Listener Questions 31: Photons, aliens, and baseball

00:00:08
Speaker 1: Hey, Daniel, I have a question. You have to be really good at math to be a physicist? Well, you know, it depends a bit on what whether you want to be a good physicist or a bad physicist. Actually, I think that the most evil physicists are probably the ones that are best at math. Do you say that because you're not good at math? I say that because I'm not an evil physicist. That's what all evil physicists say. That's my answer to that question. But to answer your other question, I think it depends a little bit on the kind of math you have to do. What do you mean, like complex or simple? Well, you know, for example, I have no trouble doing calculations and boosts and rotations and special relativity, but I mess up time zones at least once a week. Yeah, those time zones can be super complicated. You have to like add numbers and subtract numbers. That's crazy. Sometimes you have to subtract different numbers based on where you live and where I live. It's crazy, man. Yeah, I know. There's there's like twenty four times. That's a lot for one simple brain to handle. Too much for me. Does not compute po A. We're late for our recording. Hi am or handmte cartoonist and the co author of Frequently Asked Questions about the Universe. Hi. I'm Daniel. I'm a particle physicist and a professor at u C Irvine. And the thing that's preventing me from having a far flung evil empire is the time zones. Oh man, you're like lex Luthor with a special weakness. Like, all we have to do is what schedule and meeting with you, and you'll be defeating exactly. I'll show up at the wrong time and get frustrated and my plans would just fall apart and SWAT team will be waiting for you to arrestue. But you know, it's more complicated than you make it sound, because it's not just that they're twenty four time zones around the globe and that my team is actually spread out over several of them. But the time zones shift independently. There's two weeks of the year when Europe doesn't have daylight Saving Time and we do, and then there's some states in the US that do and don't. It's a nightmare. Well, they have this new thing called computers, Daniel, that will do all of these calculations for you. I don't know if you've are up on this technology, but all you have to do is some type in your local times on the computer and will tell you what time it is in other parts of the planet. That's a good idea. We should use computers to help with physics. I don't think anybody ever thought of that before. I'm gonna get right on that. You don't even need a I or anything. You just need I. But anyways, welcome to our podcast, Daniel and Jorge Explain the Universe, a production of I Heart Radio in which we tried to translate things much more complicated than the local time in Geneva. We want to understand the very nature of the universe itself. If you dig down into the firmament of human knowledge, can we penetrate even below that, understand the actual bedrock foundation of the universe. Can we take it all apart and understand the very basic pieces of reality and translate those into our minds so we can play with them, contemplate them, and understand why the universe is the way that it is not some other way. We ask all those big and hard and difficult questions on the podcast, and sometimes we even answer a few of them. Yeah, because life seems pretty normal, pretty sensical on an everyday basis. But as you drill down into the universe, and you already look out into the cosmos, things get a little bit complicated. Even time itself is more complicated than most people think. It's relative, and it's different depending on where you are in the universe, not just here on Earth. And the way the universe works at the smallest skills and in the vicinity of black holes is very different from the way the universe seems to work in our normal, everyday lives. So we're forced to try to translate this unknown, unfamiliar universe into rules that we do find familiar, and along the way, we use mathematics as a bridge to guide us into the depths of the unknown truth. Because the way we familiarize ourselves with the universe is by asking questions, wondering how it all works, how can it all make sense? And what kind of math do I need to know to predict what's going to happen? And we ask questions about the universe because we are curious people, and we know that you ask questions about the universe because you are all curious people, and we want to encourage that. We love to hear your questions. We want you not just to listen to us blah blah blah about the nature of the universe, but to ask your own questions to make sure the ideas we are talking about are really clicking together in your mind, that you can do more than just listen along and not but that you can take these ideas and apply them to new situations. And if that doesn't quite work, we want you to reach out and send us an email to Questions at Daniel and Jorge dot com so we can help straighten it out for you. Yeah, because everybody has questions, and sometimes the questions you might have about the universe are the same questions that leading edge physicists have about what's going on that's right, Like what time is it right now in Geneva? Yeah, I guess technically you're a leading edge physicist and you don't know what time it is. So it's cutting edge research to look at your watch, Daniel. It's the very forefront of human knowledge. Like am I the only one here because I'm late for this meeting? Or am I early for this meeting? Or is this even the right month? For this meeting. Well, maybe you should upgrade from using you know, sand clocks or sun dials to know what time it is. I know you'd like to be like O. G physicists, but you know that those computers nowadays are pretty good. Yeah, they are pretty good. But I think I need even more basic health than that. I've shown them for flights at the wrong day, I've shown for flights at the wrong airport. I've landed the wrong airport. You know, sometimes I think there's even a limit to what computers can do to help somebody. And then you say I'm the one that's always late. It sounds like you know, the one with bigger problem here. Well, I'm just glad you're here at the right time, at the same time as me. It's one of the deepest questions in the universe, this Daniel actually know what he's doing and where he's supposed to be. We do get questions from listeners, and we love to answer them here on the podcast because we get some pretty amazing questions. Our listeners are pretty awesome, pretty curious, and also they sort of know their stuff right, they really do. I got a lot of really sophisticated and well thought out questions. So, if you're out there and you've been listening to the podcast for several years and you have burning questions about the universe, don't be shy. Please write to us. We really do want to hear from you, and you really will hear back from us right to questions at Daniel and Jorge dot com. So today we have three awesome questions from listeners and they range from how do you see photons? What color photons are? And also what are the ingredients for life or the not ingredients for not life? I guess it's kind of a complex question. It's also involving baseball. So to the on the podcast, we'll be tackling listener questions thirty one, which somehow is coming after listener questions two. Who says we have to