Listener Questions #30

00:00:07
Speaker 1: From twitching leaves to thinking minds, Where does I begin? Is it wiring roots or loops that inspires thinking?

00:00:16
Speaker 2: Birds have been around for one hundred and fifty million years, but chickens less than half of that. So did chickens come first? Or was it eggs? Go ahead, have a guess it. It was kind of long.

00:00:29
Speaker 1: These rhymes get better every time. To see the early universe, we need neutrinos or gravitational ways. But how will we know what to look for in all of that particle haze?

00:00:41
Speaker 2: Whatever questions keep you up at night, Daniel and Kelly's answers will make it right.

00:00:46
Speaker 1: Welcome to Daniel and Kelly's Extraordinary Universe.

00:00:49
Speaker 2: Listener Questions, Episode thirty.

00:01:05
Speaker 3: Hi.

00:01:06
Speaker 1: I'm Daniel. I'm a particle physicist, and I never get tired of hearing questions from listeners.

00:01:12
Speaker 2: Hello. I'm Kelly Leadersmith. I study parasites and space, and I also never get tired of your questions. They're always wonderful. And Daniel, I have a question for you. Do you prefer eggs that have been sitting in the refrigerator or eggs that have been sitting on your counter?

00:01:25
Speaker 1: Oh my gosh, I am not prepared to have an opinion about that. Oh, why do they taste the same?

00:01:30
Speaker 2: Well, you know, I just kind of they probably taste pretty similar. But I've noticed that there are cultural differences. I think in Europe you're more likely to get eggs that don't need to be refrigerated, and so the differences in the United States. I think we've rinse off our eggs, and once you've rinsed them off, they need to be refrigerated. But if you don't rinse off your eggs, they come out of the chicken with a layer called a bloom, which protects against bacteria and stuff like that. And so you can just leave chickens on your counter for a while.

00:02:00
Speaker 1: You mean eggs on your counter.

00:02:02
Speaker 2: We're chickens. Yeah, I wouldn't recommend it, but yes, eggs.

00:02:08
Speaker 1: Come to Kelly's Deli where chickens roam the counter.

00:02:12
Speaker 2: Yeah, I bet I probably would not get a very good health rating if we didn't.

00:02:17
Speaker 1: Then, yeah, well there's something fascinating there that eggs are protected from infection. But we usually rinse things because we want them clean and uninfected. But here rinsing things makes them more vulnerable to infection.

00:02:31
Speaker 2: Yeah, I feel like in America, we want like ultimate control over everything, and we just feel like we have more control if we've shoved things in the fridge. And also, I suppose every once in a while when an egg comes out, it gets a little poo on it, and so if you can rinse it and then stick it in a fridge, you know, maybe you feel better about it that way.

00:02:50
Speaker 1: I don't really want any poo on my counter, is the truth.

00:02:53
Speaker 2: Yeah, yeah, no, I get that. I get that. That is one of the downsides of farm fresh chicken eggs is every once in a while you're like, oh, yes, biology happened here and there is some.

00:03:02
Speaker 1: Poo and on your counter in your house at home on the science farm, are there unwashed chicken eggs and occasional pooh?

00:03:10
Speaker 2: There are unwashed chicken eggs? Like, the answer is yes. I was gonna try to figure out a nice way to say it. You know, we've got like brushes to clean them off before you crack them, to make sure that none of that pooh ends up. Please come back to our house and visit.

00:03:28
Speaker 1: Sure, I will. Well, why don't you rinse them before you crack them, because once you rinse them, they're not protected but there's then there's just moments before you crack them.

00:03:35
Speaker 2: Oh, we rinse and brush well, I mean, you know, when the poo dries, it's harder to get off, and so it's nice to have a brush, and so yeah, we clean it all off right before we crack it to make sure that, like you know, sometimes when I crack eggs, I get shell in the bowl and we just want to make sure that that's clean, because I'm not so good at cracking eggs.

00:03:55
Speaker 1: But you are very good at answering questions from listeners. And that's what we're doing today on the podcast. We are hearing from all of you everything that makes you wonder about the universe, all the extraordinary fascinating mysteries about the universe that you want to hear about. And so today we are tackling three fascinating topics from biology to physics, to the origins of the universe to the origins of chickens and eggs.

00:04:18
Speaker 2: Yes we are, so let's jump right in and hear our question from Jared.

00:04:22
Speaker 3: Hello. My name is Jared, and I'm a huge fan of you both. I absolutely love your show. My three children enjoyed the podcast. Also, my two preteen sons and Joy Kelly's gross biology explanations, and my six year old daughter likes to fall asleep to Daniel's voice during car rides. My question today is about how we classify and explain the different levels of self awareness in the universe. I've been reading about how across the spectrum from reactivity to sapiens, living systems exhibit increasingly complex forms of awareness, ranging from basic stimulus response to sentience, self awareness, and ultimately sapiens, which I now know is different than santhians. I've been reading about how concepts like metacognition, reflective consciousness, and theory of minds see the mark pivotal transitions along this continuum. But the boundaries we've set up to define and described as kind of spectrum of awareness are still fuzzy to me, and it's led me to having like a ton of smaller questions, like what's the difference between plants and machines in terms of reactivity? Could mammals have moments of sapience or could the boundaries be crossed accidentally temporarily? So I was just hoping, with your distinct scientific advantage points that you could help explain the fundamental physical or biological thresholds that enable these higher levels of awareness to emerge from simpler matter in life. And perhaps even let me know if there are any overlooked mechanisms or principles perhaps at the intersection of physics and biology that would be cool that could help explain not only how these layers of awareness arise, but also the current limits of our scientific understanding of awareness and what might be the next breakthrough that could reshape how we define or recognize it in the universe. All right, thank you very.

