Daniel and Kelly’s Extraordinary Universe - Can you sail on light?

Episode Date: June 27, 2019

How can we travel through the universe without running out of fuel? Find out today with Daniel and Jorge. Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

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On the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, luckily, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend's been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now he's insisting we get to know each other, but I just want or gone. Hold up. Isn't that against school policy? That seems inappropriate.

Maybe find out how it ends by listening to the OK Storytime podcast and the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. In sitcoms, when someone has a problem, they just blurt it out and move on. Well, I lost my job and my parakeet is missing. How is your day? But the real world is different. Managing life's challenges can be overwhelming. So what do we do? We get support. The Huntsman Mental Health Institute and the Ad Council have mental health resources available for you at loveyourmindday.org.

That's loveyourmindtay.org. See how much further you can go when you take care of your mental health. Hey, Daniel, you like the outdoors. You're an outdoorsy kind of person. Are you a fan of sailing? Oh, man. love sailing. There's so much to appreciate the wind, the quiet, but mostly it's because it's about applied physics. That's the part you love the most about it, is the physics of sailing.

Yeah, you know, you've got the wind coming in one way, and the boat is pointing another way, and you have the, you know, the keel underneath and the rudder. It's a big complicated calculation, all happening in real time under you. Yeah, and you might die or get stranded out and see if you mess it up. That's right. That's right. So physics can save your life. It's good to understand vectors. But no, yeah, I always find it really confusing. You know, it's like if you want to go one way, you actually have to point the boat the other way, but then you have to move the cell in line with the wind. And so there's like the Bernoulli effect. I just, I find it always really confusing. It is confusing. Basically, you know, all you need to know is if you want to go

one way, make sure you point the boat a different direction, right? That's the only way to get there. Never point to where you're going. No, that's a classic rookie mistake. Hi, I'm Jorge, I'm a cartoonist and the creator of Ph.D. Comics. Hi, I'm Daniel. I'm a particle physicist and the co-author of our book together. We have no idea, a guide to the unknown universe. And right now you're listening to our podcast, Daniel and Jorge, Explain the Universe, a production of iHeartRadio. in which we try to find weird, crazy, wacky, interesting, amazing things about the universe that will blow your mind and explain them to you

in a way that makes you understand them and also laugh along the way. That's right. We take you to all the corners of the universe, in rockets, in spaceships, in warp drives potentially, and also maybe using sailboats. That's right. We want to navigate your brain from here to there and all around, and we're willing to do it in any sort of mental capsule that's possible. And so today on the program,

we're going to be answering a listener question who was wondering if there are better ways to travel through space. That's right. You guys might be familiar with the question of how do we get from here to there, right? And if you want to fly from Earth to Mars or Earth to Jupiter or even to another star, you've got to push yourself there, right? You've got to get your ship going at a certain speed, and that requires energy. And most of the technologies that we have currently are basically just like a fire spewing out the back. and that requires some sort of fuel. That's right. You need fuel. And unfortunately, there are no gas stations between here and Mars.

And so you kind of have to bring it all with you. But there might be Tesla supercharger stations, for all we know, right? Isn't that Elon Musk's plan? How's that company doing these days? I haven't really checked my stock portfolio. But, you know, the guy thinks big. So probably as SpaceX goes to Mars, he's going to stop along the way and leave, you know, charging stations. Yeah, so today on the program, we'll be talking about an interesting idea about traveling to the stars.

we'll be talking about solar sales. How do they work? Do you really sail? Are solar cells on sale, right? What does this thing even mean? That'd be nice if they're on sale. Everyone can get one.

That's right. That's right. More than just our listeners in Delaware. Remember that podcast when we were going to cover the state of Delaware with solar cells? Oh, yeah. Do we get any feedback from Delawareans?

Oh, actually, we did. First of all, commented that we need to also include Maryland. And they weren't offended at all. Actually, they were just glad to have any sort of Delaware shout out. They say that they don't often get mentioned. Never happens, I guess. So we love you, Delaware.

Keep listening. Yeah, so it's kind of an interesting idea that you can make a sail to sail the deep blue blackness of space. Yeah, it's really kind of an awesome idea. I mean, we're familiar with the wind, right? And the wind is a wonderful way to use a sailboat because you don't have to bring any fuel with you, right? You go on a motorboat, you got to bring all that fuel with you. It makes your boat heavier. It's loud. It's noisy. It's obnoxious. Right.