do listener questions in order anyway? Man, you say we try, we'll somehow back in time Daniel. Yeah, that's a much simpler explanation than Daniel got confused and scheduled these out of order. We've gone back in time to answer ancient listener questions. Did you schedule in the wrong time zone or something? Or are weally like thirty two time zones back? Any number bigger than thirty is basically infinity. You know, I like dealing with very small things and very small numbers of things. There's a reason we don't have thirty quarks in the standard model. You know, we just lose track. Boy, we pay you to be a physicist. I'm starting to think maybe we should see some bona fides or have you do do a test or something. Maybe because you did rely on the computer to organize these podcasts, I thought you did. Don't you have an Excel spreadsheet with the numbers and stuff. Are you saying there's a user error here? It is possible to make mistakes in Excel? That's true. But this is the thirty guests technically thirty second time we answer listener questions, even though this is the thirty first episode, right, this is the second time we've said it's the thirty second time, and we love answering listener questions. Let's jump right into it. Today's first question comes from Sam, who is a question about how we see photons. Hello Daniel and hard Day, and thank you for your wonderful podcast and especially thank you for being so accessible to answer listener questions. I have a follow up question to a recent listeners question. In that podcast, there was discussion about photons and their speed around black holes. The discussion made references to things like two observers of a photons movements and seeing photons moving away from us. I understand that we infer the direction, velocity, and composition of objects based on the information conveyed by the stream of photons that I received, which I or my instruments used to constructed details of that object. But I was confused about the discussion an idea of two observers seeing the same photon or seeing a photon moving away, as I didn't know how that information could be sent by a photon and to two observers at the same time. Thanks again for helping me and others better understand this weird universe. Alright, awesome question, Thank you, Sam. And it's I guess it's a follow up question to a question we had in a in another episode. But is it from an episode we did in the future or in the past. It's an episode we haven't yet done in the past, and so Sam is psychic. Maybe Sam is just many times zones ahead of us somehow in Geneva is seeing Denmark or something They're pretty smart. In Denmark, they are pretty smart. You can see the future. But I guess this question is has to do with this thought experiment we talked about in an episode before about how do you tell if if photons changed their path around a black hole? Yeah, we were talking about photons having different speeds than just the speed of light, and if you were far away from a black hole, for example, you could see photons get bent around a black hole. You could see them crawl out of the gravitational well, very very slowly. And we had a whole conversation about how the speed of light for photons is really just the speed of light locally, and that far away photons might have all sorts of weird different speeds. It's a really complicated topic in general relativity, right. I think the experiment was that you know, if you have you have a black hole out there in space, and there are two photons kind of flying near it, you know, one near it or one less near it, they're going to do different things. And I think Sam's question is, like, how do we know what those photons are doing if they're moving away from us or they're moving perpendicular to us, Like, how do you see a photon moving if it's not you know, hitting your eyeball. Yeah. So it's a really great question because Sam is thinking, like, how do you actually do this experiment? Is this something physicists or just thinking about, or is this something you could actually measure in the universe, which is a really important thing to do, because physics is more than just like thinking about things. It's also about going out there in the universe and making measurements. Many times we thought the universe worked one way and then went out there to confirm it and discovered oops, nope, the universe works a different way. So definitely doing experiments and making measurements a vital part of learning about the universe. Yeah, so I guess maybe let's break it down Daniel, Like, you have a photon out there flying through space, how do you actually see it. If you can't see it, your mental picture of a photon is probably misleading. You're imagining like some pulse of light that flows through the universe. Maybe it flies past you, and you might even be thinking about it, like glowing that you could see a photon fly by you, because in the end, it's light, right, you can see light. The truth is that you can only see photons that actually hit your eyeballs. Like if you're in a dark room and a photon flies right in front of your nose but doesn't hit your eyeball, you can't see it. It's invisible to you. You would never know that it's there. I mean, it's not like a laser beam in a Star Wars movie, right, like a laser gun shot, right, you won't see a stream of light flying pass here, exactly like in those spy movies when they have to do it dance through a room full of laser beams and not interrupt any of them. The reason you see those laser beams is because they're reflecting off dust in the air, or if they're really intense, maybe they're even ionizing the air so the air glows. But in a vacuum, if the photon is moving unobstructed in front of you, you wouldn't see it would just pass right in front of you and be totally invisible. Right. And also in the case of the laser that you can see, it's like it's shooting a whole bunch of photons and some of them are hitting the dust particles or the smoke particles in the air and then bouncing into your eyeballs, but the other ones are just going right through right exactly. And in the more realistic spy movies, the lasers are invisible and then throw a handful of sawdust into the air to make the lasers visible again. So the point is that you can't actually see photons unless they hit your eyeball or some detector. So he's absolutely right that a photon passing by a black hole and getting bent and shot off in another direction, you couldn't literally see that with your eyeballs right in a vacuum, although they don't. We talk about once some special materials or some special situations where like a photon makes like a wake or something. We did talk about the really amazing experiments that show that the human eyeball can see a single photon, and they do this by splitting a photon in two. There are special materials that will take a photon and like split it into two of lower energy, and so then you can see one while the other one is like undisturbed. But that's not technically the same thing. So a single photon traveling out there in the vacuum, you can't actually see it go pass unless it hits your eyeball exactly, or unless you have a friend whose eyeball it hits and then they tell you about it. So then you couldn't see a photon traveling away from you either, right, yeah, exactly. You shoot a laser beam out into the universe, you're not going to see that beam unless it hits