00:06:00
Speaker 1: Much, so thank you Jared number one for sharing the podcast with your kids and helping raise the next generation of curious people in the universe. Awesome, we love that. Thank you so much. And also for asking such a hard, such a deep question about the nature of sentience and consciousness and whether we can understand how that emerges from like core physical activity.

00:06:25
Speaker 2: And I'd also like to note that I am so glad that the next generation is still excited about gross stuff. So thank you to the preteens for digging the gross biology. But anyway, yes, wow, where do we start with this difficult question? Daniel?

00:06:38
Speaker 1: Yes, so we got to start by saying we're not going to be offering any solid answers because there are none. Right, we just do not understand this stuff. There are so many issues here, from never being able to probe the awareness of another object in the universe, not to mention another human being right, first person experience this like subjective existence that we have where I feel like I'm in my head and I'm feeling my body. That's not something I can share with you, not something you can probe from the outside, not something you can verify. I don't even know, Kelly, if you are any different fundamentally from a rock in terms of your inner life.

00:07:17
Speaker 2: Thanks Daniel.

00:07:17
Speaker 1: I mean I think that you are. You seem different, but I don't know from a philosophical skeptical point of view, and that's fundamentally going to limit us from having any solid answers.

00:07:26
Speaker 2: Well, I think the good news is that people don't really come to our podcast for solid answers. They come to our podcast for the we don't really know version of answers and so, and.

00:07:37
Speaker 1: You do that much better than a rock does that. By the way, You're much better podcast host than like a lump of granite.

00:07:43
Speaker 2: Thanks question Mark.

00:07:49
Speaker 1: But Jared is asking a really interesting question. About like the spectrum of reactivity, right, Like, how do we categorize these things? How do things get more complicated? Is there a way that we can under stand not just reactivity, but like sentience and conscious experience by gradually scanning up from simple reactivity to the universe all the way up to you know, having a first person experience. So let's take a walk from the simplest to the more complex. We can start with like physical reactivity. Things in the universe react to other things, you know, like if you have a rock out there in the sun, it will absorb photons, it will gain mass, it will change the nature of the chemical bonds, it will store that energy. So that's you know, direct causal reaction to something outside the universe, just like if you press a button on your toaster or you write a program for your computer. The universe seems to be causal. It seems like you can influence the future, and so things that happen in the universe affect the future. Right, that's like the most basic level at which things in the universe interact.

00:08:53
Speaker 2: Got it, Yes, rocks and Kelly warm up. Let's uh, let's move to more comp.

00:09:00
Speaker 1: Before we get to more complex though you can already ask does the rock feel anything like the rock is sitting in the sun, it's getting warmed up. Does it go in its own rocky way? Like, mmm, that feels nice, the way like when you have your face in the sun, it feels nice. Obviously, what it's like to be a rock is not going to be what it's like to be Kelly or Daniel or Jared or any of his kids. But there might be something it's like to be that rock, and we can't say that it isn't. And there are even theories out there that everything in the universe is aware, it is conscious at some level, so that by the time we get to podcast host, we can say that that podcast hosts rich inner life, which enjoys poo free eggs, for example, comes emerges from the basic elements of consciousness that begin with fundamental particles. You know that electrons have like a little bit of consciousness and it comes together. I'm not ascribing to that theory. I'm just saying there are people who already, at this level of interaction with the universe put a little dot of awareness and experience.

00:10:10
Speaker 2: Is there an interesting question to be asked here about, like if you asked AI, and it gave you an answer about its experienced, like because it can answer. Is that an interesting answer?

00:10:19
Speaker 1: Well, it's interesting because an AI, unlike a rock, can tell you that it has an inner life. Right, if you ask Gemini or chat GPT, they can tell you that they think that they feel that they have thoughts whatever. You can't tell the difference between them having those thoughts and claiming those thoughts, or them not having those thoughts and yet claiming those thoughts, because you could write a program which claims those thoughts and you don't know that it actually has them. Right, Claiming them and having them are different things. And in philosophy we have this concept of a philosophical zombie, and the thought experiment is like, could, for example, there be a version of Kelly who claims to have a rich inner life and acts unless she has a rich inner life, and yet doesn't.

00:11:03
Speaker 2: You did compare me to a rock earlier.

00:11:06
Speaker 1: In a flattering, complimentary west You're better than a rock, much much better than thank you. In fact, you rock, Kelly. But the point of that thought experiment, the philosophical zombie, is to point out that the subjective experience we're talking about that inner life is not revealed by your actions. That there's nothing on the exterior you can do to probe it, so that even somebody who seems to have it, even somebody you fall in love with, might not have an interior life. And there are examples of people out there who like fall in love with ch at GPT and have like AI boyfriends and feel real emotions about them, and imagine that the AI also feels real emotions in response, even if it doesn't. So my point is that already at this level, the philosophical questions are complicated.

00:11:54
Speaker 2: M hm, yes, and I am already sort of feeling existential dreads. So all right, let's move on to the next level.

00:11:59
Speaker 1: All right, So the next level is like biological. We have simple plants that can do things like organize their cells. They maintain gradients across cell walls. Plants can orient their leaves to the sun. This is more than just like a rock absorbing a photon. There's like a feedback here, there's like memory, you know, there's maybe even goal like behavior. The plants move towards the sun, trees grow up, the roots go down. There's goal like behavior here, but sort of implicit, right, We don't know if the plant is like stretching towards the sun and enjoying having its leaves toasted, but it's definitely more self organized and reactive to the universe than just a rock. And there are some cases that some people tout slime molds for example of you know what seems like maybe intelligent behavior exploring a maze. Though I know, Kelly, that you are not in the top ten list of people who are impressed by slime mold intelligence.