One of the things I love about sailing is that it's quiet, right? First of all, you don't have to fuel up because your fuel is just the wind. And then when you're sailing, there's no obnoxious motor sound to listen to. So the idea of traveling from one planet to another through space using something similar, like being propelled without bringing along your own fuel, it's a beautiful idea. Yeah, it's kind of cool to think that you can ride something out in space, right? Like there's something already going there and you can just kind of latch onto it and it'll push it to where you want to go. That's right. And you might be tempted to say, what's pushing the sail? Like obviously on Earth here, it's air, but what's pushing your sail out in space? Because

there's no air in space. And you're right. We're not sailing in that same way. And then you might be tempted to say, what about the solar wind? These guys have told us about all the particles shooting out from the sun. Is it the solar wind? Is it the solar wind? that a solar sail would be riding but that's not even the case it's not the solar wind that a solar sail works off of though that would be some sort of

poetic you know beautiful parallel wait so it's not the solar wind that you would sail on in space no it seems tempting right you'd like to have a solar sailboat using the solar wind for this beautiful analogy for our whiskey fueled adventures on the high seas here

but it's not actually the solar wind that pushes along a solar sail oh man the solar wind does it give you a sunburn and chapped lips at the same time. That's right. It gives you that solar wind-tousled hair also. You have deep fried, probably. Exactly.

Not recommended, folks. Not recommended. It's like a Brazilian blowout, but crispier. If you're listening to this podcast on the space station, do not stick your head at the window to get a solar wind-tousled look. Yeah. Instead, write us because that'd be really cool to hear from you. Exactly.

Exactly. Yeah. So we'll be talking today about this solar, sails, the idea that you can go between planets or stars or galaxies using a sail to catch something out there in space to take you there. And so as we mentioned, this question came to us from Derek from Cleveland. And so here is Derek asking his question. Hey Daniel and Jorge. This is Derek from Cleveland, Ohio. My question is how does solar sails work? If photons are massless, how can they impart momentum to a satellite? And how is the conservation of momentum upheld?

I quickly want to say hi to my brother-in-law, Tim, who I'm sure will listen and to discuss your answer with me later. Thanks, guys. All right. Thank you, Derek. That's a pretty interesting question. I mean, it sounds like he's heard of solar sails, and he knows they work by catching light. But his question was, how does that work if photons have no mass? Yeah, so many good questions here, right? Like, how does the solar sail work? He seems to understand that it catches light, but he doesn't understand, like, does light have momentum? Because he's probably thinking that momentum is mass times velocity, right?

which is the case for slow-moving massive objects. So he's wondering if the mass term is zero, how can you have any momentum? Like, how do things with no mass have any momentum? And if they don't have momentum, how can they push along a solar sail? It's a great question. Right.

I mean, I think it means, like, you know, if light has nothing to it in terms of, like, mass, how can it push you? Exactly. That's the question. And so I was wondering what people thought about this. Are people aware of solar sails? Do they understand photons and momentum

and all this kind of stuff? And so I went around and I asked people what they knew about solar sails. And before you listen to these answers, think to yourself, do you know how a solar sail works? Do you understand how light can have momentum if it doesn't have mass? Here's what they had to say. I feel like I've heard of it, but I'm not sure. I mean, I've seen, like, fixed ones, but I haven't seen. I know that they're transitioning like Tesla's doing the roof tiles and stuff that are a solar day,

but I don't know if I've seen those. a big, like, I guess kind of a sheet of sunlight. Yes, actually I have. A solar sail is basically a really big sail that doesn't get pushed by wind. It gets pushed by energy from the sun. So basically energy has a little bit of movement in it, and that big movement, a little bit of movement, can push it. Because it's not too much movement, but it's a lot of energy in a big area that will push it.

I'm honestly not sure. I couldn't even guess. Like maybe the stunted price on solar system or something like that. Okay, I like it. All right. I love these answers. I feel like they're all correct. Like, is it a boat powered by solar power?

Yes, technically that would be a solar. Would that be like a boat with an electric engine on it that's powered by solar cells? That's pretty cool. Yeah, sure. Yeah, that's like a solar boat for sure. Or like a discount. I like the person who said, is it like a discount on solar panels? Like a solar sale?