something and bounces back. Right. If it hits dust or smoke in front of you, you'll see where it is. Like at night, if you shine a flashlight up at the sky, you can see the beam a little bit if it's reflecting off of dust, but mostly it's invisible. The aliens on Alpha centauri that receive your photons, they can see it eventually, but you can't see the photons unless they've hit something and come back to you. Right. So, then in these thought experiments where you shoot in a photon at a black hole, in theory, the photon will slow down right as it approaches the black hole and move lower than the speed of light to you, but you won't actually be able to see it doing that. Right, So, to be very precise and specific, if you're just a single observer and you're shooting that photon towards black hole. Then Sam is exactly right, you won't see it. But this is a thought experiment, and we do this in physics all the time. We try to imagine what might happen in various scenarios. In those thought experiments were often skipping an implied step. If we were to actually do that experiment, it would look different. We would set up detectors everywhere, or we would have huge teams of observers in lots of different places so they could see stuff. And that's kind of boring in a lot of work, so we don't talk about that stuff when we set up the thought experiment. But Sam's exactly right that in order to actually detect those photons, to do that experiment, you would have to have more than just the one observer. You have to have whole teams of observers and careful rules about how they synchronize and communicate that information. Yeah, you have to figure out what time zones are in I mean that would just be impossible for physicists. You just sit there in the zoom waiting right all by yourself for somebody to send you the details, and we're never going to get this paper app right. I think what you're saying is that in order to see what happens to a photon that flies near a black hole, you would have to maybe put a detector near the black hole or something right, and measure how long it takes for the photon to get to that detector. Yeah, exactly, And this is true. And lots of thought experiments we do about special relativity, lots of examples of people going near the speed of light and measuring their time and looking at each other's times. You often have to have like whole teams of observers to actually conduct those experiments in real life. So we've thought about how that might work, and we've proven ourselves that technically it's possible to make these observations if you have the right team. And we don't usually talk about that part in the thought experiment because it's like the boring details and you would actually have to organize to make things work, right. I think maybe what Sam is getting at is that in the thought experiment, you talk about what happens to one photon as it goes near a black hole, it would slow down, But maybe in a real life experiment it wouldn't just be one photon like you shoot, maybe two photons at the same time, and one of them you would measure halfway through and the other one you would measure in another point. Do you know what I mean? Like you, you would need more than one photon. You can't just know what's going to happen or what is happening to one photon. Yeah, sometimes you can measure what happens to just one photon, although a lot of these experiments you want to know what would happen in various circumstances. So you're right, you would need multiple photons, and anyway you'd want to replicate your experiments and make multiple measurements. So practically speaking, that's exactly right. You'd want a stream of photons. So sometimes you want to separate them so you know which photon is which. Like an experiment where we're figuring out if the human eye can see a single photon, it's very important to know when one photon arrives at the eye, so you can know if it arrived and if the person saw a real photon were just made of a flash. So sometimes you want them to be well separated, right, So I guess that's the answer to the question, then, is that you can't see a photon moving away from you, but you could set up a detector ahead of you to catch that photon right, and then that way you would know what happened to that photon. And you can imagine filling the universe with detectors or with assistance, you know, to take note of things and later seem chronize them against your clocks. And so if you add that sort of implicitly to all the thought experiments, you can think more concretely about how you would actually do these things right. But unfortunately that's boring and a lot of work, which apparently physicists are not willing to do because then you have to get out of your couch. I guess, well, you have to organize it, and everybody shows up at the wrong time and so like yeah, and then so it's practically impossible. At least one physicist answered, you should try harder working on Do you see what they say? Idea that means the work is on you, Sam. All right, well, let's get to some of these other questions about the ingredients of life and maybe other planets, and also about the red shifting of photons. But first let's take a quick break. All right, we are answering there there no questions here today, and we have some awesome questions here from people about the ingredients of life and also the color of photons. Our next question is from Christian. Hi, there, Daniel, and Jorge. I just wanted to start off by saying, I love your podcast. I've been watching baseball lately and that's inspired my question. So in baseball, we see a lot of teams do what's called recreation in the aggregate. So they maybe lose a good player or a great player, and they try to recreate that player's effect with multiple good players. So my question is this, you're the GM of the universe. For whatever reason, we lose the crucial elements of life, water, carbon, oxygen, etcetera. Maybe they're traded to the Mets, whatever, How would you, as GM of the universe, recreate these crucial elements in the aggregate? Are these elements so unique that no other elements or combination of elements could recreate their effect? What qualities in particular make these elements so conducive to life and why might they be unique? Thanks again for taking the time to review my question and go twins. Awesome question from Christian, Although he made a crucial mistake in that question? What's that he assumed we followed sports. We can't answer your question, Christian, because we have no idea what you're talking about. Sorry, yeah, next question. No, I'm just kidding a. Let's see the movie Moneyball, So I think I'm sort of qualified answer this question. That's right, Jorge did his homework, that's right. Yeah, and uh, in this case, the GM is Brad Pitt? Right exactly? Is Brad Pitt can also play you in the movie about your life? Yeah? I should play Brad Pitt in his movie, right, that's definitely happening. Yeah, So this is an interesting question. It's almost like fantasy football mixed with physics. Or would you say it's fantasy physics. It's more like fantasy chemistry. Yeah, but it's really interesting question about like how life might operate without the basic building blocks that we use. And it's not just a fantasy, you know, biochemists have been thinking about this for a while. Is the recipe of life that we have here on Earth? The only possible recipe are we