The Rest Is Science - The Science of Putting Sunglasses on The Sun

Episode Date: August 9, 2026

Why does the cartoon Sun always wear sunglasses? And how big would a real pair need to be? Hannah Fry and Michael Stevens investigate space mirrors, Reflect Orbital and solar eclipses to find out. Starting with a pencil held at arm’s length, they use the Sun’s angular diameter to calculate how big a pair of solar sunglasses would need to be for one eye, two eyes, everyone in London and eventually the entire planet. Their hypothetical answer is a strange structure more than a million kilometres wide, positioned deep in space. Entirely practical. They compare its extraordinary scale with NASA’s Parker Solar Probe, the real spacecraft flying closer to the Sun than anything ever built, before using Lagrange points to work out where their creation could possibly go. But could putting something between Earth and the Sun ever be useful? Real proposals for space sunshades and climate geo-engineering suggest that blocking a small fraction of sunlight could help cool the planet. Moving from shade to reflection, they revisit Soviet attempts to reflect sunlight onto Earth at night and explore how Reflect Orbital’s Earendil 1 space mirror experiment might one day extend solar energy beyond daylight hours. That leads them to the strange physics of light itself. Photons can push solar sails despite having no rest mass, revealing why E=mc² is only part of the full energy momentum equation from special relativity. Finally, there is the optical phenomenon known as the Arago spot to contend with. It helps explain why NASA’s starshade concepts, future technology designed for hunting exoplanets, look like enormous sunflowers. ------------------- For more information about Cancer Research UK, their research, breakthroughs and how you can support them, visit https://www.cancerresearchuk.org/our-research/rest-is-science Cancer Research UK is a registered charity in England and Wales (1089464), Scotland (SC041666), the Isle of Man (1103) and Jersey (247). A company limited by guarantee. Registered company in England and Wales (4325234) and the Isle of Man (5713F). Registered address: 2 Redman Place, London, E20 1JQ. ------------------- Find The Rest Is Science all over the internet by ⁠⁠clicking here.⁠⁠ ------------------- Video Producer: Adam Thornton + Oli Oakley + Jack Meek Animator: Sam Benson Video & Social: Bex Tyrrell Assistant Producer: Lucy Lipscombe Producer: Simona Rata Senior Producer: Lauren Armstrong-Carter Chief Digital Officer: Samuel Oakley Exec Producer: Neil Fearn Learn more about your ad choices. Visit podcastchoices.com/adchoices

Welcome to the rest is science. I am Michael Stevens. And I'm Hannah Fry. And today, Hannah helped me with this episode. We're going to be figuring out how to put sunglasses on the sun, a cartoonist's dream. It's the simple questions that we are here to answer. So let's get into the science. You're probably sitting there thinking putting sunglasses on the sun, that's never going to work.

Why? Because the sun doesn't have ears or a nose. going to fall right off. It wasn't my first thought. Oh, it wasn't your... Well, it was my first thought. So I spent hours trying to figure out, does the sun have anything on it that is kind of like an ear?

There's no sound in space, but there is sound inside the sun. The vibrations of the gas moving around, all of that really does create pressure waves that are like low frequency sound waves in the sun. But can it hear itself? No, I just kept coming back to the sun. It doesn't have ears. It doesn't have ears. It doesn't have a nose.

And then I arrived at another problem, which I don't know if you thought of this one, but the sun can't really wear sunglasses because it's, well, it's the sun. It's too hot. That one was, I would say it was still probably about fourth or fifth on my list of things, but that one didn't get to me. Okay. All right. What was your number one?

Why? Oh, yes. Okay. Yeah. Why should we do this? Funny enough, we began thinking that this was just a big old goof. And then as it turns out, there is an answer to the why question. And it's a pretty serious one.

I don't want to spill it all right now. But there could be a good reason to do this. You've done a hook and tease there, Michael, and I'm here for it. I've done a few hooks and teases. But there's one more. There's one more. Not only is occluding the sun in some way potentially a good idea by exploring. how to put sunglasses on the sun

to make it a really cool dude sun, I think we're also going to discover that E equals MC squared is incomplete. Yeah. As usual, we're going to be absurdly deep today and deeply absurd. This episode is brought to you by Cancer Research UK.

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You should have ordered from Wayfair. With Wayfair, there's no what if. Just style you love and quality you can trust. Visit Wayfair.ca. Wayfair, every style, every homes. Okay, first things first. We want to put sunglasses on the sun. We can't get close enough to actually put a physical pair of sunglasses

made of any known material actually on the surface of the sun because it's too hot. And this is because, this is not because necessarily the gravitational pull of it, but this is because the radiation that it's giving off is so gargantuan. Essentially every material that we reliably use on Earth would be obliterated. The Parker Solar probe was the instrument that humans have brought closest to the sun, and it only approached about six million kilometers away. But it can stay there for a long time.

If you get closer, you get burned up in a shorter and shorter amount of time. Hang on a second. How far away are we from the sun? We're 150 million kilometers. 150 million. Okay, so this was six million kilometers away. Wow, that is actually really close. That's really close.

So it's about four million miles. Right. Parker Solar Probe got. I mean, it got into the very outer parts of the sun's atmosphere. So in a way, it visited the sun, even though it was still six million kilometers. away. That's close than I was expecting. And that's not quite on the sun yet, obviously. But you bring up another good point, which is that anything you put on the sun is going to fall right into it, because it doesn't have a hard, solid surface like my noggin does. It can hold glasses really

easily. So we're not out of luck, though, because we don't necessarily need to put the sunglasses on the sun itself. We just, I'm okay just making it look like the sun is wearing sunglasses. So almost like I'm holding up a pair of glasses in front of your face. Exactly. And from my perspective, it looks like you're wearing them. Exactly. So this brings us to angular diameter. This is how we're going to crack this nut.