00:12:57
Speaker 2: Check out one of our earlier Listener Questions episode to hear a Kelly throw cold water on slimbles solved mazes.

00:13:05
Speaker 1: And you do that even better than a bucket of cold water. I have to.

00:13:08
Speaker 2: Say, thank you, and maybe better than a rock. And there's all kinds of inanimate objects that I can outperform.

00:13:15
Speaker 1: All right, So now let's take one more step up the perceptual ladder to critters that have like explicit sensory organs, you know, even simple things like ants and flies. They have eyes, they can experience the world. They have chemical sensors. They communicate with each other, They leave trails for each other, you know, they make sounds, they leave chemicals. They definitely can learn. I have a friend who does experiments on fruit flies, and they definitely can learn sounds and songs and all sorts of stuff. We don't know what it's like to be an ant. There doesn't have to be anything it's like to be an ant or fruitfly. You could have like a little robot which accomplishes exactly the same thing and doesn't have any internal state. But there also could be something it's like to be an ant or a fruit fly. We just don't know.

00:14:03
Speaker 2: Do you think that there's some chance that we're sort of biasing this towards ourselves by saying, like, oh, they need to have sense organs, like the kinds of sense organs I recognize in myself, you know, because like plants are detecting where the sun is so that they can turn towards it, so they've got something like sense organs. Are we essentially defining oh yeah, things, yeah, to match what we do.

00:14:25
Speaker 1: Absolutely and obviously, and I don't know that we could do anything else. The only thing we can do is ask about similar experience. Is we can try to think about what it might be like to be something else, But in the end, we're always translating the unfamiliar back into the language of the familiar. You know, this is like a big theme of my book about alien physics is that it's really hard to think outside of your own little box. And so it could be that there's something it's like to be a rock and a plant which is very, very different from what it's like to be human, and it's rich and complicated in a way we just can't underst stand or even conceive of. Even if we could talk to them and they could try to explain it to us, we might never really be able to crock it because there are some things that are just untranslatable.

00:15:10
Speaker 2: Do aliens speak? Physics available through fine bookstores everywhere.

00:15:15
Speaker 1: And also terrible bookstores. Yeah, so we've gone from rocks to like plants to now critters with explicit sensory organs. You can take them the next step up and say, well, what about more intelligent animals, Animals that have a model of the world within them. You know that they can integrate sensory information over time, They have memory, they can be trained, they can make predictions. You know, they don't just react to the world and have basic memory. They have like a model of themselves in the world. And they use that to make predictions. That's clearly a more sophisticated way to respond to the world. And in that case, it's tempting to say, look, if you have a mind, and in that mind you have a model of yourself, then clearly referring to yourself. And isn't that a kind of experience. It seems very likely. And you know, when I interact with my dog, it's very easy for me to see parallels in my dog's emotional response to my own, Like he likes being scratched, and I can tell that he likes it, right, Or if I'm upset with him, he knows, and I can tell that he doesn't like when I'm upset with him. All these things, And again, maybe it's just the slice of humanity that is reflected in the dog, but there's definitely some overlap there. Right, whatever it's like to be a dog, there are parts of it that are similar enough to what it's like to be human that we can have that emotional connection, right, And so it's very tempting to say, well, clearly my dog has an inner life. It is something it's like to be Daniel's dog. But again, how do I really know if somebody came along and like magically removed that experience from my dog but kept all the same behavior. Obviously, I couldn't tell by construction. So it's frustratingly opaque.

00:16:57
Speaker 2: Yeah, it does kind of feel like you were a little bit more will to entertain the idea that your dog has a rich inner life than you were to entertain the idea that your co host has a rich inner life.

00:17:08
Speaker 1: I'll say, in my defense, I made that argument as an example of ridiculous but unrefutable arguments.

00:17:14
Speaker 2: Right, I'm just giving you a hard time.

00:17:17
Speaker 1: Okay, go on, No, but I mean I only have a dog in my house. You have a whole spectrum of critters. Give us a sordid list from most to least likely to have an inner life.

00:17:27
Speaker 2: Chickens, no inner life.

00:17:31
Speaker 1: Chickens are just robots, you're saying.

00:17:33
Speaker 2: Just robots, just robots. And my doggy milo very rich inner life. And my goats, you know, I think my goats are very frustrated when I don't let them out on time or when I come out without animal crackers, and they've got a rich inner life.

00:17:49
Speaker 1: And then you know, the next step, of course, is full sapience. You know where you can think, you have language, you can have abstract concepts, you can think about thinking, you can argue about it, arguing to have a rich inner life and a model of the world that includes yourself and your own model of the world in it. And it's recursive all the way down. Where along this spectrum does experience emerge, We just don't know, right This is what they call the hard problem of consciousness. Even if you can understand mechanically how the brain works, signals go up the optic nerve dot dot dot, that doesn't tell you why there's something it's like to be a person. And so you know, there's all these various approaches that people take in the philosophical community. We mentioned one of them already, pan psychism, where mentality is a fundamental aspect of reality, like mass or charge. It's not the idea that, like electrons have political opinions, but that there's some sort of minimal experiential properties of all matter at the most basic level, and that the experience doesn't emerge suddenly but gradually from the simple experiences combining into richer experiences of complex systems. That's a not of like widely held or mainstream view, but it is an opinion I've seen out there.

00:19:07
Speaker 2: I feel like I've sort of lost track of what we mean by experience and mentality at this point, So like, experience must mean more than like a photon has hit me and I have recognized that the photon has hit me, and mentality must be Yeah, Like, what do we mean now by experience and mentality?