being like narrow minded when we look for biosignatures on other planets that are similar to the ones on our planets. Shouldn't we be thinking about other ways life might evolve so that we can anticipate it and look for it more effectively in other places. I think it's a really cool thing to think about. Yeah, and so I guess specifically, his question is like, if you're the general manager of the universe, I guess, or Earth, and you're trying to make life, and you have these ingredients water, carbon, and oxygen, but somebody took away one of your ingredients or they got traded to I don't know, another universe or another planet. Could you find a way to replace these elements to still make life? Yeah, you know, I know that baseball fanatics are pretty fanatic, but he's basically putting the GM at the god level of the universe here, Yeah, godly manager. I guess baseball is Christians religion. But it's a really interesting question whether you could make life with other fundamental bits of biochemistry. And Christians specifically asked about carbon and water and oxygen, and he's right, those are essential bits in our kind of life, and so it's fun to think about whether you could build life without them, right, And I guess specifically, like, you know, we should go through each one like if you took out carbon, could you still find something to replace it or a set of other molecules or atoms to replace it to make life? Yeah, And so to answer that, you have to think about like, well, why do we use carbon? Why is life carbon based? What is the utility of carbon? If you're going to replace it, what do you kind of thing you're gonna look for? And carbon is pretty ubiquitous in life. I mean, what we call organic molecules are the ones that have carbon in them, right, And there's a reason for that because carbon is very flexible. The way that it's electrons or organized means that it can build all sorts of really interesting bonds. It's like that really useful lego brick that you're can attach other stuff too. And so you can make all sorts of really interesting molecules and complicated molecules that can swap around a lot. And so it allows for us to build really complex things like DNA that can store a lot of information asian, and it allows us to create really complicated metabolisms right to move energy around and create the processes that we need for life. So it's really at the foundation of all the biochemistry of life, as we know it interesting, right, Is it true that all life as we know it uses carbon? Like, do we know of any life that doesn't use carbon? We do not, absolutely not. We've never seen any life on Earth that doesn't use carbon. And you're saying it's because carbon has something unique about it. What is it that's unique about it? Like it has its electrons or the right number of electron orbitals, or the orbitals are a special precision. What is it about carbon? Yeah, So the chemical properties of any element are determined by like how many electrons it has and how many empty slots it has in its outermost ring, and carbon has just the right number that it makes it easy to like stick them together, to make these bonds in a useful way, and also to stick other things onto it. So you can stick like iron and magnesium and zinc and nitrogen onto these like chains of carbons. Carbon is useful because you can stick a couple of carbons together and still have room for another one and another one, So it can make these very long chains, and then you can have like other elements stuck onto the side. It's not limited in that way. Other elements like xeno and for example, all their orbitals are just full, so they don't like to interact with anything. And yet other elements you can stick them together in a couple of ways, but they're sort of limited because the number of the electrons they have free in their outer orbital So carbon is just like a very versatile element, right, it's versatile, But is there something unique about it that lets you make complex molecules that can make complex molecules out of something else or just not as well you're saying, So it is possible. Actually, if you look through the periodic table, there are other elements that have similar behaviors. Silicon is the most famous example. You can also build really long chains of itself, so you can get big, complex molecules, molecules that can carry a lot of biological information. And so it's been famously proposed that life elsewhere in the universe might be made out of silicon. In out of carbon. It's like an alternative, you know, it's like do blow bricks instead of lego bricks the knockoff. But I guess what's the difference between carbon and silicon. Do they have the same number of electrons? Do they have different you know, orbitals or atomic weight? Well, carbon is much further down on the periodic table, right, it's element number six, where silicon is fourteen. And so you might think, oh, well, that makes carbon much more common in the universe and therefore much more just likely to be useful for life. And it's true the carbon is much more common in the universe because remember where these elements come from. They come from fusion at the hearts of stars. You start with just hydrogen from the Big Bang, you stick it together, you get helium. In the hearts of really really hot stars, you can make carbon, and you build from there to make the heavier elements. So in the broader universe, carbon is much more common. There's like ten times as much carbon in the universe as there is silicon. But actually here on Earth, silicon is nine hundred times more common in the Earth's crust then car been, so we're actually sort of drowning in silicon here on Earth. But of course our life is made out of carbon. So that sort of suggests that like, carbon is much more useful, it's much easier way to start life than silicon is. Even though silicon is much more common here on Earth, you're saying silicon has a higher etomic weight like it's heavier, it has more protons and neutrons and the nucleus, and does it also have more electrons and in its orbit, Yeah, the neutral atom will have the same number of protons and electrons. So carbon has six protons and silicon has fourteen protons, which means it also has fourteen electrons. But when't having more electrons give you more ways to like interact or form bonds with other atoms. It's not just the number of electrons in total, right, It depends on the number of electrons, mostly in the outer layer, because those are the ones that do the interacting. When you click elements together, you do it by having their outer shells interact. Electrons don't really go deeper into the lower shells. That really just has to do with how many you have free in the outer shells that like, you click these things together like lego bricks, right, And silicon can't form bonds with other important atoms, right, that's one of its problems. Yeah, So carbon is really cool because it can easily make bonds with like phosphorus and sulfur and metals, And while silicon can make long chains of itself, it's not as good at connecting with these other kinds of things, and so like oxygen and nitrogen phosphorus, it's not so easy to build like biochemical molecules with all these other little bits in it out of silicon than carbon. So from that perspective, carbon is a better choice for making a diversity of chemical combinations. I see, I think you're saying that it's it's