Okay? So Hannah, you already know all of this. But for the listeners out there, we have talked about angular diameter before, but it describes how large something is, not in reality, but how large it appears to you, how wide across in your field of view it is. And so when you have an object, it's got a really large angular diameter when it's close to your eyes. But the further away it gets, the smaller it looks, right?

From far away, I can crush people's heads. And the way we measure this is by imagining 360 degrees all the way around our bodies. That's this whole field. And then we ask what angle does the object subtend from one end to the other? and if an object is really big, then, you know, its angle, when it's far away, will be, you know, something large. But a smaller object would fill that angle if it was close.

I don't think my visual here, if you're watching, really helped. But I'm trying to use my hands to show an angle. Holding up a tape measure. Yeah, and I'm showing, I'm holding a tape measure between my fingers. But the same object could fit between my palms, and it would be a lot smaller and still take up the same angle of my field of view. So we've got degrees, and then the degrees of something's width can be cut into pieces, and they can be cut into 60ths to give us what are called arc minutes. So something that's an arc minute wide in your field of view is a 60th of a degree of a circle all the way around you.

That's pretty small. That's about the smallest width the human eye can differentiate as actually having width and not just being a point, one arc minute, a six. 60th of a degree. In the sky, the sun takes up about 32 arc minutes of a room. All right? So that's about half a degree. Yeah, I came up with actually a very similar answer, but I did it a very different way. Oh. Well, maybe not very different. I don't think it deserves the very, but a slightly different way, should we say. Okay, so here's what I was thinking. Imagine your eye is like a single point. You've got one eye, one eye open and you're looking at the sun, right? And now imagine that there is a triangle shooting out from your eye, okay?

And please, I want to make sure that everyone's only imagining this. Yes. Important point. Don't do this at home. Okay? Yes, this is how the ancient Greeks thought the light worked, but from the purposes of this podcast, it's an imagination thing only. Okay, so you've got this triangle that is sort of shooting out of your eye.

One side of the triangle meets up with one edge of the sun, the other side of the of the triangle meets up with the other edge of the sun. So that essentially, if you're kind of of looking top down at you viewing the sun, you see this flat triangle where the width of it, at the end of it is the exact width of the sun and then it kind of draws its lines backwards towards your eye to form this triangle. When it comes to the sun itself, we know exactly what that triangle looks like because we know that the width of the sun is 1.39 million kilometres and we know that it's 149.6 million kilometres away. So you can work out this triangle to give you that exact angle.

Essentially, that tells you the ratio of how far away something needs to be and how wide it is to cover that object. So when you work it out for the sun, it's basically one 107th. So any object that you have that you hold up in front of the sun as long as it is at least one one hundred and seventh as wide as it is far away, it will cover the sun. So if I make a disc, right, and I hold up and it's at least one one hundred and seventh as wide as it is far away, then I can be sure that it will cover the sun.

Yeah. So here's a specific example. I think there's some overlap in our calculations. In order to, in order for an object held at arm's length, which I'm assuming is about 70 centimeters. In order for an object to just be exactly the same width as the sun in the sky from Earth, that object would need to be 0.65 centimeters wide. Okay? If you held such an object out in front of you at arm's length, it would block the sun. And that happens to be almost exactly how wide a pencil is. Right. Okay? So at arm's length, a pencil will completely block out

the disk of the sun, assuming your arms are 70 centimeters long. Don't try this at home, though, because it's only going to just cover the sun, and you will hurt your eyes. You will. By trying this. This leads to a really cool fact that we can add on to that classic one about how solar eclipses happen, because we always know that there's this weird coincidence, which is that the sun is 400 times bigger than the moon. But the moon is 400 times closer to us. So they appear the same size. They take up the same angular diameter in the sky,

so the moon can perfectly cover the sun. Where this is going is that if you made a tiny little pair of sunglasses that were only as wide as a pencil, you could hold them out at arm's length and put them over the sun, and the sun would look like it was wearing sunglasses. But also, you would damage your eyes, because most of the sun would not be covered.

Sunglasses only cover like 15% of the face that they're on. So don't do it that way. No, no, unless you don't value your eyesight in that one eye that you're using. No, please. Don't even give them ideas. As it turns out, you need to dim the sun a lot more than just covering like 15 to 30% of it. The ISO standard for safe solar viewing is that you need to decrease the sun's light by 100,000 times. It needs to be 100,000th as bright as it normally is to safely look at. And when we say safely, what we're talking about here is, I mean, it's literally sunburn on the inside of your eye.

Yeah, your retina gets burned, and it gets burned fast and usually permanently. I actually found some pictures of people's retinas that were damaged by looking at the most recent solar eclipse. And guess what? We won't show it because it's very gory. But it's basically exactly the same as another picture I saw of a soldier's retina that was damaged because he watched. an atomic bomb go off. So don't do it. Don't do it.

You know what else is almost exactly the same? People who have had laser pointers shined in their eyes. Oh. Same kind of retinal damage. This just hot spot where it's just burned and that will never see again. That is one of, you know,

I often think about this as one of the great collaborations of humanity. Bear with me for one moment. which is that when early lasers were being developed, people realized that it would be very possible to create a laser that could instantly blind people and that it could be used as a weapon of war. You know, imagine how powerful that would be that you go onto a battlefield, press a button and blind all of your opponents. And there was, I mean, essentially before the technology had even been fully developed, there was an international agreement that we would never do that. nobody on this planet Earth wanted to live on an earth where that was an option.

Every now and then we do actually manage to properly collaborate as an entire species. Yeah, and I'm glad when it happens. But the point is, don't look at the sun. I found a chair of the ophthalmology department at the University of Washington pointed out that if you look at the sun, you're getting a million billion photons per second onto your retina. And ten 10 seconds of looking at the sun is the equivalent of dropping a double a battery right onto your retina from a foot up. Same amount of energy. Right. Okay.

