#128 - Paul M. Sutter - The Universe, Consciousness & Why We Might Be Alone

Summary

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The Peter McCormack Show #128 with Paul M. Sutter

Title: The Universe, Consciousness & Why We Might Be Alone
Release Date: November 13, 2025
Host: Peter McCormack
Guest: Paul M. Sutter (Astrophysicist, Author, Science Communicator)

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Episode Overview

In this expansive, mind-bending conversation, Peter McCormack sits down once again with astrophysicist Paul M. Sutter to dive deep into cosmic mysteries: the scale of the universe, the fundamental nature of matter and physics, the enigma of dark matter and energy, the search for extraterrestrial life, and our prospects for venturing out of planet Earth. Blending scientific rigor with philosophical reflection, they explore why space fascinates, humbles, and sometimes consoles us—and wrestle with questions about meaning, our cosmic loneliness, and the future of humanity among the stars.
The tone is probing, humorous, reverent, and occasionally emotional, capturing both the awe and humility that come with contemplating existence at its grandest scale.

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Key Topics & Insights

1. The Therapeutic Power ("Astrotherapy") of Cosmology

[02:13 – 03:32]

• Paul's Role: Paul explains the comfort many find in cosmic thinking:

  “Talking about these topics, like sitting under a dark sky, letting our minds wander throughout the universe...it does have a therapeutic benefit.” — Paul [02:48]

• Escapism: Peter notes the stark contrast between political chaos and the purity of space, to which Paul responds with the idea of "Astrotherapy"—the solace and perspective gained from pondering cosmic questions.

2. The Structure and Scale of the Universe

[04:35 – 19:46]

• Is There an Edge or Other Universes? Paul discusses the Big Bang as the boundary of "all there is," and the uncertainty about other universes:

  “We don't even know if we're asking the right questions when it comes to the origin of the universe.” — Paul [05:27]

• Observable Universe & Horizons:
  • Cosmological event horizon marks what we can ever see—about 90 billion light years across.
  • The universe beyond may be much, much larger, possibly infinite, but fundamentally unknowable.
• Homogeneity:

  “There is no privileged position...on average is any different than anywhere else.” — Paul [13:26]

• Cosmic Web: Paul, a leading expert on cosmic voids, describes the universe’s large-scale structure:

  “It looks like a giant web...galaxies are just tiny dots of light. That's how far out you're looking.” — Paul [16:13]

• Void Expertise:

  “I like to think of myself as one of the top five experts on cosmic voids in the world, because there are about five people working on cosmic voids in the world.” — Paul [16:13]

3. Dark Matter, Dark Energy, and the Limits of Physics

[24:13 – 38:01]

• Current Theories/Hypotheses:
  • Dark matter and dark energy are labels for things we observe but don’t fundamentally understand.
  • Dark matter: “Everything’s acting as if there is more matter than what we can see.” — Paul [24:33]
  • Dark energy: Explains why the expansion of the universe is accelerating.
• Alternatives and Scientific Conservatism:

  “Dark matter isn’t a great idea, but it's the best we got.” — Paul [27:30]

  • Alternative theories (like modified gravity) can’t yet explain all evidence.
• Higgs Boson vs. Dark Matter:
  • Higgs is a verified particle that gives mass to others, confirmed via experiments.
  • Dark matter remains hypothetical, with no direct evidence yet.

4. Quantum Fields & What is a Particle?

[41:33 – 47:04]

• Paul explains particles as excitations in quantum fields:

  “Most of the time these fields exist at a low energy level...every once in a while a little localized vibration...we call that a particle.” — Paul [41:33]

• This modern view (quantum field theory) is mathematically messy but extremely powerful and predictive.

5. The Question of Fine-Tuning and the Multiverse

[46:04 – 52:39]

• Peter wonders: is our universe “lucky” or inevitable?

  “We find ourselves here in a universe that appears to be tuned, designed for us...these are fruitful philosophical conversations, and they hurt the brain. They also make it feel so, so good.” — Paul [47:14]

6. Cosmic Perspective: Insignificance and Meaning

[53:00 – 56:09]

• Paul reflects on the emotional impact of cosmic scale:

  “This is the only known place in the universe where music happens, where art happens, where engineering happens, where Bitcoin happens...Let’s lean into what makes us special.” — Paul [54:10]

• The universe’s enormity inspires stewardship and appreciation for Earth’s uniqueness.

7. The Search for Extraterrestrial Life

[56:09 – 66:55]

• Are We Alone?
  • “All available evidence tells us that we are alone. We have absolutely no evidence anywhere...that there is life, or especially intelligent life out there.” — Paul [56:13]
  • But emotionally, Paul hopes we're not:

    “I want to share it. I don’t want to be alone in this universe.” — Paul [56:13]

• Exoplanets and Habitability:
  • About 5 billion Earth-like planets in just the Milky Way’s Goldilocks zones.
  • “Red dwarf” stars offer more opportunities but present new hazards (like stellar flares).
• The Problem of “Looking for Ourselves”:
  • Our search prioritizes Earth-like chemistry/life because it’s what we know—carbon, water, etc.—but Paul acknowledges life could be fundamentally different elsewhere.
• SETI, technosignatures & the “Wow!” Signal:
  • Despite decades of searching, intelligent tech signals remain elusive.
  • The “Wow!” signal (1977) remains unexplained but also unrepeatable.

8. The Fermi Paradox & The Great Filter

[71:10 – 73:17]

• Fermi Paradox:
  • If nothing special is going on here and the galaxy is old, "where is everybody?"
  • Perhaps something (the "Great Filter") makes intelligent life rare or short-lived.

9. Searching for Life via Planetary Atmospheres

[74:33 – 79:07]

• James Webb Space Telescope and its possible successor (Habitable Worlds Observatory) are designed to detect biosignatures—chemical evidence of life—in exoplanetary atmospheres.

10. Mars Exploration and Colonization

[87:27 – 109:48]

• Is Mars Colonization Possible?
  • “There is no law of physics that prevents us...but my best guess is getting to Mars, even sending a single mission, we’re two or maybe three generations out from that.” — Paul [87:51]
• Technical, Financial & Moral Challenges:
  • Enormous engineering problems: launch windows, survival, cosmic radiation, growing food, needing underground shelters, and multi-billion or trillion-dollar costs.
  • On terraforming Mars:

    “Not physically impossible, but we can’t even terraform the Earth and we're here. The thought of terraforming another planet…the problem with Mars is it's already dead.” — Paul [105:16]

• Is it a waste?

  “Given how difficult it is, given how much engineering effort has to go into it, it's almost certainly a waste of time.” — Paul [109:25]

  • But: the technological spin-offs may still benefit humanity.

11. Cosmic Interlopers: Oumuamua, 3I/Atlas & Alien “Clickbait”

[112:29 – 120:28]

• On Avi Loeb’s claims about interstellar objects (e.g., 3I/Atlas being a spacecraft):
  • “It’s not that the astronomical community rejects Avi because he thinks there might be aliens...It’s because he's misrepresenting the data. That’s why we don't like Avi anymore.” — Paul [113:48]
• Comets vs. asteroids: Comets are icier, asteroids are rockier—both are cosmic leftovers, and most interstellar objects encountered are statistical oddities, not alien probes.

12. The Emotional and Philosophical Side of Science

[121:40 – End]

• Paul’s awe at the scale of the universe:

  “Here we are, monkeys on the surface—apes, sorry biologists—of an unremarkable planet in the corner of a spur of a spiral arm, can sit here and talk about supernova, interstellar visitors, the origins of the universe itself. That’s what gets me.” — Paul [121:40]

• Paul opens up about how family and love have shifted his outlook, emphasizing the value of human connection alongside scientific wonder.

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Notable Quotes (with Timestamps)

• On therapeutic benefits of cosmic thinking:

  “I call it Astro Therapy ...sitting under a dark sky, letting our minds wander...does have a therapeutic benefit. It does for me.” — Paul [02:48]

• On the edge of what we can know:

  “We don’t even know if we’re asking the right questions when it comes to the origin of the universe.” — Paul [05:27]

• On cosmic insignificance versus meaning:

  “The enormity of the universe imbues me, it animates me with meaning and significance.” — Paul [54:10]

• On being alone in the universe:

  “All available evidence tells us that we are alone...but I don’t want humanity to be alone. I want everything I just said about what’s happening here...to share it with someone else.” — Paul [56:13]

• On searching for life:

  “If we see a bunch of biosignatures, then we’ll have confidence, not proof yet...that this planet is being changed by life.” — Paul [74:33]

• On Mars colonization:

  “There is no law of physics that prevents us...That said, my best guess...we’re two, maybe three generations out from that.” — Paul [87:51]

• On fine-tuning and meaning:

  “These are fruitful philosophical conversations, and they hurt the brain. They also make it feel so, so good.” — Paul [47:14]

• On the privilege and emotion of discovery:

  “I center my life on love, and like, what’s special and good about humanity. ...Science is an expression of their humanity. ...There’s so many different ways to answer our place in the universe, and I’m just lucky to be a part of it.” — Paul [124:28]

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Key Segments (Timestamps)

| Time | Segment | |------------|--------------------------------------------------------------------| | 02:13-03:32| Why cosmology is a therapeutic escape (“Astrotherapy”) | | 04:35-19:46| Structure, scale, and mystery at the edge of the universe | | 24:13-38:01| Dark matter, dark energy, scientific skepticism | | 41:33-47:04| What is a particle? Quantum fields explained | | 53:00-56:09| Cosmic insignificance and meaning/purpose | | 56:09-66:55| Fermi Paradox, exoplanets, technosignatures, the absence of aliens | | 74:33-79:07| Biosignature detection and next-gen telescopes | | 87:27-109:48| Mars: colonization, difficulties, morality, and practicality | | 112:29-120:28| Interstellar visitors—science vs. speculation | | 121:40-End | Paul on awe, emotion, and the meaning of curiosity and love |

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Memorable Moments

• Paul's humility and humor: Claiming “top five expert” status simply because only five study cosmic voids [16:13].
• The “Astrotherapy” concept: Turning cosmic awe into an informal kind of therapy [02:48].
• Confronting the loneliness of intelligence in the universe: Paul toggling between scientific caution and emotional hope [56:13].
• Peter’s clear, layman’s curiosity: “So there’s no galaxy where there’s a Paul and Peter sat there...and there’s just galaxies over here?” [14:45]
• Reflection on technology and spin-offs: Even if Mars missions aren’t practical, the effort brings real, immediate benefits to life on Earth [109:48].
• The closing, emotional exchange: Where Paul connects scientific awe and family love, acknowledging the limits and beauty of human significance [121:40–end].

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Concluding Sentiment

This episode is a masterclass in mixing the rigor and precision of science with wide-eyed, philosophical wonder. Paul Sutter elegantly weaves together the hardest questions of cosmology with open-hearted reflections on what it all means for humanity, our place in the universe, and the unique project of being alive together under the stars. If you want to feel both infinitely small and deeply privileged at once, this conversation delivers.

Transcript

[Paul]

What gets me is, is what we talked about earlier, the enormity of it, the scale of it, that I can open up my computer, write a piece of software that encodes some physics and some knowledge of the universe and is able to replicate the vast majority of the history of our universe at large scales. Or I can write down an equation that captures it, that here we are, monkeys on the surface. Apes. Apes, sorry, biologists. Apes on the surface of a unremarkable planet in the corner of a spur of a spiral arm can sit here and talk about supernova, interstellar visitors traveling to Mars, the origins of the universe itself. That's what gets me.

[Peter]

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[Paul]

All right, Good clap.

[Peter]

This is a solid clap, Mr. Spaceman.

[Paul]

I get one clap for my entry. Usually I get more when people introduce me, but this show is just one clap.

[Peter]

Yeah, we're a tough crowd. Hey, everyone is excited you're back. Even my dad.

[Paul]

My dad.

[Peter]

Hey, dad, did you hear Granddad last night? He was like, when's the spaceman back on? I was like, he's on tomorrow. I was like, how did you know? He was like, no, I heard you talking about it.

[Paul]

He listened to the last one. All right, all right. That's one listener confirmed. We love it.

[Peter]

We all love the Spaceman. Listen, Paul, you know how much I love your show. You know how excited I was last time. But when you messaged me and said, let's do it again, I'm like, okay, when?

