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Speaker 1: We know so much more about the universe than our

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Speaker 1: ancestors did. Go far enough back, and they didn't even

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Speaker 1: know that the pinpricks of light they see in the

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Speaker 1: sky are other suns. A few thousand years ago, they

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Speaker 1: had no idea how far away those other stars were,

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Speaker 1: and a few decades ago nobody knew for sure whether

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Speaker 1: they were planets around those stars. We know so much

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Speaker 1: more than they do, But we've also visited exactly the

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Speaker 1: same number of solar systems as they have, just the one.

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Speaker 1: Will we ever get out of our solar system and

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Speaker 1: make a home for humanity around an alien star? Is

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Speaker 1: there a physics obstacle? Or is it just political will

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Speaker 1: or lots of engineering. If it's actually impossible, that might

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Speaker 1: explain another great mystery why no aliens have visited us.

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Speaker 1: Maybe we aren't alone in being marooned on our home stars.

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Speaker 1: Maybe everyone is just stuck at home. Today on the pod,

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Speaker 1: we'll dive into the challenges, the technologies, and the potential

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Speaker 1: for taking humanity to those distant stars. Welcome to Daniel

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Speaker 1: and Kelly's Extraordinary Accessible Universe.

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Speaker 2: Hello.

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Speaker 3: I'm Kelly Winer Smith. I study parasites and space, and

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Speaker 3: if I could travel to the next nearest star, I wouldn't.

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Speaker 1: What about you, Daniel, Hi, I'm Daniel. I'm a particle physicist,

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Speaker 1: and I want to send somebody to the nearest star,

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Speaker 1: but I definitely don't want to go myself.

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Speaker 3: So why would you not want to go yourself? Can

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Speaker 3: you imagine all the physics stuff you could ponder and

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Speaker 3: maybe even figure out on an interstellar trip.

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Speaker 1: Oh yeah, I'd be desperate to talk to the aliens

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Speaker 1: about physics, to see what kind of weird technology they've invented.

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Speaker 1: But I'm just not that much of a traveler these Honestly,

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Speaker 1: I don't even like to get on an airplane, So

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Speaker 1: a spaceship absolutely not. The seeds you're gonna be uncomfortable

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Speaker 1: and the snacks are gonna be weird. You know, I'm

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Speaker 1: a homebody these days.

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Speaker 3: But you were born in one country, lived in another country,

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Speaker 3: and had kids in a third country.

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Speaker 4: Right.

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Speaker 3: You used to be an amazing traveler, but now it's home.

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Speaker 1: Huh time marches on? Absolutely? Yes, I can no longer

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Speaker 1: sleep anywhere anytime. My stomach is more sensitive. You know,

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Speaker 1: youth is wasted on the young.

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Speaker 3: Well, it sounds like you made good use of your

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Speaker 3: youth traveling all those places.

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Speaker 1: How about you, Why don't you want to go to

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Speaker 1: another planet.

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Speaker 3: If we ended up in another planet and there was

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Speaker 3: life there, that would be incredible. But I feel like

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Speaker 3: you don't necessarily know what you're gonna get until you

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Speaker 3: get there. But the thought of leaving, Like, so it's

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Speaker 3: spring while we're recording, which means in the next couple

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Speaker 3: weeks on the side of my barn, the light that's

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Speaker 3: on outside is going to attract little tree frogs and

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Speaker 3: all kinds of colorful moths. I just can't imagine leaving

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Speaker 3: this planet and leaving all that stuff behind to spend

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Speaker 3: like decades traveling in a tin can. But maybe they'd

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Speaker 3: have even better moths, and then I would feel regret.

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Speaker 1: It'd be amazing, though, if we got to that planet

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Speaker 1: and then we're like, this place is kind of ugly,

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Speaker 1: you know. I wonder if, like every planet has its

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Speaker 1: own beauty, or if our evolutionary history on Earth primes

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Speaker 1: us to only find, you know, the Sierras and the

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Speaker 1: Blue Ridge Mountains beautiful. See how I included Virginia.

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Speaker 3: I appreciate that. Yeah, No, we're being nice to each

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Speaker 3: other on this episode. I guess that's great. I also

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Speaker 3: it would really stink to know that you were never

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Speaker 3: going to see any anybody else that you had known

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Speaker 3: your whole life ever again. And like the farther away

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Speaker 3: you get, the harder it is to communicate. But so

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Speaker 3: let's dig into the to the meat of our discussion today,

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Speaker 3: and we're talking about is it possible for humans to

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Speaker 3: travel to other stars?

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Speaker 1: Yeah? And I think this question is interesting and important

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Speaker 1: because while we want to explore the universe robotically and

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Speaker 1: gather information telescopically, I think also we have a primal

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Speaker 1: need to explore, to go places, and to expand out

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Speaker 1: into the universe. I think it's a question a lot

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Speaker 1: of people have about whether it's possible today, whether it

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Speaker 1: might be possible in a thousand years, or whether it

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Speaker 1: might never be possible for humans to cross the vast

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Speaker 1: oceans of space to other stars. So I went out

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Speaker 1: and I asked our listeners if they thought it was possible.

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Speaker 1: If you would like to play for this part of

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Speaker 1: the podcast in the future, please don't be shy. Write

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Speaker 1: to us at questions at Danielankelly dot org. We would

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Speaker 1: love to have your voice on the pod. So think

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Speaker 1: about it for a minute. Do you think it's possible

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Speaker 1: for humans to travel to other stars? Here's what our

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Speaker 1: audience had to say.

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Speaker 5: We can imagine traveling to other solar systems, but can

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Speaker 5: we deal with all the questions radiation, food, power sources, generationships.

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Speaker 5: We just don't know enough at this point.

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Speaker 1: I would say no for the foreseeable future, but in

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Speaker 1: multiple generations, after multiple generations, I think that would be possible.

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Speaker 1: What it would take thousand of years and the ship

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Speaker 1: would have to survive. You'd go through accidents, there would

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Speaker 1: be warring factions on the ship. You need a multi

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Speaker 1: generational ship.

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Speaker 6: Well, I'd say it's possible, but not probable within the

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Speaker 6: next one hundred years. There are a lot of hurdles

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Speaker 6: to overcome, propulsion being a major one in supplies. Maybe

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Speaker 6: if you had a fusion powered plasma or something.

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Speaker 7: I bet we could get a human being there in

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Speaker 7: their lifetime with acceleration that won't kill them, But I

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Speaker 7: think stopping will be really hard and definitely turning around

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Speaker 7: will be nearly impossible, so they can't come back.

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Speaker 4: Humans don't have enough time to live, and our bodies

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Speaker 4: would be destroyed by the acceleration required to reach another

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Speaker 4: solar system.

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Speaker 1: With today's technology. I don't believe it is strictly possible.

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Speaker 1: I think it's definitely possible. There's no law that says

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Speaker 1: we couldn't do it. There's still some major challenges ahead

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Speaker 1: of us. Anything is possible, but humans traveling to another

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Speaker 1: solar system may be a stretch. Now it is impossible.

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Speaker 5: I don't think a single person could make it to

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Speaker 5: another solar system, but maybe multiple generations.

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Speaker 8: Even if you could travel at the speed of light,

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Speaker 8: it would still take years to get to the nearest star,

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Speaker 8: which we don't even know if there's a solar system around,

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Speaker 8: and you'd have to confirm that first. Even if we

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Speaker 8: could technology got better, we'd still probably need a generational

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Speaker 8: star here.

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Speaker 9: Unless we destroy ourselves with war or refusal to confront

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Speaker 9: climate change. We will eventually reach other solar systems.

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Speaker 10: Maybe if money isn't a problem in the future, if

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Speaker 10: we tackles certain things, maybe we could. But I think

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Speaker 10: it's for now the ultimate pipe dream.

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Speaker 2: Yes it is possible, but whether it is probable is

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Speaker 2: a different question. And even if it is probable, and

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Speaker 2: even if it's undertaken, I don't think that the humans

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Speaker 2: who would leave our solar system to get to the

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Speaker 2: other solar system would be alive. When we get to

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Speaker 2: the other.

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Speaker 1: Solar system, we should assume that the aliens at the

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Speaker 1: solar systems will be hostile, and therefore we should send

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Speaker 1: all the people that we dislike the most.

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Speaker 3: Maybe through like a cryo sleep or human hibernation type thing,

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Speaker 3: something like that.

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Speaker 9: I believe we are marooned here.

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Speaker 3: No, we can't do that right now, but maybe some

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Speaker 3: day in the future.

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Speaker 8: From a physical point yes, From engineering point likely no.

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Speaker 3: I loved the variability of answers that we got here,

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Speaker 3: and I should say that as someone who interacts with

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Speaker 3: the space settlement community, I have no doubt that even

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Speaker 3: if somebody were to say, like, we've made a generationship,

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Speaker 3: there's a one percent chance it's going to make it.

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Speaker 3: Every seat on that ship would get filled. So, you know,

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Speaker 3: I think there's a lot of people who really love

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Speaker 3: this idea.

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Speaker 1: Well, why do you think we would have no shortage

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Speaker 1: of volunteers? You think there are people who, like in reality,

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Speaker 1: would actually sign up to go. They're not just like

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Speaker 1: excited about the concept.

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Speaker 3: Oh my gosh, they send me angry emails. There have

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Speaker 3: been so many people who have written me to tell

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Speaker 3: me that I cannot stop them from settling space, and

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Speaker 3: I write them back and I say, I cannot stop you.

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Speaker 3: That's right, And I'm not crying too. I don't think

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Speaker 3: I have any power over these kinds of decisions. I

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Speaker 3: just wrote a book saying it's kind of dangerous.

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Speaker 1: And maybe we should think this all through before we go.

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Speaker 3: But hey, do what you want, Yep, yep, do your things.

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Speaker 3: So anyway, I'm sure there'd be a lot of people,

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Speaker 3: and you know, it would be an absolutely incredible thing

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Speaker 3: if our species did send a generationship, for example, to

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Speaker 3: another star.

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Speaker 1: It would be incredible. And I love how this topic

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Speaker 1: is so deeply inspired and informed by science fiction. You know,

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Speaker 1: obviously there's science here, and we're going to talk about

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Speaker 1: all the nerdy details of propulsion mechanisms, et cetera. But

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Speaker 1: so many the ideas here come from the creativity of

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Speaker 1: science fiction authors casting their minds forward to imagine what

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Speaker 1: we might be able to build, what we might need

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Speaker 1: to build, what we might have to do to survive.

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Speaker 3: Yeah, what is your favorite interstellar travel sci fi book?

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Speaker 6: Oh?

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Speaker 1: Wow, such a good question. One of my favorites is

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Speaker 1: a book by Alistair Reynolds. I think it's called the

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Speaker 1: House of Suns, in which they tackle this problem by

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Speaker 1: dragging stars closer to each other. So they want to

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Speaker 1: have like a galactic empire across many solar systems, but

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Speaker 1: they don't have faster than light travel, and they recognize

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Speaker 1: that it's basically impossible to govern somebody if you're there

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Speaker 1: so far away, So they bring a bunch of suns

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Speaker 1: closer to each other, make a little solar neighborhood, so

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Speaker 1: you can have different solar systems but they're not so

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Speaker 1: far away.

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Speaker 3: I like that idea, but it sounds kind of dangerous.

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Speaker 1: Well, we're going to talk about that technology, which isn't

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Speaker 1: as far fetched as you might imagine at the end

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Speaker 1: of the episode.

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Speaker 3: So let's go ahead and dig right in. But first,

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Speaker 3: let's talk about where would we be going. Where is

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Speaker 3: our closest option here?

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Speaker 1: Yes, so the Milky Way galaxy has hundreds of billions

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Speaker 1: of stars, but the whole thing is like one hundred

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Speaker 1: thousand light years across, which is really big, and the

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Speaker 1: density of stars in our neighborhood is not so high.

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Speaker 1: It actually varies a lot. In the center of the

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Speaker 1: Milky Way. It's much much denser. But around where we are,

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Speaker 1: we're like in the suburbs, not quite the ex serbs,

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Speaker 1: in the very fringes of the Milky Way. But out

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Speaker 1: here in the suburbs, you can expect to find a

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Speaker 1: star a few light years away, and that's what we find.

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Speaker 1: Alpha Centauri and Proxima Centari are like just around four

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Speaker 1: light years away. So if you wanted to get to

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Speaker 1: the nearest star uneasy mode, you'd be going to the

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Speaker 1: closest one. It's still four light years away. And remember

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Speaker 1: the speed of light, super duper fast. If you shined

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Speaker 1: a laser beam at one of these stars, it'd be

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Speaker 1: zipping through the cosmos at an incredible speed for four

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Speaker 1: full years before it got there.

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Speaker 3: And so say you get to Alpha Centauri, do we

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Speaker 3: know that there are earth like planets there that we

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Speaker 3: could try to explore? What would we see once we

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Speaker 3: got there?

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Speaker 1: Yeah, there's actually good news there. You know, until like

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Speaker 1: twenty ish years ago, we had no idea what planets

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Speaker 1: were like around other stars, or if there even were any.

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Speaker 1: We'd only ever seen the planets in our Solar system

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Speaker 1: until the mid nineties, when we started developing the technology

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Speaker 1: to see exoplanets. Now we specifically identified five thousand exo planets.