So we're going to need to come up with a different way to put sunglasses on the sun. What I'm thinking on a small scale is that you get a big sheet of safe solar viewing film, which is essentially opaque. You cannot see anything else through this stuff except the sun, an arc from welding. That's about it. But if you had that, and then you put little tiny, you drew little tiny sunglasses on it somehow that were completely opaque and were only 0.65 centimeters across. You could then cover the sun with this sheet. You would see the sun as like a kind of a dimmer ball and you could line up the sunglasses to appear to be on the sun and we're done. Except the end.

That's the end of the episode. But it shouldn't be because I don't want to enjoy this alone. I want everyone around me to also go, it looks like the sun is wearing sunglasses. How silly. Well, hold on. I imagine you want to enjoy it with both of your eyes even, right? The description that you should have come up with is one eye peering through.

Oh, but look at it, both eyes. There's no, there's no joy there to be had. Okay, so yeah, let's take one little baby step here. How do we make this work for two eyes? Okay. So, I mean, actually, technically, to even get it to work for one eye, we've sort of assumed that your one eye is a single point in space at the moment. But actually, your pupil is about four millimeters across, right?

So really, if you want it to fully work for the actual shape of your eye, you have to take that four millimeters into account. And so instead of being six and a half millimeters wide, it actually needs to be 10.5 millimeters wide. You need to be about a centimeter. So what would it look like if it was only 6.5 millimeters wide? Would it be... It would just be a bit janky. It would work for sort of one point of your retina and not the rest of it, but your retina is going to be, you know, amalgamating the image. So it wouldn't really work. Okay, so that's really good to know. So we need, you're saying, 10 millimeters.

But your eyes are on average about six centimeters apart. So binocular viewing, you need to account for the fact that there are all of those points across. So you basically need to add on that six centimeters to where you started. So in total, for both eyes, you actually need more like 7.05 centimeters. Whoa, that's big. It is because because you're so, you know, because the distance of your eyes is so big compared to the distance that you are, you're sort of holding away. Right. So I've got a tape measure here. I'm going to get seven centimeters. I mean, that's

actually not very big. So for those of you watching, there's seven centimeters. I would need a pair of sunglasses drawn on a piece of solar viewing film that wide so that when I hold it up, that seems so wide, though. Unfortunately, your eyes are wide. But the sun isn't this wide when I, if I were to look at it. No, but think about how much things jump. I mean, you've done the trick where you hold up a thumb, you close one eye and you hold up a thumb and you line it up with an object in the distance and then change eyes and see just how much it jumps. So is this calculation for making it so that when I switch my eyes, the sun is still within this boundary?

Exactly. Okay, I see. So let me just... For those of you who are listening only... I'm looking at other circles around my office that are about 32 R2. arc minutes wide and I'm covering them with seven centimeters of material. And I think, but if I, if I focus on the distant sun, then this is like, looks like this. I've got this huge thing. I know. Look, look, Michael, I'm sorry, but it's not going to be perfect. Unless you can shrink

your eye down to one point. It's, uh. Okay. I see, I see what you're saying, though, because this is actually really cool. I've got this baby head on my wall over there. That's about 32 arc minutes wide from where I'm sitting. And if I put the baby head, so with one eye, I see it here, and then I open my other eye, it pops over to the other end. So this is exactly that shift because of my eyes. But the effect is not cool. It doesn't look like the baby is wearing a tape measure mask. And I think, unfortunately, that's because you've got it at arm's length. I think the only way to make it work effectively at arm's length is because the distance of your eyes is such a dominant factor essentially at such a short distance. You know, it's about 10% of the distance. It's about 10%

that you're holding. I think the only way to get it to work at such a short distance would be closing one eye. That's so cool. See, this is why we're a good team because I just assumed one eye, that's what we're going to do. Everyone's going to be fine. And you're like, no, Michael, we can do better. If you want both of your eyes to do it, I just assumed it would still be fine. But no, you're right. It jumps seven centimeters across the thing I'm holding. Exactly. Okay. So this gets better as we get bigger. Right. Because because you said about sharing this effect with other people and in a lot of ways, that's the same problem, right? You jump from one eye to the other. You jump from one human to the next. Yeah. So how big do the glasses have to be? Like,

obviously, just to put an end on this spectrum, if the sun somehow was truly wearing a pair of sunglasses, it would look like the sun had them on from no matter where you were on Earth, no matter where you were in the universe. But that, again, as we've said, is not possible. The sun is just too hot and it's too gaseous or plasmatic or whatever. But the point is, how big of a pair of glasses do we have to get such that two-eyed viewing

is a pleasant, funny scene? Okay, so I think basically you just need to get it far enough away that the six centimeters of your eyes is like a rounding error, essentially. So I think even if you're not, you know, you get up to, let's say, 10 meters, right? I think that would work. I think that would work, right?

Yeah, I'm imagining this now. Like, I'm imagining a large pair of sunglasses at the top of, like, a skyscraper. And if I line myself up just right, they appear to be on the sun. Yeah. Ten meters is kind of not that much. Yeah, right? Let's say 100 meters. Okay, so 100 meters, right?

10,000 centimeters. Goodness me, centimeters are a stupid unit, aren't they? Divided by 107. those are how wide it needs to be, which is 93 centimetres, but then you need to add the distance between your eyes, which is six centimeters. So it would be about 100 centimeters, so it'd be about a meter. I mean, look, you can basically divide it by 100, about a meter. About a meter.