still possible to make life with silicon, but maybe because it's not as versatile, you couldn't maybe do as maybe neat tricks with the with your molecules as you could with carbon, which maybe it would make it harder to kind of evolve life. I imagine it might make it harder. There's certainly fewer things you can do with silicon than carbon. Though, actually being prevented from like latching onto all these weird other things can also protect life. Right For example, the basic building blocks of your life can't grab onto heavy metals magnesium and zinc, then you're sort of shielded from some of those impurities because they don't engage with your biochemistry. So like silicon based life might be more protected from heavy metals, for example, whereas we find like mercury and lead poisonous in our biochemistry. So there's sort of a pro andacon there. And as you said, there's much more silicon here on Earth than carbon, and yet life chose carbon as its building ball. Yeah, exactly, And so even though there's more carbon in the universe here on Earth, we don't have like an average scoop of the universe stuff. Right, Hydrogen is the most common thing in the universe by far, but we don't have very much hydrogen here on Earth because it was mostly gobbled up by the Sun and by Jupiter. So the process that formed the Earth didn't get like an equal sampling of everything. And especially here on the crust, there's a lot more silicon. We think that the carbon based molecules were more volatile and they sort of like boiled away early on. And so you're right, even though we have more silicon than carbon, we ended up making life out of carbon. And that's just you know, one example. We don't know if that's typical, if it's common, if everywhere life will start from carbon, it might be unusual. It might been like a single flash in the pan. So it's carbon super unique to make life, or can physicists and chemists imagine using another atom to make life like I know, silicon, Maybe it's not a great candidate, but are there others? There are not a lot of other great candidates in terms of replacements for carbon. It's basically silicon or nothing. Oh wow, So if there is life out there in the universe, it's probably carbon too, right, probably carbon or silicon or weirder than anything we have imagined so far, which could be very unlikely or very very common. What do you mean, we're like it uses um, I don't know that titanium. Well, we're starting from some assumptions that the biochemical processes and information storage that's part of our life will be necessary for other kinds of life. And maybe that's not true, and so maybe there's a completely different way to organize self sustaining information. You know, loops of plasma currents inside of stars that can just be made out of hydrogen, for example, where the complexity comes from, you know, the structure of the plasma instead of the structure of the atoms that you're making out of heavier elements. We don't know what we haven't yet imagined about the ways that life can be, right, right, I wonder if like all life and the universe being made out of carbon means that we're more likely to be eaten by aliens. We're more likely to be edible to aliens. Yeah, absolutely, that's what I mean. We know, I mean, we're all, you know, tasty to each other. Perhaps, all right, well, let's tackle some of the other ingredients of life. What if we had all of the ingredients of life except another one of these crucial ones, water, Like, what would happen if we didn't have water. It's a great question, and maybe not a necessary one because remember that like water is everywhere in the universe. It's not like water is that hard to find. I know, on space operas they are always talking about finding water and selling water. But you know, we have like whole planets of water out there, Neptune and Uranus. They're called ice giants for a reason. There really is a lot of water out there in the universe. But anyway, it's fun to think about where life might start if there isn't much water around. You know, for example, there are moons of Jupiter and Saturn that have oceans that could be made out of other kinds of liquids ammonia for example, or methane, And so it's fun to think about whether or not you could have life that uses other solvents. Right. The role of water in life basically is to dissolve stuff so that things can slosh around in exchange. It's hard to have life if everything is like a solid crystal, because then they can't like exchange information and transfer energy. You need some flow, some movement so that energy and information can sort of move around and make things happen. It's like you need it as a medium, right, not just for life to develop in and for like books to move around in, but also like inside of our bodies, you need water so that you can circulate stuff, right, and ions can move from one place to the other. Yeah, you need these basic processes to happen, and so you need some kind of flow. Just like if you have a party but nobody's talking to each other, then nothing's really going on. And so to get the party started, you need some way for these bits and pieces to interact, and the best way we know is to dissolve them all in water, and then they can just sort of slash around. When they bump into each other, good stuff happens. And so people have thought about whether this is possible in other kinds of chemicals, and one fun alternative is ammonia. Ammonia is also fairly common in the universe, and like water, it's liquid over a large temperature range and can also dissolve a wide variety of compounds. Wait, so do all life on Earth as we know it use water as its basis? Do we know? But any other life that doesn't use water. We don't know of any life that doesn't use water. It's all water based, and you know, the basic cell has water inside of it. Life basically is a bag of water with other stuff dissolved into it. But how don't they found bacteria and like, you know, sulfur pools and you know, at the bottom of volcanoes and things like that, they have found bacteria basically every were but they are all little bags of water. Okay, So then ammonia is interesting because it's also a liquid. And what's the chemical formula for ammonia. Ammonia is n H three, so it's nitrogen and three hydrogens. And you know, there's plenty of hydrogen out there in the universe, and nitrogen is also not that rare, although it's not as common as oxygen. But there's plenty of ammonia out there in the universe. Okay, So then out of all the liquids out there that could form the basis of life, why is ammonia better or a candidate than everything else, but maybe not as good as water. Well, it's a good candidate because it has some of the same properties as water, meaning that it's liquid in a large temperature range. For life to happen in ammonia, you need ammonia to be liquid. To be liquid, so for this to be likely, you wanted to not have to have very special circumstances, and so, like water has a hundred celsius degrees in which it's liquid, ammonia also has a pretty broad range. It's liquid from negative seventy eight to negative thirty three C. There are other liquids that are liquid over a wide range. What makes ammonia special, Well, ammonia can dissolve a bunch of stuff. Also, ammonia has a large heat of vaporization. That means if you have like a lake of the stuff, it's harder for it to just like evaporate into the atmosphere. And