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Speaker 1: At least the number keeps going up and up and

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Speaker 1: up and up. It's like a real pivot point in

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Speaker 1: human history. And because of that we can make all

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Speaker 1: sorts of really interesting statistical statements, like, on average, stars

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Speaker 1: have a good number of planets, and specifically Proximusentari and

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Speaker 1: Alpha Centauri do have some planets, and so it's very

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Speaker 1: unusual actually for stars to have no planets as far

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Speaker 1: as we can tell. So if you're going to go

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Speaker 1: to a nearby star, it's very likely you'll find some

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Speaker 1: planets there. Whether they're Earth like and whether they are

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Speaker 1: capable of supporting life a whole other question that we

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Speaker 1: think the next generation of space telescopes will really help

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Speaker 1: us crack. But from the point of view today's conversation,

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Speaker 1: let's just imagine getting to that Solar system, not necessarily

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Speaker 1: finding a cozy how there.

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Speaker 3: Okay, so let's see I'm forty two. Now, if I

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Speaker 3: were going to jump on one of these ships, and

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Speaker 3: I was hoping that we would arrive by you know,

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Speaker 3: the average lifespan of a human woman, So what that's

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Speaker 3: like eighty six or something like that. So we've got

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Speaker 3: let's say we've got about forty years to get there.

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Speaker 3: How fast do we need to go?

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Speaker 1: Yeah, so if you traveled at the speed of light,

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Speaker 1: you get there in four years. Of course, you can't

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Speaker 1: travel at the speed of light because nothing that has

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Speaker 1: mask can travel at the speed of light. So let's

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Speaker 1: say you could go at ten percent of the speed

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Speaker 1: of light already blazingly fast, much much faster than any

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Speaker 1: human ship has achieved crude or uncrued. But if you

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Speaker 1: did somehow manage that, you would get to altha centauri

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Speaker 1: in about forty years, right, a tenth of the speed

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Speaker 1: of light four light years, so forty years. So that's

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Speaker 1: basically what you need to achieve. But the sort of

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Speaker 1: space technology we have now really just isn't capable of that.

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Speaker 1: Like the fastest crude rocket or the Space Shuttle, for example,

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Speaker 1: their top speeds would take them about eighty thousand years

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Speaker 1: to get there, not to mention the question of like

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Speaker 1: bringing in a fuel that will dig into in a minute.

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Speaker 1: And even the uncrewed stuff like the Parker solar Probe

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Speaker 1: is the fastest thing humanity has ever built. Its top

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Speaker 1: speed is about zero point zero six four percent of

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Speaker 1: the speed of light. Oh no, you take about seven

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Speaker 1: thousand years to get to Alpha Centauri. So nothing we've

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Speaker 1: built can go nearly fast enough to get Kelly to

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Speaker 1: Alpha Centauri before her eighty fifth birthday.

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Speaker 3: Oh that's right. I wasn't going to go anyway, although

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Speaker 3: maybe maybe if they had really great moths. I'm disappointed.

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Speaker 3: But so I feel like there's there's a couple problems here.

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Speaker 3: It's like, one, can you even get to the speed

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Speaker 3: that you want? But then two, how do you get

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Speaker 3: to that speed? Because like, if you're sending humans, we've

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Speaker 3: got these squishy bodies, and if you accelerate us too fast,

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Speaker 3: we like we break and smoosh, and so you need

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Speaker 3: to like get fast but not too fast.

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Speaker 1: Yeah, so there's a lot going on here. I mean,

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Speaker 1: one thing is just the limitation of relativity. Number one.

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Speaker 1: You can't get faster than the speed of light. We'll

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Speaker 1: talk about warp drives in a minute, but assuming that

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Speaker 1: you're going through space, through flat space, you can't travel

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Speaker 1: faster than that. And that's a hard limit. And I

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Speaker 1: think it's important for people to think about that as

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Speaker 1: sort of setting the length scale of the universe, Because

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Speaker 1: we talked a minute ago about like, wow, it's super

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Speaker 1: duper fast. It is super duper fast. But space is

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Speaker 1: vast compared to the speed of light. Like, we wouldn't

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Speaker 1: think space was so big if the speed of light

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Speaker 1: was ten times or one hundred times what it is,

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Speaker 1: because then these things would be like less than a

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Speaker 1: light year away, or we would think space was much

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Speaker 1: bigger if the speed of light was smaller. So the

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Speaker 1: speed of light sort of determines like what is far

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Speaker 1: and what is close, And it just so happens that

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Speaker 1: because of our galactic dynamics, things are a few light

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Speaker 1: years away instead of tenths of light year away. But

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Speaker 1: even if you're not going to get to the speed

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Speaker 1: of light, this limit at the speed of light makes

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Speaker 1: it hard to accelerate. Like you keep pouring energy into

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Speaker 1: your rocket, you're not going to increase your velocity by

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Speaker 1: the same amount. As you go faster and faster, it

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Speaker 1: takes more and more energy to increase your velocity. And

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Speaker 1: as I think you were hinting, there are also limits

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Speaker 1: on how quickly you can accelerate, like biologically.

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Speaker 3: Yeah, so that's the interesting part.

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Speaker 1: Well, it's true that we do want to deliver our

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Speaker 1: passengers to Alvis Centauri, not as bags of dead goo. Right,

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Speaker 1: we want to take care of all their fragile little

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Speaker 1: organs and make sure that they actually get there. And

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Speaker 1: so if you want to get to some sort of

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Speaker 1: reasonable speed so your trip doesn't take too long, you

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Speaker 1: need to accelerate, and humans are not really built for

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Speaker 1: huge acceleration. I was reading some papers that said the

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Speaker 1: humans can tolerate like twenty G of acceleration G there,

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Speaker 1: of course referring to the acceleration of gravity here on

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Speaker 1: Earth as basic standard units of one G. So twenty

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Speaker 1: G is pretty intense, and we can't really tolerate that

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Speaker 1: for more than like a few seconds, maybe ten seconds. Humans,

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Speaker 1: like the really tough ones, can tolerate like ten G

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Speaker 1: for a minute, five G for a few minutes. But

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Speaker 1: imagine being on this ship. You're going to be on

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Speaker 1: it for years at least. You don't want more than

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Speaker 1: like one G or maybe even two G for long periods.

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Speaker 3: You know, we got a lot of the early data

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Speaker 3: on how many g's humans can survive because there was

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Speaker 3: the one scientist who kept getting in a sled and

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Speaker 3: then slamming himself into a foam wall. And so anyway,

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Speaker 3: human ingenuity. I love it, so just to make sure

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Speaker 3: I have the physics understanding of this. So like if

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Speaker 3: you speed up and then you stay at that speed,

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Speaker 3: you only experience the G as you're accelerating, right, not

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Speaker 3: just because you're going fast, but because you are going

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Speaker 3: faster every second. Is that right?

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Speaker 1: That's right? Okay, that's right. You can't experience velocity directly.

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Speaker 1: It's a relative thing right inside your ship. You can't

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Speaker 1: tell how faster ship is going. But if your ship

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Speaker 1: turns on the engines and tries to increase its speed,

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Speaker 1: you can measure acceleration locally. It's not relative, So as

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Speaker 1: your ship tries to increase its speed, you can feel that.

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Speaker 1: And something that's sort of surprising to me is that

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Speaker 1: you can actually accelerate at one G and reach near

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Speaker 1: the speed of light in a reasonable amount of time.

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Speaker 1: Like if you're on a rocket that can do one

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Speaker 1: G of acceleration, you can just do that for a year,

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Speaker 1: and you'll get up to like ninety nine percent of

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Speaker 1: the speed of light relative to your departure location.

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Speaker 3: And in that case, you would get there in less

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Speaker 3: than forty years. Right, because now instead of going ten

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Speaker 3: percent the speed of light, you're going the speed of light.

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Speaker 1: Yeah, that's right, but you need a technology that can

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Speaker 1: provide one g of acceleration for a whole year, as

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Speaker 1: we're going to talk about. That's not so easy to do, right.

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Speaker 1: That's an enormous amount of thrust or momentum you're imparting

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Speaker 1: on your ship.

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Speaker 3: There's always something in the way.

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Speaker 1: There's always something in the way. And the flip side

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Speaker 1: of all of this is deceleration or negative acceleration, because

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Speaker 1: you could get up to near the speed of light,

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Speaker 1: and then you could get to Alpha Centauri, but then

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Speaker 1: you're going to be in that Solar system for about

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Speaker 1: zero point zero seven seconds if you're traveling at near

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Speaker 1: the speed of light. But what you want to do

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Speaker 1: is arrive there and stop, which means decelerating. And you

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Speaker 1: don't want to decelerate from the speed of light to

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Speaker 1: zero too quickly, otherwise you'll again go splat.

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Speaker 3: Yeah, humans, it's a shame. We're so squishy.

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Speaker 1: And I think on the next episode we're going to

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Speaker 1: talk about making humans less squishy by like turning into

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Speaker 1: human sickles, and that might be a better way to

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Speaker 1: accelerate human bodies. I don't know, you'll have to tell

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Speaker 1: me all about it.

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Speaker 3: We are going to talk about the human side of

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Speaker 3: things in the next episode. I'm not sure that human

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Speaker 3: sickles is on my outline, but we'll see what I

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Speaker 3: come up with.

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Speaker 1: It is now, because I'm going to ask you about it.

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Speaker 3: Okay, great.

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Speaker 1: And so a typical strategy is to accelerate on the

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Speaker 1: first half of the trip and then basically turn your

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Speaker 1: ship around and decelerate all the way back to your

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Speaker 1: initial velocity now relative to your destination. And so you

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Speaker 1: accelerate and you reach top speed momentarily halfway there, and

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Speaker 1: you turn around and you're slowing down the whole second

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Speaker 1: half of the trip. And this is actually kind of

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Speaker 1: cool because along the way you might want to feel

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Speaker 1: some artificial gravity. As you're probably going to tell us,

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Speaker 1: humans don't like to float in space forever. It's not

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Speaker 1: good for us, and so you want to feel one G.

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Speaker 1: And so having one G of acceleration and then one

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Speaker 1: G of deceleration the whole trip is actually kind of cozy.

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Speaker 3: So if you had one G of acceleration for one year,

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Speaker 3: you would still have what two or three years just

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Speaker 3: staying at that velocity before you start decelerating, so there

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Speaker 3: would be a period where you would have no g's

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Speaker 3: in between.

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Speaker 1: Yeah, absolutely, depending on the length of the trip. If

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Speaker 1: you wanted to go further. For example, you could accelerate

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Speaker 1: at one G for a year, get up to near

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Speaker 1: the speed of light, zoom around super duper fast, and

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Speaker 1: then flip around and decelerate. So, yeah, you can have

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Speaker 1: a period in the middle where you're not accelerating or decelerating.

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Speaker 1: Then you got to solve that gravity problem another way,

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Speaker 1: all right.

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Speaker 3: All right, and we'll talk about that in the next episode.

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Speaker 1: And that's not the only thing that's going to potentially

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Speaker 1: kill you along the way. You know, we think of

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Speaker 1: space as empty, but it's not really like there's a

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Speaker 1: lot of particles out there. There's huge amounts of gas

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Speaker 1: the interstellar medium. There's lots of little bits of tiny rocks.

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Speaker 1: We call that dust. It's out there, and if you're

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Speaker 1: traveling at relativistic speeds relative to that dust, you can

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Speaker 1: be in danger. You know, these tiny particles, A millimeter

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Speaker 1: sized particle at like even if half of the speed

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Speaker 1: of light is an enormous amount of energy deposited on

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Speaker 1: your ship. And so you got to really worry about

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Speaker 1: this and cosmic rays and radiation, So your ship has

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Speaker 1: to be pretty robust. You need shielding, you need like

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Speaker 1: titanium or water or lead or something. All this is

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Speaker 1: going to make your ship heavier. So we'll dig into

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Speaker 1: that more in the next episode where we talk about

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Speaker 1: the fragility of the human body and how to survive this.

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Speaker 1: But keep that in mind as we're talking about the

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Speaker 1: propulsion designs, because it's going to affect how much you

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Speaker 1: got to move on the way to another star.

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Speaker 3: So to me, the dust feels like the first showstopper

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Speaker 3: that we've encountered. What makes us think that, you know,

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Speaker 3: when each piece of dust hitting us is like getting

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Speaker 3: hit with a bomb, what makes us think that we

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Speaker 3: can like, I mean, we're clearly not going to dodge

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Speaker 3: the dust. So what is the dust solution?

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Speaker 1: Well, you know, I've read about some cool shields. There's

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Speaker 1: like these whipple shields. I basically break up the dust

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Speaker 1: into smaller pieces so that none of them are likely

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Speaker 1: to like, really be devastating. There's some cool technology like

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Speaker 1: self healing shields. So I think it's an engineering problem

437
00:20:53,720 --> 00:20:56,320
Speaker 1: and one that we're likely to be able to crack.

438
00:20:57,080 --> 00:20:58,720
Speaker 1: But Yeah, it's definitely an important one.

439
00:20:58,760 --> 00:21:02,119
Speaker 3: I love your optimism, Dan, I always love your optimism,

440
00:21:03,520 --> 00:21:06,000
Speaker 3: all right, So we're going to be talking about ways

441
00:21:06,040 --> 00:21:07,760
Speaker 3: to get there. Are the ways that you're going to

442
00:21:07,800 --> 00:21:10,080
Speaker 3: talk to us about ways that could get us there

443
00:21:10,119 --> 00:21:12,280
Speaker 3: in a lifetime or is there anything else that might

444
00:21:12,320 --> 00:21:13,080
Speaker 3: work for us here?