Yeah, 100 meters away. That's very doable. That's very doable. We can make a meter-wide pair of sunglasses. Now, keep in mind, we can't just put them up at the top of a building, like on a flagpole and then ask people to, you know, stand where they appear to be on the sun. Because the sun will still, 85% of it will still be shining right into their eye, destroying their retina. So we've got to actually put this on a large solar viewing sheet, like a big pain of solar viewing film that dims the sun a hundred thousand times.

And then the glasses are painted on or stuck on there and they're completely opaque. Then the illusion works for both eyes. And how many people can see this? Is there like one little spot you're going to have to stand at where the illusion works, but someone next to you is not going to like it? Correct. I mean, you probably even have to put your head into a vice to make sure that you're, I mean, this has only got like six centimeters of tolerance, this one.

So you could watch it with somebody else if you both used only one eye and you put your heads together. Okay. But I am falling in love with this, Hannah. I didn't realize what these numbers would sound like. That this was so easy. Have I ever told you one of my dreams for like a legacy when I get really old, I want to make sure this happens. I want to build a sculpture garden, like a free sculpture garden for people, but all the sculptures are illusions, right? They look like impossible shapes from certain angles or on a certain day of the year.

The way the sun hits them causes a really weird, funny shadow. And I want there to be like 365 of these, 366 for the leap day years. So every day that you come, there's some new thing happening like right at noon, a cool shadow. And I think that there should be one of these solar viewing films with sunglasses drawn on it so you can finally see the cool sun the cartoons promised us our whole lives. I like this. And I need to know how to build it. Okay. So now I know that I can please one person at a time with a meter wide pair of sunglasses that's 100 meters away from them.

Exactly. But let's go up. Can we also, in this sculpture garden, can we just to backwreck for previous episodes, can we also make sure that this is where your skeleton resides, picking its own? knows. Oh, yeah. Yeah, and people can, I can be dressed up for different holidays. Yeah, the Halloween version is going to be easy. That would be easy, just naked. I agree, though. Let's make this bigger. Let's be more ambitious. We don't want one person at a time. We want more. Should we jump all the way to outer space? Do we need to go that far for, say, everyone in London to see the sun wearing sunglasses? You want to go, you want to go? You want to.

go higher, let's go to the ISS, which is not that high. I mean, it's out of space, but it's not, it's not crazy high. No, it's not. 400 kilometers? That's nothing. I feel like we, every time that the height of the ISS comes up, I forget what the number is and then have to look it up again. But I think it's, and every time we bring up the ISS height, we say the same thing, which is, is that all? That's puny. That's nothing. We've got to up those numbers, ISS. Guys, pathetic. But it's true. I mean, if the Earth was the size of an apple, the international space station would be like on the surface basically. Like it's compared to the diameter of the Earth, its altitude is nothing. It's nothing. Okay, so 400 kilometers up, divided by 107,

we'll tell you how wide it needs to be. So if it's just you, it's going to be 3.7 kilometers big. That's how it needs to be. Whoa. Whoa. We've gone up by order of magnitude here. That's big. That's big. That's big, right? But it's further away. So it's going to take up, it needs to be much bigger in order to take up the same angle of your field of view. One benefit that you do get here, though, is that at 3.7 kilometers, the six centimeters for your eyes doesn't make any difference anymore. Right. So two-eye viewing is fine. We don't need to even worry about that anymore. Absolutely fine. But that's only going to look good from one person's perspective. From one person's perspective. And that's just, I mean, pathetic, frankly. So let's say all of London, being a bit selfish about this, I'm going to choose my hometown.

Yeah. But if you want to include all of London, which is, let's say, 40 kilometers wide, I mean, changes in different places, but let's say, you know, about 40 kilometers wide, you need to sort of add that 40 kilometers to the distance so that it works all the way across. So you're talking 44 kilometers at that point. That's, so that's how wide this pair of sunglasses would need to be so that when it transited the sun, it looked like to everyone in London that the sun was wearing sunglasses. Exactly. 44 kilometers is big, but it is doable. It's doable. I feel like, we could we could build such a thing. I think if we really put the effort in, one tiny problem,

it will also pass over in about six seconds because of how the eye sex is moving. So you're going to have to be quick. Going to have to be quick. Oh, shoot. Yeah. It's going to be so it's going to be passing through the sky and then it will transit the sun, which means it'll go in between the sun and us, but not cover the sun completely. It's going to just transit the sun. It's going to take six seconds to completely start covering the sun and then leave. But there will only be like a moment where it really appears to be on the sun like it should be as a pair of sunglasses. So there'll be this like moment where everyone goes, whoa, yeah. Oh. Yeah. Yeah. Yeah. This is the problem. If you want if you want binocular vision, you know, you're still too close at 400 kilometers away. You're still way

too close to get it to work really properly. You're going to need to go much, much further out. I know. So that the distance of between people in London, for instance, is like a mid, like tiny, tiny, tiny, tiny, rounding area for how wide the sunglasses are. Yeah. Now, if instead of orbiting, we put these 44-kilometer wide sunglasses at the top of a structure that was 400 kilometers tall, then it wouldn't be, the limiting factor wouldn't be the speed of the glass's orbit. It would be the speed of Earth turning us away from the sun. So you'd probably have a longer moment. I don't know how long, though, we should calculate this.

How many seconds or even maybe like a couple of minutes, the illusion would hold. And it would look if you stood in London like the sun had sunglasses on. Okay, so I just looked it up. The sun, the sun moves across the sky at a speed of about a quarter of. of a degree a minute. But the sun is only half a degree wide in our field of views. So you're gonna have like what a minute where the illusion kinda works.

Your minute will begin when the glasses are a little bit like off to the side of the sun. And then a minute later they will be right on the sun perfectly. And then a minute after that, they'll be only cover, Yeah, they'll be halfway off the sun. Is that right? Yeah, that's right. But that's only if they were perfectly set up for a small number of people to see them.