[Paul]

Well, it's such a pleasure doing the show because I love. You have more questions than I had to answer, like during my thesis defense. And so this hour or like two hours, however long we spend, this is more intense than a physics graduate record exam. This is. This is testing my knowledge of everything. And I love it. I love a good challenge.

[Peter]

Well, we do a lot of politics. I told you that before. It gets a bit samey, Conor. If I could just do one subject all day, every day, what would it be? Space. Space. Space, Space. I think it's an escape from all the shit of politics.

[Paul]

Well, that's. That's a real thing. That's a real thing. A lot of people listen to my show, read books. I enc. Lot of people, they'll email me and say. They'll say, thank you, Paul. Like, I just, you know, just. The world is messy and it's complex and it's got me down. Or I'm going through personal hardship and heartache and I just listen to your show to just escape, to enter another world. And so I have a name for it. I call it Astro Therapy, which is just totally made up and not professional. Do not take any therapeutic advice. Please seek a professional for assistance. But I do know that talking about these topics, like sitting under a dark sky, letting our minds wander throughout the universe, and it does have a therapeutic benefit. It does for me. It's one of the reasons I love it so much, and it does for other people, so. What a gift.

[Peter]

Well, it's escapism from the world in that there's no politics with asteroids. There's no. Well, there might be.

[Paul]

Only if there's one headed towards us.

[Peter]

Yeah, but. But it's. It's pure escapism. But also some of the concepts that you talk about, some of the podcasts you've made are so wild. Some of, like, even this morning. I'm listening. I'm listen to the show about the edge of the universe. I'm like, yeah, but there must be an edge. No, there isn't. That's just it.

[Paul]

Stop it, stop it. Stop thinking that's just it.

[Peter]

But. And then there's things that just, like, totally fry my brain. Like, I was. Even when you were talking on the show about the edge of the universe, you were talking about the Big Bang was the universe.

[Paul]

It happened right here.

[Peter]

Yeah, it was just. That was the entirety of the universe. And then I went down that rabbit hole that I'm sure you know people who go down. So. Okay, but what started it? What triggered it? How did it happen? Why did it happen? If there's one, there, can there be one somewhere else? And then my brain fries.

[Paul]

But the Big Bang was all the Elsies there was.

[Peter]

Well, so I have a question on that.

[Paul]

Let's do it.

[Peter]

Could there have been other big bangs in other. Could there be other universe? Not the multiverse like Just another universe. Who?

[Paul]

That's a fun question. That's a good one. What a way to open up this discussion. It depends on what you mean by universe. We have our universe, which by definition is all the things. It's all the stuff.

[Peter]

Yes.

[Paul]

So it's the entirety of material existence in that.

[Peter]

In our universe.

[Paul]

The universe.

[Peter]

In the universe.

[Paul]

The universe. But.

[Peter]

But we do that. We say that with a. With the knowledge of our universe. But if our universe could exist, pop into this unknown space, unknown time, for unknown reason, there could be others. Yeah, I mean, unknown spaces.

[Paul]

Absolutely. There. There. There's a lot we don't know about the universe. There's a lot we do, which is why we have professional cosmologists, but there's a lot we don't, and especially we do not understand. The earliest moments of the Big Bang, the earliest moments of the universe, where things get so cr. So wild, was so far beyond our current understanding of physics that even our normal conceptions of time, of space, of length, of duration, of cause and effect crammed down into this quantum mush where we can't make heads or tails of it. And we don't even know. We don't even know if we're asking the right questions when it comes to the origin of the universe. Like the word origin applies. A cause, an agent, a beginning, a start. We don't even know if those are the right words to describe what is happening in those moments where we might be limited by, like, a fundamental bias of our consciousness that puts order, that. That is grounded in evolution, that is Grounded in our 3D, our perceptions of space and time, where those are so baked into our. Our DNA and how we approach the world that maybe we're missing something big. That's the kind of stuff that I like to think about when I look out at a dark, starry sky and let my mind wander. Is maybe we're missing stuff. And so in. In questions like this, get to that. Questions like that poke at. At the edge of our knowledge, the edge of what we can even define sensibly as a science or even as a philosophy. And those are delightful questions. We don't have answers. I. I can't tell you. Like, yes, there's another universe, or yes, there are other dimensions, or yes, there are of reality or existence. However, whatever kind of language you want to dress it up in, what we have access to is our observable universe, which is about 90 billion light years across because we have the.

[Peter]

What was it? The cosmological event horizon.

[Paul]

Yes.

[Peter]

Is the edge of the observable universe.

[Paul]

Exactly. You nailed it. Cosmological event horizon, also called the particle horizon, has a few other names, and that is the limit of information that has reached us or can reach us in the future.

[Peter]

About 18 billion light years, is it.

[Paul]

The 18 billion light years is. So there's. There are a few different horizons, There are a few different edges in our universe. One edge is of just under 14 billion light years away. This is called the Hubble radius or, or the Hubble distance. And our universe is expanding. It's getting bigger and bigger every single day. Galaxies, on average, are getting further apart from each other. The farther out you go in space, the faster the galaxies appear to be receding away from us because there's more space to do, stretching between us and that and that galaxy. And at that turnover point, at about 14 billion light years away, galaxies appear to be receding from us faster than light. So we can see those galaxies right now because the light they emitted started off when the galaxies were really, really close to us, and then they emitted a little bit of light, and then the expansion universe carried that galaxy away. And then the light finally hits us. So we can see the galaxy right now. But if we were to get in a rocket ship and blast off, we'll never, ever, ever be able to reach that galaxy because the expansion of the universe is carrying it too far away from us for. For us to ever catch up. So eventually those galaxies will fade from view. Eventually, the light that they are emitting right now, like right now, at that instant, there is a distant galaxy that is emitting a bit of light. That bit of light will never, ever, ever reach the Earth because the expansion of the universe is too fast. It's too long, it's too far, it's too much.

[Peter]

So the parts of the universe we can't observe, the unobservable. Can we have any concept of how, how far, how big it is, or is it immeasurable? Could it be infinite?

[Paul]

It could be infinite. We honestly don't know, and we probably can never know because there is a limit to how far we can see. There's a limit to how far we can ever see into the future. Assuming, assuming that the expansion of the universe continues as it is, which we don't know if it might change. But as of now, everything we measure, everything we observe suggests that it will continue to expand. If the universe continues to expand, then there are regions of the universe that are so far away that we'll never see them, that their light will never, ever reach us. And it's never reached us in the entire history of the universe. How big the universe is outside of our little observable bubble, we don't know. It could be incredibly large. It could be medium large. It could be infinitely large. We don't know.

[Peter]

Does it have a shape?

[Paul]

We don't know. Lots. You're going to hear that a lot today. Like, it's just, we don't know. So we do know that our observable universe, the patch of the universe that we can see, which is about 90 billion light years across, is as far as we can tell, as flat as flat can be. It's geometrically flat, which means if you send out two light beams and they're racing in parallel, they will stay parallel forever, you know, unless they, like, hit a black hole or something. But that's small stuff on average, on very, very big scales. Once you smooth out all the matter, these light beams will stay parallel forever. That is the definition of geometric flatness. However, my backyard looks pretty flat, even though I know the Earth is curved, but it's curved at a scale beyond my horizon, beyond what I can measure the universe, we suspect is much, much, much larger than the little patch that we can observe. And it could have any shape it wants. Parallel light beams could converge together. They could diverge away from each other. They could do weird, twisty, flippy stuff. They could come back around to where they started. But we don't know. And we unlikely will have never have access to that information because it is, by definition, outside of our observable limit.

[Peter]

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[Paul]

As far as we understand, one of our basic, basic foundational assumptions about the universe is that it's called homogeneous, like homogenized milk. It's, it's all the same that there is no privileged position, that there's no privileged perspective, that there's no privileged location. There's nothing that on average is any different than anywhere else. So if we stand here in the Milky Way galaxy, which we tend to do, and we look around, we see galaxies everywhere we look, the cosmological principle, this idea that the universe is homogeneous, tells us that no matter where we go, if you pick any galaxy in any of our surveys, anything we've mapped in the universe, and if you were to snap your fingers and instantly transport yourself there and you'll look around, you'll see different galaxies. You won't have an Andromeda next to you, you won't have a Laniakea supercluster over there, you'll have a different arrangement. But still, everywhere you look, you'll see roughly the same kinds of galaxies with the same numbers, the same typical sizes, the same average distances that no matter where you go in the universe, your universe looks roughly the same.

[Peter]

So there's no galaxy where there's a. There's a Paul and a Peter sat there, and there's, oh, there's no galaxies in that direction. They're just over here.

[Paul]

Exactly, exactly. On average, on very large scales. Like, obviously, if we look in our local universe, and if you make a small enough box, say it's 10 million light years on a side, there's an Andromeda galaxy right there. I don't know if I'm pointing to the Andromeda galaxy right now, but like, say there's an Andromeda galaxy right there, and then there isn't one there. There's just a blank space right there. So in any local patch, in any small patch, and for cosmology, 10 million light years is kind of small. It's very local. You can have all sorts of differences. And if we were to transport you to a different Galaxy? Yeah, there might be a completely different. Oh, there, there are a few galaxies over here and there's nothing over here. You go to a different galaxy somewhere else in the universe, oh, there's a bunch of galaxies above us and Nothing below us, etc. Etc. But once you make your box big enough, once you start averaging out and that scale is around 100 million light years across, it all evens out. We call this the scale of homogeneity. We've actually been able to measure this with our most massive and most complete galaxy surveys. We've seen this transition point to where the universe, if you zoom out enough, looks pretty much the same.

[Peter]

There are weird patches of emptiness though, right?

[Paul]

Oh yes, there are many weird patches of emptiness. This is one of my favorite topics in cosmology. These are called the cosmic voids. I like to think of myself as one of the top five experts on cosmic voids in the world because there are about five people working on cosmic voids in the world. And yes. So the cosmic voids are absolutely fascinating. I absolutely love them. You know, there's this joke that an expert is someone who knows more and more about less and less. I, I'm an expert on absolutely nothing. This is what I spend my research time investigating is, is at the very largest scales in our universe. When you zoom all the way out, and I'm talking all the way out, where you're not talking about solar systems, you're not talking about spiral arms, you're not even talking about galaxies or, or clusters of galaxies, you're zooming so far out, you're taking such a broad perspective that entire galaxies, galaxies are home to hundreds of billions of stars. But in our cosmological perspective, galaxies are not, are just tiny dots of light. That's how far out you're looking. You're looking at instead not at individual galaxies, but how galaxies are placed and arranged in our universe. And we call this the large scale structure of the universe. It's pretty, pretty basic name, but it gets the job done. But it's also called the cosmic web. And it's called the cosmic web because it looks like a giant web.

[Peter]

We, there's pictures of it.

[Paul]

There are pictures of it. Can we pull up do large scale structure of the universe or cosmic web.

[Peter]

Is it American football shaped? It's kind of oblong. It's not a perfect circle when we see it.

[Paul]

Yeah, like that, That's a cube.

[Peter]

It's like a side egg.

[Paul]

Oh, so the side egg. So what this is. Yeah, go ahead and pull, pull that image up, what this is, what you're looking at is the whole entire sky. So if you ever look at a, like a two dimensional map of the Earth, so that's not the universe, it's the universe that's our sky. And it's taking the whole entire sky and wrapping it up into a certain kind of projection that's called a Mulvid projection. And what this is, dead center right in the middle, that is looking towards the center of our galaxy. And you see that bright patch that, that's Sagittarius Complex, that's right there, the core of the galaxy. And then the point at the back pointing in the complete opposite direction as the center of the galaxy is actually spread out across that entire outer rim of this egg. Just like if you look at a Mercator projection of a map of the Earth. The north pole is the entire top line of the map and the south pole is the entire bottom line of the map. That's a similar kind of projection that takes our entire sky and squishes it down so we can print it on a piece of paper like to do. But you can see all these maps. There you go. See that green one? This is what we typically get out of a galaxy survey.

[Peter]

Looks like a brain.