445
00:21:13,240 --> 00:21:15,080
Speaker 1: Some of these solutions really can get you there in

446
00:21:15,119 --> 00:21:19,680
Speaker 1: a lifetime. But because it's physics, time is a slippery concept,

447
00:21:19,760 --> 00:21:21,720
Speaker 1: like are we talking about the lifetime for the people

448
00:21:21,760 --> 00:21:25,280
Speaker 1: you left behind or lifetime for people on board? Because

449
00:21:25,320 --> 00:21:27,320
Speaker 1: as soon as you get up to really high speed

450
00:21:27,400 --> 00:21:31,439
Speaker 1: relative to your departure planet, those are not the same thing. So,

451
00:21:31,520 --> 00:21:34,960
Speaker 1: for example, say you accelerate at one G and you

452
00:21:34,960 --> 00:21:37,120
Speaker 1: get up to near the speed of light, you could

453
00:21:37,119 --> 00:21:39,840
Speaker 1: travel for just a few years your time, a decade

454
00:21:39,880 --> 00:21:42,359
Speaker 1: your time, and like one hundred thousand years will have

455
00:21:42,440 --> 00:21:45,040
Speaker 1: passed back home. And if you're traveling near the speed

456
00:21:45,040 --> 00:21:47,879
Speaker 1: of light, one hundred thousand years is enough time to

457
00:21:47,920 --> 00:21:51,440
Speaker 1: get you across the galaxy in only like a decade

458
00:21:51,480 --> 00:21:54,760
Speaker 1: of your time. So Kelly gets on board the ship.

459
00:21:55,160 --> 00:21:58,200
Speaker 1: She arrives at the other side of the Milky Way

460
00:21:58,280 --> 00:22:00,879
Speaker 1: that no human has even clearly seen before because all

461
00:22:00,960 --> 00:22:04,280
Speaker 1: a gasl and dust and she's only fifty ish. Meanwhile,

462
00:22:04,320 --> 00:22:06,840
Speaker 1: back home, Zach is one hundred thousand years old.

463
00:22:07,040 --> 00:22:08,960
Speaker 3: Oh my gosh. And I'm a narcissist. So what I

464
00:22:09,000 --> 00:22:12,560
Speaker 3: care about is how long it takes me. When we

465
00:22:12,600 --> 00:22:14,880
Speaker 3: say it's gonna take eighty it would take like eighty

466
00:22:14,960 --> 00:22:16,800
Speaker 3: years to get there if you went ten percent the

467
00:22:16,800 --> 00:22:20,399
Speaker 3: speed of light. Is that that's eighty my years as

468
00:22:20,440 --> 00:22:22,399
Speaker 3: a person on the ship, right, So our frame of

469
00:22:22,440 --> 00:22:24,040
Speaker 3: reference is always the people on the ship.

470
00:22:24,119 --> 00:22:25,960
Speaker 1: Well, it was gonna take forty years to get there

471
00:22:26,000 --> 00:22:28,879
Speaker 1: at ten percent the speed of light in human years,

472
00:22:29,440 --> 00:22:31,200
Speaker 1: but at ten percent the speed of light is not

473
00:22:31,320 --> 00:22:34,400
Speaker 1: that much of a relativistic time dilation effect. That really

474
00:22:34,480 --> 00:22:36,720
Speaker 1: kicks up when you go half or three quarters the

475
00:22:36,760 --> 00:22:39,920
Speaker 1: speed of light, So that's still going to be decades

476
00:22:40,000 --> 00:22:42,720
Speaker 1: earth time and ship time. If you do get like

477
00:22:42,960 --> 00:22:45,720
Speaker 1: up above fifty sixty seventy percent the speed of light,

478
00:22:46,000 --> 00:22:49,000
Speaker 1: then you start to benefit from these time dilation effects.

479
00:22:49,119 --> 00:22:50,879
Speaker 1: So on the ship it takes less time.

480
00:22:51,200 --> 00:22:53,320
Speaker 3: Got it, Okay? And on the next episode we're going

481
00:22:53,400 --> 00:22:56,440
Speaker 3: to talk about generationships where if you just accept it's

482
00:22:56,440 --> 00:22:58,719
Speaker 3: not going to happen in a lifetime. Because your technology

483
00:22:58,720 --> 00:23:01,560
Speaker 3: can't get you that fast, how do you carry generations

484
00:23:01,560 --> 00:23:04,200
Speaker 3: of humans to still get there? But we're going to

485
00:23:04,280 --> 00:23:05,959
Speaker 3: take a break now, and when we get back from

486
00:23:06,000 --> 00:23:08,880
Speaker 3: the break, Daniel's going to walk us through our rocket

487
00:23:08,920 --> 00:23:29,840
Speaker 3: options for our trip to the stars. All right, let's

488
00:23:29,880 --> 00:23:33,600
Speaker 3: talk about our transport methods to get us to Alpha Centauri,

489
00:23:33,720 --> 00:23:37,760
Speaker 3: starting with the most near term likely technology.

490
00:23:38,160 --> 00:23:40,440
Speaker 1: So we want to get to Alpha Centauri, which means

491
00:23:40,480 --> 00:23:43,439
Speaker 1: we've got to move away from Earth, which means we

492
00:23:43,480 --> 00:23:47,440
Speaker 1: need to gain momentum away from Earth. In our universe,

493
00:23:47,560 --> 00:23:50,640
Speaker 1: momentum is conserved. So you have your ship. You wanted

494
00:23:50,680 --> 00:23:53,240
Speaker 1: to gain momentum in one direction, there needs to be

495
00:23:53,280 --> 00:23:57,280
Speaker 1: some sort of compensating momentum in the other direction. This

496
00:23:57,480 --> 00:23:59,720
Speaker 1: is something you feel if you like fire a gun,

497
00:23:59,760 --> 00:24:04,040
Speaker 1: for example, you feel that kickback. That's the conservation of momentum.

498
00:24:04,080 --> 00:24:06,919
Speaker 1: The rifle is shooting the bullet super duper fast, but

499
00:24:06,960 --> 00:24:09,680
Speaker 1: the bullet has a small mass, and the rifle itself

500
00:24:09,760 --> 00:24:12,760
Speaker 1: has that larger mass is moving backwards in the other

501
00:24:12,880 --> 00:24:15,159
Speaker 1: direction with the compensating velocity.

502
00:24:15,200 --> 00:24:17,240
Speaker 3: See I always imagine it as I'm trying to get

503
00:24:17,240 --> 00:24:19,480
Speaker 3: a boat to move and I'm imagining Daniel on a

504
00:24:19,520 --> 00:24:22,000
Speaker 3: cruise ship taking all of the white chocolate and throwing

505
00:24:22,040 --> 00:24:24,480
Speaker 3: it in the ocean to get the cruise ship to

506
00:24:24,560 --> 00:24:27,160
Speaker 3: move faster while also getting rid of the bad chocolate.

507
00:24:27,400 --> 00:24:30,560
Speaker 1: Yeah, that's exactly right. You need to build momentum in

508
00:24:30,600 --> 00:24:32,600
Speaker 1: the other direction. So imagine you are on a boat

509
00:24:32,600 --> 00:24:36,480
Speaker 1: and you're tossing stones or equivalently, white chocolate or hot

510
00:24:36,560 --> 00:24:40,000
Speaker 1: garbage or whatever useless stuff you happen to have on

511
00:24:40,040 --> 00:24:43,320
Speaker 1: the boat. Right, you create momentum in one direction for

512
00:24:43,359 --> 00:24:46,480
Speaker 1: the stones, and in recoil you go the other way.

513
00:24:47,040 --> 00:24:50,880
Speaker 1: And so all rocket drives operate under this same principle.

514
00:24:51,119 --> 00:24:53,119
Speaker 1: You need two things. You need energy and then you

515
00:24:53,200 --> 00:24:55,760
Speaker 1: need mass. So you use the energy to throw the

516
00:24:55,840 --> 00:24:58,600
Speaker 1: mass out the back and you go the other way.

517
00:24:58,840 --> 00:25:00,920
Speaker 1: That's the way all the rockets we're going to talk

518
00:25:00,960 --> 00:25:01,480
Speaker 1: about work.

519
00:25:01,600 --> 00:25:05,080
Speaker 3: And that's how like the Falcon nine or starship works

520
00:25:05,080 --> 00:25:06,359
Speaker 3: when it takes off too right.

521
00:25:06,600 --> 00:25:09,760
Speaker 1: Yeah, exactly. And the issue here is that you need

522
00:25:09,800 --> 00:25:12,800
Speaker 1: something to produce that energy, and you need something to

523
00:25:12,880 --> 00:25:14,639
Speaker 1: throw out the back, and when you run out of that,

524
00:25:14,720 --> 00:25:17,000
Speaker 1: you can't go anymore. And because you have to bring

525
00:25:17,040 --> 00:25:19,960
Speaker 1: that fuel with you, you need enough fuel to push that fuel,

526
00:25:20,000 --> 00:25:22,040
Speaker 1: and then you need more fuel to push that fuel.

527
00:25:22,520 --> 00:25:25,679
Speaker 1: And so there's this famous rocket equation which tells you

528
00:25:25,760 --> 00:25:27,840
Speaker 1: like how much fuel you need to get up to

529
00:25:27,880 --> 00:25:30,119
Speaker 1: a certain velocity. It depends on the mass of the

530
00:25:30,119 --> 00:25:33,200
Speaker 1: ship and also depends on the specific impulse that your

531
00:25:33,240 --> 00:25:35,840
Speaker 1: engine is able to provide. It's just basically just like

532
00:25:35,880 --> 00:25:37,439
Speaker 1: a number. Some of them are high, some of them

533
00:25:37,480 --> 00:25:39,680
Speaker 1: are low. But the bottom line is that the math

534
00:25:39,760 --> 00:25:43,720
Speaker 1: tells us that there's an exponential need for fuel. If

535
00:25:43,720 --> 00:25:46,199
Speaker 1: you want to get up to higher velocity. So you

536
00:25:46,240 --> 00:25:48,160
Speaker 1: want to go twice as fast, you don't need twice

537
00:25:48,160 --> 00:25:50,280
Speaker 1: as much fuel, You need much much more. You need

538
00:25:50,320 --> 00:25:53,919
Speaker 1: exponentially more fuel, and as you increase that velocity, the

539
00:25:53,960 --> 00:25:57,239
Speaker 1: amount of fuel grows ridiculously. So for example, even like

540
00:25:57,280 --> 00:25:59,760
Speaker 1: the Saturn rockets, the ones that took us to the Moon,

541
00:26:00,080 --> 00:26:02,800
Speaker 1: when they launched, they were like ninety five percent fuel.

542
00:26:02,880 --> 00:26:05,720
Speaker 1: It's mostly fuel being taken off and that fuel is

543
00:26:05,720 --> 00:26:08,040
Speaker 1: mostly being used to push the rest of the fuel.

544
00:26:08,160 --> 00:26:10,840
Speaker 3: That absolutely blew my mind when I first learned it

545
00:26:10,920 --> 00:26:14,640
Speaker 3: that like less than ten percent of that giant that

546
00:26:14,760 --> 00:26:16,840
Speaker 3: you know, that giant tube was actually going to be

547
00:26:16,880 --> 00:26:17,680
Speaker 3: going to the Moon.

548
00:26:17,920 --> 00:26:22,719
Speaker 1: And people are often confused about rockets versus escape velocity. Remember,

549
00:26:22,840 --> 00:26:25,000
Speaker 1: escape velocity is a calculation you do if you're like

550
00:26:25,119 --> 00:26:28,040
Speaker 1: throwing something from the surface of the Earth, you need

551
00:26:28,040 --> 00:26:30,560
Speaker 1: a certain velocity because gravity is going to slow you down,

552
00:26:30,600 --> 00:26:32,879
Speaker 1: and if you have higher than the escape velocity, you

553
00:26:32,880 --> 00:26:35,840
Speaker 1: can leave the orbit. But rockets are not about escape

554
00:26:35,880 --> 00:26:39,240
Speaker 1: velocity because rockets have constant thrust. Rockets can lift off

555
00:26:39,280 --> 00:26:42,600
Speaker 1: it basically zero points zero zero zero zero zero one

556
00:26:42,720 --> 00:26:45,399
Speaker 1: meters per second and still make it to space because

557
00:26:45,400 --> 00:26:49,199
Speaker 1: they're pushing themselves constantly. They're like climbing a ladder rather

558
00:26:49,280 --> 00:26:52,520
Speaker 1: than just getting a single push. So escape velocity is

559
00:26:52,560 --> 00:26:55,959
Speaker 1: not relevant for rockets. What is relevant for rockets is

560
00:26:56,000 --> 00:26:59,040
Speaker 1: this specific impulse and how fast you want to go.

561
00:26:59,520 --> 00:27:01,359
Speaker 3: So in this case, the rocket would be not just

562
00:27:01,400 --> 00:27:03,800
Speaker 3: getting us off Earth, but it would stay with us

563
00:27:03,800 --> 00:27:05,639
Speaker 3: and it would continue to propel us through space.

564
00:27:05,880 --> 00:27:08,760
Speaker 1: Yeah, exactly. And the sort of bog standard rocket we

565
00:27:08,800 --> 00:27:11,640
Speaker 1: have is a chemical rocket where the thing that you're

566
00:27:11,640 --> 00:27:15,159
Speaker 1: throwing at the back is also the way you're getting energy. Basically,

567
00:27:15,240 --> 00:27:18,080
Speaker 1: you have like exploding stones that you're throwing out the back.