I think that guy might have thought I was actually trying to sell him solar panels. Like he looked kind of wary. He's like, hmm, are you another one of those shady solar salesman discounts? They are pretty shady, quote unquote. That's right, exactly. Their business wouldn't stand up to sunlight. You have to be pretty bright.

And there was one guy who actually had a pretty solid answer. Was this your physics student slash sale instructor? No, it was not. Actually, that was my 11-year-old son, who I think overheard me talking about solar sales to somebody else before I asked him. So he had a preview of the answer and just wanted to sound smart. You're saying your son cheated.

I'm saying I asked him the question and he knew the answer and so he answered it. All right. That's right. It wasn't a test. He had a bit more of a head start than the rest of the other folks that we asked. So it's not something that a lot of people seem to know about

or recognize the name of. That's right. It's not a common concept. And that surprised me a little bit because I thought that people had heard more about, like, how to move through space or the kinds of engines you might use, but I guess not, which makes an excellent topic for today's podcast. Yeah. Well, I have to admit, my only reference to a solar sail-powered spaceship is from Star Wars. Do they do solar sails in Star Wars?

I don't even remember that. I thought they all had ion engines and stuff. Yeah, no. I mean, if you've watched the prequels, which I'm sure we can get into a whole episode about it, But Count Duku, that character, has rise around in a ship that has solar sails or what looks like, what looked like solar sails. Oh my gosh, why, you have like an encyclopedic knowledge of all the ships in every science fiction movie ever? That's impressive. And I have an encyclopedic knowledge of all nerd movies, probably.

So that's what you do it for in the afternoon when you're not feeling in the mood to do cartooning. It's like turn on some science fiction movie? Yeah. Isn't that what everybody does? Yes, yes, that is exactly what everybody does in the middle of the afternoon. No, but you're right, these things are in science fiction. I read lots of books with solar sail-powered ships in them. It's a pretty common idea in terms of how to get from here to there.

And you know what? We don't have that many ideas for how to get from one planet to another or one star to another. And so it's on a pretty short list. Well, this is how it kind of worked in Star Wars. So, Count Duky gets on his ship. He takes off, he flies up into orbit or space, and then he like unfurls this huge giant sail, this like giant sheet that looks kind of like it's made out of gold,

and then then he starts going. So it's like he opened a giant umbrella, and then that pushed them forward. Yeah, that's basically it. Solar sails are giant umbrellas. Podcast over. You nailed it. Star Wars for the win.

Yeah, let's get into it, Daniel. What is a solar sail? So a solar sail is an enormous flat sheet, just like a sail on a sailboat. And the thing that it captures is not wind like in air, because there is no wind in space. And it's not the solar wind, because the solar wind, remember, is protons being shot out by the sun.

And those could push the sail, but there's just not that much of them. There's just not that many of them. There's not enough of them. What is capturing is light. So the light from the sun is zooming out from the sun, and it's carrying energy with it. And we'll dig into that in a moment, but photons have momentum.

And so what happens when they hit the sale, is that they give it a little push. And you get enough little pushes and you can actually get going somewhere. So this is a real thing. Like people have built these? Like there are functioning solar wind sailboats out there in space?

Yes, this is a real thing. It's like physics says there's no reason why it shouldn't work. People have big plans to make huge solar sails that can go all around the solar system or maybe even to other stars. And somebody has actually built one of these things and made it work.

The Japanese, they launched one several years ago and showed that it actually worked. Like, the physics isn't just theoretical. Like, there is one thing out there that's solar sailing right now. Oh, that's pretty cool. The Japanese. The Japanese, nice job.

But the thing about solar sails is that it's gentle, right? There's not really, really powerful winds of light out there for you to capture with your sails. So if you have, like, even a really big sail, like 800 meters by 800, meters, which is, you know, enormous, right? Then that only gets five

newtons of force. And five newtons is not that much. It's like how much a force there is on like a one pound object on Earth. So like a one pound rock, you know, think about how much that feels in your hand. That's the force of the Earth's gravity on a one pound rock.

That's the same amount of force that the sun would push on a 800 meter by 800 meter sail about the distance from of the Earth. Which is huge, Right? I mean, it's like several city blocks. Yeah, that is not a small thing to build and to unfurl and to keep from getting shredded, right, by like micrometeorites and whatever. But you're saying if I made a tarp that was about a kilometer on each side over Manhattan, it would get pushed down, not just by the weight of it, but also by the sun that's hitting it.