[Paul]

Looks like a brain. A lot of people, you know, when you, when you look at the cosmic web, one of the first things it you identify it as, it looks like a collection of neurons. And so a very common question I get is, well, is the universe a brain? Because it kind of sort of looks like a brain. As far as we can tell, it is not a brain.

[Peter]

Is there a quantum argument that it is a brain?

[Paul]

No, I think it is one of these things that is just a pure coincidence. What's happening here, how you build a cosmic web and you might be able to pull up a movie, let's say Evolution of the cosmic web or growth of the cosmic web. We have a lot of simulations of this. We can't, we can't watch it in real time because how the cosmic web has grown has taken billions of years. And no one could get funding for that amount of time. So instead we perform computer simulations of the growth of structures and what it is. It's an action of gravity. And so, yeah, there's, these are snapshots going from the past to the present day. If you wind back the clock billions of years and you might even be able to pull up Movies on YouTube of this. If you wind back the clock billions of years, the universe is pretty homogeneous. Even more Homogeneous than it is today, even at small scales, is pretty much the same from place to place. There are no galaxies, there are no stars, there are no clusters. There's just gas and dark matter all filling up the volume of the universe. Hydrogen and some hydrogen, helium, a little bit of other. And then a lot of dark matter hanging out. And then there are, but there are random pockets, little seeds in this early universe that are just randomly, by pure chance, slightly more dense than their surroundings by like one part in a million. And that's enough, that's all it takes. Because that little tiny pocket that has just a little bit more matter than everywhere else, has a little bit stronger gravitational pull, has a little bit more mass so it can pull on its surroundings. It accumulates a little bit of matter, and then that makes the, the, the, that little pocket even more dense. And now it has even more gravity, so it has even more gravitational pull. So it's surround, it pulls on even more of its surroundings and then gets more massive and more massive and more massive. And then as the evolution proceeds in the universe, the rich get richer and the poor get poor. If you have a little bit of mass at the beginning, you end up with a lot of mass because you have a lot more stronger gravitational pull. And then if you don't have any mass, you get emptied out. And so what we see through this process of just random seeds, random little fluctuations, variations in the density in the early universe, you allow gravity to just do its thing and all it does is pull. You take this process over hundreds of millions of years, billions of years, and you end up with this complex, tangled filamentary network where you have incredibly dense knots of galaxies. We call these the clusters. They're home to thousands of galaxies at a time. You have these broad walls that can stretch for tens of millions of light years. You have these long thin filaments that connect the clusters together. And then you have the vast empty regions which we call the voids, which are like the deserts. These are places that are, have been emptied out of matter to, to increase the density. Like our galaxy, our Milky Way. The material that it took to build the Milky Way had to come from somewhere. It came from the nearby local void billions of years ago. That's where all these atoms were. And then they got glued onto our Milky Way galaxy. So a lot of cosmologists study the cosmic web because it tells us about the history of the universe. If you change how the universe works, if you change what it's made of, if you change the forces that operate in the universe, then you change the appearance of this cosmic web. You change what it looks like. You change its statistical properties.

[Peter]

This never happened. This would never have happened. You change one, we wouldn't be here now in this moment.

[Paul]

There are some things, like if you change some basic physics. Yeah. Thing like if you change the charge on the electron or the speed of light, then like stars don't ignite. But what we're looking at are properties of, like dark matter and dark energy.

[Peter]

Well, so we had a guy and it was Peter McCulloch. I think I emailed you about him.

[Paul]

You did? Yes.

[Peter]

So he says, he said there's no such thing as dark energy and there's no such thing as dark matter. He says it's purely a thesis. It's never been proven.

[Paul]

That is absolutely correct. What we call dark matter and dark energy are labels that we give to observations that we cannot ignore. We have hypotheses, we do have guesses about what is powering dark matter, what is powering dark energy, but we do not know what they fundamentally are. And these two sets of observations that we have when it comes to dark matter, when what we observe in the universe is that matter in the universe inside of galaxies, the way galaxies operate, the way galaxies move around in clusters, the way that this cosmic web has grown over billions of years, everything's acting as if there is more matter than what we can see.

[Peter]

Quantized inertia theory.

[Paul]

Yes. Yes. So we have this set of observations when we look out in the universe, everything is acting as if it's heavier than. Than what it seem. When it comes to dark energy. What we observe is that the expansion of the universe is accelerating. We can't get away from these observations. These are raw observations. These are, these are indisputable. Like we, we go out and we see distant supernova and they, they are dimmer than they're supposed to be. We go out and measure things like something called the baryon acoustic oscillations. When with the DESI results that came out earlier this year has the shape that we expect based on the existence of dark energy. Like, we can't get away from these observations. Now we're trying to explain it. Why does matter appear to be heavier than it looks? Why does, why do galaxies appear to have more matter than. Than what is being emitted by light? Why does the universe. Why does the expansion of the universe accelerate? So we have hypotheses for both of these and we treat these two problems separately. Although there is a lot of work, including work I've done that suggests that maybe there are connections between dark matter and dark energy. And for dark matter, we strongly believe that there is a particle or set of particles that we have yet to discover. These are particles that exist outside the standard model of physics that we have not encountered in any of our experiments or in laboratory yet. That this particle floods the universe, makes up roughly 80% of the mass of the universe, but does not interact with light or with normal matter. But it does have gravity, which allows it to bind together galaxies at very, very large scales. That's our best guess. It is just a guess. It is just a hypothesis. We have not identified a dark matter particle. We've been looking for them for a couple decades now.

[Peter]

Are there alternative, alternative theories?

[Paul]

So there are alternative theories. Of course there are. You know, if you get 10 physicists in a room, you get 12 opinions. There are alternatives, but alternatives face enormous challenges. What I like to say is that the dark matter theory, this idea that dark matter to explain this raft of observations that we can't get away from, it is not a great idea, but it's the best we got. Because this one simple idea that, hey, maybe there's a particle that floods the universe that doesn't interact with light, this one idea has so much explanatory power. It is the simplest idea that we can come up with that explains the most amount of data. So this idea that there is a particle that doesn't interact with light, this explains the properties of the light we get from the very early universe, something we call the cosmic microwave background. It explains the structure and evolution of the cosmic web. It explains galaxy rotation curves, stars moving around in their galaxies faster than they should. It explains what happens when galaxy clusters merge together, explains those observations, explosions. It. We can tick off the boxes of what this hypothesis is able to explain, which is why we're so interested in this hypothesis and why we think we're on the right track, because it has the best ability to explain observations on everything from galaxies up to hundreds of millions, billions of light years and stretching back billions of years in the history of the universe. Universe. Major weakness. We, we haven't identified the dark matter particle. And we know that we're, we're not, we are perfectly aware of that fact. But, and, and, but if you start proposing alternatives, which you're welcome to do, I have other people. I have, like, people do it all the time, especially when we're really bored and experiments aren't, you know, taking a while to get funded. You know, you got to kill some time. So you kill some time by coming up with some wild ideas.

[Peter]

Are there any you like?

[Paul]

No.

[Peter]

Is there? There's no second place to dark matter.

[Paul]

Not really. And the problem is, the problem is if you come up with a theory, say one of the most popular alternatives to dark matter is, maybe we're misunderstanding gravity. Maybe we, maybe Einstein's gravity, maybe Newton's gravity, maybe once we get out to galaxy level scales, you know, who said that our understanding of gravity has to match with, with how the universe actually operates at large scales. So there have been a lot of attempts to, to modify gravity, to adjust our theory of gravity. Every single one of those has failed some observational test or another. And so, yeah, dark matter isn't all that great, but it checks all the boxes and alternatives to dark matter. Only check some of the boxes. And what you end up happening once you dig deep into these theories and you start to make predictions about how stars should operate in galaxies, how galaxies should operate in clusters, how the large scale structure of the universe should evolve, how the early universe should behave, once you start doing the work of, of trying to meet all observations, you end up coming short every single time. And you end up having to invoke the existence of dark matter, no matter what. Maybe less dark matter, but still some dark matter to be able to account for all of our observations. And so scientists are, are conservative. Not like Maga conservative, but conservative because we try, we force ourselves to use the simplest explanation possible for the widest array of observations. And we are locked, our hands are tied by the data. Nature is the ultimate arbiter of all of our decisions and all of our ideas. Who cares if an idea is good or bad? What matters is if it agrees with the data. And right now, dark matter, as bad as an idea it is. And it has weaknesses, it has flaws, has the most explanatory power.

[Peter]

Dark matter isn't the God particle. Or is it the God?

[Paul]

It's very, very different than the God particle. It's the devil particle.

[Peter]

It's the devil particle. Hold on. So the God particle, the Higgs boson.

[Paul]

The Higgs boson, what is that? The Higgs boson is not a hypothetical particle. It's a real deal. We've hypothesized it way back in the 1960s, and then in 20, you feel free to fact check that date. We'd, we observed it directly with a large hadron collider. So the, the Higgs boson, named after Peter Higgs. That looks like an image from a reconstruction of tracks in a particle Collider, which is great. That's. That's exactly what we're talking about. The God particle, which comes from the title of a popular science book. No one in physics called it the God particle. In fact, some of them called it the goddamn particle because it was so hard to find. What this does, what the Higgs boson does, is two things in our universe is a very, very important concept, and one of the key concepts behind the standard model of particle physics. We know of four forces of nature. Gravity, electromagnetism. So lights, the magnets on your fridge, lightning bolts, all of that, all in radiation.

[Peter]

Let's. Let's test my knowledge. Is it the. The strong and the weak nuclear.

[Paul]

The strong and weak nuclear forces? Yes.

[Peter]

See, I have been listening.

[Paul]

Electromagnetism in weak. What we discovered in the 1950s is that at high enough energies, when we crank up our particle accelerator experiments, these two forces merge together. So when you run an experiment, like at the Large Hadron Collider or any other collider, if you reach a certain energy threshold in that experiment, in that brief moment when everything's colliding and the energies are up, and then temperatures and densities are all up, there are only three forces in nature. There's gravity, strong nuclear, and then something we call the electroweak force. In our everyday existence, Electromagnetism in the weak force couldn't be any more different from each other. The electromagnetic force is carried by the photon. It has infinite range. We. We experience it in our everyday world as electricity, magnetism, and light. The weak nuclear force is carried by three particles. These particles are so massive, they're called the W and Z bosons. These particles are so massive, they're more massive than protons. They're more massive than many of the particles that. That make up our everyday existence. They have incredibly short range. They reach like a femtometer or something like that, 10 to the mice, 15 meters. They're incredibly short range. They do not live long. And the weak nuclear force is responsible for certain kinds of radioactive decay. These two forces couldn't be any more different than each other. And yet at high energies, they merged together into a single unified force. That's kind of weird. That's kind of a mystery. Like, how did these two forces that couldn't be any different than each other. It's like. It's like the worst rom com you've ever seen. Where. Where, where, like the couple, they. They are complete opposites and they hate each other. But then you put them in the same room and you Turn up the chemistry a little bit, and all of a sudden, they fall in love. Like. Like, what is going on?

[Peter]

It's Paul Abdul and the cat.

[Paul]

Yes, exactly. What the Higgs boson does. What was proposed by Peter Higgs and many and. And quite a few others in the 50s and 60s was that there's another ingredient in the unit universe. There's this other particle that does the job of driving a wedge between these two forces that at high energies, these forces have enough energy that they can ignore the Higs. They don't talk about it. But then at low energies, the higs comes in and splits them apart and drives a wedge between them and keeps them separate as a bonus. So that's the job of the Higgs, is to split up electricity and electromagnetism in the weak nuclear force. Peter Higgs discovered that the presence of this entity, the presence of this particle, does something else. It explains why particles like the electron have mass, because the electrons are forced to interact with the Higgs. Because the Higgs is here. It's everywhere you look. The. The Higgs just subsumes or, you know, is absorbed by all of. All of reality. It's just here. So if you're a particle, if you're an electron, you have to talk to the Higgs, you have to interact with the Higgs, and then that interaction is your mass. It manifests as mass in our everyday world. And so it's like this extra special bonus, you know, the. The reason that Peter Higgs derived or proposed the existence of this particle was to create this separation between electromagnetism and weak nuclear. And then, as a bonus, it's able to explain why particles have mass in the first place.

[Peter]

So with dark matter, we're at the stage similar to the Higgs boson. We have the thesis, but we haven't.