568
00:27:18,200 --> 00:27:21,320
Speaker 1: The stones throw themselves out the back, right, because the

569
00:27:21,400 --> 00:27:24,280
Speaker 1: fuel is the propellant and the source of energy. You

570
00:27:24,359 --> 00:27:27,160
Speaker 1: light it on fire and the explosion goes out the back.

571
00:27:27,320 --> 00:27:30,199
Speaker 1: You get pushed the other direction, and so that's cool.

572
00:27:30,320 --> 00:27:32,720
Speaker 1: And you know, obviously fuel we can find here on Earth,

573
00:27:33,160 --> 00:27:37,560
Speaker 1: but the specific impulse of these engines is not huge, right,

574
00:27:37,600 --> 00:27:39,840
Speaker 1: So it's not a great way to get going really

575
00:27:39,880 --> 00:27:44,480
Speaker 1: really fast unless you have incredible quantities of fuel. So

576
00:27:44,520 --> 00:27:47,479
Speaker 1: this is the rocket equation at work here. So if

577
00:27:47,480 --> 00:27:49,520
Speaker 1: you do a little calculation, like how much fuel does

578
00:27:49,560 --> 00:27:52,439
Speaker 1: it take to get off of Earth and to the

579
00:27:52,480 --> 00:27:56,479
Speaker 1: Moon an enormous quantity, right, filling a huge Saturn rocket.

580
00:27:56,840 --> 00:27:59,399
Speaker 1: How much fuel does it take to get to Alpha

581
00:27:59,440 --> 00:28:01,800
Speaker 1: Centauri if you've got to burn that chemical engine the

582
00:28:01,840 --> 00:28:05,320
Speaker 1: whole way, Well, that goes exponential, and the fuel tank

583
00:28:05,400 --> 00:28:07,080
Speaker 1: is something like the size of Jupiter.

584
00:28:07,400 --> 00:28:11,160
Speaker 3: What there's a showstopper. Kelly's gonna keep track of these

585
00:28:11,160 --> 00:28:13,600
Speaker 3: showstoppers as we go because she's the wet blanket.

586
00:28:13,640 --> 00:28:16,440
Speaker 1: But I'm gonna be optimistic because in the end I'm

587
00:28:16,480 --> 00:28:18,800
Speaker 1: really hopeful that we do get to another star, and

588
00:28:18,880 --> 00:28:22,520
Speaker 1: we do, or somebody, not me, but some human gets

589
00:28:22,520 --> 00:28:24,800
Speaker 1: to go and set their eyes on an alien planet.

590
00:28:24,960 --> 00:28:26,080
Speaker 3: I think we will eventually.

591
00:28:26,119 --> 00:28:27,879
Speaker 1: All Right, you heard it there, folks said it.

592
00:28:29,320 --> 00:28:31,280
Speaker 3: I do, I do, but I'm not gonna put any

593
00:28:31,280 --> 00:28:33,240
Speaker 3: money on a date, all right. So when I was

594
00:28:33,280 --> 00:28:35,920
Speaker 3: writing a city on Mars, the engineers would get grumpy

595
00:28:35,960 --> 00:28:41,040
Speaker 3: with me for occasionally using the words fuel and propellant interchangeably,

596
00:28:41,080 --> 00:28:44,080
Speaker 3: which we didn't do in the final manuscript. Nobody needs

597
00:28:44,080 --> 00:28:45,680
Speaker 3: to freak out and write me. Now, this was in

598
00:28:45,720 --> 00:28:48,320
Speaker 3: an early draft. So, Daniel, what is the difference between

599
00:28:48,360 --> 00:28:49,880
Speaker 3: fuel and propellant?

600
00:28:50,040 --> 00:28:51,880
Speaker 1: So, propellant is anything you want to throw out the

601
00:28:51,880 --> 00:28:55,440
Speaker 1: back of your rockets, right, and fuel is a special

602
00:28:55,440 --> 00:28:58,440
Speaker 1: combination which is both a source of energy and a propellant,

603
00:28:58,560 --> 00:29:01,160
Speaker 1: but it doesn't have to be. Another example of a

604
00:29:01,200 --> 00:29:05,480
Speaker 1: propellant that separates these things is a nuclear rocket. So

605
00:29:05,640 --> 00:29:09,400
Speaker 1: rather than using fuel to explode and create energy and

606
00:29:09,520 --> 00:29:14,400
Speaker 1: propellant simultaneously, use something like a nuclear reactor a fission

607
00:29:14,480 --> 00:29:17,440
Speaker 1: reactor to produce the energy, which you then use to

608
00:29:17,440 --> 00:29:20,120
Speaker 1: throw some inert mass out the back. You heat up

609
00:29:20,120 --> 00:29:22,920
Speaker 1: a gas, for example, and it bubbles out the back

610
00:29:23,080 --> 00:29:23,959
Speaker 1: of your rocket.

611
00:29:24,000 --> 00:29:24,240
Speaker 6: Chip.

612
00:29:24,360 --> 00:29:27,120
Speaker 1: The fuel there is like uranium which is powering your

613
00:29:27,200 --> 00:29:30,120
Speaker 1: nuclear reactor, which is providing the energy to toss the

614
00:29:30,120 --> 00:29:32,800
Speaker 1: propellant out the back. The propellant and the fuel are

615
00:29:32,920 --> 00:29:35,440
Speaker 1: very separate in this technology, and.

616
00:29:35,400 --> 00:29:38,680
Speaker 3: So with the nuclear rocket, what would the propellant be.

617
00:29:39,280 --> 00:29:40,920
Speaker 3: Could it be like anything that you heat up.

618
00:29:41,120 --> 00:29:42,560
Speaker 1: Yeah, it could be anything you can heat up. But

619
00:29:42,600 --> 00:29:45,280
Speaker 1: you've got to bring some mass to throw out the back, right, stones,

620
00:29:45,360 --> 00:29:49,240
Speaker 1: white chocolate, xenon, whatever, you want. Something pretty inert so

621
00:29:49,320 --> 00:29:52,000
Speaker 1: it's not reacting, but you also need to bring enough

622
00:29:52,040 --> 00:29:53,720
Speaker 1: of it, and it's going to be dense enough that

623
00:29:53,720 --> 00:29:56,120
Speaker 1: it's not going to be huge. And nuclear rockets are

624
00:29:56,160 --> 00:29:58,200
Speaker 1: cool because it's something we've actually built. We had an

625
00:29:58,240 --> 00:30:01,040
Speaker 1: episode where you and I talked about new clear jet planes,

626
00:30:01,040 --> 00:30:04,240
Speaker 1: and it's the same principle, right, A jet engine operates,

627
00:30:04,360 --> 00:30:06,640
Speaker 1: and the same principle is very similar to a rocket.

628
00:30:06,720 --> 00:30:08,880
Speaker 1: You have the fuel which explodes and pushes something out

629
00:30:08,920 --> 00:30:12,000
Speaker 1: the jet airplane, this whole air compression thing. So jets

630
00:30:12,040 --> 00:30:13,960
Speaker 1: don't work in space, but you could also have a

631
00:30:14,040 --> 00:30:17,160
Speaker 1: nuclear jet engine. We're using a nuclear reactor to heat

632
00:30:17,200 --> 00:30:19,600
Speaker 1: the stuff up and shoot it out the back, same

633
00:30:19,640 --> 00:30:23,120
Speaker 1: basic principle, and that applies to rockets in space as well.

634
00:30:23,520 --> 00:30:25,400
Speaker 1: So in this case, you heat the stuff up and

635
00:30:25,440 --> 00:30:27,400
Speaker 1: you shoot the gas at the back, and that could

636
00:30:27,400 --> 00:30:28,360
Speaker 1: be a nuclear rocket.

637
00:30:28,400 --> 00:30:31,239
Speaker 3: But we haven't actually sent a nuclear rocket to space, right.

638
00:30:31,280 --> 00:30:33,280
Speaker 3: The only kind of rocket we've ever sent to space

639
00:30:33,320 --> 00:30:34,280
Speaker 3: is the chemical one.

640
00:30:34,120 --> 00:30:36,880
Speaker 1: That's right. We do have test nuclear engines which people

641
00:30:36,960 --> 00:30:39,120
Speaker 1: have built and tested and shown to work, and they

642
00:30:39,120 --> 00:30:42,280
Speaker 1: once did fly an airplane with a working nuclear reactor

643
00:30:42,400 --> 00:30:45,720
Speaker 1: on board. Scary stuff, but it wasn't actually powering the

644
00:30:45,760 --> 00:30:49,160
Speaker 1: plane anyway. This is like a viable technology, not just

645
00:30:49,320 --> 00:30:49,960
Speaker 1: science fiction.

646
00:30:50,160 --> 00:30:54,200
Speaker 3: And so you said that for chemical rockets, the container

647
00:30:54,240 --> 00:30:55,760
Speaker 3: that would store the fuel would need to be as

648
00:30:55,800 --> 00:30:59,360
Speaker 3: big as Jupiter. How big are we working on now?

649
00:30:59,400 --> 00:31:00,960
Speaker 3: If it's a new So.

650
00:31:00,920 --> 00:31:02,840
Speaker 1: It doesn't have to be nearly as big because the

651
00:31:02,880 --> 00:31:06,600
Speaker 1: fuel is much more dense, right, Uranium incredibly dense compared

652
00:31:06,640 --> 00:31:10,640
Speaker 1: to like diesel or even like oxygen or whatever you're

653
00:31:10,720 --> 00:31:13,880
Speaker 1: using as fuel, and so that doesn't need to be

654
00:31:13,920 --> 00:31:17,120
Speaker 1: nearly as big. But you'd still have to bring the propellant, right,

655
00:31:17,120 --> 00:31:19,120
Speaker 1: You still need a lot of stuff to throw out

656
00:31:19,160 --> 00:31:21,720
Speaker 1: the back. So we're not talking about the massa jubutter,

657
00:31:21,840 --> 00:31:24,320
Speaker 1: but we're still talking a very very large ship with

658
00:31:24,360 --> 00:31:27,160
Speaker 1: a huge amount of propellant. Now, there's some folks that

659
00:31:27,200 --> 00:31:30,239
Speaker 1: have ideas for like gathering propellant along the way that

660
00:31:30,360 --> 00:31:33,880
Speaker 1: dust you talked about, or the interstellar medium that's stuff, right,

661
00:31:34,200 --> 00:31:36,560
Speaker 1: you could use that as propellant. So there are technologies

662
00:31:36,640 --> 00:31:39,760
Speaker 1: like ramjets or buzzard jets that people talk about where

663
00:31:39,760 --> 00:31:42,440
Speaker 1: you have like a scoop that gathers propellant up and

664
00:31:42,480 --> 00:31:45,200
Speaker 1: then your engine whatever you're using, a nuclear reactor or

665
00:31:45,240 --> 00:31:48,040
Speaker 1: something else, for example, is throwing that out the back.

666
00:31:48,240 --> 00:31:51,080
Speaker 1: And so there are ways to avoid like having to

667
00:31:51,120 --> 00:31:54,160
Speaker 1: have a cataclysmically large ship in that way. Though there

668
00:31:54,160 --> 00:31:55,960
Speaker 1: are also a lot of people who think that those

669
00:31:56,040 --> 00:31:59,040
Speaker 1: ramjets and bussard jets are totally impractical for other reasons.

670
00:31:59,440 --> 00:32:05,240
Speaker 1: Same enough said.

671
00:32:05,920 --> 00:32:09,320
Speaker 3: What if the thing that you're throwing out the back

672
00:32:09,440 --> 00:32:14,640
Speaker 3: of your rocket is nuclear bombs? Cause why not?

673
00:32:14,880 --> 00:32:15,080
Speaker 10: Right?

674
00:32:16,080 --> 00:32:18,640
Speaker 1: Why now? This is actually not a terrible idea in

675
00:32:18,680 --> 00:32:21,840
Speaker 1: some ways because it separates the ship from the propulsion

676
00:32:22,040 --> 00:32:24,680
Speaker 1: in a way that we'll talk about for solar sales.

677
00:32:24,920 --> 00:32:27,600
Speaker 1: If you could blow up a series of nuclear weapons

678
00:32:27,640 --> 00:32:31,080
Speaker 1: between here and Alpha Centauri, and you had a ship

679
00:32:31,120 --> 00:32:33,640
Speaker 1: with like a huge shield in the back that could

680
00:32:33,640 --> 00:32:36,880
Speaker 1: absorb all the radiation and the energy that was dumped

681
00:32:36,920 --> 00:32:39,120
Speaker 1: out by the nuclear bombs. Then you could just sort

682
00:32:39,120 --> 00:32:42,320
Speaker 1: of like ride this wave of nuclear explosions all the

683
00:32:42,320 --> 00:32:45,200
Speaker 1: way to Alpha Centauri. And you know, this is the

684
00:32:45,200 --> 00:32:48,360
Speaker 1: basis of Project Orion. And then later Project Data lists

685
00:32:48,560 --> 00:32:52,000
Speaker 1: the idea having like a series of small bombs providing

686
00:32:52,040 --> 00:32:55,200
Speaker 1: like this smooth acceleration. Now you know, how do you

687
00:32:55,240 --> 00:32:57,840
Speaker 1: get those bombs? How do you lay a trail of

688
00:32:57,920 --> 00:33:00,400
Speaker 1: bombs from here to the next star. It was more

689
00:33:00,440 --> 00:33:04,040
Speaker 1: about like near Earth navigation or getting things off planet

690
00:33:04,200 --> 00:33:07,200
Speaker 1: than like actually going from star to star. But we

691
00:33:07,200 --> 00:33:10,400
Speaker 1: can't not talk about blowing up nuclear bombs as a

692
00:33:10,440 --> 00:33:12,200
Speaker 1: way to propel a ship. It's just got to be

693
00:33:12,240 --> 00:33:13,000
Speaker 1: in the conversation.