Yes, exactly. And every time a photon hits you, you're getting pushed. Like, photons are actually pushy. They are kind of rude, aren't they? they just like zoom along wherever they want to go they don't ask questions they don't take turns or they just go in straight lines wherever they need to no photons care momentum and every time they hit something they give it a little push so when you turn when you flip the switch and turn on the light you get pushed down a tiny little bit and you might think what i can't feel it and you're right because it's a small effect which is why solar sails are very gentle and you need a huge one to add up to any measurable force well at step through a little bit of how this works. I mean, so you're saying if I take a flashlight and I flash it at you, I am technically kind of pushing you with it. You're basically punching me in the face with light, yeah. Yeah, that's pretty mean. Because we don't think of light as

having substance to it, right? Like you, I mean, we sort of associate with energy and heat and warmth, but not force. That's right. We don't think of photons as having mass because they don't, but they do have energy, right? Photons are energy. It's just pure energy. And, and, And if you have energy, that means you have momentum. And it's complicated because we're only used to thinking about things having momentum when they have mass. We think about you give something momentum because it's heavy and it's hard to get going. And once you've pushed it, it keeps going. It has momentum, right?

So something that's like light and fluffy and, you know, weighs nothing, it's hard to understand how that can have momentum. Well, I think we're all pretty familiar with, like, if I shine a flashlight on you or a laser, like your body's going to absorb that energy or, you know, warm up a little bit or something, but you're saying that if I have an atom on my skin and you're flashing a flashlight on it, the photons actually sort of hit it and the atom wants to go the other way? Yes, exactly. Think about what happens with a mirror, right? It's a little bit more complicated when the light gets absorbed.

So let's think about a mirror where the light gets reflected. The light's zooming in one direction. It hits the mirror and the lights going in the other direction, right? How does the light change direction? Right? What changes the direction of the light? It's the mirror. instead of thinking about

light in a mirror think about a ping pong ball and a paddle right if you get hit if a ping pong paddle gets hit by the ball then the ball

bounces the other direction but the paddle gets pushed back a little bit right that balances the momentum remember momentum is conserved so in the same way when the light hits

the mirror it gives that mirror a little push and the mirror pushes back and that's what turns the light the other direction and so when light

reflects off of something it's giving it a little push so pure energy can push you basically. Exactly. It can result in something wanting to move the other way. That's right.

And this is one of the cool things in physics when you learn that a concept you thought you had a firm grasp on like momentum is actually just a special case of sort of a larger concept. Like we're familiar with momentum as mass times velocity. But that's not its definition.

That's just how you calculate it for slow moving things with mass. You can calculate momentum for things that don't have mass because momentum is a larger concept. It just, it captures like the quantity of motion of something, not just its mass times velocity. It's just that it's more like the total energy. Yeah, but it's fascinating because energy is just a number.

It doesn't have a direction, right? And physics energy is a scalar, not a vector. Like, it doesn't have a direction just a magnitude, whereas momentum has a direction. Like, you know, pointed in one direction is different from pointed in the other direction, right? Oh, I see. So light has momentum. Light has momentum. It has energy and it has momentum, but it has no mass.

One way that some people like to think about it is you can think about momentum is sort of the difference between the energy and the mass, right? Because in relativity, we think of the total energy as the energy stored in the mass plus the energy of the momentum. So you can sort of invert that equation and say the momentum is the difference between the total energy and the mass. And in the case of the photon, there is no mass. So the momentum just comes from the energy. Whereas in the case of another particle, right, it has a bunch of energy. some of that is in the mass and some of it is in its motion. But for the photon, the energy is just in its motion.

So it just has momentum and no mass. All right. Solar sails are a real thing. And they work by taking the momentum that's in light, absorbing it, and then using that to push you along in space. That's right. And it's the light from the sun that's doing this, not the protons from the solar wind.

And everybody actually can see this if you just have seen a comet. You know, a comet is just a big ice ball and it falls towards the sun. And as it does so, it gets a big tail, right? And that's the tail of it, like the stuff melting and dripping out the back. And the tail points in a specific direction away from the sun. Not in the direction of motion. People think, like, you know, it's like a fuzzy line behind something that's moving fast. But the comet actually always points away from the sun.