[Paul]

Got the proof, maybe even a couple steps behind that. Because, yes, there are candidate dark matter particles we have hypothesized, not just this broad category of, like, yeah, it's a particle that doesn't interact with light. We have proposed very specific particles with very specific properties that play certain roles in physics. We've gone looking for those particles because they, okay, if this particle exists, then if I run this kind of experiment, it very rarely interacts with matter, but sometimes it does. So maybe I can capture it. We've seen nothing. We have not seen any evidence for any of our candidate dark matter particles. What does this mean? Well, I mean, this is science. We're not guaranteed. Our first guess isn't guaranteed to be right or the easiest explanation isn't guaranteed to be the, the best explanation for any of the data. So we're, we're going to keep looking. So we're going to keep searching for dark matter particles. We're going to keep accumulating evidence observationally for the influence that dark matter by Have. Yeah. And we'll keep investigating alternatives to dark matter. We'll keep investigating theories of modified gravity, seeing if we can find one that is able to account for all the evidence. We're just going to keep working because that's what we do in science. We don't just give up. We're like, oh, shoot. Well, I guess we're going to go back to being ignorant again. No, we wake up tomorrow and we try again.

[Peter]

Okay, some dumb questions. The Higgs boson, if it's here, there.

[Paul]

And everywhere.

[Peter]

What is it?

[Paul]

Care Bear, it's here, there and everywhere.

[Peter]

What's it made up of?

[Paul]

What is, is itself. It's a new. It's a. It's an entity in the universe. The same way that electrons are electrons, top quarks are top quarks, Neutrinos are neutrinos. We have a zoo, a variety of particles that appear to be fundamental, that appear to be not made up of anything else that as far as we can tell, they simply exist. They simply are. The Higgs boson is one of those. It is one of the characters as part of the main cast of the play of our universe. And we can't break it down into smaller components. It's not made of anything else. Why does the universe have electrons, quarks, neutrinos, Higgs boson? We don't know.

[Peter]

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[Paul]

One of the coolest ways to view a particle is to not think of them as particles at all. Okay, so in, in our modern view of physics, which does not get enough airplay, but is absolutely breathtaking in its view of the universe. Our view of the universe is, is powered by quantum mechanics, by the physics that we understand of how very, very small things work. It's also powered by special relativity, by how things operate at high energies and at fast speeds. And when we combine quantum mechanics with special relativity, we get a completely radical, radically different view of the fundamental components of the universe. We call this quantum field theory. Quantum field theory powers all of modern physics. So everything we understand about forces, everything we understand about fundamental particle interactions is fed looked at through the lens of quantum field theory. And in quantum field theory, you don't think of particles, you think of fields. You think of these substances, these entities that exist throughout all of space and time. Each one of these fields correspond to a recognizable particle. So the electron gets a field, the electronic, the electron field, also known as the Dirac field, that spreads throughout all space and time. The up quark gets its own field. Each neutrino gets its own field. The photon gets its own field called the electromagnetic field. Everywhere you go in the universe. Love it. Everywhere you go in the universe, there there are these overlapping fields that, that soak space of time like, like olive oil and vinegar in your bread. Most of the time. These fields exist at a very low energy level, just humming in the background. Every once in a while, pocket of that field can get an excitation, can get more energy, a little localized vibration. And that little localized vibration can then just travel down just like a ripple in a pond. We call that localized excitation of a field a particle. It appears to us and manifests to us as a particle. But really what it is, is a pinched off part of a field that exists throughout all of space and time and is and is a fundamental aspect of material existence, a fundamental aspect of reality. This lens has enormous power. The standard model of physics is baked. Is, is based on, it's the, the quantum field theory is, is baked into the standard model. This is how we understand fundamental interactions. This allows us to explain things like how can particles appear and disappear, how can particles transition, transform themselves from one kind of particle to another. We look at this through the lens of fields, where if there's a lot of energy in one patch of the field, then we see a lot of particles, and then that energy can dissipate and we count fewer and fewer particles. When one particle transforms into another particle during a reaction, what it is is vibrations in one field, exciting vibrations in another field and transferring that energy from field to field and manifests as the transformation of particles into other particles. So it's a much more powerful framework. It is a nasty mess of mathematics. People like Richard Feynman got Nobel prizes for giving us tools to navigate the mathematical mess. It's. It's very heavy mathematics, but it works and it's powerful and it's able to explain.

[Peter]

Most stuff.

[Paul]

A lot of stuff. There are a lot of unknowns. There are a lot of things we do not understand about particle physics, but the stuff we do understand, we measure to an insanely high prediction, and it matches exactly what we expect from quantum field theory.

[Peter]

It's all a bit weird.

[Paul]

Yeah, isn't it?

[Peter]

When you think about it.

[Paul]

Yeah. Life is. Well.

[Peter]

So whether the standard model of physics was born as part of the Big Bang. You can correct even my questions if they're wrong, but I think you'll know what I'm trying to ask. You say physics always gets a bit weird at the. Oh, yeah, yeah. At the very early universe level. But we end up with this standard model of physics that creates galaxies and creates our stars and the planets that go around and eventually the gases and everything we need to create life. So you and I sit here with two podcasts, and we can make something that gets sent around the world, but it's weird that it all works just in the right way so this can happen. And so is that luck, chance? Or is there the argument that there is a multiverse trying out all the different infinite number of models of physics, and this is one that works like this.

[Paul]

Oh, yeah.

[Peter]

How do I even. What is the question I'm trying to ask you here?

[Paul]

I think you're asking why is there something rather than nothing thing?

[Peter]

Yeah, that all works.

[Paul]

How come it all works? Because like we talked about earlier, we have the standard model. We understand that there are certain quantum fields that inhabit the universe. They have certain properties that they do. We are not able to predict some of the properties of these fields. Some we can, but others we can't. Fundamental constants of nature, we. We can't predict. We don't know why the speed of light is the speed it is. We don't know why the electron has the Mass and the charge that it does. Yes, the electron gets its mass through its interaction with the Higgs, but it's a strength of interaction. How strongly it is connected to the Higgs determines its mass. So why does it have that connection and not another connection? We do not know why the electromagnetic force is really strong. We do not know why the strong force is even stronger. We do not know why gravity is so dang weak. It is billions of times weaker than any other force. You can list between one and two dozen numbers that we must feed into our theories, we must feed into the Standard model in order to get predictions out at the other end. Once you observationally determine those numbers, once you make those measurements and you feed it into the machine, then we can explain all of those. All? Like, not all, but we can explain a lot of particle physics, so we know we're on the right track. But there appear to be numbers that we can't explain. If you were to change any of these numbers, then you end up with a different universe. Then you end up with universes where galaxies never form. You end up with universes where nuclear fusion never happens. You end up. And there are even more, even deeper fundamental numbers. Some of the numbers I like to think about. Like, we have three dimensions of space and one of time. If you have more than one dimension of time, then, like, all of causality breaks down. If you have more than three dimensions of space, then light, radiation dilutes too much, and you have no starlight, and you have no electrical interaction, and you just have a dark, empty universe. So we find ourselves here in a universe that appears to be tuned, designed, designed for us, that if you were to change any of these fundamental numbers, then we wouldn't be here talking about these fundamental numbers. There are. There. There's no answer to this question. There are responses there. There are lines of thinking that we can. That we can approach when we talk about. About these. One is that just because these numbers appear fundamental to us does not mean that they are actually fundamental. We do not have a complete theory of physics. If we did, I would be out of a job, probably making more money, but I'd be out of a job, at least a physics job, because we'd be done. We know we're not done.

[Peter]

Out of a job as a researcher, not as an explainer.

[Paul]

Okay, fair enough.

[Peter]

Still do this.

[Paul]

I might still do this. Talking about something else. Maybe I'd be talking about politics.

[Peter]

Oh, no, I still want to explain. But you'll just have. Oh, I know the answer.

[Paul]

Oh, I Know the answer.

[Peter]

Is there an energy universe? Yes, there actually is.

[Paul]

I'd be saying, I don't know, a lot less.

[Peter]

Yeah.

[Paul]

It could be that as we develop more complete theories of physics, as we push to higher energies, as we search for more fundamental ideas, that some or all of these numbers become folded into the theory itself, that we can explain why the electron, like the electron mass, has this mass. Right now, we don't know why, and if it had any other number, you know, our universe would blow up or something. But there could be a reason for it. There could be a particular interaction or fact or facet of reality that forces the electron that had no other choice, that the universe. One way to put this, B. It could be that if we understand fundamental physics at a very deep level, that the universe could have no choice but to have the properties that it does. In which case our existence would be an inevitable conclusion because there's no other possibility that's satisfying to one level, unsatisfying at another level, which is, at the end of the day, you still have physical laws. And you can ask, well, okay, if we can explain how the electron got its mass, what about the rule that led to the fact that the electron had this mass? Why is there a physics in the first place? Like, why did the universe have these laws instead of some other set of laws? We can sit down a piece of paper, we can come up with all sorts, ask AI for like, alternative laws of physics that don't, that don't exist. This. Why? Why? Of all the possible laws of physics that could govern how the universe behaves, why this one? Why is there a universe rather than no universe? Why is there even existence when there didn't have to be existence? These are very, very deep and very fruitful philosophical conversations, and they hurt the brain. They also make it feel so, so good.

[Peter]

But do, do they? Like, does your growing understanding of space and cosmology, does it. Do you think it brings us closer to feeling connected or more further and just make us feel even more insignificant in this tiny little part of this galaxy? Have you met my son, the deep philosophical thinker?

[Paul]

No, but. No, that's a very common reaction where you look out at the stars, we pull up the cosmic web where those images you showed earlier, our entire galaxy isn't even a pixel in one of those images. And it's tempting, it's very tempting to, to shrink from that, to just fall into an existentialist nightmare of cosmic insignificance, of faced with all these forces that operate over billions of years and over billions of light years that. Where. Where you could snap your fingers, erase the Earth from existence, and the universe just wouldn't even notice. It's. It's hard to find meaning there. It's hard to find purpose there. I counter that, and that's because that's not how I feel at all. It is how I felt up until, I don't know, roughly when I had a family and I realized that there is something special happening here on Earth. We're the only known place in the universe to host life. And even if we're not the only place, then by certainly we are amongst rare company. There is something special. This is the only known place in the universe that isn't just alive. This is the only known place in the universe where music happens, where art happens, where engineering happens, where Bitcoin happens, where. Where there is something special happening on the surface of this ball of dirt and water that no, nowhere else in the universe that we know of, gets to participate in. And to me, that brings enormous significance, that brings enormous meaning, and it. And it forces me to think, to be like a steward of the Earth, you know, to. To protect the environment, because this is the only environment that we know of.

[Peter]

Let's not fuck it up.

[Paul]

Yeah, I mean, this is it, folks. And to preserve our heritage and to keep making art and to keep doing science and to keep having politics, because there's nowhere else in the universe that gets to do it. So let's do it. Let's be humans. Let's be alive. Let's. Let's lean into what makes us special. Like, take your kids out and watch a sunrise. Nowhere, nowhere else in the universe is anyone enjoying a sunrise. All right, so enjoy it. Get into a debate about politics. That random. The Andromeda galaxy, as far as we know, no one's debating politics. So let's debate politics because it's something special that's happening here. It imbues the. The, the enormity of the universe imbues me. It animates me with. With meaning and significance. Thank you for coming to my TED Talk.

[Peter]

He always asks the best question.

[Paul]

He does. It's a good question.

[Peter]

But do you think we're alone?

[Paul]

I have to preface this, because there's a lot. There's a lot of ways to twist what a scientist says for a nefarious purposes. All available evidence tells us that we are alone. We have absolutely no evidence anywhere from any observation whatsoever that there is life or especially intelligent life out there in the universe. That said, if you go out in the middle of the desert and you get a clear dark sky free from light pollution, free from atmospheric turbulence. You'll see about 3,000 stars in your. From horizon to horizon. And if you haven't done that, you absolutely should because it's a transformative experience. The sky as our ancestors knew it is completely unlike the skies we're used to in the modern world. Just that, just 3,000 stars. A tiny insignificant percentage of all the stars in the Milky Way galaxy. There are 300 billion stars in the Milky Way. There are 2 trillion galaxies in our observable universe. And the whole entire universe might be infinitely large for all we know. But just that taste, just that taste of 3,000 stars in the sky. I cannot sleep at night thinking that's all for us, that this is it. That every star, every gas cloud, every black hole and neutron star, every cosmic void and galaxy cluster is meant for just us to understand, to appreciate and enjoy. I want to share it. I don't want to be alone in this universe. I don't want humanity to be alone. I want everything I just said about what's happening here. It's certainly rare, but I would love to share it with someone else. And so I can't, I can't fathom the thought. This is a very unscientific approach, but that's okay because science is my day job. I'm allowed to be a non scientist when I'm off the clock. And it's to, to hope that there is someone else out there.