we think that probably life formed in like lakes and oceans, maybe brackish water where like waves were lapping up and mixing stuff around. So you need sort of like stable pools of this liquid for life to form. And ammonia, like water, has this large heat of vaporization takes a lot of energy to evaporate it into the atmosphere. Interesting, why is that? Why does water an ammonia have this property. So it's getting deep into chemistry territory, which is not my expertise, but I think it has to do with the intermolecular forces. Basically, how hard is it to pull these things apart. Each of these atoms are pretty stable, but they're also a little bit sticky. When they get near each other, they like to clump together. And so this just depends on how much energy it takes to pull the individual molecules apart to change it from a lick wid into a gas, and that depends on the details of the chemical structure. Yeah, I guess if you had like a large lake of alcohol, it would just evaporate pretty quickly, exactly. So for different chemicals, either you need a lot of energy to evaporate them or not very much. And so for ammonia you have a fairly large heated vaporization, though not as big as for water. So water sort of better at forming big stable pools than ammonia is. All right, So ammonia it might be a good replacement for water, But life on Earth didn't use ammonia. Why aren't there any ammonia based life forms on Earth. Well, again, we don't know. It's just luck. But water does have some advantages that ammonia doesn't have. For example, ice floats on liquid water. When you freeze water, it actually grows in volume, so it's density drops, which is why lakes, for example, in the winter, freeze from the top down. The liquid water can stay underneath, and like fishes and microbes or whatever can sometimes survive through the winter under the ice, whereas that would be trickier if they froze all at once, for example. And so this very strange property of water allows it to float on liquid water, and that doesn't happen for ammonia for example. Also, water is stable in the presence of oxygen. A lot of things out there, when you put them near oxygen, they can combust, right, they can burn, or they can oxydize. The water is actually stable in the presence of oxygen because it's actually the product of combustion. You take hydrogen and oxygen together and you light a match, you get water, And so water is stable in the presence of oxygen, which is nice if you want to have oxygen in your atmosphere and not have it beyond fire all the time. Right. Also, I imagine water is much more abundant here on Earth, right, Like we don't have large lakes of ammonia, but we do have a whole ocean of water. We certainly have a lot more water than ammonia. In other places in the Solar system there are lakes of ammonia or methane for example. Is it also sort of a property of its solvent but properties you know, like maybe like if you try to grow something in kerosene, it which is can dissolve and and die. Is it water like soluble but not too soluble. They're both really good at being solvents. But one disadvantage for ammonia is that it's liquid at lower temperatures, right like negative seventy eight negative thirty three C. That means if you have life that's ammonia based, it's going to move slower, It's going to evolve more slowly. Like the whole time scale for things to happen is going to be slower just because things are colder. So water based life might just like outpace and outrace ammonia based life. Interesting, So it is possible for life out there in the universe to be ammonia base. If there's a planet where there's no water, but there is there are oceans of ammonia, maybe life could develop there. Yeah, it seems like it's totally possible. Yeah, And so they would be drinking a glassful of ammonia every day. They might think that water stinks, right, maybe they use it to clean all right. The last ingredient that Christian mentioned was oxygen. Do if you lose oxygen, can you still have life? And it seems like oxen it's part of water too, So I guess the questions are kind of related. Yeah, I suppose. So oxygen is a part of water that's not a part of ammonia. But when you think about oxygen life, you're mostly thinking about breathing oxygen, like atmospheric oxygen O two within the atmosphere that you pass through your lungs and that many many things on Earth rely on. And we often think about oxygen is like a biosignature. We're looking on other planets to see if there's maybe life in their atmosphere. We're checking out to see if there's oxygen there. Like, are you saying, if we had maybe water and carbon but not a lot of oxygen gas, could you still have life or what would you used to replace oxygen? Yeah? And it turns out you actually don't need oxygen, and we didn't have oxygen here on Earth when life evolved. Oxygen itself is a product of photosynthesis. So life started here on Earth when there was no oxygen in the atmosphere. It was ani aerobic to begin with. Right. There are bacterias that grow without any oxygen, right, Yeah, Like the bacteria in your gut are mostly ania aerobic microbes because there isn't a whole lot of oxygen in there. Right, But eventually life produced to oxygen and that's what we require right now, So what is oxygen good for them? So oxygen was originally a waste product? Right, Microbes learned to do photosynthesis and oxygen is the byproduct of photosynthesis. It's just like their garbage. And it turns out that some kinds of metabolisms that involve oxygen are much more efficient than the anaerobic ways, and so a bunch of other microbes figured out how to take advantage of that waste product and use it to make themselves more efficient. So it's sort of like supercharges life's metabolisms. And that's just like a lesson about microbes. Microbes will always figure out how to use someone else's garbage and turn it into their food. It sounds like it's super charges life. So could you have complex life or life as we know it without oxygen? We don't know. We didn't have a lot of atmospheric oxygen on Earth until about eight hundred and fifty million years ago, and that's also about when things started to get much more complicated. So it's possible that you sort of need oxygen or something similar to supercharge and metable is M and allow things to get complicated, or it's possible that it would have done it without oxygen. We only really have this one experiment, so we don't know. If we didn't have it, could you replace it, or you know, if we didn't have those victoria making it and you wanted to supercharge life, there's something else you could use. Oxygen is pretty special because it's so reactive, and it's very good at like accepting electrons at the end of this metabolism cycle. But there are other things you can do. People think that like sulfur, for example, could also serve as part of the like respiration process for alien life. Though nothing really is as good as oxygen. Right, It's probably won't smell as good. We're talking about aliens sipping ammonia and smelling like sulfur, smelling like ron eggs. All right, well, I think that answers christians question, which is that if you lose anyone in your life team, it'd be pretty hard to replace them. It seems like that you could try, but you probably won't win the World Series. We don't know if you'll be as competitive. But then again, we're just looking at the one example we have