And that's because of this effect of light. That's light pushing the tail of the comet. Really? It's not like a trail of a dust that you leave behind? No, because as the comet is moving towards the sun, the tail is behind it. But as the comet goes around the sun and then leaves, the tail is in front of it. Wow. So it shouldn't be called the tail once again.

I guess, or maybe it's like backing away from the sun as it leaves. It's like, whoa, that was close. All right, let's get into will it work and how can we make it work? But first, let's take a quick break. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal. Apparently the explosion actually impelled metal glass.

The injured were being loaded into ambulances, just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism. Law and Order Criminal Justice System is back. In Season 2, we're turning our focus to a threat that hides in plain sight. That's harder to predict and even harder to stop. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts.

My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Oh, wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other, but I just want her gone. Now, hold up.

Isn't that against school policy? That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professional. and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him because he now wants them both to meet.

So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. I'm Dr. Joy Harden Bradford. And in session 421 of Therapy for Black Girls, I sit down with Dr. Othia and Billy Shaka to explore how our hair connects to our identity, mental health, and the ways we heal. Because I think hair is a complex language system, right? In terms of it can tell how old you are, your marital status, where you're from, you're a spiritual belief.

But I think with social media, there's like a hyper fixation and observation of our hair, right? That this is sometimes the first thing someone sees when we make a post or a reel. It's how our hair is styled. We talk about the important role hairstylist play in our community. the pressure to always look put together and how breaking up with perfection can actually free us. Plus, if you're someone who gets anxious about flying,

don't miss session 418 with Dr. Angela Neil Barnett, where we dive into managing flight anxiety. Listen to therapy for black girls on the IHeartRadio app, Apple Podcasts, or wherever you get your podcast. All right. So that's solar sales, Daniel. That's pretty cool. The question now I think is, does it work? If you build it, will it take us to other planets and maybe other galaxies? Yeah, it seems like it will. And, you know, we know a lot about it. We can do these calculations. We know how much light there is. We can calculate how it will reflect and how much will be absorbed. And we know all the numbers we need. And so people have plugged all this stuff into calculations. And they said, if you build a solar sail that's like a kilometer by a kilometer and you have a really light ship. you know, not too heavy, how long would it take to get to Mars or to get to Jupiter? And the thing you have to understand is that the strength of the light, of course, gets weaker as you get further from the sun.

So the solar sail is very powerful close to the sun because it's capturing more light. And then as you get further and further away from the sun, it gets weaker and weaker. So solar sails are great for navigating around the inner parts of a solar system. Well, the question I have is, you know, these sails are catch the rays from the sun, right? they catch the light from the sun and push it, get pushed away from the sun. But what if you want to travel towards the sun or perpendicular to the sun? How would you do that? If you want to move towards the sun, it's not hard, right? You just need to use gravity, right? The sun is going to pull you towards the sun. So that part's not hard. But the only way you can use the sail to build energy is moving away from the sun.

So you can play this game of gravity versus the solar sail depending on which way you want to go. If you're facing the sun, can it push you sideways? Because gravity is pushing me towards the sun and the solar cell is pushing me away from the sun. How do I gain speed sideways? Whoa, that's a really good question. I hadn't even thought about that. How do you steer it?

Because the photons are only coming out from the sun. So can you move in a direction that's not out away from the sun? My first thought is, let's think about how a sail works on a sailboat, right? On a sailboat, you can move in a different direction than the wind, if you put the sails sort of across from the wind. But the problem is a sailboat has a keel, right? It has something underneath it. It keeps it from sliding sideways.

And so it can only use the part of the wind that it wants by pointing in the right direction. A solar sail, of course, on a spaceship doesn't have a keel. So at first thought you might think, oh, a solar sail can only take you in the direction the photons are going, right? Well, let's think about it for a moment. what happens if you tilt the sail so that it's not pointing flat away from the sun, right? If it's at an angle with respect to the photons, you might think, well, it doesn't really matter because the photons hit it and bounce off and they're giving a push the direction they were going, right? It's actually a tiny bit more complicated if the photons hit it at an angle,

then they also bounce off at an angle, right? So if the photons are coming directly out from the sun and they hit flat on the solar sail, then they bounce back the opposite direction. And the momentum they've given is in the direction they were going. But if they come out from the sun and they hit the solar cell at an angle, then they reflect off.