[Peter]

Mathematically there's been research done that mathematically the odds are that there should be other planets with the conditions that we have here that we know support life.

[Paul]

Yes. Oh, in fact we know that, we know that we can estimate. So we know of around 5 to 6,000 planets outside of the Earth.

[Peter]

Hold on, didn't even in the last few weeks we find a moon of Jupiter that could perh. Support life.

[Paul]

Oh yeah, yeah, yeah. Oh yeah. There's, there are so many potential homes for life. And this is, this is both good and bad news. Because the good news is we're finding a lot of potential homes for life. The bad news is every time we've looked more deeply, it turns out to not be alive. And so it makes life even more precious and even, even more fragile. But we know of around 6,000 exoplanets. We, we suspect there are around a trillion in the Milky Way galaxy. You know, what's a few hundred billion amongst friends? But it's like roughly a trillion planets in our galaxy. If we were to narrow this to the subset of just planets about the size of the Earth, orbiting around stars like the sun in just the right distance from their stars to be able to have liquid water. We're looking at around 5 billion copies of the Earth in the Milky Way galaxy alone.

[Peter]

One.

[Paul]

Okay, yeah.

[Peter]

Is that the Goldilocks zone?

[Paul]

It's the Goldilocks zone where you're not too close, where all your water evaporates and not too far away, where all your water freezes, where you can potentially have liquid water on the surface of a planet. Plus on top of that. But we have not found a copy of the Earth yet. We, we've been trying but we haven't spotted one yet. But we do know of Earth like planets in the Goldilocks zone around small red dwarf stars. In fact, our nearest neighbor star, Proxima Centauri has an Earth like rocky planet in the habitable zone around it. We found lots and lots and lots of examples of those.

[Peter]

Is that a problem that it's around a red dwarf?

[Paul]

You know, one man's trash is another man's treasure. There's, there's, there's definitely downsides to being around a red dwarf. One is that red dwarf star. These are stars like 10 to 20% the mass of the Sun. They are very temperamental. They can get star spots that cover half their faces. They can have enormous flares and that's generally bad when there are huge doses of radiation. Life tends not to appreciate that. Plus and to get in the habitable zone of a much dimmer star, you have to be like right up close to it, like, like Proxima B. The planet that orbits Proxima Centauri is closer to its star than Mercury is to our sun.

[Peter]

Okay.

[Paul]

But the star is much dimmer so it can survive. But anytime there's any little flare, you're getting a face full of it. On the other hand, on the other hand, red dwarf stars live much longer lives than stars like the Sun. So our sun is middle aged. It's about four and a half billion years old. It's got about four and change billion years left before it turns into a red giant and we all die. So life on the Earth. Good night everybody. Life on Earth has about a 10 billion year span.

[Peter]

Yeah.

[Paul]

To make it a red dwarf star can last for 10 trillion years or longer. So there are a lot more chances for life to gain a foothold. And if a flare wipes out all life except for one tiny little microbe, it's got time. It can play the Long game. So there are a lot more chances for life to develop around a red dwarf star. Also, red dwarf stars are much more common than the bigger stars that the the universe. It's easy to make small stuff, it's hard to make big stuff. So there, there are hundreds. Like if you look at the night sky and you look at your 3000 stars on your horizon, if you go to the distance of the most distant one that you can observe with the naked eye, and I forget exactly how far away it is, it's a few thousand light years. And if you take draw that sphere within that sphere, including both horizons, there are about 6,000 visible stars. There are about a million more that you can't see with the naked eye. These are the red dwarfs. You can't even see Proxima Centauri, our nearest neighbor with the naked eye. So red dwarf stars are by far the most common kind of star. So you're increasing the odds.

[Peter]

Okay, and 5 billion within the Milky.

[Paul]

Way of Earth like copies around sun like stars.

[Peter]

Is that the issue though? Are we looking too much for humans and not for life? If you know what I mean. Saying like, who's to say that they need water?

[Paul]

That's an excellent question. And this is one of the major driving forces behind exobiology. So searches for life outside of the Earth. Not just intelligent life, but any kind of life. We'd be happy, we'd be happy with a microbe, you know, we could shake. Maybe it's not his hand, but it's Celia or something.

[Peter]

It's a start.

[Paul]

It's a start. All right. And then we would know that life can be seeded elsewhere. We do focus most of our efforts on searching for life like our own life that uses carbon as a basis, that uses water as a solvent, that uses carbon dioxide and, or oxygen. We look, we are focusing our efforts, most of our efforts, not all of them, but most of our efforts on Earth like life, because we know what to look for and because the chemistry that makes life possible here on the Earth is pretty standard. What do we use? We use carbon and oxygen, which we use water. Water is the most common molecule in the universe. Carbon and oxygen are amongst the most common elements in the universe. We use phosphorus, we use hydrogen, like if you. Nitrogen. If you look at the base ingredients of life, it's all the really common stuff. So again, adopting this principle that maybe there's nothing special happening here, then if life used this chemistry to get started here on Earth, then it stands to reason that there's likely copies of us elsewhere, there's similar Earth like life somewhere else in the universe. Plus we know what it, what life on Earth does. We know its kind of byproducts, we know its kind of signatures, we know its chemical pathways. And when we're going out and we're sifting through the data, we're looking at alien atmospheres, we're looking for evidence for life, we know what our kind of life looks like. So we are intentionally narrowing our search path. We understand we are doing this, we are making a trade off, that even though we're looking for less chances of life overall, that if we find it, we'll hit jackpot. And we'll know it, we'll know it when we see it.

[Peter]

But we're also looking for technology.

[Paul]

There is an entirely different branch which is not generally to a large part, part of mainstream astronomy. There are some professional astronomers at universities and institutions that do look for signs of technology. Especially this is the search for extraterrestrial intelligence. Most of their funding comes from private donors, most granting agencies, most. The community of astronomers isn't very interested in this for, for two reasons. One is that there is a large social stigma attached to it, whether we like it or not. And two, after we started SETI programs in the 1950s and we've, we've seen nothing. We've seen no radio signals, we've seen no detection of any alien intelligence elsewhere in the universe. We've done studies, we've done maps. As far as we could tell, the galaxy is quiet.

[Peter]

The wow. Signal.

[Paul]

The wow. Signal. It is interesting. We do have anomalies which, if you browse the papers published every day in astronomy, there's 40 to 60 papers published every day. Half of them are about anomaly anomalies. Like, there's a bunch of stuff in the universe that we don't, that we can't explain. There's weird stuff happening all the time. The wow. Signal, which was detected in the 1970s, I believe, 1977, if I had to guess right, at the Big Ear Telescope outside of Columbus, Ohio. I can't, couldn't make this up if I tried. It was a radio telescope that had served its primary astronomical mission and then was repurposed for SETI searches and was scanning the sky eyes looking for interesting radio signals. This signal came in out of nowhere, lasted, I think, a few seconds, was incredibly bright, incredibly powerful and energetic, and then faded away. It became the wow. Signal because the guy who was reviewing the data, the printouts of the data, saw this big spike and circled it, wrote wow. And so that's wow signal. It has never been repeated. We've done multiple scans multiple times in that same area of the sky and have it. There it is, the printout of the data. Wow, great handwriting. No one writes cursive like that anymore.

[Peter]

That means. Does it, when you look at all those numbers, does that mean anything to you?

[Paul]

Absolutely nothing.

[Peter]

It just looks like the matrix.

[Paul]

Yeah, there's Agent Smith in the bottom right hand corner. There's NEO there, that's six there, there. I know. So this is a printout. This is code that represents the strength and timing of certain signals. And they, they developed a certain standard with this telescope. Those numbers don't, don't mean anything to me or probably most professional astronomers nowadays.

[Peter]

So the truth is of course everything we found nothing yet. But we're still looking.

[Paul]

Of course we're still looking. Professional astronomers, astronomers attached to institutions, NASA. We are very, very interested in life, life outside the Earth. We are very curious if we are alone. We believe that the most likely way to find life outside of the Earth is to, to hunt for non intelligent life. If intelligent life was common, you can make a reasonable argument. People disagree with this argument. So, so please feel free to disagree with this argument that if intelligent life was common, we would have, we would have talked to them by now. They would know that we exist. We would know that they exist and we'd, we'd start chatting. We would be receiving signals from distant civilizations. We would see evidence for alien architecture megaprojects throughout the galaxy that.

[Peter]

But how difficult say would it be for us to get a signal to a different part of the Milky Way? Is that actually quite complicated? If it's a certain distance away way.

[Paul]

It'S actually exceedingly difficult. In fact, our most powerful radio broadcasts the, the broad range broadcast the globe spanning radio emissions. They don't even make it to Proxima Centauri before they sink into the background or just consumed, subsumed into the noise, the background general noise of radio emission in the galaxy.

[Peter]

So it's difficult.

[Paul]

It's very difficult.

[Peter]

So they could just be nearby. We just can't communicate with each other.

[Paul]

Exactly. Like aliens. Intelligent civilizations may be closer than we think. But intelligent civilizations are almost certainly not to have, are almost certainly guaranteed to not have the same level of technological development as us. Like we just figured out radio 100 years ago, which is basically yesterday. It's not even yesterday, it's an eye blank ago. Yes, and any random technological civilization is either going to, if you just had to randomly guess where they're gonna be. They're either still banging rocks together or they're, like, hopping around the stars, you know, Star Trek style.

[Peter]

Well, they've destroyed themselves.

[Paul]

You know, there's that, too.

[Peter]

Do you know the Fermi Paradox?

[Paul]

Fermi paradox.

[Peter]

So let me do my version.

[Paul]

Go for it.

[Peter]

And then you do the proper version. The Fermi paradox is the thesis that might not even be the correct word, that the reason we haven't talked to other civilizations is at a certain point they destroy themselves. Is that a fair. They can't get beyond a certain.

[Paul]

That's more. The Great Filter.

[Peter]

Oh, is that the Great Filter?

[Paul]

The Fermi Paradox is more fundamental than that. The Fermi Paradox is the question itself, which is, if there's nothing really special happening here, we're an average planet around an average star. If life isn't special, then where is everybody?

[Peter]

So, something asking questions. Yeah, I'll go back to it. I've got. I've done. I've done a couple. Okay. Today I've learned something great.

[Paul]

You've been great. So the Fermi Paradox is just that, like, okay, if everything about our situation is not very special, which is a very safe assumption to make, then there should be life everywhere, and we should have seen it by now. But we don't. Which means something has to make intelligent life largely unobservable because the galaxy's been around for a long time. The Milky Way galaxy is over 10 billion years old. Human civilization, radio communication, has been here for a century. Humans have, like, humanity. Modern humans have been here for, like, what, 40,000 years? And then anatomical humans, like, 200,000. Like, that's nothing. There are hundreds of billions of stars that have been around for 10 billion years. Surely someone should have cracked how to, you know, spread themselves amongst the stars, do whatever they want. We should see probes everywhere. We should see monoliths, like, in our backyard. We should see giant smiley faces carved into moons, like, we should see evidence for it everywhere. So some. Something in this line of thinking breaks.