694
00:33:13,200 --> 00:33:16,480
Speaker 3: Project Datalus had a follow up project called Project Icarus

695
00:33:16,480 --> 00:33:20,400
Speaker 3: because Icarus was Datalus's son. But Icris is the one

696
00:33:20,440 --> 00:33:23,440
Speaker 3: who flew too close to the Sun and his wings

697
00:33:23,440 --> 00:33:25,400
Speaker 3: melted and he fell down and died. And I always

698
00:33:25,400 --> 00:33:29,000
Speaker 3: remember feeling like, isn't this supposed to be inspirational and like?

699
00:33:29,680 --> 00:33:32,000
Speaker 3: But but I was told I just wasn't looking at

700
00:33:32,040 --> 00:33:33,640
Speaker 3: it the right way. And again, this is why I

701
00:33:33,640 --> 00:33:35,040
Speaker 3: don't get invited to the space parties.

702
00:33:35,080 --> 00:33:37,000
Speaker 1: Do you think it's hard to sign up test pilots

703
00:33:37,000 --> 00:33:38,400
Speaker 1: for Project Icarus.

704
00:33:39,600 --> 00:33:42,240
Speaker 3: It could be, but again, I bet somebody would show

705
00:33:42,320 --> 00:33:44,600
Speaker 3: would sign up. There's a lot of people who are

706
00:33:44,680 --> 00:33:45,480
Speaker 3: much braver than I.

707
00:33:45,440 --> 00:33:50,480
Speaker 1: Am looking for volunteers for a project Crash and Burn. Anybody, anybody, nobody,

708
00:33:51,360 --> 00:33:55,320
Speaker 1: Probably a lot. Anyway, that's a cool technology, and the

709
00:33:55,360 --> 00:33:58,000
Speaker 1: cool thing there is if you could somehow manage it.

710
00:33:58,000 --> 00:34:01,320
Speaker 1: It separates the ship from the source of energy, right,

711
00:34:01,360 --> 00:34:04,280
Speaker 1: and also from the propellant, and so the ship itself

712
00:34:04,320 --> 00:34:06,280
Speaker 1: doesn't have to be very big. Of course, that's sort

713
00:34:06,320 --> 00:34:09,080
Speaker 1: of assuming a solution to the core problem, which is

714
00:34:09,239 --> 00:34:11,719
Speaker 1: how to get all these nuclear bombs from here to

715
00:34:11,840 --> 00:34:13,680
Speaker 1: Alpha Centauri, which is basically impossible.

716
00:34:13,719 --> 00:34:15,799
Speaker 3: What do you think the aliens would think as we

717
00:34:15,800 --> 00:34:19,160
Speaker 3: were like leaving a trail of nuclear explosions on our

718
00:34:19,200 --> 00:34:21,479
Speaker 3: way to their galaxy? Do you think they'd be like, Wow,

719
00:34:21,560 --> 00:34:24,400
Speaker 3: they've really conquered technology. Or do you think they'd be like,

720
00:34:24,520 --> 00:34:26,840
Speaker 3: oh my gosh, how do we get them to turn around?

721
00:34:26,960 --> 00:34:27,200
Speaker 2: Yeah?

722
00:34:27,239 --> 00:34:29,520
Speaker 1: I can't wait for them to show up, right. I

723
00:34:29,560 --> 00:34:32,000
Speaker 1: think it's cool because we can imagine how we might

724
00:34:32,040 --> 00:34:34,799
Speaker 1: detect aliens doing the same, Right, Like, if aliens have

725
00:34:34,840 --> 00:34:37,040
Speaker 1: come up with this idea, and they're using it around

726
00:34:37,080 --> 00:34:39,640
Speaker 1: their star. We might be able to detect it if

727
00:34:39,680 --> 00:34:42,520
Speaker 1: they're close enough, So that's pretty cool. But yeah, I

728
00:34:42,520 --> 00:34:44,279
Speaker 1: don't think it'd be a great way to announce our

729
00:34:44,280 --> 00:34:45,360
Speaker 1: presence to the universe.

730
00:34:45,480 --> 00:34:47,480
Speaker 3: They would definitely have time to set up the welcome

731
00:34:47,640 --> 00:34:49,520
Speaker 3: party or the go home party.

732
00:34:50,360 --> 00:34:52,560
Speaker 1: But along these lines, there's lots of permutations on this

733
00:34:52,640 --> 00:34:57,680
Speaker 1: kind of propulsion once you separate the explosions from the propellant. So,

734
00:34:57,800 --> 00:35:01,040
Speaker 1: for example, there are other ways to accelerate stuff, Like

735
00:35:01,120 --> 00:35:04,400
Speaker 1: you could have an electric field and you have ions.

736
00:35:04,640 --> 00:35:07,200
Speaker 1: An electric field will push ions, that's what it does,

737
00:35:07,800 --> 00:35:09,759
Speaker 1: and so if you had like an electric field and

738
00:35:09,840 --> 00:35:12,600
Speaker 1: a bunch of ionized propellant, you could shoot that out

739
00:35:12,680 --> 00:35:15,879
Speaker 1: the back. Basically, we're talking about a particle accelerator. That's

740
00:35:15,960 --> 00:35:19,000
Speaker 1: exactly what a particle accelerator like the large hadron collider does.

741
00:35:19,440 --> 00:35:22,239
Speaker 1: It pushes particles with electric fields and makes them go

742
00:35:22,320 --> 00:35:25,520
Speaker 1: really really fast. So build a particle accelerator, point it

743
00:35:25,560 --> 00:35:27,640
Speaker 1: out the back of your ship. That's going to give

744
00:35:27,719 --> 00:35:28,760
Speaker 1: you some impulse.

745
00:35:29,080 --> 00:35:32,560
Speaker 3: This seems like another very large design, right How big

746
00:35:32,560 --> 00:35:34,279
Speaker 3: would your particle accelerator need to be?

747
00:35:34,520 --> 00:35:36,800
Speaker 1: Well, not that big. Actually, and it's cool because it

748
00:35:36,920 --> 00:35:40,480
Speaker 1: separates the two systems, and so your power source can

749
00:35:40,520 --> 00:35:42,600
Speaker 1: be anything. It could be solar power, it could be

750
00:35:42,680 --> 00:35:45,640
Speaker 1: some other crazy system that doesn't necessarily have to be

751
00:35:45,719 --> 00:35:48,120
Speaker 1: super duper big. In this case, it's nice because it

752
00:35:48,120 --> 00:35:50,279
Speaker 1: doesn't even have to generate a lot of heat, right,

753
00:35:50,400 --> 00:35:53,319
Speaker 1: and so for those hand wringers aboard, you don't have

754
00:35:53,320 --> 00:35:56,160
Speaker 1: to worry about it like melting down or something like that.

755
00:35:56,320 --> 00:35:59,040
Speaker 1: The downside to this is that the thrust is really

756
00:35:59,080 --> 00:36:03,440
Speaker 1: tiny accelerating particles and particles don't have a lot of mass,

757
00:36:03,840 --> 00:36:06,200
Speaker 1: and they sort of limit to how many particles you

758
00:36:06,239 --> 00:36:09,359
Speaker 1: can effectively shoot out the back, and so it can

759
00:36:09,360 --> 00:36:13,279
Speaker 1: provide very long term gentle thrust, which is nice for

760
00:36:13,400 --> 00:36:16,480
Speaker 1: constant acceleration, but it can't really give you a lot

761
00:36:16,520 --> 00:36:19,560
Speaker 1: of specific impulse, and so it's not a great way

762
00:36:19,600 --> 00:36:22,040
Speaker 1: to like get up to a high speed in a

763
00:36:22,080 --> 00:36:24,560
Speaker 1: short amount of time. But it's cool for like navigating

764
00:36:24,600 --> 00:36:25,799
Speaker 1: around space a little bit.

765
00:36:26,000 --> 00:36:29,000
Speaker 3: So this could be like a generation ship thing. And

766
00:36:29,040 --> 00:36:31,560
Speaker 3: so can you remember what the difference is between thrust

767
00:36:31,640 --> 00:36:32,680
Speaker 3: and specific impulse.

768
00:36:33,080 --> 00:36:36,120
Speaker 1: They're basically the same thrust a specific impulse times the

769
00:36:36,200 --> 00:36:39,080
Speaker 1: constant of gravity, but you can think of them as interchangeable.

770
00:36:39,080 --> 00:36:40,600
Speaker 1: They're just different by units essentially.

771
00:36:40,800 --> 00:36:42,680
Speaker 3: All Right, we're going to take a break now, and

772
00:36:42,800 --> 00:36:44,799
Speaker 3: when we come back, we're going to talk about using

773
00:36:44,960 --> 00:37:05,440
Speaker 3: anti matter to get you to the stars. All right,

774
00:37:05,440 --> 00:37:08,160
Speaker 3: So we just finished talking about ion drives as a

775
00:37:08,200 --> 00:37:10,399
Speaker 3: way to get you to the stars, and I see

776
00:37:10,400 --> 00:37:12,799
Speaker 3: that next we're going to talk about antimatter, and I

777
00:37:12,800 --> 00:37:17,520
Speaker 3: am immediately thinking that dangerous explosions are maybe not what

778
00:37:17,640 --> 00:37:20,120
Speaker 3: I want happening, you know, on the ship that I'm

779
00:37:20,160 --> 00:37:22,680
Speaker 3: living on. But why is Kelly being a wimp?

780
00:37:23,360 --> 00:37:26,160
Speaker 1: No, Kelly is not being a wimp. We are steadily

781
00:37:26,200 --> 00:37:30,480
Speaker 1: moving from reliable technologies we know can work and probably

782
00:37:30,480 --> 00:37:34,040
Speaker 1: won't kill you, to crazy ideas that might not ever

783
00:37:34,160 --> 00:37:37,240
Speaker 1: work and are much more likely to kill anybody on board.

784
00:37:37,760 --> 00:37:39,359
Speaker 3: O good, all right.

785
00:37:40,480 --> 00:37:44,000
Speaker 1: But antimatter is cool because it's the most efficient way

786
00:37:44,040 --> 00:37:48,280
Speaker 1: to store energy. Like matter, and antimatter annihilation is perfect

787
00:37:48,320 --> 00:37:52,000
Speaker 1: conversion of matter into energy. Compare that to for example,

788
00:37:52,480 --> 00:37:55,320
Speaker 1: chemical fuel. Right, chemical fuel has a lot of energy

789
00:37:55,360 --> 00:37:57,040
Speaker 1: in it, but when you burn it, you only release

790
00:37:57,080 --> 00:37:59,400
Speaker 1: a little bit of that energy from the chemical bonds.

791
00:37:59,600 --> 00:38:02,319
Speaker 1: But inside those protons and inside those electrons is an

792
00:38:02,440 --> 00:38:05,279
Speaker 1: enormous amount of stored energy, which we call mass. If

793
00:38:05,280 --> 00:38:07,319
Speaker 1: you could capture all that will release all of that,

794
00:38:07,600 --> 00:38:10,520
Speaker 1: you would need to bring less fuel, right, and so

795
00:38:10,719 --> 00:38:13,480
Speaker 1: matter antimatter annihilation is the best way to do that.

796
00:38:13,520 --> 00:38:16,799
Speaker 1: You have protons and anti protons. They turn directly into

797
00:38:16,800 --> 00:38:19,400
Speaker 1: photons which you can shoot out the back of your ship.

798
00:38:19,520 --> 00:38:22,279
Speaker 1: And that's awesome because the propellant there is moving at

799
00:38:22,320 --> 00:38:24,600
Speaker 1: the speed of light, right, so like you can't be

800
00:38:24,760 --> 00:38:28,560
Speaker 1: that for maximum thrust and impulse. So far this sounds

801
00:38:28,560 --> 00:38:31,759
Speaker 1: great now. The downsides are, of course, Kelly worries about

802
00:38:31,840 --> 00:38:36,640
Speaker 1: being annihilated herself because antimatter is pretty dangerous stuff. Yeah,

803
00:38:36,680 --> 00:38:39,520
Speaker 1: so you need some sort of magnetic confinement for antimatter,

804
00:38:39,760 --> 00:38:42,080
Speaker 1: basically a bottle that doesn't touch it. You know, a

805
00:38:42,120 --> 00:38:45,080
Speaker 1: bottle made of matter that builds a magnetic field that

806
00:38:45,120 --> 00:38:47,600
Speaker 1: confines it, sort of the way we do for plasmas

807
00:38:47,880 --> 00:38:52,160
Speaker 1: in Tokomax infusion reactors. That's not totally implausible, But then again,

808
00:38:52,320 --> 00:38:55,480
Speaker 1: you basically have a bomb on board and any loss

809
00:38:55,480 --> 00:38:58,760
Speaker 1: of containment and everybody's dead, yeah before you can do anything.