00:19:23
Speaker 1: I mean that there's something it's like to be you. Okay, you know that you're having a first person experience, got it?

00:19:30
Speaker 2: Okay?

00:19:30
Speaker 1: And there are people who deny that, right, Folks like Daniel Dennett, a school of thought called reductive physicalism, say there's no first person experience, that there is no moment of Now. What you think you are experiencing right now is just your brain analyzing what recently happened, right that the moment of the present itself is an illusion, and it's constructed by your brain putting together a bunch of sensor reinformation telling a story about what just happened. And it's so recent. You surf along the edge of it and it feels like there's a you, but there isn't really, So you weirdly remember being conscious, but never really are. It's a fascinating idea.

00:20:12
Speaker 2: Are we in like a simulation or we're just like.

00:20:15
Speaker 1: No, no, we are not in a simulation. We are just remembering a present we never experienced. This is a fascinating idea and it's hard to wrap your mind around. It's in Daniel Denni's book Consciousness Explained, which is like, wow, ambitious title. Right, Yeah, it's a really fun book and we should dive into it more another time. Another idea is called functionalism. It says, look, it's all about information. It doesn't matter what matter it is. It's not like the sentience is built into the electron and then it all comes together. It's about how this stuff is arranged, and it's about the model in your head of the universe. But there's no real explanation there for like how that emerges, Like where along that spectrum we just described it begins that there's something that's like to be an ant or a bird, just that it comes out of the information. And here the implication is that if you build a simulation of Kelly, it would have the same experience as Kelly. It's nothing about the wet weear or the kellyness of your particles. It's just the arrangements of the stuff.

00:21:21
Speaker 2: It's arrangement.

00:21:23
Speaker 1: And then the last sort of broad philosophical approach is called strong emergence, and it says, hey, this whole argument that things need to bubble up from the littlest bits, that somehow the first person experience needs to be emerging from the towing and froing of the little particles inside. You forget all that, even though it seems to be like the foundation of modern science and physics at least, and say, look, things emerge because there are just new fundamental laws at every level. So it's not like the behavior the biggest stuff bubbles up somehow from the behavior of the smallest stuff. It's got its own laws, and maybe things flow the other way. And like consciousness emergence because there's some weird new law of the universe and it can control the microscopic instead of the microscopic controlling the macroscopic. So you know, the short answer is nobody knows the answer, and there's an enormous variety of totally contradictory approaches in the philosophical community to this very very hard problem.

00:22:22
Speaker 2: I feel like this is the kind of conversation where I need to like, hear a sentence and then sit for ten or fifteen minutes to be like, what did that sentence mean? And then start again.

00:22:33
Speaker 1: Yeah, yeah, yeah, that's philosophy for you, exactly, and you're going to go all the way down to like what does meaning mean? Anyway?

00:22:41
Speaker 2: That's right? Am I real? Is this is any of this real? What is real?

00:22:46
Speaker 1: Yeah? Exactly, And then you'll discover that at the foundations of philosophy you know nothing and we know nothing, and you know, that's where de Karte was and it's very hard to go anywhere from there. So you just got to make some assumptions and move forward as best you can because it's not clear what we know and what we don't know and what knowing even means. All right, So I hope we've confused you enough. Jared. Let us know if that helped you at all. And thank you again for your question.

00:23:14
Speaker 4: Wow.

00:23:15
Speaker 3: Thank you so much, Daniel and Kelly for the amazing and detailed answer. You've certainly given us all a lot to think about. We promise our next question won't be as difficult next time. We'll keep it simpler. Certainly next time when we're talking about our cat oreo and we're talking about her learned behavior over time and how she's picked up on certain human words. We'll now have a more context to kind of discuss that. And yeah, we don't have any follow up questions. Just keep up the great work. We love the podcast.

00:23:43
Speaker 4: Kelly.

00:24:04
Speaker 1: Okay, we're back and we're answering questions from listeners. And today we're tackling deep philosophical questions like do rocks feel pain? And also ancient questions like what came first? The chicken or the egg?

00:24:18
Speaker 2: And this is a question that people, you know, sometimes enjoy having long, deep philosophical questions about. But I love runing fun and evolution has a clear answer.

00:24:28
Speaker 1: Oh my gosh. Wow.

00:24:30
Speaker 2: And so let's hear Noah's question and then I'm gonna give you a clear answer.

00:24:34
Speaker 4: Nice, Hi, Daniel and Kelly. I would love to hear about the evolutionary history of chickens and eggs? Is there an answer to which came first?

00:24:42
Speaker 1: You're just going to give a clear answer to make me look bad because of my philosophical ramblings.

00:24:46
Speaker 2: Yeah, you should have just said no moving. I'm gonna saved us all twenty minutes, Daniel, No, that was fun.

00:24:55
Speaker 1: All right, So great question. Noah Kelly, tell us what a science say about the chicken versus egg debate.

00:25:02
Speaker 2: Well, eggs have been around for a really long time, Okay, So, like we think of women as having eggs and men as having sperm, and so if you think of it that way, then eggs have been around for you know, since we've had fish and since we've had amphibians and millions and millions and millions of years. But I understand that that's not actually what we're talking about. We're talking about you know, chicken eggs as in like having that hard shell. But let's take a few steps back. Okay, So initially we had you know, fish swimming around in the oceans, and we had amphibians and they were laying eggs in water. When you lay eggs in water, you've got this sort of perk that you're in this aquatic environment, so when you lay your eggs, you don't have to worry about them drying out and dying.

00:25:42
Speaker 1: But is that where eggs begin with amphibians in the water or are their precursors to that.