If you're trying to do it for all of London at once, I think the glasses are always going to look too big. Yeah. So I'm just thinking, is this going to be fun? Like, if you're watching at home, I'm holding up my own glasses in front of my face. And I've got the nose bridge part at the very edge of one side of my face. And that's how it could start. And you might say, oh, the sun's putting them on. and then a minute passes and they're here

and it looks perfect and then another minute passes and they're half off. So you've got like a solid... I just want to add for anyone who's not watching these visuals it's the most delightful thing because of the effect of the lens

on Michael's glasses for a moment there when it was perfectly lined up he looked like a normal headed man with teeny teeny tiny eyes. You've got, I'd say maybe a minute where it's going to look good and that's it. But that's a minute every day.

That's a minute every day. And everyone's going to have to... Well, you have to worry about north and south as well there, don't you? I was just thinking about that. How do we fix that? Because this works for everyone in London, but the sun is going to trace a different path every day. You're going to have to move it north and south.

This is going to have to be a moving flag. Oh, I see, yes, we don't have to make it the tower taller. We just have to move it north and south every day. Look, I think the best solution here is... is to go further out. I think 400 kilometers is nowhere near enough. Okay, let's go further out. I think if you push it out to geostationary orbit, for example, then we're talking,

which as I learned approximately one week ago is really, really far away. It's really far away. 35,786 kilometers. Far enough away that, one, we solve the problem of motion because everyone on one side of the earth, could they see the sun appear to wear sunglasses? all day? Well, no, because the sun does move. But a geostationary satellite stays in one place above them. If you put a pair of sunglasses up in geosynchronous orbit, then how many people could all enjoy a sun-wearing sunglasses illusion at the same time? I mean, definitely one.

What do you mean one? I mean, look, you do it for yourself at a geostatory orbit, and then it would need to be 334 kilometers wide. And that would be fine. That would be great. How wide? 334 kilometers. Oh, so we went from 44 kilometers to over 300. That's not a huge jump. No, it's fine. It's easy just to make it a slightly bigger flag. But only one person would enjoy it? I mean, look, that's the number for one person. But you could have people space, you know, five kilometers apart and they'd still be able to see largely the illusion. I mean, what kind of tolerance So do you want here within 1% then you can only be within a space of three kilometers?

Oh, I see what you're saying. Yeah. We've got two things to figure out. We've got how far away the thing is it's going to look smaller, so it needs to be built bigger. But then also we need to consider how wide a swath of surface on the earth we want the viewing platform to be. And that viewing platform gets added on to the total.

It's like, from your eye is a triangle, but you and the next person is a rectangle, essentially, right? Ah, this gets terrible because if you wanted the entire illuminated part of the Earth, like anywhere on Earth where you could see the sun, to see sunglasses on the sun, the sunglasses are going to have to be so big, they don't fit on the sun. Exactly, that it will just ruin the illusion.

Right. Because at that distance, even at 35,000 kilometers away, the radius of the Earth is not a rounding error. It's so big. really what we would be building are glasses that would in some way occlude the sun for everyone who was looking at the sun, but they would only look like they were being worn properly by the sun for a small group or maybe no one, because they would just be too big. I think for no one. They would be too big. So is there some magic point where this solves itself and suddenly, obviously when they're on the sun itself, then everyone gets to enjoy it?

then it's fine. But this is it. The closer that you get to the sun, the smaller the earth gets in the distance. Yeah. And the smaller, the distance between people on the earth becomes as part of the overall picture. True. So, you know, as you said, if you are at the sun, the distance between you and me doesn't make a difference. This is between my eyeballs doesn't make a difference. We're basically all at the same point. So you want to get to the stage where the triangle, as it were, between the sunglasses and the observer where the distance between observers is basically, it makes no difference.

So we are talking way, way, way, way, way closer to the sun than geostationary orbit, for it to actually probably work for more people than just you and your maid who's standing right next to you. I didn't even think of this until now, but you're right. We started by trying to fix the distance between one person's two eyes.

And then we said, but what if your eyes were as wide apart from each other as the edges of London? Right. Now we're looking at the edges of the earth. Do you have figures for that? How big and how far away do these glasses have to be so that everyone who can see the sun

sees the sun wearing sunglasses? So look, the final point that I figured, I mean, I was like, look, that's just pick sensible places, right? So the final point that I thought about was the Lagrange point. Yeah. Do you know about the Lagrange point?

I do. Do you want to talk about it? No. You go ahead about what the Lagrange point is. Yes. The Lagrange point, specifically Lagrange Point 1, was what I started to think about. So it's different than a geosynchronous orbit in that it's much further from the Earth. But you reach a point where you're also falling towards the sun.

It's not stable, though, at L1. That's the point in between the sun and the Earth. Because you move a little closer to Earth, now the Earth's pole becomes stronger. It winds out and you fall to Earth. You get closer to the sun, you follow the sun. But you can just manipulate with a little amount of energy where you are and you can stay there. And it's kind of a nice place. And you would always be right in between the Earth and the Sun.

Earth's rotation wouldn't get into the way. So you'd always be right there in front of anyone's view of the sun. Yes, exactly. Now, the thing about this point is that it is that the L1 sits at, one and a half million kilometers from Earth. Okay. All right. So if it's at the Lagrange point, it needs to be 14,000 kilometers wide.

14,000 kilometers wide. Again, I think we could do it. You think we could do it? And this would allow everyone in London to see sunglasses on the sun. What's the benefit of doing the Lagrange point? You get more than London for that. I reckon if you're willing to accept sort of 10% tolerance. One way or the other.

Then you, you know, you can have a thousand kilometers, easy. Oh, sweet. Yeah. Okay. So that's the advantage to putting them further away. We gain a little bit more radius of our where the illusion works. If we allow the glasses to be 10% off to the right or off to the left, then LaGrange point one. There are five, by the way.