810
00:38:59,040 --> 00:39:01,600
Speaker 1: So that's bad. But on the flip side, antimatter is

811
00:39:01,640 --> 00:39:05,040
Speaker 1: basically impossible to make in large enough quantities, so you're

812
00:39:05,080 --> 00:39:08,319
Speaker 1: pretty much safe. You know, we make antimatter. We made

813
00:39:08,360 --> 00:39:10,719
Speaker 1: it for the previous collider. We used to have the Tevatron,

814
00:39:10,960 --> 00:39:14,280
Speaker 1: which was a proton anti proton machine, and we produced

815
00:39:14,280 --> 00:39:17,520
Speaker 1: antimatter at the Large Hadron Collider all the time in collisions,

816
00:39:17,840 --> 00:39:20,719
Speaker 1: so it's not actually that exotic. It's made in the atmosphere,

817
00:39:20,800 --> 00:39:24,320
Speaker 1: like cosmic rays hit the atmosphere turn into a antimatter briefly.

818
00:39:24,520 --> 00:39:29,239
Speaker 1: But the quantities we're talking about are like nanograms of antimatter.

819
00:39:29,280 --> 00:39:31,560
Speaker 1: You know, we can like count the atoms of antimatter

820
00:39:31,640 --> 00:39:35,719
Speaker 1: we make. There's no large scale production of antimatter in

821
00:39:35,800 --> 00:39:39,200
Speaker 1: order to make enough fuel to get anybody near Alpha Centauri.

822
00:39:39,760 --> 00:39:43,160
Speaker 1: I read one estimate that said making one hundred milligrams

823
00:39:43,200 --> 00:39:46,160
Speaker 1: of antimatter would cost about one hundred trillion dollars.

824
00:39:46,200 --> 00:39:49,000
Speaker 3: Oh my gosh. All right, so I'm curious since we're

825
00:39:49,040 --> 00:39:51,440
Speaker 3: starting to get towards the really crazy ones. Out of

826
00:39:51,440 --> 00:39:54,680
Speaker 3: the technologies we've talked about so far, if you had

827
00:39:54,719 --> 00:39:57,800
Speaker 3: to go to Alpha Centauri, which one of these would

828
00:39:57,800 --> 00:39:58,520
Speaker 3: you want to use?

829
00:39:58,760 --> 00:40:03,920
Speaker 1: Probably none of these? Okay, my favorite is one we

830
00:40:03,960 --> 00:40:06,840
Speaker 1: haven't talked about yet it's a little bit ridiculous and speculative,

831
00:40:06,880 --> 00:40:08,120
Speaker 1: but it's still my favorite.

832
00:40:08,200 --> 00:40:11,080
Speaker 3: All right, let's keep going. Then, what's next next?

833
00:40:11,120 --> 00:40:13,440
Speaker 1: I want to talk about a nonsense idea which is

834
00:40:13,480 --> 00:40:16,439
Speaker 1: out there people are probably imagining might save the day,

835
00:40:16,920 --> 00:40:20,920
Speaker 1: and that's propulsion list drives. People have been thinking, okay, well,

836
00:40:20,960 --> 00:40:24,040
Speaker 1: conservation of momentum requires we throw something out the back.

837
00:40:24,080 --> 00:40:26,319
Speaker 1: We're tossing stones or white chocolate out the back of

838
00:40:26,360 --> 00:40:30,200
Speaker 1: our spaceboat to get it moving. That's frustrating that it

839
00:40:30,239 --> 00:40:31,800
Speaker 1: limits us, right because you've got to bring all this

840
00:40:31,840 --> 00:40:33,680
Speaker 1: stuff to throw out the back. Wouldn't it be amazing

841
00:40:34,160 --> 00:40:37,280
Speaker 1: if we could generate a drive which didn't need that, Yeah,

842
00:40:37,280 --> 00:40:40,680
Speaker 1: that would be amazing and also violate conservation of momentum.

843
00:40:40,880 --> 00:40:42,920
Speaker 1: But that has to stop people from trying and go

844
00:40:43,040 --> 00:40:45,359
Speaker 1: for it. Guys, like it wouldn't be the first time

845
00:40:45,400 --> 00:40:48,319
Speaker 1: that we discovered and sit you something that revealed we

846
00:40:48,320 --> 00:40:50,640
Speaker 1: didn't understand the universe. So I'm all in favor of

847
00:40:50,640 --> 00:40:52,120
Speaker 1: people doing crazy experiments.

848
00:40:52,239 --> 00:40:54,440
Speaker 3: That's just like a Friday in physics, right where you

849
00:40:54,480 --> 00:40:56,040
Speaker 3: discover you were wrong about something.

850
00:40:56,480 --> 00:40:59,040
Speaker 1: Yeah, those are the best moments in physics, So nobody

851
00:40:59,080 --> 00:41:02,520
Speaker 1: should be limited by like conventional wisdom about what's possible

852
00:41:02,640 --> 00:41:05,640
Speaker 1: or impossible, but we should also be clear eyed about

853
00:41:05,680 --> 00:41:08,440
Speaker 1: what we have actually proven. And there are folks out

854
00:41:08,440 --> 00:41:10,640
Speaker 1: there who claim to have built one of these things.

855
00:41:10,640 --> 00:41:13,359
Speaker 1: It's called an em drive, and about fifteen years ago

856
00:41:13,400 --> 00:41:14,840
Speaker 1: there was a lot of hoopla about it. There's a

857
00:41:14,880 --> 00:41:17,840
Speaker 1: lot of coverage and the New Scientist. But these folks

858
00:41:18,040 --> 00:41:21,560
Speaker 1: who had some like tenuous NASA affiliation, who claim to

859
00:41:21,600 --> 00:41:25,160
Speaker 1: have built the impossible space drive, And if you look

860
00:41:25,160 --> 00:41:27,600
Speaker 1: for articles, you'll see them there in Popular Mechanics, they're

861
00:41:27,600 --> 00:41:30,759
Speaker 1: and wired, they're in the New Scientist. But the journalists

862
00:41:30,760 --> 00:41:33,359
Speaker 1: here really didn't do their work, Like if you look

863
00:41:33,440 --> 00:41:36,160
Speaker 1: carefully at the claims, you see that the thrust that

864
00:41:36,200 --> 00:41:40,040
Speaker 1: these things produce is really really tiny. It's basically smaller

865
00:41:40,080 --> 00:41:43,120
Speaker 1: than the uncertainties, you know, like they just have jitter

866
00:41:43,239 --> 00:41:46,279
Speaker 1: in their measurements that have sources of noise and they

867
00:41:46,320 --> 00:41:49,120
Speaker 1: measure a thrust, but the thrust is consistent with zero

868
00:41:49,280 --> 00:41:53,200
Speaker 1: within errors. So while I'm all for crazy new technologies

869
00:41:53,239 --> 00:41:56,279
Speaker 1: and exploding understanding the universe, the EM drive is not

870
00:41:56,400 --> 00:42:00,160
Speaker 1: something that's done that. These are fascinating ideas, and there's

871
00:42:00,160 --> 00:42:02,920
Speaker 1: not nothing to support the concepts. One idea is that

872
00:42:02,960 --> 00:42:05,520
Speaker 1: there's a vacuum in space, and that vacuum has energy

873
00:42:05,560 --> 00:42:08,839
Speaker 1: to it, and experiments like the Casimir effects show us

874
00:42:09,160 --> 00:42:11,640
Speaker 1: that the vacuum is real and it's there, and people

875
00:42:11,680 --> 00:42:13,880
Speaker 1: wonder if we can extract energy from the vacuum and

876
00:42:13,960 --> 00:42:16,720
Speaker 1: use it to propel ourselves. But you know, the vacuum

877
00:42:16,760 --> 00:42:19,360
Speaker 1: is special. You can't like row against the vacuum. You

878
00:42:19,360 --> 00:42:23,040
Speaker 1: can't like absorb momentum or get momentum. It's emotional the

879
00:42:23,040 --> 00:42:25,400
Speaker 1: way space is. For example, you can't like put an

880
00:42:25,440 --> 00:42:28,239
Speaker 1: ore down and row through space in the same way.

881
00:42:28,280 --> 00:42:32,120
Speaker 1: And this is part of space. So anyway, em drives

882
00:42:32,160 --> 00:42:34,840
Speaker 1: not something we can rely on and not something I

883
00:42:34,880 --> 00:42:37,040
Speaker 1: would bet on. But hey, if you're out there and

884
00:42:37,080 --> 00:42:39,760
Speaker 1: you're building em drive, I hope you make it work.

885
00:42:39,880 --> 00:42:43,560
Speaker 3: Fingers crossed, all right? So I have heard proposals where

886
00:42:43,680 --> 00:42:46,800
Speaker 3: you know, the Sun is shooting out photons all the time.

887
00:42:47,000 --> 00:42:49,239
Speaker 3: What if you could capture those photons and let the

888
00:42:49,280 --> 00:42:52,080
Speaker 3: Sun sort of push you forward? How would that work?

889
00:42:52,200 --> 00:42:56,080
Speaker 1: This is my favorite idea because it separates the ship

890
00:42:56,200 --> 00:42:59,160
Speaker 1: from the propulsion completely, right. So this is called a

891
00:42:59,200 --> 00:43:02,560
Speaker 1: solar sale, and the idea is that you're right. The

892
00:43:02,600 --> 00:43:05,480
Speaker 1: sun is putting out photons, and not just photons but

893
00:43:05,560 --> 00:43:09,719
Speaker 1: other particles. The solar wind has momentum, So why like

894
00:43:09,920 --> 00:43:14,799
Speaker 1: generate momentum if we have an enormous momentum generating machine already,

895
00:43:15,480 --> 00:43:17,840
Speaker 1: and so all you need to do to capture that

896
00:43:17,880 --> 00:43:20,759
Speaker 1: momentum is build a huge sail. So you know, when

897
00:43:20,800 --> 00:43:23,040
Speaker 1: you're on a sailboat, a sail is just a piece

898
00:43:23,040 --> 00:43:26,120
Speaker 1: of cloth that gathers that momentum. Here, the best kind

899
00:43:26,120 --> 00:43:28,280
Speaker 1: of sale would be something very thin, so low mass

900
00:43:28,320 --> 00:43:32,279
Speaker 1: and reflective. And imagine a photon hits the sail, it

901
00:43:32,360 --> 00:43:34,720
Speaker 1: bounces off the same way a photon hits a mirror

902
00:43:34,760 --> 00:43:37,400
Speaker 1: and bounces off. Right, what happens, Well, the photon is

903
00:43:37,440 --> 00:43:39,879
Speaker 1: now changing its momentum. It's going one way. Now it's

904
00:43:39,920 --> 00:43:43,040
Speaker 1: going the other way. Conservation momentum says that can't happen

905
00:43:43,239 --> 00:43:45,880
Speaker 1: unless something is going the opposite direction. Right, something is

906
00:43:45,880 --> 00:43:50,520
Speaker 1: now going the way the photon originally was to conserve momentum,

907
00:43:50,680 --> 00:43:53,600
Speaker 1: and that's the sail. This is a confusing concept for

908
00:43:53,640 --> 00:43:56,880
Speaker 1: people because it's hard to imagine like light pushing something

909
00:43:56,920 --> 00:43:59,680
Speaker 1: because light has no mass, and you're probably thinking, well,

910
00:43:59,800 --> 00:44:03,480
Speaker 1: momentum is mass times velocity, and photons have no mass,

911
00:44:03,520 --> 00:44:06,960
Speaker 1: so therefore they have no momentum. Right, Yeah, wrong, And

912
00:44:07,000 --> 00:44:10,520
Speaker 1: the reason is that momentum is mass times velocity only

913
00:44:10,520 --> 00:44:13,680
Speaker 1: for very slow stuff. As you approach the speed of light,

914
00:44:13,719 --> 00:44:16,719
Speaker 1: the equation changes a little bit. So photons do in

915
00:44:16,760 --> 00:44:18,920
Speaker 1: fact have a momentum even though they have no mass.

916
00:44:19,040 --> 00:44:22,000
Speaker 1: So yeah, their momentum can push along a sail. So

917
00:44:22,200 --> 00:44:26,160
Speaker 1: imagine a tiny little ship with an enormous sail and

918
00:44:26,200 --> 00:44:28,520
Speaker 1: the photons are bouncing off of it and giving it

919
00:44:28,560 --> 00:44:30,880
Speaker 1: a push. Basically, you don't need an engine.

920
00:44:30,960 --> 00:44:34,040
Speaker 3: So one of the things that always sounded limiting to

921
00:44:34,080 --> 00:44:36,719
Speaker 3: me with this method is that it seems like it

922
00:44:36,719 --> 00:44:39,000
Speaker 3: would work great when you're close to the sun. But

923
00:44:39,120 --> 00:44:41,480
Speaker 3: the farther you get from the Sun, the fewer photons

924
00:44:41,520 --> 00:44:43,400
Speaker 3: are going to be hitting your sail. How would this

925
00:44:43,440 --> 00:44:45,080
Speaker 3: work when you get too far away from the sun.