00:25:47
Speaker 2: Well, invertebrates like starfish also make eggs. But if we're talking about vertebrates, making eggs. Then shark and fish were making eggs before the amphibians were. But so when four limbed verts like reptiles started leaving the ocean to move on land, we started having this problem, which is that, well, now that we're out of the water, our eggs are gonna start drying out, and so what do we do. Our eggs needed to become more complicated, and thus arose the amniotes, and that's just kind of a fancy word for saying we ended up getting fancier eggs, and so amniotes includes birds, reptiles, and mammals, and so amniotes these are fancy eggs that have three extra layers. And what these three extra layers do is they first they provide an extra little fluid filled sack and this is like the amnion and essentially encloses the embryo and it's like a protective fluid. And so if you are egg were to go rolling down a hill, which you probably should, try to make sure your egg doesn't do. But if it does, it like will protect it against bumps and bruises and sort of give it a bit of a cushion and it just sort of suspends the embryo, and it's almost like you've brought your aquatic environment with you by putting it in this like sac.

00:27:05
Speaker 1: It's like we're still stuck on ocean based life and all of land based life is like carring around little bags of ocean.

00:27:12
Speaker 2: Yes, yes, we are carrying our past with us in that sense, which is kind of.

00:27:17
Speaker 1: Cool, which is fascinating because like all of the life that we build, like robots, it's all dry. Right, why don't we build robots that are based on guie bags.

00:27:26
Speaker 2: Well, you're the computer scientist. My sense is that when you start adding water to computers, things don't go real well.

00:27:35
Speaker 1: All right, so we have the amnion. What are the other extra layers that the amniotes added?

00:27:40
Speaker 2: All right, so you also have the coreon and the alantois. I'm sure that I am mispronouncing those as everyone has come to expect it. Anyway, those two layers are helpful for gas exchange. So you still need to be able to get oxygen into the egg to give that oxygen to the embryo inside, and you need to be able to manage waste. And so these two layers essentially allow for gas exchange, and they contain the waste that's produced by the embryo inside.

00:28:07
Speaker 1: Waste related question, huh are the amniotes the first ones to accidentally pooh on their eggs? Or did fish do that? Also?

00:28:15
Speaker 2: Oh, let's see. Okay, so that's really great question, Daniel.

00:28:22
Speaker 1: How did you not research that?

00:28:23
Speaker 2: Did I not research that? I have had the experience of mixing gammeats from fish, which essentially means you very gently run your fingers along their abdomen to get them to release eggs or sperm, and they have occasionally released waste as well.

00:28:44
Speaker 1: What's the furb you used to describe that?

00:28:47
Speaker 2: Some people call it milking. I wasn't gonna go there, but.

00:28:52
Speaker 1: The way you might, like, you know, milk a bowl.

00:28:56
Speaker 2: Yep, yep, that way, that way.

00:29:00
Speaker 1: The glorious labor of science.

00:29:02
Speaker 2: Yes, so the world of an ecologist and so anyway, So yeah, so these extra layers made our eggs more complicated and allowed us to come on land. But I think the chicken in the egg question isn't about you know, this slightly more complicated egg. So you know, for example, in humans, we essentially brought a lot of this system inside of our bodies, so we have an amniotic sack. So we've got this fluid filled sack. We put the ocean inside of our bodies, and we allowed gas exchange with like our placenta and stuff like that. But birds and reptiles they made this system where you can essentially have the whole thing outside of the body and you can like lay it in a nest.

00:29:46
Speaker 1: Seems like a better plan, doesn't it.

00:29:48
Speaker 2: Yeah, yeah, I mean there's there's some benefits to being able to carry the baby around with you all the time. You always know where it is. There's there's some definite benefits, but it is also a bit difficult, I will admit. Okay. But so then the question is when did like bird eggs as we come to think of them come about. And the answer is that birds evolved during the Jurassic period, which was one hundred and fifty million years ago, So what we think of as bird eggs arose one hundred and fifty million years ago. Amniotic eggs in general are three hundred million years old, so older than birds. But now the question is when do we get chickens?

00:30:29
Speaker 1: All right, wait, so already eggs came before birds broadly.

00:30:33
Speaker 2: Yes, yeah, eggs, so like reptiles have eggy things. Also, they're a little bit different than what you think of as a chicken egg, but like amniotic eggs three hundred million years old. Birds in general one hundred and fifty million years old, but chickens weren't like the first birds. Chickens come later, and chickens appear to be about sixty six million years old. There's a fossil that appears to be the ancestor of chickens and ducks. And they have named this fossil wonder chicken. No, yes, no, really, wonder chicken.

00:31:07
Speaker 1: Wonderful name.

00:31:08
Speaker 4: Yeah.

00:31:08
Speaker 2: I wasn't able to find a lot more information. I mean, I suppose it could have been they found it in like Germany and it was like vondo chicken or like don't I don't know the details.

00:31:17
Speaker 1: Was it like six feet tall and eight hundred pounds or something.

00:31:20
Speaker 2: I hope.

00:31:20
Speaker 1: So when it walked, the earth shook.

00:31:25
Speaker 2: That's right.

00:31:30
Speaker 1: Here come the wonder chicken.

00:31:32
Speaker 2: That's right, Your dinner this time?

00:31:36
Speaker 1: Netflix, please call us.

00:31:38
Speaker 2: That's right. I'm available to consult. I'll write jokes too, but not poems. Don't worry, okay, so, but so, so, what we really want to know is like, all right, so we've had chickens in the wild, and there are wild chickens. So, for example, there are a red jungle fowl that you can find in Southeast Asia, like so in China and India and stuff like that. And there's green jungle fowl and gray jungle fowl and the red jungle fowl in particular, if you look up pictures of them on like Wikipedia, they look like the kind of chicken you'd find in your backyard actually kind of surprisingly. They have like the beautiful colors and the you know, the males look like any rooster that you would expect to see in your backyard.