We can talk more in depth about them because there's other ones that don't really help us with today's illusion. but L1 would require a 14,000 kilometre wide pair of sunglasses. I think that's, honestly, I think that's our best bet so far. Can we do better? How big do you want to go? Well, what I want is for everyone who can see the sun to see sunglasses on the sun all day. I think you only need 140 million kilometers. 140 million kilometers wide.

But everyone on earth, yeah. So how big do the sun? sunglasses need to be? Sunglasses need to be 1.3 million. Okay. 1.3 million kilometers wide. That's how big we need to build this pair of sunglasses. And then we put it...

140 million kilometers. 140 million kilometers away from Earth, in between the Earth and the sun. And then, for everyone who can see the sun, the sun will appear to have sunglasses on. Yeah, they will. They will. And they'll only be 1% too big. Right. Right. Okay, so the sunglasses are one percent bigger than they need to be. Yeah. It'll still look fine. It'll still look cool. Still look great. Still look great. And everybody will have this experience, I mean, depending on how you're doing the propulsion system, but everybody can't have this experience of the sun kind of moving through the sunglasses.

So with a propulsion system, keeping this pair of sunglasses exactly between the earth and the sun, a pair of. A pair of, sunglasses that's 140 million kilometers away, but 1.3 million kilometers wide, the sun will appear to be wearing sunglasses all day for everyone who can see it. And what better monument to your life would there be than that? It's not a monument to my life. It's a monument to life itself. It's a monument to not just human achievement, but the human kind of. concept of being too cool for school. And a little bit absurd because at the end of the day, why is the sun wearing sunglasses? Well, we're going to take a quick break and we're going to talk about why we might actually

want the sun to wear sunglasses because, I'll give you a hint, if you put sunglasses on the sun, you're also kind of putting them on earth. Hey, y'all, it's Kelly Clarkson with Wayfair. Ever order furniture online and wonder what if? Like, what if it doesn't hold up? That sofa was four days old. You should have ordered from Wayfair. With Wayfair, there's no what-if. Just style you love and quality you can trust.

Visit Wayfair.ca. Wayfair, every style, every home. Ready to take your investing knowledge to pro-level. This is Fidelity Connects, your daily edge in the markets. Get deep insights on real-time market topics that may impact your investment portfolio. Listen to Fidelity Connects on Spotify today and power your next move tomorrow. Okay, welcome back. So we have just, and by we I mean Hannah,

has just calculated the exact blueprint needed for us to do the most amazing thing ever, make it look like the sun is wearing sunglasses all the time. And as it turns out, you're going to need to build a disc. I'm just going to give our final answer here for those of you that joined us halfway through, which is nobody. But I love this. Not how YouTube works. Go on.

You're going to need a disc, a disk of safe solar viewing film that reduces the sun's brightness by 100,000 times so we can all look at it and look up in the sky and see a safe. to look at ball, okay, bright ball. And then in the middle of that disc, you're going to draw sunglasses. And this disc needs to be 1.3 million kilometers across, and it needs to be 140 million kilometers away from Earth. No big deal.

Except it is a huge deal, because it would be hilarious and awesome and totally rad for the sun to wear sunglasses, but life on Earth would not enjoy it because we would be blocking an enormous amount of the suns, light. Yeah. Yeah. And I think life on Earth quite likes the sun's light. Yes. It would be as dark on earth as it is during a total solar eclipse. Okay. It would, it would, it would really mess up photosynthesis. It would mess up. Birds wouldn't know what hit them. Birds would, birds would not know.

They would be very unhappy. And I don't think birds would go, yeah, but it was worth it. Dude, look, the sun's got sunglasses on. It doesn't make any sense. You'd have owls hooting in the middle of the day. It's just like the sun on the hot tamales box. However, there are some realistic proposals that are less silly that have said, yeah, but you know, if you dim the sun only one or two percent, that would actually cool the earth down by the same amount that all of our carbon emissions are increasing the Earth's temperature. So rather than cleaning up and polluting less,

what if we just blocked the sun, again, 1 to 2%, we could stop at least one consequence of climate change. A? I mean, guys, it feels like there's easier ways to do this, but sure. Go on. Anyway, this idea is a real idea, and it's called a space sunshade. If we put something up there that covered some of the sun, we don't need to cover the whole sun, even just part of it, doesn't need to be covered by a solid disk thing. It could just be a scattering of dust. One idea was that we could literally put a colony on the moon that just mined the moon

and then flung that dust out into space between the earth and the sun. It would have to constantly do this because the dust wouldn't stay there, but it would just dim the sun by, you know, one to two percent, and then we would counteract the warming effect of climate change.

We would not, of course, stop toxic chemicals in the air, the acidification of the oceans, the increased CO2 in the air, in the air, which our brains don't like, that would all keep happening. So, of course, many organizations like Greenpeace have said, oh, great, yeah, let's build a sunshade in space and then give ourselves moral license to just keep polluting or pollute more. Yeah. You know that story about the woman who swallowed a fly? Yes, exactly. Sort of feels a little bit like that. Guys, why don't we just

go and mine the moon and then spray out loads of moon dust all over, like that we have no control over, and that may end up like falling as rocks on Earth, but no big deal. Guys, guys, guys, don't swallow the fly. Yeah, don't take the fly out of your stomach. Just swallow a frog. And then you can still have the fly. Oh, shoot, but now you've got a frog. Well, just swallow a dog.