926
00:44:45,239 --> 00:44:47,359
Speaker 1: Yeah, this is tricky. As you say, you get further

927
00:44:47,400 --> 00:44:50,120
Speaker 1: from the Sun, the photon density drops by one over

928
00:44:50,200 --> 00:44:53,040
Speaker 1: are squared. That's bad. So this is a good idea

929
00:44:53,080 --> 00:44:56,720
Speaker 1: for moving around the Solar system, like navigating from here

930
00:44:56,840 --> 00:45:00,760
Speaker 1: to Mercury or here to Neptune. A very light without

931
00:45:00,840 --> 00:45:03,839
Speaker 1: fuel would be awesome. Getting from here to another star

932
00:45:03,960 --> 00:45:06,520
Speaker 1: would be hard. And what you need to do is

933
00:45:06,560 --> 00:45:10,880
Speaker 1: build an enormous laser. Like think about a really big laser,

934
00:45:11,160 --> 00:45:14,520
Speaker 1: now make it ten times bigger. That's too small. You

935
00:45:14,600 --> 00:45:18,600
Speaker 1: need an enormous laser, right, really huge laser, or like

936
00:45:18,640 --> 00:45:21,920
Speaker 1: a big laser array that I'll focus their energy on

937
00:45:22,000 --> 00:45:24,839
Speaker 1: this sale. But the cool thing is, again, you can

938
00:45:24,880 --> 00:45:26,839
Speaker 1: build this on Earth, or you can have it in

939
00:45:26,920 --> 00:45:29,080
Speaker 1: space or something. You don't need to bring it with you,

940
00:45:29,600 --> 00:45:31,800
Speaker 1: and you can point it at your ship and push

941
00:45:31,800 --> 00:45:35,720
Speaker 1: it to another star. So it's not a solar sale anymore.

942
00:45:35,760 --> 00:45:37,160
Speaker 1: It's like a photonic sail.

943
00:45:37,920 --> 00:45:40,760
Speaker 3: And I can't imagine that a laser of that size

944
00:45:40,800 --> 00:45:45,000
Speaker 3: is going to cause any geopolitical conflict at all. A

945
00:45:45,040 --> 00:45:48,120
Speaker 3: weapon of that magnitude.

946
00:45:48,480 --> 00:45:51,919
Speaker 1: Yeah, we're building the Death Star basically for good reasons

947
00:45:52,360 --> 00:45:55,279
Speaker 1: to go to space. We're just making space smores. What's

948
00:45:55,320 --> 00:45:58,640
Speaker 1: the big deal, right, But there's a project to do this.

949
00:45:58,719 --> 00:46:01,719
Speaker 1: It's called Breakthrough Star Shot and they want to take

950
00:46:01,760 --> 00:46:05,319
Speaker 1: a bunch of nanocraft like tiny little devices, and they

951
00:46:05,320 --> 00:46:08,400
Speaker 1: want to build ground based lasers and send those devices

952
00:46:08,520 --> 00:46:11,880
Speaker 1: to Alpha Centauri. Now you push these tiny little devices

953
00:46:11,920 --> 00:46:14,120
Speaker 1: long enough you can get them up to like twenty

954
00:46:14,160 --> 00:46:16,799
Speaker 1: percent of the speed of light. And so you do

955
00:46:16,880 --> 00:46:20,000
Speaker 1: the math and these things. They're estimating to launch them

956
00:46:20,040 --> 00:46:23,799
Speaker 1: in like twenty thirty ish twenty thirty five, they would

957
00:46:23,840 --> 00:46:26,240
Speaker 1: take about twenty years. They'd be there about like twenty

958
00:46:26,320 --> 00:46:29,839
Speaker 1: fifty five. So if I'm lucky, i'd be around when

959
00:46:29,840 --> 00:46:33,279
Speaker 1: the signal comes back, you know, from Alpha Centauri. This

960
00:46:33,320 --> 00:46:34,960
Speaker 1: is something that really could happen, which is why I

961
00:46:34,960 --> 00:46:37,799
Speaker 1: think it's my favorite technology. The challenge, of course, is

962
00:46:37,840 --> 00:46:40,480
Speaker 1: getting a big enough sale to push a ship with

963
00:46:40,560 --> 00:46:42,879
Speaker 1: people on it. You know, so far we're just talking

964
00:46:42,920 --> 00:46:46,000
Speaker 1: about sending tiny nano robots. But you know, if I

965
00:46:46,040 --> 00:46:47,680
Speaker 1: want to go there, you got to bring me and

966
00:46:47,760 --> 00:46:50,880
Speaker 1: my toilet, my bed, you know, all sorts of stuff

967
00:46:51,320 --> 00:46:53,479
Speaker 1: needs to go with me. So we're not talking nano

968
00:46:53,600 --> 00:46:57,960
Speaker 1: ships anymore. So we're talking enormous sales, and we really

969
00:46:58,040 --> 00:47:00,319
Speaker 1: need like better technology for enormous sales that are going

970
00:47:00,360 --> 00:47:04,880
Speaker 1: to somehow survive the interstellar trip those micro meteorites tearing

971
00:47:04,880 --> 00:47:07,680
Speaker 1: it apart. So you know, there's potential there, but there's

972
00:47:07,680 --> 00:47:09,600
Speaker 1: a lot of engineering challenges to solve.

973
00:47:10,000 --> 00:47:12,120
Speaker 3: Yeah, this is a cool technology. Are the are the

974
00:47:12,280 --> 00:47:16,000
Speaker 3: little nanoships that break through starshot is sending Are they

975
00:47:16,000 --> 00:47:18,359
Speaker 3: going to have like cameras and scientific instruments on them

976
00:47:18,400 --> 00:47:20,200
Speaker 3: or are they just able to say we're here and

977
00:47:20,200 --> 00:47:22,080
Speaker 3: that's it TBD.

978
00:47:22,239 --> 00:47:24,000
Speaker 1: But I hope they're gonna put some cameras on there.

979
00:47:24,040 --> 00:47:27,560
Speaker 1: I mean to be amazingly ridiculous to get something all

980
00:47:27,600 --> 00:47:29,480
Speaker 1: the way there and take no data, right.

981
00:47:29,400 --> 00:47:32,120
Speaker 3: Yeah, that would be a major bummer. We haven't talked

982
00:47:32,200 --> 00:47:34,799
Speaker 3: yet about a method to me that seems perhaps likely

983
00:47:34,840 --> 00:47:38,160
Speaker 3: something that we have some experience with, which is gravity slingshots,

984
00:47:38,239 --> 00:47:41,560
Speaker 3: which which we're used in Aurora Kim Stanley Robinson's book

985
00:47:41,760 --> 00:47:44,200
Speaker 3: to slow down on the way back to Earth. Is

986
00:47:44,239 --> 00:47:46,239
Speaker 3: that something that we could use to speed up to

987
00:47:46,239 --> 00:47:46,640
Speaker 3: get there?

988
00:47:46,840 --> 00:47:50,640
Speaker 1: Absolutely, Gravitational slingshots are amazing. You know, you whiz near

989
00:47:50,680 --> 00:47:53,520
Speaker 1: a planet basically steal a little bit of its speed.

990
00:47:53,640 --> 00:47:55,080
Speaker 1: We should dig into the physics of that in a

991
00:47:55,080 --> 00:47:58,240
Speaker 1: whole episode because there's some subtleties there about like why

992
00:47:58,520 --> 00:48:00,520
Speaker 1: you end up with a little bit of speed, And

993
00:48:00,560 --> 00:48:02,640
Speaker 1: the short version of it is that you slow down

994
00:48:02,680 --> 00:48:05,720
Speaker 1: the planet's rotation around the star, which is really cool,

995
00:48:05,840 --> 00:48:08,240
Speaker 1: and we've done this. You know, Voyager one, for example,

996
00:48:08,360 --> 00:48:11,640
Speaker 1: one of our only interstellar probes. It's swung around the Sun,

997
00:48:11,800 --> 00:48:14,120
Speaker 1: but it's not going that fast. You know, it's traveling

998
00:48:14,200 --> 00:48:17,960
Speaker 1: like a light year in about eighteen thousand years. So

999
00:48:18,120 --> 00:48:21,279
Speaker 1: you can't get going to like interstellar speeds unless you're

1000
00:48:21,280 --> 00:48:23,799
Speaker 1: getting crazy close to the star, and that's got its

1001
00:48:23,840 --> 00:48:26,680
Speaker 1: own dangers. So gravitational slingshots are a good way to

1002
00:48:26,719 --> 00:48:29,160
Speaker 1: boost your speed and to get going, but on their

1003
00:48:29,200 --> 00:48:30,960
Speaker 1: own they're not going to provide the speed that you

1004
00:48:31,040 --> 00:48:32,160
Speaker 1: need to get to another star.

1005
00:48:32,640 --> 00:48:34,880
Speaker 3: Got it all right, So let's wrap things up on

1006
00:48:34,960 --> 00:48:40,080
Speaker 3: the most sci fi methods. So what can we do

1007
00:48:40,160 --> 00:48:42,560
Speaker 3: to can we like bend space or time to make

1008
00:48:42,600 --> 00:48:43,120
Speaker 3: this happen?

1009
00:48:43,400 --> 00:48:46,680
Speaker 1: Yeah, so far we're considering flat space. We're imagining you know,

1010
00:48:46,800 --> 00:48:48,600
Speaker 1: light is going to take a few years to get there.

1011
00:48:48,640 --> 00:48:50,680
Speaker 1: What can we do to approach the speed of light?

1012
00:48:51,040 --> 00:48:53,240
Speaker 1: But of course we know that space is not just flat.

1013
00:48:53,280 --> 00:48:56,120
Speaker 1: Space bends, it curves, and in the presence of mass,

1014
00:48:56,120 --> 00:48:57,880
Speaker 1: it can do all sorts of things. They can wiggle,

1015
00:48:58,120 --> 00:49:00,680
Speaker 1: not something we fully understand, but you know, we know

1016
00:49:00,719 --> 00:49:02,719
Speaker 1: that this kind of thing is possible, and so in

1017
00:49:02,800 --> 00:49:05,000
Speaker 1: the last few years or so, people have been thinking about, like,

1018
00:49:05,040 --> 00:49:08,239
Speaker 1: could we actually build a warp drive. This would be

1019
00:49:08,280 --> 00:49:12,160
Speaker 1: something that bends space so that effectively the journey is shorter.

1020
00:49:12,320 --> 00:49:15,240
Speaker 1: And that's really what space curvature means, that you're changing

1021
00:49:15,440 --> 00:49:18,279
Speaker 1: the relative distance between two points. So hey, why not

1022
00:49:18,360 --> 00:49:21,080
Speaker 1: make Alpha centaur really really close so that doesn't take

1023
00:49:21,120 --> 00:49:23,680
Speaker 1: as long to get there. And that's the idea of

1024
00:49:23,680 --> 00:49:25,920
Speaker 1: a warp bubble that you like, shrink the space between

1025
00:49:25,920 --> 00:49:28,239
Speaker 1: you and the star and expand the space behind you.

1026
00:49:28,880 --> 00:49:30,319
Speaker 1: And then when you get there, you pop out of

1027
00:49:30,320 --> 00:49:32,000
Speaker 1: this warp bubble and you're like, hey, that wasn't a

1028
00:49:32,000 --> 00:49:32,479
Speaker 1: big deal.

1029
00:49:32,719 --> 00:49:36,480
Speaker 3: How likely is it that these warp bubbles actually exist

1030
00:49:36,640 --> 00:49:37,560
Speaker 3: or could be created?

1031
00:49:37,719 --> 00:49:40,600
Speaker 1: That's a topic of hot debate. On the positive side,

1032
00:49:40,960 --> 00:49:44,120
Speaker 1: there's a guy who's figured out that warp bubbles do

1033
00:49:44,239 --> 00:49:48,120
Speaker 1: not violate general relativity, meaning like a warp bubble doesn't

1034
00:49:48,120 --> 00:49:50,799
Speaker 1: break any of those rules. That doesn't mean that a

1035
00:49:50,840 --> 00:49:54,279
Speaker 1: warp bubble could actually exist in the universe because you

1036
00:49:54,360 --> 00:49:57,080
Speaker 1: create something because it's allowed in the universe. Like everybody

1037
00:49:57,080 --> 00:50:00,040
Speaker 1: knows chocolatesou fleas are allowed in the universe, Does I

1038
00:50:00,160 --> 00:50:02,040
Speaker 1: mean everybody knows how to make them? You have to

1039
00:50:02,040 --> 00:50:05,280
Speaker 1: have a very delicate process to get from no chocolate

1040
00:50:05,360 --> 00:50:07,799
Speaker 1: sooufle to chocolates sooufle, right, and there's lots of ways

1041
00:50:07,840 --> 00:50:10,560
Speaker 1: to fail. We don't have a recipe for building a

1042
00:50:10,600 --> 00:50:13,160
Speaker 1: warp drive, but just know that the resulting drive is

1043
00:50:13,200 --> 00:50:15,600
Speaker 1: not disallowed by general relativity. It could be that some

1044
00:50:15,680 --> 00:50:19,160
Speaker 1: step between no warp drive and warp drive is disallowed

1045
00:50:19,239 --> 00:50:22,080
Speaker 1: or is impossible. And so if you could just like

1046
00:50:22,280 --> 00:50:26,000
Speaker 1: magically pop a warp drive into existence, then physics is

1047
00:50:26,000 --> 00:50:28,520
Speaker 1: cool with it. But we don't know if it's possible

1048
00:50:28,760 --> 00:50:30,719
Speaker 1: to create one in our universe.