[Peter]

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[Paul]

Yes, and this is a huge program within NASA and this is actually one of the target missions of the James Webb Space Telescope and then one of the target missions for follow up missions to the James Webb Space Telescope, which is to hunt for what we call bio signatures. These are the signatures of life existing on a planet. The key idea here is that what life does to a planet is throwing it out of equilibrium. If you just take a ball of rock, slap some water on it, give it, give it an atmosphere, eventually it will find some equilibrium. Certain gases will, will evaporate and float off into space. Others will get caught up in the water, others might get bound up into the rocks, the rocks might gas out a little. But eventually, if you give a planet enough time, it will just, just hang out being a planet with a certain mixture of gases. But then you add life to the mix. Life changes that equilibrium because life takes in certain elements and spits out other elements. The biggest example here on the Earth is the presence of oxygen. Oxygen is rarely, if ever in abundance in an atmosphere because oxygen can be broken down by ultraviolet radiation from the, from any star like the sun. But we have a lot of oxygen on the Earth or in our atmosphere. We have a lot of oxygen because it's a byproduct of photosynthesis. The presence of life on Earth has changed the equilibrium of what our planet's atmosphere should be. So let's go out and look at some planets. We'll look at types of biosignatures. Yeah, this is, this is even more detailed than that because this is going down into samples that we can collect from the Martian surface or from moons in the outer solar system. But the same principle applies where, if, like, where life changes, what should have been, what would happen inorganically. So if we look at an alien atmosphere. And we can, because every once in a while, when we look at these, these planets around other stars, sometimes the planet swings in front of the face of its star. In fact, this is how we detect it. And in that time, the light from that star passes through the atmosphere of the planet before traveling through space and then reaching our telescopes. So we can look like at the light filtered through the atmosphere. And we can use that to figure out what's in the atmosphere. And we've done. We do this all the time. The James Webb Space Telescope is doing it all the time, characterizing the atmospheres of alien planets. And if we happen to see a planet with multiple biosignatures, if we see a lot of oxygen, if we see a lot of maybe suppressed carbon dioxide, if we see a bunch of methane, which is a byproduct of life, if we, if we see a bunch of biosignatures, then we'll have confidence, not proof yet, that will take a lot more work, but confidence that this planet is being changed by life. It's being thrown out of equilibrium because of metabolism, because of life. And that's very interesting.

[Peter]

Is there a successor plan for the James Webb?

[Paul]

There's a concept of a plan. It's called the Habitable Worlds Observatory, or hwo, which is like James Webb but bigger. Right now it's, it is just a concept. It's in planning, it's in science definition phase. Also. NASA's kind of going through a moment right now where we're, we're not even talking about present missions that are ready to go on the launch pad, so let alone missions that won't launch for another decade. So we are. Yes. And the point of the habitable world's observatory is to find, is to have a list of say, a one to two dozen target planets that we have hints of life for and then really dig in and get a lot of high quality data about their atmospheres to really. I don't know, is that what came up with hwo, I believe. Oh, I mean, it's fair because there are all sorts of concepts and plans out there. Look at that thing.

[Peter]

When the James Webb launched, how anxious were you during launch? Because I was, I'd followed it for years.

[Paul]

Yeah. It was like this thing is a billion dollars over budget, maybe more. $10 billion a decade late.

[Peter]

Yeah.

[Paul]

Oh my gosh. If it blows up on the launch pad or one little thing gets stuck in deployment that may have been so damaging that modern astronomy as we know it, it would, would cease to exist because so Much money. So many resources were sunk into the James Web. So many astronomers spent their entire careers preparing for the James Webb and are currently, you know, directed in lines of research that utilize the James Webb. It may have been such a tremendous catastrophe that whole sections of modern astronomy would have just withered on the vine. And then the public and political, political appetite for funding astronomy may have dried up.

[Peter]

A lot of pressure. What's the, what's your favorite thing that's come from the James Webb?

[Paul]

One of the other reasons that the James Webb was built, it's not a single purpose instrument. It is an observatory. It's a multi purpose observatory. But it had several goals in mind. Like we designed it with a certain set of characteristics and properties and capabilities to achieve certain goals. One was hunting for life outside the Earth. Another one was pushing back into the early universe. The further out we go in space, the deeper we go into time because that light has taken longer and longer and longer to reach us. So by pushing out billions of years in observing ever more distant galaxies, we are observing the younger and younger universe. The James Webb was designed to push the, all the way back to the dawn of the first stars, the emergence of the first galaxies. This is a completely unobserved epoch in our universe. We have maps of the local universe. We have light that has survived from the very early universe. But then that middle part, when the first stars came on, when the first galaxies formed, we don't have any data. We, we do not know how the first stars and galaxies emerged. And what the James Webb is finding is that galaxies emerged very quickly, much faster than we thought they would. Not enough to break our understanding of cosmology, not enough to break our overall understanding of the history of the universe. But, but definitely the James Webb is teaching us that there are, that there were physical processes happening in the early universe that we certainly don't understand and may have been very different than the physics that dominates galaxies and stars of the present day.

[Peter]

Could that have been dark energy being a lot more powerful in the early. Or is it any of that?

[Paul]

Actually, dark energy we know in the very distant past was actually very, very weak.

[Peter]

Okay.

[Paul]

Or another way to put it, the simplest model of dark energy. Again, we do not understand dark energy. We only have these observations. But the simplest explanation for dark energy is that it's been a constant throughout the entire history of the universe, that its strength hasn't changed. This might be upset by some recent observations made with the DESI telescope, but, but leaving that alone, it certainly wasn't very strong. In the past. And our best guess is that it's been constant throughout all of time. But what's different about the past is that the universe was smaller. We live in an expanding universe. Everything's getting further away from everything else, which means in the distant past, the universe was smaller, which means it was denser and hotter and more energetic. When you wind back the clock billions of years, all the galaxies are closer together, all the matter is tighter. And when you have that density of matter, dark energy doesn't matter. Dark energy doesn't care. It can't. It can't. It can't show up. It's too weak to do anything. Only once all the matter dilutes, and once the universe thins out, that this weak dark energy that's been lurking in the background the whole time can finally start to dominate. What happens at large scales in this transition point happened around 5 billion years ago. About 5 billion years ago, matter in our universe diluted enough, became weak enough that dark energy, even though it's always been weak, was finally the strongest thing left.

[Peter]

Left.

[Paul]

That transition point happened about 5 billion years ago. There are some models, there are some. Some theories that. That posit that maybe in the very early universe, dark energy had a period of being very strong and then got weaker. Those are. Those are very hypothetical. We're not exactly sure how those ideas work or if they're even viable. But in this period of star formation in the early universe, this is a period when the universe is a few hundred million years old, so less than a billion years old, when the first stars and galaxies emerged.

[Peter]

And that was a surprise.

[Paul]

We knew that it happened here. What we thought was that this would be a nice, slow, gradual process where the first stars would come, and then a few hundred million years later, the first galaxies would emerge and they'd be really tiny, and then they would slowly build themselves up over billions of years. What we're seeing instead is we go back 500 million years after the big bang, 600 million years after the big bang, and we have nearly mature galaxies. It's like walking into a kindergarten class and seeing teenagers crammed into those tiny desks. They're not fully adults, but they're certainly not little kids. And so this was a surprise. This is very, very interesting. This is telling us that our naive models and theories of how the first stars and galaxies emerged. It's probably wrong, which is very exciting, because then we get to learn something new.

[Peter]

Connor, can you get up some of the James Webb images? Because I do have a question. It's a very simple question regarding these. But when you see these beautiful images from the James Webb. Go. Let me pick a different one. Go, go. Yeah, see, see the Oregon public. See that one?

[Paul]

Okay.

[Peter]

Are these actual colors or do they choose colors to make the image observable and so we can understand it?

[Paul]

These are false color images.

[Peter]

Okay.

[Paul]

They represent, this represents real information, but it is not as the human eye would see this.

[Peter]

So the color is used so we can understand it and observe it.

[Paul]

Exactly. Because the James Webb Space Telescope is an infrared telescope. It has like night vision goggles and it does this. So it can. Because this is a great wavelength for studying the elements in alien atmospheres. This is a great wavelength for studying the early universe is a great wavelength in this case for looking at, at star forming regions. And so they take very specific wavelengths of infrared and map that onto a visual color spectrum so that we can have a better understanding visually. Human brains are really good at picking out structures and patterns.

[Peter]

Is that likely Hubble vs. James Webb? Tell us the more detailed information.

[Paul]

If I had to guess, yes.

[Peter]

Yeah. Yeah, looks like it. Connor, should we talk about Mars? Yeah. Connor has been saying to me ever since the last show. We have to get Paul back. Okay. And we have to talk about life on Mars.

[Paul]

Life on Mars. Let's do it.

[Peter]

You gotta ask the first question. When do we go?

[Paul]

Oh, our life on Mars, we want not. Who cares about stupid aliens? No, who you want?

[Peter]

We're messing up this beautiful planet that you talked about.

[Paul]

So let's, let's try again with an even worse planet.

[Peter]

Yeah, yeah. It's life of miles possible.

[Paul]

Yes it is. There is no law of physics that prevents us from establishing short term or long term or even permanent presence on Mars. That said, my best guess, and this is purely a guess guess, is that getting to Mars, even sending a single mission to Mars, we're two, maybe three generations out from that. So you know, 40, 60 years from boots on the ground in Mar on Mars. A long term presence, that's a generational problem. That is a century level intelligence endeavor. Centuries level endeavor. And that can, that assumes our current pace of technological sophistication and developments. That assumes current pace of funding appetites from the public and from policymakers. That assumes certain levels of continued investment that even, even with that we are very, very far away from Mars. It's not impossible, but it's exceedingly difficult to put some things in perspective. A minimum with our current technology of rockets which use chemical reactions to power themselves, that sets a certain speed limit that Sets a certain mass limit. It puts hard physics limits on how powerful and how big of a rocket you can get to Mars and how quickly you can do it. What with our current technology. A typical. The minimum Mars duration. Minimum duration Mars mission is around two years to get there. It's about six months to get there.

[Peter]

Okay.

[Paul]

Then you gotta wait for our orbits to align again so we're on the same side of the solar system. And then six months to get back.

[Peter]

So how many launch windows are there a year?

[Paul]

It's every two years. There's a launch window.

[Peter]

Wow.

[Paul]

So we only get a chance to go to Mars roughly every couple of years. There are some other ways to do it. Like the escapade mission to Mars was supposed to launch yesterday. Actually they got delayed, if I remember right, because there was a cruise ship near the landing platform. And so they had to call it off. Which I wouldn't be surprised. This was a Blue Origins launch. This is Jeff Bezos's company. I wouldn't be surprised if Elon Musk hired the cruise ship to. To drive by and scrub the launch Billionaire games. There are some other ways to do it, but it's very slow because you have to do some long loping orbits. You have to do some gravity assist maneuvers. The direct route is you only get a shot every couple of years. So that puts another major impediment on that. Like imagine building a car, but you only get to run the car once every two years to see if it works.

[Peter]

How long is that window in that Two years. Sorry. They said cloud cover prevented it from taking off.

[Paul]

I think that was one of the delays. And then there was another delay because there were launch interference or landing interference. I could be wrong. This is Internet knowledge. So.

[Peter]

But is the window itself an hour a day?

[Paul]

It's a few months.

[Peter]

Oh, it's a few months.

[Paul]

Two or three months.

[Peter]

So if we get to the point when. When we do have, say, life on Mars in that few months, we might send a few rockets up it.

[Paul]

Exactly. And then there are also. That's for the fastest route. Route, which is the route we'd have to send humans on.

[Peter]

Yeah.

[Paul]

For cargo. If you have a capsule, if you have a design that can spend a few years or like a good chunk of a year in orbit before reaching Mars, then you can launch anytime you want. And so you can have like a supply wagon train headed to Mars on these really long orbits. Hopefully you didn't pack fresh fruits or anything perishable in that capsule. Then you can have a steady supply of, of things you need from food to walls, you know, just stuff you need for anything to have on Mars.

[Peter]

So the launch window is really about the preservation of human years.

[Paul]

Exactly, exactly. And right now we are, because we're trying to get humans on Mars. We need to test human capable craft. So we can't test a spacecraft that's just going to hang out orbiting the sun for a couple years before it finally reaches to Mars to give us good information on what it's like to send a crew to mission. So a crewed mission, even the tests, even just uncrewed empty probes that are paving pathways for human missions. We only get to do that every two years. Okay. Two years is longer than any human has ever been in space. Two years. And this is two years. And at minimum distance like 300 times further away than the moon. Something crazy like that. Like some gigantic number. The lunar missions were over and done with in roughly a week. Spending no more than two or three days on the lunar surface. A crew sent to Mars would be the most distant humans have ever been from Earth. With no hope of rescue or resupply. Unless it was all planned in advance with multiple stages and multiple missions, with things already on the surface, new things, backup equipment already en route.