Think about light hitting a mirror, right? It doesn't come back the way it was going. It reflects off at an angle. And so the push that it gives is actually in the direction that the solar sail was facing. So I think that means that you can steer a solar sail. You just turn it the way it wants to go, and it will catch that part of the photon's momentum that pushes it in the direction it's facing.

You can't just point in that direction and drive the way you can with your car. You have to take an account all these limitations. But you can do it, and you can take a pretty heavy load, you know, a few tons, to Mercury, and it just takes a few years. If you want to go to Venus, it takes, you know, about a year. If you want to go the other direction, it starts taking longer because the radiation from the sun drops, right? So if you want to go to Mars, it takes like a year and a half, maybe two. It takes like two years to get to Jupiter, three to get to Saturn, and then like six years and nine

years to get out to the outer planets. Wow. That's a lot of whiskey drinking on board. That's your fuel after all, right? There's no solar whiskey. You'd be using it up. You could have burned it to evade that asteroid, but no, you had to drink it. Yeah, well, you know, it depends on how well you get along with your crewmates,

depending, that determines how much whiskey you have to drink. Can you imagine being stuck in a spaceship with your physics student for nine years, Dano? No, but I also can't imagine being in a spaceship by myself for nine years, right? Like, what do you think would be easier to handle? Total isolation or being stuck with one person in a tin can for nine years? Oh, for me, would definitely be by myself, yeah. You and a big stack of science fiction movies, right?

That's all you need. And a cartooning pad, obviously. So I can document my descent into madness. That's right. Your further descent into madness, you meant surely. My first, that's right. Thank you for reminding me. But yes, but what about beyond the solar system?

Could you use the solar sail to leave the solar system? You could a little bit. I mean, what you can do is try, one strategy is to just try to get going as fast as you can using solar sails and gravity and then zoom off in the direction of another star. So you're like, you slingshot around the sun to get some speed up. And then as you're leaving the sun, you unfurl your sails, and it pushes you away from the sun as hard as it can. But then once you leave the solar system, it's really going to stop pushing you very much,

and so your speed doesn't pick up anymore. But, you know, if you do it right and you have a light enough object, you could get up to a reasonable speed and head off in that direction. Yeah, I mean, at some point when you leave the solar system, it's like there's no wind. It's like being on a sailboat with no wind. There's nothing to push you anywhere. Yeah, and, you know, there is radiation out there,

and there are particles, but it's very low density. It's not enough to really. to really boost you. One idea people have, and I love this idea because it's so crazy, plus ambitious, which is my favorite combination, is to basically beam light at these things. Like if you're in a solar sailboat and you're leaving the solar system, maybe we could build a huge laser and beam the energy at your solar sail to give you a push. What if you punch a hole through the sail with your laser?

Yeah, exactly. It can't be too intense. but you know these sails will be very reflective right they are essentially they're big sheets of aluminum or maybe plastic that's covered with aluminum so that they're super reflective so if it's reflective enough then even a really really powerful laser won't punch a hole right because punching a hole means the energy gets absorbed and so like melts and destroys the sail if it's reflective enough then you should be able to shoot even a really powerful laser and have all the energy be transferred into the momentum of the sail

It's like blowing on a little sailboat. Yeah, exactly. Or I'm sure I've seen some science fiction movie where somebody like reflects a laser blaster with a mirror, right? Oh, you just have like a pure mirror, shoot at it, and then that pushes you forward. Yeah, or if somebody shoots you with a laser blaster and you have a mirror, you can just reflect their, you know, energy pulse or whatever, back at them. All right. Well, let's get into how you would actually build a solar sail, even if it wasn't on sale. But first, let's take a quick break.

December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal. Apparently, the explosion actually impelled metal. glad. The injured were being loaded into ambulances, just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay.

Terrorism. Law and Order Criminal Justice System is back. In season two, we're turning our focus to a threat that hides in plain sight. That's harder to predict and even harder to stop. Listen to the new season of Law and Order Criminal Justice System on the IHRour, Heart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Wait a minute, Sam, maybe her boyfriend's just looking for extra credit.

Well, Dakota, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other, but I just want her gone. Now hold up, isn't that against school policy? That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professor and they're the same age. And it's even more likely that they're cheating.