1049
00:50:31,080 --> 00:50:32,839
Speaker 3: All right, Well, I'm going to hope that it is,

1050
00:50:33,280 --> 00:50:36,440
Speaker 3: because that would make things really convenient. At the beginning

1051
00:50:36,520 --> 00:50:39,520
Speaker 3: of the show, you mentioned that in your favorite book

1052
00:50:39,760 --> 00:50:43,800
Speaker 3: they just moved stars closer together. How would that work?

1053
00:50:43,920 --> 00:50:45,600
Speaker 3: And why would everyone be dead?

1054
00:50:47,440 --> 00:50:50,360
Speaker 1: This is basically like the think big version of the

1055
00:50:50,400 --> 00:50:53,920
Speaker 1: solar sale. Right. In this version, you build a huge

1056
00:50:54,000 --> 00:50:57,839
Speaker 1: sale like half the size of the sun. Yeah, that's right,

1057
00:50:57,880 --> 00:51:00,719
Speaker 1: half the size of the sun. Wow, wrap half of

1058
00:51:00,760 --> 00:51:04,400
Speaker 1: the sun a big mirror that points back at the Sun. Okay,

1059
00:51:04,400 --> 00:51:06,359
Speaker 1: And so you might think, well, what's gonna happen? That

1060
00:51:06,400 --> 00:51:08,719
Speaker 1: mirror is just gonna shoot off it's a big solar sale.

1061
00:51:08,719 --> 00:51:10,719
Speaker 1: It gets pushed away by the Sun. Right, Well, you

1062
00:51:10,760 --> 00:51:12,560
Speaker 1: bring it close to enough and you make it massive

1063
00:51:12,680 --> 00:51:16,680
Speaker 1: enough that it's gravitationally captured by the Sun. So now

1064
00:51:16,719 --> 00:51:18,720
Speaker 1: basically the mirror and the Sun are like a single

1065
00:51:18,760 --> 00:51:22,480
Speaker 1: gravitational object. The Sun is shooting half of its photons

1066
00:51:22,480 --> 00:51:25,680
Speaker 1: to the mirror, but they get bounced back so basically recaptured.

1067
00:51:26,000 --> 00:51:28,560
Speaker 1: On the other side, the Sun is shooting off its

1068
00:51:28,560 --> 00:51:31,800
Speaker 1: photons out into space. So now it's like an ion drive.

1069
00:51:32,120 --> 00:51:35,239
Speaker 1: So one half of the Sun is basically captured and nullified,

1070
00:51:35,280 --> 00:51:39,200
Speaker 1: the other half is not. Now the Sun can move right.

1071
00:51:39,840 --> 00:51:43,480
Speaker 1: The Sun is basically like a rocket, and so this

1072
00:51:43,520 --> 00:51:46,960
Speaker 1: could move the whole Solar system. And Kelly should feel

1073
00:51:46,960 --> 00:51:50,399
Speaker 1: great about this because you could travel to another star

1074
00:51:50,760 --> 00:51:53,280
Speaker 1: without even leaving your house. You could like literally sleep

1075
00:51:53,280 --> 00:51:55,319
Speaker 1: in your bed at home and we could go visit

1076
00:51:55,400 --> 00:51:58,360
Speaker 1: Alpha Centauri move the whole Solar system.

1077
00:51:58,520 --> 00:52:00,640
Speaker 3: Okay, all right, so that sounds awesome. I love that

1078
00:52:00,680 --> 00:52:03,560
Speaker 3: you dream big. But like, so you know we've talked before,

1079
00:52:03,560 --> 00:52:05,480
Speaker 3: if like suns get too close to each other, one

1080
00:52:05,480 --> 00:52:07,880
Speaker 3: of them gets like thrown off into the vastness of space.

1081
00:52:08,120 --> 00:52:10,640
Speaker 3: This feels like a high risk method.

1082
00:52:13,000 --> 00:52:15,120
Speaker 1: Well, it's hard to turn a star, you know, if

1083
00:52:15,160 --> 00:52:17,880
Speaker 1: you realize you're going in the wrong direction. This is

1084
00:52:17,920 --> 00:52:20,040
Speaker 1: harder to turn than like one of those U hauls

1085
00:52:20,040 --> 00:52:23,840
Speaker 1: that are already pretty hard to turn. Yeah, there's a

1086
00:52:23,880 --> 00:52:26,600
Speaker 1: lot of ways this could go wrong. You know, maybe

1087
00:52:26,600 --> 00:52:30,640
Speaker 1: a safer method is to use a black hole instead, because.

1088
00:52:30,440 --> 00:52:35,360
Speaker 3: Black holes, You physicists, wouldn't it be safer if we

1089
00:52:35,440 --> 00:52:36,360
Speaker 3: used a black hole?

1090
00:52:37,160 --> 00:52:39,200
Speaker 1: I like, you just laugh in my face at that one.

1091
00:52:39,600 --> 00:52:40,160
Speaker 3: I'm sorry.

1092
00:52:40,320 --> 00:52:44,560
Speaker 1: I mean a black hole also converts mass into energy. Right,

1093
00:52:44,600 --> 00:52:47,879
Speaker 1: black holes evaporate, they have energy stored inside them because

1094
00:52:47,920 --> 00:52:50,840
Speaker 1: of their mass, but they generate Hawking radiation, which is energy.

1095
00:52:50,960 --> 00:52:53,440
Speaker 1: So put a black hole next to a mirror and

1096
00:52:53,480 --> 00:52:56,720
Speaker 1: in the same way, it will generate propulsion in one direction,

1097
00:52:57,040 --> 00:52:59,839
Speaker 1: right if it's gravitationally captured the mirror, and so that's

1098
00:53:00,160 --> 00:53:03,160
Speaker 1: absorbing that radiation. Now you have a black hole which

1099
00:53:03,200 --> 00:53:06,520
Speaker 1: is turning its mass into radiation and pushing your ship

1100
00:53:06,600 --> 00:53:09,440
Speaker 1: so you don't have to move a whole star. Now

1101
00:53:09,440 --> 00:53:12,040
Speaker 1: you have a black hole power and spaceship. And of

1102
00:53:12,080 --> 00:53:14,160
Speaker 1: course there's technical problems here, like how do you actually

1103
00:53:14,160 --> 00:53:16,319
Speaker 1: make the black hole? We don't know how to do that.

1104
00:53:16,680 --> 00:53:18,520
Speaker 1: Maybe you could find a black hole. We don't know

1105
00:53:18,520 --> 00:53:20,960
Speaker 1: where any of them are. Also, there are some risks

1106
00:53:21,000 --> 00:53:23,800
Speaker 1: involved in having a black hole on board your ship.

1107
00:53:23,960 --> 00:53:27,439
Speaker 1: Please sign these waivers, all.

1108
00:53:27,400 --> 00:53:29,439
Speaker 3: Right, So I'm going to ask myself the question, which

1109
00:53:29,440 --> 00:53:31,960
Speaker 3: one of those methods do I think I would use

1110
00:53:32,080 --> 00:53:34,840
Speaker 3: if I was forced to go on a ship to

1111
00:53:34,880 --> 00:53:37,719
Speaker 3: Alpha Centauri. I think that I would agree with you

1112
00:53:37,800 --> 00:53:40,000
Speaker 3: about the solar sale technique. But what would make me

1113
00:53:40,160 --> 00:53:44,400
Speaker 3: nervous is that somebody else is in control of the

1114
00:53:44,440 --> 00:53:48,400
Speaker 3: propulsion and so like, I imagine that keeping a giant

1115
00:53:48,600 --> 00:53:51,640
Speaker 3: laser constantly powered has got to take a lot of energy.

1116
00:53:51,640 --> 00:53:54,200
Speaker 3: And so what if one day, you know, the Americans

1117
00:53:54,239 --> 00:53:57,520
Speaker 3: are like, you know what, We're not powering this laser anymore.

1118
00:53:57,560 --> 00:53:59,920
Speaker 3: It's just too expensive. And then what do you do?

1119
00:54:00,520 --> 00:54:02,360
Speaker 1: Yeah, well there's not much you can do.

1120
00:54:02,920 --> 00:54:03,120
Speaker 4: You know.

1121
00:54:03,160 --> 00:54:05,440
Speaker 1: The other issue with a solar sale is slowing down.

1122
00:54:05,640 --> 00:54:07,279
Speaker 1: Like it gets you up to near the speed of

1123
00:54:07,360 --> 00:54:10,680
Speaker 1: light using that big laser, then you have to use

1124
00:54:10,800 --> 00:54:13,640
Speaker 1: the destination sun to slow down, but it is no

1125
00:54:13,800 --> 00:54:16,800
Speaker 1: laser there to give you that boost, and so you

1126
00:54:16,880 --> 00:54:21,920
Speaker 1: got to like combine that with gravitational sling shots. It's tricky. Yeah,

1127
00:54:21,960 --> 00:54:24,319
Speaker 1: there's no way I'm getting on any of these ships ever,

1128
00:54:25,560 --> 00:54:28,040
Speaker 1: But I encourage all of you to, like, please go

1129
00:54:28,200 --> 00:54:30,319
Speaker 1: explore the universe and tell us all about it.

1130
00:54:30,400 --> 00:54:31,320
Speaker 3: Send me a postcard.

1131
00:54:32,600 --> 00:54:34,640
Speaker 1: All right. So, I think we surveyed some of the

1132
00:54:34,680 --> 00:54:37,719
Speaker 1: technologies that might get us to other stars, and my

1133
00:54:37,920 --> 00:54:40,560
Speaker 1: take is that there's some promise here. Obviously there are

1134
00:54:40,640 --> 00:54:43,440
Speaker 1: kinks to be worked out, and Kelly and her legal

1135
00:54:43,440 --> 00:54:45,640
Speaker 1: team need to be put at ease about the black

1136
00:54:45,680 --> 00:54:48,919
Speaker 1: hole on board, you know, or moving the entire sun.

1137
00:54:48,960 --> 00:54:50,640
Speaker 1: Do we need to take a vote before we do that.

1138
00:54:50,800 --> 00:54:54,839
Speaker 1: I'm not sure, But to me, these feel like solvable problems.

1139
00:54:54,880 --> 00:54:58,000
Speaker 1: And you know, we're young as a species technologically. In

1140
00:54:58,000 --> 00:55:00,600
Speaker 1: one hundred years and a thousand years will good this out,

1141
00:55:00,600 --> 00:55:02,640
Speaker 1: and maybe even by then somebody will have built an

1142
00:55:02,680 --> 00:55:03,360
Speaker 1: em drive.

1143
00:55:03,680 --> 00:55:06,799
Speaker 3: Well, And to surprise everybody, I am actually optimistic about

1144
00:55:06,840 --> 00:55:08,680
Speaker 3: some of this stuff, and I feel like these are

1145
00:55:08,719 --> 00:55:11,920
Speaker 3: really interesting problems that we have to solve, and imagine

1146
00:55:11,960 --> 00:55:13,919
Speaker 3: the other things that we're gonna learn along the way,

1147
00:55:13,960 --> 00:55:16,560
Speaker 3: where the new technologies will come up with as we

1148
00:55:16,600 --> 00:55:18,759
Speaker 3: try to make some of these methods work. I think

1149
00:55:18,760 --> 00:55:19,480
Speaker 3: it's all very.

1150
00:55:19,320 --> 00:55:22,640
Speaker 1: Exciting, all right, But before you get too excited, next episode,

1151
00:55:22,640 --> 00:55:25,040
Speaker 1: we're gonna talk about all the other tricky problems you

1152
00:55:25,040 --> 00:55:27,520
Speaker 1: would have to solve to get humans to another solar system,

1153
00:55:27,600 --> 00:55:29,960
Speaker 1: giving birth on board? Is it okay to have children

1154
00:55:30,080 --> 00:55:35,400
Speaker 1: born between planets? Embryos, robots, cryogenics, radiation, all that good stuff.

1155
00:55:35,719 --> 00:55:38,520
Speaker 1: So tune in next time for Kelly to throw a

1156
00:55:38,520 --> 00:55:40,480
Speaker 1: wet blanket on your interstellar dreams.

1157
00:55:40,520 --> 00:55:47,240
Speaker 3: That's what I do, so well out, all right.

1158
00:55:47,120 --> 00:55:48,280
Speaker 1: Tune in next time everyone.

1159
00:55:55,239 --> 00:55:59,040
Speaker 3: Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio. We

1160
00:55:59,080 --> 00:56:01,520
Speaker 3: would love to hear from you, We really would.

1161
00:56:01,680 --> 00:56:04,320
Speaker 1: We want to know what questions do you have about

1162
00:56:04,320 --> 00:56:06,320
Speaker 1: this Extraordinary Universe.

1163
00:56:06,400 --> 00:56:09,359
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1164
00:56:09,400 --> 00:56:12,399
Speaker 3: for future shows. If you contact us, we will get

1165
00:56:12,440 --> 00:56:12,840
Speaker 3: back to you.

1166
00:56:13,040 --> 00:56:16,560
Speaker 1: We really mean it. We answer every message. Email us

1167
00:56:16,600 --> 00:56:19,360
Speaker 1: at Questions at Danielankelly dot.

1168
00:56:19,239 --> 00:56:21,080
Speaker 3: Org, or you can find us on social media. We

1169
00:56:21,160 --> 00:56:25,000
Speaker 3: have accounts on x, Instagram, Blue Sky and on all

1170
00:56:25,080 --> 00:56:27,360
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1171
00:56:27,760 --> 00:56:28,760
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1172
00:56:28,920 --> 00:56:30,400
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