[Peter]

Is that, sorry, is that something we would likely should do, is send things in advance?

[Paul]

We would have to, we would have to have things in advance. We would have to have things coming after. We would have to have this whole, whole thing tightly choreographed and if something goes wrong, they're not, they're not coming back. This isn't the Martian.

[Peter]

Yeah. And, and then, then when we do send human crews, we've, we've got to do a pretty good job of trying to land it in the same location. Which won't be simple.

[Paul]

It won't be simple. We've landed, we've gotten kind of good at landing on the surface of Mars. Nothing with the, the weight of a human mission. So far we've landed up to roughly 1 ton rovers. We would need a lot more tons to support a human mission and like. But none of this is impossible. None of this is, is, is pure science fiction. But it is enormously difficult. We have not solved the vast majority of technical challenges we would need to solve to land a crew on Mars, let alone set up a long term presence.

[Peter]

Okay. So let's start with land in the crew on Mars. Elon Musk is very keen on this. Sure is developing bigger and bigger rockets. I would say he will have the belief he could solve getting a crew to Mars and landing it. How about once we're on Mars, say the crew wants to come back. Is it harder because, I don't know the gravity of Mars. Is it harder to escape from Mars to launch a rocket of Mars, or is it easier?

[Paul]

It's easier in the sense that Mars has less gravity and essentially no atmosphere. Okay, so that is easier to launch off the surface. It's harder because there's no, there's no gas, there's no fuel on Mars.

[Peter]

We have to take the fuel with us.

[Paul]

We have to take the fuel with us or we have to design equipment. There are methods to take what the little thin atmosphere, the carbon dioxide in the atmosphere, and transform it into methane. There are ways to do it, but that requires industry, that requires equipment, that requires stuff that needs to exist on Mars and operate in a condition unlike anything else we've seen on Earth. So the advantage of Earth, even though we have a really thick atmosphere, even though we have a deep gravitational well, we've got, got, we've got gas like laying all over the place. We have the, the, the combustion elements we need to power a rocket right here. Mars doesn't have that. So we have to take our fuel with us or send it there, which everything, again, everything is all possible. But then you think all this through and the total amount of stuff you need, you need a minimum of a hundred tons, probably 10 to 100 times more than that to support a single mission to Mars. Cost estimates are all over the place because a lot of this is based on technologies that we do not have.

[Peter]

Could it be about a trillion dollars?

[Paul]

Roughly? A trillion dollars?

[Peter]

That's what I said this morning. Why does Elon need a trillion dollars? I think I know why Elon needs a trillion dollars. Okay, but, but assume we can get them there, all right? And assume we can get them back.

[Paul]

And they're still alive.

[Peter]

Maybe it is a one way mission and they're okay with that. Maybe survival. I went to a south by southwest around, gosh, it was about 15, 20 years ago. And I went to a session talking about life on Mars and said the biggest challenge is the radiation which will be hitting.

[Paul]

Huh. I mean, there we go.

[Peter]

Yeah, it's done.

[Paul]

Oh, we figured it out. Yeah, there it is.

[Peter]

We missed it.

[Paul]

Oh, wow.

[Peter]

Sorry. People are listening. Connor's just brought up a city on Mars, but well, looking at that, should we just try and establish life on the moon first? Just as a test? Would that be useful?

[Paul]

This, this is a very tough question to answer because the moon has a lot of advantages. It's close. We've been there before. We kind of know what we're doing. We have a, it's easier to get to. There are a lot more failure options that allow for crew survival. On the other hand, the moon has less gravity than Mars. We know that underneath the martian surface there's a lot of frozen water that, and there are also frozen ice caps that we can take advantage of. So we know water is present on Mars. The moon does have some water in its regolith in the dirt. And there are some permanently shadowed craters that we suspect have pockets of ice water. That water is much, much harder to get than it is on Mars, but it is a lot closer there. I don't have a dog in this fight. I think they're very solid arguments to be made on both sides.

[Peter]

Okay, so we're going to need drilling equipment for the ice and a way to convert that into water as well.

[Paul]

So we need sources of energy. We need almost certainly we need nuclear reactors on Mars, which we've never operated a nuclear reactor in a near vacuum at temperatures averaging 100 degrees below zero. A dust is also a problem. So the martian dust has been blowing around that planet for billions of years. It is super, super fine grain. It's almost like talcum powder. It gets everywhere. It, it erodes, seals, it degrades equipment. It's actually, it covers solar panels. It actually, it's unlike any dust we have on the Earth. So are any kind of equipment, any kind of building is going to have to navigate the dust?

[Peter]

Are there any craters that they can put themselves in that escapes the dust?

[Paul]

Yeah, almost certainly. So, so if you're thinking about a, a colony on Mars, you have to make a few trade offs or you look at what you need. Do you need water? You need good sunlight because you'll want to grow crops, you'll want to use solar energy. This will almost certainly have to be supplemented by nuclear energy. And good luck getting any government to agree to launching nuclear anything into space. But assuming you can solve that, the political hurdles. You need water, you need sunlight, you need protection from cosmic radiation.

[Peter]

How serious is the cosmic radiation protection? And is that solvable?

[Paul]

It's the real deal. It's nasty. It is pretty much any astronaut on a Martian mission is almost guaranteed to get cancer. Okay, not during the mission, but at some point in their lives. They're almost certainly guaranteed to do it Here on the Earth. We have a thick atmosphere and we have a strong magnetic field that protects us from cosmic radiation. Even then, cosmic rays still make their way to the surface. I've seen estimates, I don't know how accurate these are, but roughly somewhere around 3% of all cancers on Earth are caused by cosmic radiation.

[Peter]

Okay.

[Paul]

On Mars there's no atmosphere, there's no magnetic field or there's no atmosphere to speak of. There's no magnetic field to speak of. So you have to go underground.

[Peter]

Okay.

[Paul]

Because you can't just. The one of the nasty things about cosmic radiation is you can't just build a wall wall to protect yourself because if you have a thin wall, then the cosmic rays hit the wall and then create a shower of daughter particles that then rain out on the other side of the wall, which are just as nasty as the cosmic ray itself. So you need bulk, you need a lot of material. And the best way to do that on Mars is by going underground.

[Peter]

So this, this city is kind of unrealistic in some ways because the city will probably be underground.

[Paul]

I hope they have a lot of oncologists that's for, to make that city viable. Also they don't have nearly enough food.

[Peter]

Yeah, that's.

[Paul]

Yeah. 90% of 95% of a Mars colony is going to be food. Growing their own food, importing their own food, sustaining a colony on Mars with. They'll have to grow their own food because it will be. It's ridiculously expensive to send even a kilogram of material to Mars. So feeding the colonists from Earth is going to be a non starter. There's no way we can afford that. They have to be able to grow their own food. And so 90% of any colony has to be dedicated to, to crops.

[Peter]

The, the, the challenge of growing crops doesn't seem that high.

[Paul]

The challenge is, you're right, if you have water and you have sunlight, you can build a greenhouse. We figured this out out here on Earth, but the sunlight is best near the equator, just like it is on the Earth. That's where you get the most amount of sunlight. And the sunlight at the equator is roughly equivalent to the sunlight in like Nordic countries, like sub arctic regions of the Earth, which is not zero. We can grow crops in Finland I think, but it's not easy. And that's your maximum amount of sunlight. Plus every once in a while there are dust storms that completely cover the entire planet from pole to pole, which are killed one of our rovers because it didn't have enough sunlight for long enough and generally bad for crops. But you also need protection from cosmic radiation. You can't really. We were probably not going to be able to pack giant mining equipment and like bulldozers to Mars. So you need to use natural features. There are lava tubes, there are cave tubes that you can possibly use as our first bases, our first settlements. Those tend not to be found in the equator regions. So the best. And then you also need water and the most water is at the pole poles. So you have. If all you wanted was shelter and water, your answer are the polar caps. But then you don't get sunlight. And if all you want is sunlight, your best bet is the equator. But then there's no, there's very little water and there's not a lot of natural features in the Martian terrain to give you protection. So you have to make all these trades where you get the, the best you can of all three of protection, water and sunlight. There are, there have been studies and there are some regions in the northern plains that have, that appear to have a lot of overhangs, a lot of, a lot of canyon features that we could use for natural protection. Have good but not great sunlight and then access to underground water reserves, frozen water reserves.

[Peter]

And then you still only live off potatoes and barley.

[Paul]

Hope you like your potatoes and barley. That's what Finland and, and mushrooms probably.

[Peter]

Finland grows potatoes of barley.

[Paul]

There we go.

[Peter]

When, when Elon Musk was on Joe Rogan he talked about terraforming Mars. Like it, like it's possible.

[Paul]

Again, not physically impossible. We can't even terraform the Earth and we're here. So the thought of terraforming another planet, the problem with Mars is that it's already dead. And so it's like trying to, it's, it's like putting the, the, the paddles on a cadaver. You. Just because all the, the matter is there doesn't mean you have it in the right ingredients in the right con combination nations. There is frozen water on Mars and it's in the polar X caps. It's underground. If you were to liberate all the water on Mars and liberate is a polite euphemism for blowing it up. If you were to liberate it all the water on Mars, the current martian air pressure is around 1% of the Earth. If you were to liberate all the water on Mars, you might make it to 2%. There simply isn't a lot of water. It lost most of its water. Only a small fraction of it remains frozen underneath the surface. There just aren't a lot of frozen gases. If you were to release all of the frozen carbon dioxide on Mars, you might make it to like 3% of Earth's air pressure, maybe 4, if you're lucky. And this would require more energy. I don't have the numbers off the top of my head, but to actually extract this energy, you have to blow it up. You have. Or to extract these elements, you have to blow it up. So that means sending weapons to Mars like that makes me feel a little uncomfortable. Like, yeah, let's, let's give really rich people and random governments the ability to send nuclear weapons to Mars. I, I not, I'm not comfortable with it. Yeah, it's just like, that doesn't sit well with me. Even if we were to do it, it would probably require more nuclear weapons than we've ever developed in the history of humanity. Requires more energy than we can effectively capture on Mars than we can send to Mars that we can transfer to Mars. Again, there's no physics that says we can't do it, but there are enormous practical and engineering challenges. Your best bet to raising the air pressure on Mars is to start dragging in comets and letting them bombard the surface, which would, would render Mars uninhabitable for, I don't know, a thousand years or so. But then after that, it might, might be okay.

[Peter]

So really, in some ways, the question of Mars itself and establishing a colony there, and.

[Paul]

There'S a, there's a morality.

[Peter]

Question there of putting this much time, energy, and money into it. I've been, I'm right at the end of Annie Jacobson's book Nuclear War Scenario, which I went to read after watching A House of Dynamite on Netflix just to understand what nuclear war would look like. And there's a big.

[Paul]

This is where you are right now?

[Peter]

Yeah, I'm at that place. And there's, there's a big question of morality. There is the amount of time, energy, and money that every nuclear state has spent on developing and creating a nuclear deterrent that should never be used. Where else could that money have been spent? And so, look, if Elon Musk wants to do this, this is his money.

[Paul]

If it's his money, yeah. I don't like it when people ask questions about how I spend my money, which is mostly cheese, honestly. But no one asks, and we're all good. And so if it's his money and the money of private investors, fine.

[Peter]

But there is a morality question around where else could we direct that money? Could it be directed better on this planet? I think it's a fair question to ask.

[Paul]

It's a extremely fair question. Legitimate question. Do you.

[Peter]

I don't know if you can answer this. Do you think the idea of establishing a colony on Mars is a waste of time as we are.

[Paul]

On the spot? I gotta answer this, don't I?

[Peter]

Yeah.

[Paul]

Given, yes, short version, long version, given how difficult it is, given how much engineering effort has to go into it, it's almost certainly a waste of time. But, but there's, there's always, you know, the world is rarely black and white.

[Peter]

We may have new physics in the future.