He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. I'm Dr. Joy Harden Bradford, and in session 421 of therapy for black girls, I sit down with Dr. Othia and Billy Shaka to explore how our hair connects to our identity, mental health, and the ways we heal. Because I think hair is a complex language system, right, in terms of it can tell how old you are, your marital status, where you're from, you're a spiritual belief. But I think with social media, there's like a hyperfixation and observation of our hair, right?

that this is sometimes the first thing someone sees when we make a post or a reel is how our hair is styled. We talk about the important role hairstylists play in our communities, the pressure to always look put together, and how breaking up with perfection can actually free us.

Plus, if you're someone who gets anxious about flying, don't miss session 418 with Dr. Angela Neil Barnett, where we dive into managing flight anxiety. Listen to therapy for black girls on the iHeart radio app, Apple Podcasts, or wherever you get your podcast.

That would be a pretty awesome idea for merch, like solar sale, Daniel and Jorge's solar sale, explore the universe instead of explaining the universe. That'd be pretty cool. What do you mean? Where would we sell? Sale, sale. We'd sell the solar sale.

Like, in our, we have a shop where we sell t-shirts and coffee mugs with, you know, Daniel and Jorge explain the universe on it. We should add to our internet merch account, a solar sale that you can buy. Okay, cool. Done, let's do it. And then you just get a sheet of aluminum foil. Is that the idea? That's right.

A one kilometer by one kilometer square of aluminum foil with your picture on it. There you go. And you can sail away into bankruptcy. Right. And you can shoot a laser at that picture from Earth. Dual purpose aluminum foil. You can wrap your leftovers. and go into space.

Exactly. But that's basically what a solar sail is, right? You want it to be really, really big, but you also want it to be really, really light. You want your solar sailboat to be as light as possible so that all that momentum gets turned into speed. The more mass of your sailboat, the slower it's going to go for the same amount of momentum.

So you want it really big and really thin. I mean, does it matter in the long run, how much your solar sail weighs? Sure, it does, yeah. I mean, you want to get up to like half the speed of light or a quarter the speed of light or something. it's going to take a lot longer and if you don't have a laser push

then you have a limited amount of time to get energy from the sun and so you want to get up to as high as speed as possible oh I mean but that's just in general the same for any acceleration right absolutely the lighter you are the faster it is to go faster yeah exactly and that's like

why people who you know climb mountains on their bicycles remove every tiny little thing that's not necessary because they don't want to carry that mass up the mountain you know I met a guy who was climbing matripea you and he like sawed his toothbrush in half because he didn't need the bottom half of it and you want to carry that thing up the mountain. So yeah, you want your spaceship to be as

light as possible so you can translate all of that momentum into speed. So basically that's all you need is just a thin aluminum foil. But usually they show them in movies and in pictures is gold. It looks like gold foil. Does that give you a better advantage if it's gold or golden? No, you can't just have aluminum foil because aluminum is too brittle. Like you try to make a huge sheet of aluminum foil. I mean, I can't even get like a one foot square of aluminum foil to stay together without tearing. And so you try to like fold and then unfurl a one kilometer square of aluminum foil. It's not going to work. So usually what they do is they have some sort of plastic and they spray aluminum coating on it. And so sometimes that

plastic is gold, but I don't think there's a reason why that's gold. I think that's just to look cool. All right. Well, where are we at then in terms of projects that are trying to use solar sales to get us out there? Yeah, so the best solar sale ever so far is the Icarus project launched in 2010 by Japan, and they had a 14 by 14 meter solar sale. And that sounds small compared to what we're talking about, like 800 meter by 800 meter. But 14 meters is not small. That's like, you know, the size of an apartment.

Can I just comment on their choice of names? Like, have they read the whole story of Icarus? Do they know how that story ends? I don't know. I love the hubris in choosing the name Icarus. for a solar sale project, right? They chose a story about hubris, and they did it kind of hubristically.

They're like thumb in their nose at history. I love it. That's not going to happen to us. We're going to fly really close to the sun, and nothing bad is going to happen to us. Maybe they're trying to regain the name Icarus. They're claiming it back, you know, the way some people claim back bad words.

They're going to turn this new a positive stereotype now. They want to redeem Icarus himself. That's it, exactly. Maybe they're like the descendants of Icarus himself. Yeah. So they're building it? They build it. They're going to build it.

They built it. They launched it. It worked. It's solar sailing. It's zooming around the sun right now. Really? It's out there. Sailing away.