here, and we don't know, i this is the one lucky time that the Twins actually win the World Series, or if this is a pretty typical example out there. And in the meantime, we'll just assume Christian looks like bread Pitt, or maybe Christian is bread Pint. All right, let's get to our last question of the day. But first let's take another quick break. Okay, we are answering listener questions, and we've answered awesome questions about how do you see photons moving away? And also what would happen if you lose some of the ingredients for life here on Earth. Our last question here is about the red shifting of light and it comes from Josh hid Daniel and Jorgey. I had a question about red shifted photons. I was just wondering how we can always tell the difference between a photon that's been red shifted versus it just started out more red. A few good day again into that that'd be great. Thanks to keep up the good work alright. Awesome question here from Josh. I think his question is how do you tell what color a photon was originally? Like, was it made a certain color or if it was stretched to a certain color, And the answer is that we can't. All we can do is measure the energy of a photon. Measure its wavelength or its frequency, those are all equivalent. Those determine how much energy it has. So when a photon arrives on our sensors, we measure its energy and then we can say, oh, this photon has a certain frequency or a certain wavelength and that's technically all we can know just from the photon itself, from context, from where it came from, from all the neighboring photons that arrives with, we might be able to deduce something about his history. But directly, all we can ever measure is the photon's current energy. We can't ever really measure its past energy. Really, so there's no difference between a photon that's been stretched to be read and one that was made red. Yeah, quantum particles are very simple in some way. They have a list of properties and that's it. And two photons that have the same energy and are going in the same direction are identical, right, There's no difference to them. They don't even really have an identity. You can't like say this one's Fred photon and then that one's Maria photon. Really no difference. They're just like ripples in the larger field that they're all part of. Anyway, isn't there another I don't know, a component to a photon that might be able to tell you something like, you know, if I take a photon and I stretch it so that it's red, when I lose some overall energy or something, it's supposed to maybe making a red photon that's really energetic. Then you could say, oh, this one's really energetic, this one's low energy, maybe this one was stretched. Well, the energy determines the color, and so two photons that are like the same redness have the same energy, So you can't tell if one of them earlier had more energy and then got stretched to lower energy, and you might wonder, be like, where's that energy going. Energy doesn't go anywhere when a photon gets red shifted. It's because the relative velocity between you and the source. So it really just sort of like depends on the frame of reference, doesn't really go anywhere. Well, maybe we should talk a little bit first then about what it means to wred shift something and what are the different ways that can happen, because I think it can happen in two ways. Right, whether the source of light is moving away from you, or you're moving away from the source of light, then the photon is gonna look redder. It can also happen because of the stretching of space, right, Yeah, there are two different ways to red shift of photon. If an object that shoots light at you is moving away from you really really fast, then the wavelength of that light is stretched out and so it gets redder. Remember the light always travels at the same speed, So if somebody's in a galaxy far far away and they're moving away from you really quickly and they shoot a blue laser at you, then it's still going to arrive here at the speed of light. It always travels at the speed of light, but it changes the wavelength, so it gets red shifted. This is a handy way to measure the velocity of things that are far away that we can't otherwise measure. If we can measure their red shift, then we know how fast they are going relative to us. But you're right, there's a second way that photons can get stretched out, and that's if space itself is expanding, So not just things moving through space, but space itself making more of itself, bubbling up from within to stretch itself out. And we think that's happening in the universe. The whole universe is expanding, and that expansion is accelerating, and so photons moving through the universe gets stretched out. A great example is the cosmic microwave background radiation. We measure these at very very long wavelengths, very very red light. But originally when it was generated, it was generated by a very hot plasma thousands and thousands of degrees, so it was very short wavelength. But over the timeline of the universe, those photons have gotten stretched out to very very long wavelengths. It's interesting to think that the color of a photon depends on your perspective in a way, right, Like I can make a photon here and I put a lot of energy into it, so it's really blue. But depending on how you catch it, you're gonna think or that the in color. I might think, oh, this is super low energy if you catch it while on the run. It feels weird because energy feels like a fundamental thing, and people say it's conserved, and so it feels weird to think like different people could measure different energy. There's an important difference between something being conserved and something being invariant. Something invariant means that everybody measures the same thing. Everybody always measures the speed of light to be the same, but you don't always measure energy to be the same. So you're running past me and I throw a ball. I see the ball moving really really fast, has a lot of energy. I say, but if the ball is moving at the same speed you are, then it has no velocity relative to you, and you say, no, the ball is at rest, it has no energy. So you don't even need relativity to disagree about the energy to things have. Yeah, that's super trippy, but I think what you're saying is that you know, if you just catch a photon out in space and you see that it's red, there's no way for you to know just looking at the photon whether it started out as red, or if it started out as blue, or if it was blue and a turn red. There's like no way for you to know if you don't know anything about word it came from. That's right. So you get a photon from another galaxy, it's got a specific frequency. You don't know what frequency you would see it at if you were in the rest frame of the galaxy. You just can't tell, right. But if you know something about where it came from, or do you have more of them coming from the same source, you could maybe the dues whether they were made at a certain frequency or not exactly. Because this is something we do all the time. We look at a whole galaxy and we say, oh, the life from here is red shifted. So if we can't tell from an into individual photon, how can you tell the red shift of a galaxy. The answer is, as you say, you look at all of them at once, because the galaxy emits photons at certain frequencies. It's filled with specific gases hydrogen and helium and