00:32:20
Speaker 1: They poo on their eggs.

00:32:21
Speaker 2: Probably, I mean, yeah, humans pooh on their babies sometimes too. It's like it's a it's a messy process, man. And so anyway, all right, so then the question is when did we start getting domestic chickens? Uh? And that is apparently something that scientists fight about a lot. I've got a lot of papers where they were, like, you know, arguing about methods and this person was mad at that person. And it's so it does look like domestic chickens came from red jungle fowl. There may have been some hybridization with some other wild chicken species, but mostly it came from red jungle fowl somewhere in Asia, maybe ten thousand years ago. There's some archaeological evidence, and that archaeological evidence tends to be like they found chicken eggs, and it's not necessarily clear if the chickens were there because of the eggs, or because we were eating the chickens, or because there were cock fights, and there could have been a lot of different reasons we had chickens around. But you do see things like chickens, like you know, beautiful roosters on coins in different cultures, and so chickens do look like they were important part of our cultures for a really long time. There was one study that estimated that based on like DNA stuff, maybe chickens have been with us for fifty thousand years. We've been like carrying them around with us. But anyway, definitely, we are sure that the ancient Greeks around six hundred BC, so something like two thousand, six hundred years ago, you can see chicken imagery in like the Greek pottery, and so we're sure that we had chickens at least at that point, maybe even much earlier.

00:34:00
Speaker 1: Do you think there's any relationship between domesticating chickens and agriculture? And I can understand, like domesticating dogs, when you still a hunter gatherer community, you can hunt, you kill, you share with the dogs. What about chickens. I mean, I always think about feeding chickens grains, But actually, now that I think about it, chickens eat anything, don't they. So you could have chickens eat your kill also.

00:34:23
Speaker 2: Yeah, so I can see it being much much easier to have chickens if you're staying in one place, which would be easier if you were in agricultural society. But on the other hand, yeah, I mean we feed our chickens everything.

00:34:35
Speaker 1: Including chicken, right, yeah, cannibalism for the role.

00:34:41
Speaker 2: Yes, pull out your dKu Bingo card, all right, yeah, Okay, So the answer is eggs came first, then came chickens. But you can still have fun philosophical debates, just not when Kelly's around.

00:34:53
Speaker 1: But I think that's only because you've interpreted the question as what came first the chicken or any kind of egg. But I think the question is what came first the chicken or the chicken egg?

00:35:04
Speaker 2: Oh but but no, because eggs came first, you had to have.

00:35:11
Speaker 1: Answer the same.

00:35:14
Speaker 2: The red jungle fowl came first, and at some point there was anyway domestication happened, and blah blah blah. So let's let's see if Noah has more whimsy in his heart than I do, and maybe he will disagree with my answer.

00:35:28
Speaker 4: I'm endlessly amazed at how much of the story of many millions of years that humans have accumulated previously. I kind of assumed that this answer would be neither or both just played out in time. But I agree with Kelly. Eggs seem like the clear winner here. At least there's no shortage of as yet unsolved paradoxes to think about many things to both of you, I love the show.

00:36:09
Speaker 2: All right, we are moving from eggs to gravitational waves, and next up we have a question from Gerard which sounds like a really good setup to a new sci fi book.

00:36:19
Speaker 5: I've heard that if we could read gravitational waves from the Big Thing, someday we would also be able to see further into the past than with light. My question is, how would we be able to tell which gravity waves are visionated in that very early time and which formed later. Is there some analog with lights redshifting. I've also heard the same possibility with nutrinos again. Would there be a wave of distinguishing early in nutrinos from later?

00:36:41
Speaker 1: All right, thank you very much Gerard for this wonderful question. I love digging into the early universe, the cosmic egg. If you will.

00:36:49
Speaker 2: Oh, you are so good at making connections. I think someone should write a book about aliens that can read gravitational waves. Maybe somebody has yes.

00:36:58
Speaker 1: Yes, well, we can read gravitational waves, and we hope by doing so we can learn something about the history of the universe. So far, most of what we've learned about the very, very early universe comes from photons, and this is the light, the cosmic microwave background light that comes from a moment when the universe was very hot and very dense and went from being opaque like the center of the sun, to cooling enough that protons captured electrons. It became neutral hydrogen, which is transparent like hydrogen gas. So photons that were made just before that moment, instead of getting absorbed, flew free through the universe and are still around. Any light made before that time was immediately absorbed just like light made inside the sun is absorbed. So the earliest we're used to seeing the universe like concrete data from what happened a long time ago is thirteen point eight billion years ago plus three hundred and eighty thousand years. That's how long it took for the universe to cool enough to become transparent, and.

00:37:58
Speaker 2: As far as we can imagine, there is no way for light to tell us anything about what happened before that point.

00:38:06
Speaker 1: That's right, because none of those photons are still around. If they were, we could see them and we could learn stuff. They were photons made lots and lots of lots of them, but they're not around anymore. They were gobbled up by the atoms and the electrons.

00:38:19
Speaker 2: Oh, it's like when your great great grandparents are gone and they can't tell you their stories anymore exactly.