[Paul]

We may have new physics in the future. And one of the reasons that NASA up until recently has enjoyed broad bipartisan support in the United States is that we recognize that yeah, we don't really need a space station, but the technologies we had to develop to make a space station possible end up having direct economic benefits in the world. We are able to develop new technologies, new materials, new understanding of biological systems that do have direct benefits to society here on the Earth. And that one of the reasons we continue human exploration of space is it serves as an economic driver that when we are faced with challenges of sending humans into space, sending probes to the distant solar system, et cetera, et cetera, and by extension sending humans to Mars, we have to create new technologies to make that happen. We have to do a lot of research and heavy lifting. And then those technologies we can then import and use for ourselves. That is not single purpose. Like all the technology that's used to go to Mars just stays in the Mars bucket and never leaves. It spills out and we get to enjoy those benefits. Are there other ways to achieve the same technological ends? Well then that's a probably yes. In which case that opens up a much broader discussion.

[Peter]

How much life has our International Space Station got?

[Paul]

It is going to be deorbited in the mid-2030s about a decade from now.

[Peter]

Is a successor planned?

[Paul]

Like I said, NASA's kind of going through a thing at the moment. It's kind of hard to make long term plans. The stated successor to the International Space Station is to open up and accelerate investment in private commercial activities in low Earth orbit. So there are many private companies that are vying for NASA contracts to serve as has successor station or stations in low Earth orbit where NASA becomes a buyer of those products. Where there's like a space hotel over there, space casino over there. There's, you know, there's this space den of iniquity over there and everyone's making money. And then like we can rent some space, some, some, some portion of the station to, to do science or go capitalism.

[Peter]

Right.

[Paul]

You know, if that makes More science possible. I'm all for it.

[Peter]

All right. Last thing we should talk about.

[Paul]

See, I didn't need just the last thing.

[Peter]

Well, we could go on all day. The Three Eye Atlas.

[Paul]

Three Eye Atlas.

[Peter]

Is it a mothership with probes or is it. It's definitely a comma, definitely a comet. Is there non zero chance that it's an alien spaceship?

[Paul]

Of course there's a non zero chance. We're here for that. You're here for that. I listen.

[Peter]

Do we want that?

[Paul]

To me, good thing to me, it's.

[Peter]

Independence Day and we won.

[Paul]

Kind of. Most of us died.

[Peter]

Does anyone win?

[Paul]

Does anyone win?

[Peter]

Should I tell you the big philosophical questions that's gonna sit with me, Connor?

[Paul]

So there's only one person advancing the idea that this might be an alien spacecraft, and that's Avi Loeb.

[Peter]

Yes.

[Paul]

Who said the same thing about the last interstellar object. Who said the same thing about the interstellar object before that? It's his thing, it's his game. It's. This is a very, very tricky space. I've known Avi for many years. I've collaborated with him in the past. He was a very well known and well respected astronomer in the community.

[Peter]

That was past tense.

[Paul]

That was past tense. It's not that the astronomical community rejects Avilo because he thinks there might be aliens out there. That's not the reason we reject him because he's wrong.

[Peter]

Okay?

[Paul]

And we have evidence that he's wrong. And he is, he's playing dirty pool. He's. He's claiming the mantle of scientific inquiry and, you know, freedom of research thought, which is his right. And, and like we all do, it's clickbait. It's also clickbait. And it's also, when he has provided evidence to the contrary, he is not following through with his scientific integrity, which is to put away hypotheses that the data demonstrate to be wrong. So, for example, Avi and I had a back and forth with Oumuamua, the first discovered international, technically also international, but interstellar visitor.

[Peter]

Was it called Eye Atlas or One Eye?

[Paul]

It was called One Eye, Oumuamua. Okay, so I stands for interstellar. And then we don't have a lot of them, so it's just 1, 2, 3, and then eventually we'll get 4 or 5, 6. If we end up finding a lot more, we might end up coming up with another numbering scheme.

[Peter]

So that was also weird, wasn't it?

[Paul]

So here's the thing about comets and I love this quote. I've just Found this quote this morning. Actually, comets are like cats. They have tails and they do whatever they want. That's brilliant. No two comets are alike. You could look at any comet and make a solid case that this comet is unique, this comet is special, and this comet deserves further study. And we expect interstellar comets to be even weirder because they have different histories. The comets in our solar system have spent. Spent their entire lives, billions of years orbiting the Sun. So at least they have the same common ancestry and common set of characteristics. Even with that, they're all different. They all have different personalities. They all exhibit anomalous behavior in one dimension or another, in one property or another. And then we expect interstellar comets who came from different solar systems with different kinds of abundances of elements, who traveled on their own path through the galaxy doing who knows what before encountering our solar system. So we expect them to be different. So just looking at how this comet is special doesn't really communicate much because all comets in their own way are special, unique snowflakes and. Okay, so, so, so this Comet 3i Atlas is different. Great. It also looks and acts and smells like a comet.

[Peter]

And so it doesn't have a visible tail.

[Paul]

It does. We've observed it. We had pictures of it. It's got a tail. And also some comets, we call them dark comets because that's a cool name. Also don't have tails. Not every comment has a tail. But. And in fact, there are breeds of cats, the Manx cat, that have no tails. So just like comets are cats, they just do whatever they want. All right? They're no one's boss. We work for them.

[Peter]

But there is a lot of weirdness about this.

[Paul]

Right?

[Peter]

There are things that have excited people.

[Paul]

It is genuinely interesting. We do not have a lot of interstellar visitors. There are things that are unique. There are thing properties of this comet that are currently unexplained that do not fit it. You could also say the same thing about any comet. You could say the same thing about Halley's Comet. There are things about Haley's Comet that do not match any other known comet.

[Peter]

Haley's Comet was from my childhood. Connor.

[Paul]

He'll come back around. It'll be in his kid's childhood too.

[Peter]

So, so what is. How is a comet different from an asteroid in general?

[Paul]

And there are a wide variety. There is overlap, especially the more we study small solar system buys. Another CL about Avi Loeb is that he doesn't collaborate with planetary scientists. People who have been studying solar system objects and small Rocks for their entire lives. He doesn't collaborate with any of them. His specialty through the decades of his career are more in astrophysics and cosmology. And, and so, like, where are you? Why are you engaging with the community who have been studying these kinds of objects their whole lives? It's not because it's. He's proposing that they're aliens. It's because what he. Because he's misrepresenting the data. There have been planetary scientists who have studied even Three Eye Atlas, and they'll write a paper on it and he'll misquote their paper or misattribute it or twist their conclusions, and they will confront him and say, avi, that's not literally. Not what I said. Like you, you've literally cut off portions of my graph from my paper and then presented it in a way that is disingenuous, does not represent my actual conclusions. And then, and then he just keeps going. And so that's why we don't like Avi anymore. Not because he's saying they're aliens, but because he is not committing to scientific integrity.

[Peter]

Avi, stop this. You got us excited, man.

[Paul]

But it makes. It makes headlines.

[Peter]

It gets you on YouTube.

[Paul]

Gets you on YouTube. And. But that makes science harder. But, but I forgot your question.

[Peter]

The difference between a comet and an asteroid.

[Paul]

So in general, very, very broadly, this does not apply. In all cases, comets are more icy than they are rocky. They have more water and like methane and carbon dioxide, whereas asteroids are more rocky than they are icy. Generally. Comets formed in the outskirts of the solar system, while asteroids formed a little bit closer to the sun. One. And that's about it.

[Peter]

And are they all basically tiny little planets?

[Paul]

They're. They're chunks. They're bits of planets. They're. They're the leftover bit. They're debris. When you, when you mix up the batter and there are little bits of flour on the edges of the bowl, those are the bits.

[Peter]

And 1. One becomes interstellar as it is. Is it busy Hit something and it's changed direction and it's.

[Paul]

There's so many different gravitational interactions and physical interactions. We lost probably. Probably. This is based on simulations of planetary formation. We probably lost upwards of 90% of the comets and asteroids that were here in the early solar system. They just get scattered. We may have even lost entire planets. There's a model of. We certainly lost planetesimals and protoplanetary objects. There's some highly suggestive models that say that there were five giant planets in our solar system. And we lost one of them. Most planets are probably rogue exoplanets. They are not bound to any particular star. There are countless asteroids, comets, bits of debris floating around the galaxy. But the galaxy is also really, really gigantic, which is why they only rarely intersect the solar system.

[Peter]

All right, two final things. One's going to be a curveball. Okay. Firstly, what I may. I may have asked you this last time. What is your favorite, weirdest thing within your field of work? What is the thing that, like, gets you?

[Paul]

What gets me is. Is what we talked about earlier. The enormity of it, the scale of it, that I can open up my computer, write a piece of software that encodes some physics and some knowledge of the universe and is able to replicate the vast majority of the history of our universe at large scales. Or I can write down an equation that captures it, that here we are monkeys on the surface. Apes. Apes, sorry, biologists, apes on the surface of a unremarkable planet in the corner of a spur of a spiral arm, can sit here and talk about supernova, interstellar visitors traveling to Mars, the origins of the universe itself. That's what gets me.

[Peter]

So that links nicely to my last thing, because this second time I've interviewed you now, and I think we're probably going to do it forever, for as long as we can be.

[Paul]

The holiday special.

[Peter]

The holiday special. I think in both interviews, there's moments I like, sense you get a little bit emotional.

[Paul]

Yeah, I get. I, yeah, I'm, I'm. I'm an emotional guy.

[Peter]

Yeah. But when, like, Connor asked you that question, it was quite a philosophical one, and I just sensed the emotion coming out from you. And so you, you know, do you think about all this differently? I think the answer is yes. But you think about this all this differently as a family man than when you were just like, a young nerd.

[Paul]

A young nerd roaming the streets of Paris thinking about the space above. Absolutely. The loves that I have in my life have changed my perspective, have changed my approach. I'm blessed and I'm lucky to have a home filled with love, with a wife that supports me and does amazing things. She's a modern dance choreographer, by the way, so she has her own passionate curiosity about the universe that I have the privilege. Position of getting to follow. I have two stepsons that are the lights of my life and that I'm so lucky in love and so lucky in life that that is how I. How I think about it. I center my life on the. On. On love. And, like, what's Special and good about humanity. Yes, we have a lot of rough edges. Yes, we have a lot to learn. Yes, there's a lot of suffering in this world that we need to address and that we need to fight against.

[Peter]

And.

[Paul]

But I'm not, I'm not. I don't know where, where I'm going with this except just being emotional. I'm not saying, like, like love is the answer. I know what, what I'm saying is that there is a lot in this universe that is not captured by physics. Yes, I'm in awe of what we are able to understand. I also recognize and acknowledge that there's a lot that we don't and that there's a lot of room, that science is an expression of their humanity. It's an expression of our curiosity. There are many other expressions of that humanity and many other expressions of that curiosity that I see science as one thread in this tapestry of human existence. We're here. We exist in a universe that we barely understand. And part of our humanity is to ask questions and to find answers. And if your answer is in understanding the Big bang, go for it. If you're, if your answer to that is to be at home and read a good book, then go for it. If your answer is to love your neighbor and treat them with respect, then go for it. There's so many different ways to answer our place in the universe, and I'm just lucky to be a part of it.

[Peter]

Well, I love you, man. Honestly.

[Paul]

Love you too, Peter.

[Peter]

You've been my gateway to the things I think about when I'm not working from when I first discovered your podcast and I learned about the fact that the size of something is relative. And I was, I can tell you where I was. I used to run a lot. I used to run everywhere back before I did my backend. And this is probably, I'm going to estimate about, gosh, 14 years ago. 13. When did you start the podcast?

[Paul]

Seven or eight years ago.

[Peter]

Oh, so whenever that was, Whenever that was, whenever that was. So my estimates are off. But I was running and I was running down in Devon and I was listening to the episode on special relativity or general relativity. I can't remember there was one.

[Paul]

Relativity, there was two parts probably. I think that was special, General, relative. I think I did like an eight part series on or something crazy like that.

[Peter]

And I've made so many people listen to it and, and I loved your work, your explanation. So thank you for coming again to do this. I really appreciate it and I hope we get to do it every year.

[Paul]

Thank you for having me on. It's a privilege to be on here. And it's a privilege to be able to share what I know and what I love about the universe with anyone that will listen.

[Peter]

And thank you to everyone who's listened all the way to the end. We will see you all soon. Bye.