Yeah. Exactly. Right. Exactly. But then there's the opposite of a space sunshade, which is a space mirror. And it's the opposite because instead of shadowing the earth, it actually catches sunlight and reflects it back down to earth. And it can do this during the nighttime

to produce light during the night. So to energy at nighttime. This idea is actually more real than even I knew. I'd heard of this in sci-fi, but it's less sci-fi than I thought. In 1993, the Soviet Union attempted to do just this. They built like a 60-65-foot diameter mylar mirror that they launched up and deployed

to be so high up that even when it was nighttime, this thing could reflect sunlight down onto Earth. And they thought this could be the secret we needed. Because what we can do now is during dark winter months, we can shine light on cities. And it's going to be like two, three times as bright as the full moon if we do this right. Right. So we'll increase productivity in the cities. We'll increase productivity of farms because photosynthesis can go on for longer. I mean, it's sort of unlimited energy. If you can get it Right. She's all got unlimited energy. It's burning a sun going around. Exactly. And so believe it or not, this was actually done. And the Soviet Union launched this in 1993. It produced a few miles wide patch of light during the night on the ground that was brighter than the full moon, about two to three times brighter, that moved at about eight miles a second across the surface of the Atlantic Ocean, then Europe and then into Russia before it didn't work. They couldn't control this mirror to like keep a spot of light focused on one particular place on earth.

But this happened. I cannot find any good observer statements. There's no photographs of this happening. Apparently the observers felt like they just noticed a quick flash of light and that was it. So it wasn't like, whoa, they just lit up my town at night. Where is this mirror now? Is it just floated off? It burned up in the atmosphere, like right after it was used once.

And then they built a second one, and it got caught on one of Mirra's antennas when it was deployed and ripped, and it didn't work, and they never tried again. But there is a company today that is trying to do this again. Sorry, what? So imagine that someone goes missing in the woods or a boat is missing. It's too dark. You have to turn the rescue mission off until. day. Not anymore. You get one of these space mirrors to just catch the sunlight and reflect it right down to where you need to look. Boom. You've got bright light. Hang on. There's actual

funding for this. Yeah. Right. Where? They're planning an array of 50,000 mirror-bearing satellites to orbit. The Earth. Guys, we need less energy, okay? Less energy pointed back at Earth. Please don't let rich, crazy people do this stuff without getting the buy-in from the rest of us. I think this is a really bad idea. But Hannah, it's for search and rescue. Use a torch. Okay. Well, okay, I'll tell you.

Here's the details. The startup is called Reflect Orbital. They're out of Hawthor in California. Of course they're in California. The United States government just approved a mission to launch this giant mirror to test this out. Their plan eventually is to put 50,000 mirrors into orbit. by 2035, which will allow for full noon brightness in a select spot on Earth at night. Noon brightness.

Right. I'm bothered by this deeply. I'm deeply bothered by this because, look, what you're describing here is essentially a Dyson sphere, right? Which is it's this sci-fi idea that you could do this. And if you connect up the mirrors in the right way, you can harvest more energy from the sun. and you end up with sort of more energy than your planet currently has. It's sort of like an unlimited energy thing.

And when you have unlimited free energy, you can do all kinds of crazy things, right? So, I mean, for example, stripping salt out of water, which is something that would actually be quite a good thing for people who are alive on the planet right now, but takes a lot of energy and we can't really do it because actually energy is expensive. But actually, if you had free unlimited energy, you could end water being a problem. you could turn the Sahara back into a rainforest, right? It's sort of like a big grand scale idea. I'm fine with that. But if we do it, it needs to be as an entire planet collectively. We need to like be really careful, get people's buy-in, make sure that we are considering all of the

options, make sure that that is what we actually want to do collectively. It cannot be some rich dudes who've got more money than makes sense for any human to ever have that just decide. on their own back, that they're going to do some startup and then ruin the planet for everybody else. I may have got slightly angry. I don't like it. I don't like it at all. Make it go away.

I feel like this is a lot of stuff. I feel like there's sort of like rich dudes who kind of ruin the world in a lot of ways without asking permission. And this feels like another example of that. In my defense, I want to say a couple of things. my idea of putting sunglasses on the sun is not going to happen

because I'm not a billionaire. I've only got YouTuber money, which means the 65mm version, I could do that one. Also, I was joking. But Reflect Orbital is not... Oh, this was never aimed at you. I'm fully supportive of the sunglasses idea.

Is this search and rest of one that's bothering me? Go on. Reflect Orbital is not joking. They got approval on the 9th of July of 2026, and they've got a satellite. It's called Irondell 1. That sounds like a Lord of the Rings name, by the way. Arendale.

Look at that. They're even stealing humanity's characters. It's going to launch later this year is the plan. 625 kilometers above Earth's surface. The satellite will then deploy a mirror, and it's going to be able to illuminate a patch that's 24 square kilometers on Earth's surface. Now, it won't be noon brightness, this first test.

Right. I mean, is there a world where this can be okay if, like, they only focus the light down on, like, solar panels? Yes, of course. Of course. I mean, I sort of think that there's different things you could do. But sure, yes, I agree. You know what? This reminds me of. I made this documentary once about disabilities.

And I went to go and meet loads of tech bros in Silicon Valley. And they were like, oh, we've come up with this amazing design that are glasses that can create subtitles for people who are deaf. And that there's this amazing like robotics that blah, blah, blah, blah, blah, blah. And then I went to go and talk to some disability advocates. And they were like, you know what we really need? ramps. It's boring, but that's what we actually need. And like, you know what the world needs? Like renewable energy and good batteries. You know what it doesn't need? Bricking mirrors in space. Yeah, the sexiness factor matters so much when it comes to getting funding. And at the moment,

and especially even a few years ago, space was such a sexy thing to invest in, but there just weren't enough options. And so these investment firms were like, I need something space. and someone would say, oh, I've got this thing called spin launch. We're going to spin things around and then let them go like David and Goliath and they'll go into space. And they raised millions, millions. Here's someone is like, I'm going to put mirrors in space. Think about how cool that would be.