00:38:24
Speaker 1: But we would like to dig further, right, and before we dig further, just a note on the timeline. We'll define a moment, call it T equal zero, the first moment. We don't mean that that's the first moment of the universe. It's the first moment where our laws of physics apply at all, where we can think about this stuff where we can hypothesize what might have happened, because quantum mechanics and general relativity separate enough that we can just use one of them. Before that moment, things were so hot and so dense and so nasty we can't even think about them. We can't do calculations. We don't have a theory to explain it because we don't have quantum gravity, So we don't know what happened before T equals zero T equals zero, and then forwards we can think about theoretically, and the gap there is that we can think from T equal zero to three hundred and eighty thousand years afterwards, but we can't see yet before three hundred and eighty thousand years. Does that make sense?

00:39:17
Speaker 2: Yes? And is gravitational waves going to help us get back earlier?

00:39:21
Speaker 1: Yes, exactly, And so Gerard is asking about how we can see past that boundary, not with light but with other probes, and so he talks about two of them, gravitational waves and neutrinos. And the reason you could see earlier with gravitational waves and neutritos is that the universe was transparent to those earlier, and then it was transparent to light like many things in the universe are transparent to neutrinos that are not transparent to light, like the Earth. Photons will not fly through the Earth. The Earth is opaque to photons, but it's transparent to neutrinos. Neutrinos will fly right through it. So the fact that the universe was opaque to photons for the first three hundred eight thousand years doesn't mean it was opaque to neutrinos. In fact, it was transparent to neutrinos. The same story applies to gravitational waves. Gravitational waves pass through basically everything, and they scatter a little bit or they're affected by matter, But everything but black holes are transparent to gravitational waves. So they're an amazing way to look even earlier than light can show us what happened in the early universe. And Gerard's excellent question is cool, But aren't there neutrinos and gravitational waves everywhere? How could we tell the difference between a neutrino that came from the very early universe and one that was made eight minutes ago in the sun, or gravitational waves that are made from black holes? How do we know the difference between those and gravitational waves from the very early universe.

00:40:47
Speaker 2: You check their ideas.

00:40:51
Speaker 1: That was a joke, but it's actually basically the answer, right, So let's start with neutrinos because they're a little easier. Neutrinos decoupled from matter, meaning that they stopped really interacting with matter about a second after tea equal zero. So neutrinos do interact with matter. If it's very very dense, then even neutrinos will interact with it. But it only took about a second after that te equal zero moment for the universe to become dilute enough for neutrinos to just fly through and essentially ignore everything. So for the first second, neutrinos were absorbed, but that surface of last scattering the cosmic neutrino background comes from one second after tequal zero instead of three hundred and eighty thousand years, which is amazing. Yeah, and so like wow, we could see a lot of stuff we hadn't ever seen before. Super fun. Now, the issue is that these neutrinos are very very low energy, just like the cosmic microwave background light is very very red shifted. These neutrinos have been super duper red shifted down to low energy. Like the plasma that made the cosmic microwave background light was really really hot, and when those photons were made, they were very high energy, very short wavelength. But the universe has expanded since then, and when it expands, it also expands those photons and makes them super duper red, which is why it's often said that the CMB light is like light from a black body at like three degrees kelvin, because you'd have to be that cold now to emit photons at that wavelength, and the same things happen to neutrinos. Neutrinos from the Sun, for example, are like one to ten million electron bolts and energy. Neutrinos from supernova maybe twice that down to a few MeV. But the neutrinos from the very early universe are very very very low energy, which makes them very very challenging to see. Not impossible, but it means they're not going to interact as much as neutrinos with higher energy. So we have plans to see them, and we hope to see them. Current experiments that look for dark matter, for example, are very very sen to things that go bump in the night and they very recently become sensitive enough to see like the neutrino background, this neutrino fog that fills the universe, not from the early universe yet, but from like everything else that's emitting neutrinos. And we hope on one day to be sensitive enough to these cosmic neutrino background from the very early universe, but not yet, and we'll know that they're there because we'll see them at lower energy than basically anything else makes neutrinos.

00:43:28
Speaker 2: Am I remembering correctly that you told me it's hard to measure neutrino's period, Yes.

00:43:32
Speaker 1: Because they hardly interact. You build a big detector, and like one in a trillion or one in a quadrillion neutrinos that fly through your detector will interact with it.

00:43:40
Speaker 2: Oh man, Yeah, all right.

00:43:42
Speaker 1: The lower the energy, the more challenging it is. So yeah, it's hard.

00:43:45
Speaker 2: It's a good thing. There's so much money for science.