It's out there sailing away. It's sipping whiskey and looking down on us. And that's the most successful solar sail so far. But it's not like a ship, right? It's like a satellite or a little vessel. Yeah, it's a little vessel. It's basically just to experiment. It's like, can we do this thing?

Let's see if it actually works. Because, you know, sometimes in physics, you do the calculations, they sound great, and then, you know, it doesn't actually work the way you expected because you forgot to account for something. But in this case, it pretty much worked as they expected, and that's a huge boost for all the solar sail enthusiasts. I didn't know that was such a thing. I'm a solar sail enthusiast. I'm a big fan of, first of all, I love sailing, but I'm a big fan of anything that's going to take us to other planets or take us to other stars, and isn't going to require a huge, ridiculous amount.

out of fuel. Cool. Well, and then you were telling me there's another cool project called the Breakthrough Star Shot project. Yeah. They have this awesome idea. They say, let's not send one big solar sail. Let's build a hundred, like a thousand nanosales. So there'd be a bunch of really small ones, and they would push them along with lasers between here and Alpha Centauri. The problem with building a laser that pushes a big solar sails, you need a big laser. So they were like, Okay, well, let's just have a small solar sail that can be pushed by a small laser and then just have like a tiny little craft. And so they imagine that it would take 20 years to get to Alpha Centauri with these little

nanosailers. And so they would have a giant laser gun on Earth shooting at these things, pushing them along? A thousand laser guns pushing on them. Oh, each one has their own little laser gun. Yeah, exactly. Each one needs its own little boost. But the cool thing about solar sailing is that, you know, it's a small effect, but it just adds up. And if you're traveling for a long time,

it's just like more and more acceleration. Eventually, these things can get up to a respectable fraction of the speed of light. So they can cross the distances between stars. And then they would communicate back what they find, but they can't come back, can they? They cannot come back, no, because there's no laser system over there to shoot them back. I mean, that we're aware of, maybe they'll get there

and find Elon Musk has built some station over there for recharging your solar lasers or something. But no, it's just a, it's a one-way trip. Well, that's cool. It's like instead of building a giant boat, you build a whole bunch of little rubber duckies into the river, kind of.

That's right. Exactly. That's going to be humanity's first contact with an alien species is the equivalent of a rubber ducky. Hi, look at us. We're so impressive. This is a little squeeze toy. And then the aliens are like,

this is a sign of war. That's right. Maybe the rubber ducky is like holy to them, and it's offensive that we like threw one in their face. Plus, we probably, all our lasers would be like burning their eyeballs out for 20 years while the nanocrafts are getting there. But if we fill them up with whiskey, maybe they'll like it. Yeah, they'll either love it or hate it. They'd be like, what? Scottish whiskey, I only drink Irish.

This means war. Wars have been fought over less, I'm sure. All right, so that answers Derek's question, who wanted to know how do solar our sales work. And hopefully you guys enjoyed that and are inspired to make. Maybe think about taking up sailing. That's right. And maybe someday we'll go out there and we'll sail among the stars. I think it's really beautiful and poetic to imagine using the light from the stars themselves to push ourselves from one to the other.

I really wish that could happen. All right. Thanks for listening, guys. See you next time. If you still have a question after listening to all these explanations, please drop us a line. We'd love to hear from you. You can find us at Facebook, Twitter, and Instagram at Daniel and Jorge, that's one word, or email us at Feedback at Danielandhorpe.com. Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of IHeartRadio. For more podcasts from IHeartRadio, visit the IHeartRadio app, Apple Podcasts,

or wherever you listen to your favorite shows. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, everything changed. There's been a bombing at the TWA terminal. Just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, terrorism. Listen to the new season.

Reason of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, luckily, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend's been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now he's insisting we get to know each other, but I just want or gone. Hold up. Isn't that against school policy? That seems inappropriate.

Maybe find out how it ends by listening to the OK Storytime podcast and the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. In sitcoms, when someone has a problem, they just blurt it out and move on. Well, I lost my job and my parakeet is missing. How is your day? But the real world is different. Managing life's challenges can be overwhelming. So what do we do? We get support. The Huntsman Mental Health Institute and the Ad Council have mental health resources available for you at loveyourmindday.org. That's loveyourmindtay.org.

See how much further you can go when you take care of your mental health. This is an IHeart podcast.