around in the universe and eventually those gas clouds will clump up, fall together, and create new stars. So that's your second generation of stars.

Ours then the third generation is after this happens, another cycle of time, so the like kind of elements basically is more metals with each generation and more heavier metals, as you have every time this happens, you

0:45:21 Bryan: Get more and more

0:45:21 Thomas: That's That's so metal. We going to get a star that's just a ball of pure fucking titanium? Just not even.

0:45:22 Bryan: Yeah. Yeah. You just get more and more of them out every generation and yeah, it's going to be a be a mix and even the one stars will have trace amounts of lithium beryllium, which we do call metals, though they're the lightest ones, but not really enough to make a difference. But by the next couple of generations, it slows down the burning quite a bit, but you do see overall differences in the colors of the stars. And so you can, you know, as we talked about before, looking at things like emission lines from stars, you can see what type of burning it's doing, what elements, what metals are in the star's atmosphere, or actually not just emission lines, but absorption lines, which is the opposite of emissions, just like an electron can fall down a level and emit a photon, it can absorb a photon and go up a level. So you see these gaps in the spectrum that we call absorption lines. So we can look at those, figure out what metals are in a star, and then that corresponds to what generations they are.

0:46:37 Bryan: What would be a good assumption for the requirements for life. Think I Generation 1 wouldn't fit well just because they're so short -lived and life seems to need a long time to evolve. But we've got a very small sample size on that. Maybe other places in the universe life can evolve faster, but it seemed to take a lot of time here on Earth to get life. So I'd say you'd probably need later generations of stars just so the star doesn't explode or burn out before life can form.

0:46:46 Thomas: All right.

0:47:10 Thomas: Wow. What neatly tidy there. I can't believe we had exactly the number of questions that made two perfect length episodes. Dr. Brian Gillis, thank you so much for taking the time. That was a lot of fun. Let's definitely see about out doing this again sometime in the future as your schedule allows and usual plugs, your YouTube channel, anything you want to throw out there where people can find you all.

0:47:32 Bryan: You can find me on YouTube. I've been posting videos playing through some games with good physics content like Portal or Outer Wilds and commenting as I go. I just finished my playthrough of one of the Portal fan games, Portal Reloaded, and am finishing up Outer Wilds now. My schedule changes I might have to taper off on the channel, but I hope to keep it active for a while yet with whatever comes to me. So look me up on YouTube. You can either look my name, Brian Gillis, b-r-y-a-n-g-i-l-l-i-s, or search for Astrophysicist Plays for my videos, and hope to see some of you there.

0:48:11 Thomas: Righty, thanks so much everybody. Thank you, Brian, and we'll see you all again very soon.

0:48:15 Bryan: Thank you. Bye.