00:43:49
Speaker 1: Now. Gravitational waves are also an excellent source of information about the early universe, all for the same reason as neutrinos. Neutrinos hardly interact with matter because they only use the weak force, which is very, very weak gravitational waves only use gravity, which is even weaker than the weak force, and so they decouple from everything else in the universe almost immediately. Right, So using gravitational waves you can see even further back than one second after T equals zero. Amazing yes, But again they are also affected by redshift, and so these would be very very low frequency gravitational waves, very long wavelengths. Now, the gravitational waves that we're used to thinking about are the ones from like black holes that collide with each other, and before they do, they orbit each other and emit a huge amount of energy gravitational waves. Those are fairly high frequency, and we can see those with our detectors. And so those detectors like Lago, they can't see gravitational waves with really long wavelengths because they don't make any change on the scale of like the Earth. Even you need like a galaxy size detector to see really long wavelengths gravitational waves. Amazingly, humans have a galaxy size detector for gravitational waves. People have used pulsars, which are extraordinary neutron stars that rotate with extreme regularity, and by variations and their rotations, we can tell whether space between us, and the pulsar has been squeezed or stretched. In the last couple of years, we've even seen evidence of very long wavelength gravitational waves using pulsar timing arrays. Really an amazing piece of science. But even those might be too short wavelength to see the early universe gravitational waves because they're going to be extremely low frequency. The pulsar timing arrays probably are seeing like a general gravitational wave background from all sorts of black holes and acceleration. I mean, everything you do creates gravitational waves. You wave your hand in front of you, you're creating gravitational waves because any kind of acceleration is going to create them. So this is just like a gravitational wave noise through the universe. But the ones from the early universe will be unique because they won't have any specific source. They won't come from this black hole, from that black hole. They'll just fill the universe sort of the way the cosmic microwave background light will, and they'll be very broadly spread out across various frequencies. There'll be no big peak, no clear power structure. It'll be a very broad frequency signal. Even that will be very very hard to see, and so the way people hope to see gravitational waves from the early universe is not actually by seeing the gravitational waves directly, but instead by seeing those gravitational waves affect the cosmic microwave background light. So that light we talked about earlier that was made three hundred and eighty thousand years after T equals zero. When it was made, it was affected by these gravitational waves that were already around from the early universe. Because it gives that light a special twist. Remember that light is a ripple in the electromagnetic field, and the field is just like numbers in space and the Higgs fields, for example, it's just like a number at every location in space. But light is a vector field, which means it's not just one number, it's like three numbers. Or equivalently, you can think about it like a little arrow with a length and a direction and every point in space. And as light moves, those arrows ripple, and it can do more than just move, it can also spin right. So this is what we call polarization of light. The same way that like if you have a jump rope, you can shake it up and down, or you can shake it sideways, or you can shake it in like a swirly motion. This different way for waves to propagate along that string. Same thing for photons, and mathematically you can decompose them into what are called emodes that are radial patterns and B modes that are like twisting swirling patterns. Gravitational waves are the only way we know to give B mode polarization to the CMB light. There's something about how those gravitational waves are stretching and squeezing the space while light is being formed that gives it those B modes. Other gravitational waves like black hole collisions late in the universe cannot give like a broad pattern of B mode polarization. So if you look at the cosmic microwave background light and you measure its polarization and you see B modes, that would be fascinating information about the early universe. And a few years ago an experiment called BICEP two claimed to have discovered it. Huge news rocked the science community until it turned out that they made a mistake in their analysis and they were relying on data from another experiment to remove the effect of dust, but they didn't actually have that data from that experiment. They took a screenshot of a PowerPoint slide and misinterpreted it and used that as the basis for their analysis. And they came up with these big claims and had to walk it back. Very embarrassing. Brian King wrote a book about it called Losing the Nobel Prize. It's a fun.

00:48:55
Speaker 2: Story, not for the people involved.

00:49:02
Speaker 1: He tells it with a smile on his face.

00:49:03
Speaker 2: I think was Brian Keating involved?

00:49:05
Speaker 1: Oh yes, deeply. No, he's not embarrassing other people. He's owning up to his own mistakes. Oh okay, their own mistakes. Anyway, we have not yet seen that, So Gerard, that's how we might differentiate early universe neutrinos from later universe neutrinos. Or we might spot evidence for early universe gravitational waves, either of which could tell us amazing things about what happened in the first few moments after T equal zero, none of which could tell us about what happened before T equal zero. That's a whole other question.

00:49:37
Speaker 2: Mark, which one do you think is more likely to tell us something first?

00:49:41
Speaker 1: Oh? Wow, great question. I think we probably will figure out this be mode polarization of the CMB before we figure out how to see these very low energy neutrinos. But both communities are filled with super smart people working hard and coming up with clever ideas that I could never anticipate.

00:49:58
Speaker 2: So we'll see, okay, and we'll see what Gerard thinks about the answer.

00:50:05
Speaker 1: Gerard listened to our answer and wrote back to me, and he preferred to send a written response. I'll read it for you now. Here's his reply quote. I didn't know the gravitational waves would be like photons and be stretched by their long journey through expanding space, lowering their frequency. The idea of indirectly detecting them by their effect on the CMB photon polarization is ingenious. I wonder how precise the measurements would need to be before scientists could reconstruct any earlier than CMB features. Nor did I know that neutrinos would also lose energy through stretching space. I guess I've always thought of them as particles, but we can think of them as waves and a field. I am always fascinated when science builds on an idea by extending it to another domain, as in this example. Light waves stretch, so gravity waves should stretch too. A further question evoked by your description in the hot dense early universe, what kind of structure might it have had. Would high energy simply prevent anything from coalescing. I'm sure we will be surprised by something no one has even imagined. Thank you very much for that response, Giard. Let me answer some of your follow up questions. Yes, neutrinos also lose energy as they move through space because space is stretching. This is a great example of the non conservation of energy in an expanding universe. It applies to everything, particles and waves. Particles in the end are really just ripples in quantum fields, and they are affected by the expanding universe. You also ask, what was the structure like in the hot dense early universe. It's a great question, and structure is a tough way to think about it, because in the very early universe you have these quantum fields that are filled with frothing energy. It's not like now when you have isolated energy and you can think about a little ripple in the field as a particle. It's like taking a thousand drops and putting them in a glass. You don't really think about drops anymore. Now you think about other emerging forms of that water waves and other sorts of things. And so what's going to happen the very early universe is that those quantum fields will be filled with energy and we'll get all sorts of weird bizarre effects. Thank you very much to these listeners for sending in your questions, and to everybody out there who drives this podcast forward with your personal curiosity about the universe.

00:52:25
Speaker 2: Please send us your questions at questions at danieland Kelly dot org. And if you like the podcast, do you think about leaving us a rating? We would really appreciate that, yes, exactly. Help other people find the podcast so that they can share their questions to.

00:52:40
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00:52:41
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00:53:00
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00:53:05
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00:53:11
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00:53:17
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