neon, whatever, And each of those gases admit only at certain frequencies because remember they're all quantum objects, and they have electrons whizzing around them, and those electrons like to go up or down energy levels, and those energy levels are sort of like floors in a building. The elevator stops at one, or at five or at seven. It doesn't stop at like floor four point seven two, And so the electrons give off photons of very specific energies. If you have a bunch of hydrogen gas and it's hot and glowing, it's gonna glow its specific frequencies. So if you look at the energy of the photons you're getting from a big blob of gas, you can tell is it hydrogen, is it helium, is it neon? Based on the energies of those photons. But if it was just missing one frequency, right like if the source only had one element in it, then would it would be hard to tell. It's only when you have you know, complex things like stars that you know have multiple elements in it, that you can sort of identified the light. Right, You can actually do it with just hydrogen because hydrogen has multiple levels. It has a whole set of energy levels. So hydrogen gas emits not just one frequency but many to What you do is you look at the spectrum you see and you compare it to what you expect. You say, oh, this looks like hydrogen, but it's been shifted over a little bit. So hydrogen has its own fingerprint, helium has its own fingerprint, Neon has its own fingerprint. So you can actually tell all of these things apart, and you cannot only measure the red shift. You can also measure the elemental company positions. You can tell how much helium there is, and how much hydrogen there is, and how much water vapor there is by where those peaks are. You don't you wouldn't get confused between like hydrogen and helium because the two are different. Yeah, the two aren't different even if they're shifted, because they're all shifted together typically, Right, the hydrogen and helium, and that galaxy are all moving at the same speed relative to you. Mostly. It's actually also the way we measure the rotations of galaxies. We look at like one side of the galaxy, but the other we see different shifts, which tells us that the galaxy is rotating in a certain way because parts of it are moving towards us and parts of it are moving away from us. Right. But I guess I mean if we had a whole galaxy of just hydrogen and another whole galaxy of just helium, would you be able to tell the two apart or would you be confused? It's like, oh, maybe this is hydrogen but shifted to helium, or maybe this is helium shifted to hydrogen. Well, our voices would all sound really weird if the whole universe was just helium. Right, So that's clue number one, but also clue number two. Scientifically, they do have a different spectrum, right, Helium and hydrogen have different spectrum that have different energy levels because it's a different charge in the nucleus, So the solutions to the Shorteninger equation aren't different. So the gaps between the energy levels and helium are different than in hydrogen. So there's no way to take helium and like red shifted to make it look like hydrogen. All right, So then you wouldn't need to know where it came from, or would you. I mean, once you get the light and you see these fingerprints and you instantly know whether it was red shifted or not, yeah, exactly, because there's no other way to make those fingerprints. There's no gas in the universe that emits light like hydrogen red shifted with the Z of four, right, So once you see that spectrum like, well, this has to be hydrogen, and it has to be red shifted this certain amount. There's no other way to make this pattern of light. Right. But to see I guess, to see those fingerprints, you need a whole bunch of photons of different frequencies, right, You need your source to emit a whole range of frequencies. Whereas if you just got a whole bunch of photons in one frequency, there's no way you could tell they were red shifted. Or even if you've got like a weird sampling of different photons of different frequencies, there's no way for you to know. You you would have to assume it came from you know, stars or a galaxy. Yes, not information you can get from one photon. It doesn't carry its own personal history around. It's only from a whole collection of photons that you can tell what the red shift was of the source. But so if like an alien and another galaxy shot a laser ad you that they manufactured artificially, there would be no way for you to tell whether it was red shifted, right, Yeah, exactly, we wouldn't be able to tell what the original frequency was and what the shift of the frequency was, assuming that they could make a laser of arbitrary frequency, right, which they're aliens who probably Yes, right, you're given the aliens a lot of credit here. I mean, I'm assuming they're still bound by the laws of physics, right right, You're assuming they're in the right time zone to shoot you the laser in then they know what they're doing. Maybe that's going to save us, right, Maybe they want to vaporize us, but they used the wrong time zone, and so they actually vaporized Geneva instead of us. Yeah, they get rid of the Danish. What are we gonna have for breakfast without the Danish? Yeah? And then we'd all be drinking ammonia, and you know, in Denmark, of course, they don't call Danish. Is Danish is? They just call it breakfast. They call him Vienna bread. Actually Vienna bread? Wow? What do they call him Vienna? I don't know. I've never been to Vienna. I got the time zone wrong. I was supposed to go, but I missed by flight. Somebody from Vienna right in and please educate us. That's right? And is the Danish is the pastry red shifted or not? If you eat it in Denmark or Vienna? I don't know. Is it blueberry shifted or is it raspberry shifted? Deep questions? All right, Well, I think that answer is Josh's question is that you you can't tell the difference if you just look at a photon if it's red shifted or not. But if you get a whole bunch of photons and you assume they come from you know, natural sources, then you could the dudes whether it was red shifted or not exactly. And it's a great question because it's really good to think about, like how do we actually know what we know? And are we sure we're not being confused about what we're looking at? Basically, the light has to be organic, otherwise you can't tell it has me natural at least farm raised. You know, cage free light and you can tell that's right. No pesticides please in our astronomy. All right, well, I think that answers all of our questions here today. Thank you everyone who sent in their questions. We love getting questions, we really do. It's not just something we say. Please do right to us two questions at Daniel and Jorge dot com. We love hearing from you. You might even pick the question to answer on the podcast, even if you are a Twins fan. I don't even know where the twins are from. Are they from the Twin Cities, Minnesota? Man? What is it hockey or basketball? I think it's lacrosse lacrosse. It looks like lacrosse, depending on your point of view. All right, well, we hope you enjoyed that. Thanks for joining us, See you next time. Thanks for listening, and remember that. Daniel and Jorge Explain the Universe is a production of I Heart Radio. For more podcast from my Heart Radio, visit the I Heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows. No