We could like bright, make the night bright. Cool. Here's a bunch of money. Here's a satellite. Do it. If they want to get in touch and convince us that we're wrong, I'm fine with that, by the way. I'm open to being persuaded, but right now I hate the world. Oh, Hannah, before we've found.

forget, remember how in the beginning I teased about E equals MC squared being incomplete. It is. And this becomes relevant when it comes to building any kind of sunshade or sun sunglasses out in space or even, honestly, even a solar mirror that's just around orbit and Earth. The problem is these things have a big surface area and the sun is shooting out a lot of light. and light can push things. Solar sails. Exactly, solar sails. This can be a cool way to propel a spaceship.

You just put a big sail on it that's a reflective material. Sunlight shines on it, bounces off, and the darn thing literally gets pushed by the light. So whatever giant structure we put out there, whether it be to light up the night or put sunglasses on the sun, is going to have to deal with the fact that it's going to need. to deal with and maybe try to mitigate the pressure of light pushing it. And this might bring up a question in your mind, which is, hold on, how can light push anything when it literally has no mass? Got momentum, though, don't it? It does.

It has momentum. But that doesn't really answer the question, because how can you have momentum without mass? Physics 101's told us that momentum is your mass times your velocity. Well, we know the velocity of light, but do we know the mass of light? It's zero. And zero times anything is zero, so it should have no momentum. Well, as it turns out, that's not exactly true. Light can have momentum because E equals MC squared isn't the whole equation.

All right. E equals MC squared is the famous mass energy equivalence formula. It tells us how much energy exists in... It tells us how much energy could be liberated completely from an object based on its mass. However, the answer must be different for an object at rest versus that same object moving. A moving object has more energy. So, but E equals MC squared doesn't include how fast the thing is moving. The full equation is E squared equals MC squared squared plus PC squared, the quantity PC where

P is momentum. And so looking at that equation in its full thing. form, you can see that the momentum a piece of light has is equal to its energy divided by the speed of light. And we just don't need to worry about this kind of thing when we're making calculations in our day-to-day lives about how much momentum like a bowling ball has. I mean, it's nothing in comparison to the energy that's involved in the mass. That's right, that's right. And when it comes to a photon, which has no mass, that doesn't mean that it has no momentum. It means, in fact, that it has...

as an amount of momentum equal to its amount of energy divided by the speed of light. And so it can push things. Basically, E equals MC squared is not the equation that Einstein wrote down. It's just the cute version that fits on T-shirts. It's the cute version that fits on T-shirts and describes things like baseballs and bowling balls and uranium. But it does not describe light. The full version does. So we'll have to keep this in mind as we build our...

How are you going to do that, though? What are we going to do? Put holes in it? What are you going to do? Make it a mesh? Yeah, you can make it a mesh. You're never going to get rid of the push from light altogether. But you can make a mesh. You can try to redirect so it reflects in different directions. All of this has been thought about a lot by people who are trying to design sunshades. And it's going to usually... Which people have for real? Which people have for real. Yeah. I don't think it'll ever happen because I think there are much better ideas to do what a sunshade attempts to do. Okay, I've got one final thing to say about your, I mean, all the other ideas are focus, right? All of the other ideas are like complete crazy junk, but your idea, your idea, Michael, I'm absolutely behind. I've just got one tiny little thing to add to it, which makes it even better, I think, which is that at the moment we've been talking about having a disc, right? a sort of disc, kind of opaque disc. The only tiny problem about this is that

light that's sort of bending around a smooth edge to opaque disc, it will, there'll be like a bright spot right at the dead center of its shadow. It's called the Arago spot. I don't know if you thought about this. I did not think about this.

This is going to be difficult. But there's a way around it. We can easily get around this, which is, people who've been talking about this since the 1800s, by the way. The way around this is that we can, and put petals around the outside,

and then it won't happen. Basically, I think the final solution for us is that the sunglasses that the sun is wearing need to be like petal ones. Wait, yeah, what is the deal with the petals? Because NASA is building a star shade, which we hadn't talked about, because the stars are so far away, they're too small.

They appear too small to put sunglasses on them. But for real, star shades are being made by, NASA to cover up the light of a star so that we can see exoplanets potentially orbiting around it. But every picture I've seen of a star shade has had petals on the outside. This is why. Because I was only worried about our sun, I didn't look deeper into why it had petals. Why does it have petals? So it's to prevent, because essentially, if you imagine that you've got a disc and then you shine a really bright light on it, then what happens is that you've got the kind of light going all around, right?

And the light is essentially, because you're talking about such large distances, it's going to be bending around this smooth, edged, opaque disc, and then you're going to get this central point in the middle. Oh, wow. Okay, so I'm loving this idea even more now. We're going to put sunglasses on the sun with a flower. Exactly. Okay, so what have we learned? That some people have too much money.

That's my main takeaway. What I've learned is that, that sometimes a really silly question like that leads to a lot of learning. I mean, you've taught me so much in this. I didn't even consider the Arago spot. And now I've got all this new, all these new things to research. Hey, you're welcome. You're welcome. Maybe we'll do another episode about that because, frankly, I understand it very superficially, just enough to know that petals are important. Yeah, exactly. And so, so if you out there have a question that's equally absurd, please do not be afraid to send it to us because a lot of

knowledge can be gained even by looking into the silliest things. You can reach out to us at the rest is science at goalhanger.com. Send us an email. Absolutely. Or leave us a comment wherever you are watching or listening to this podcast or hop on over to our Reddit, R slash the rest of science. And we will see you next time. Yep. See you next time. Bye bye-bye. Hey, y'all. It's Kelly Clarkson with Wayfair. Ever order furniture online and wonder what if? Like, what if it doesn't hold up? That sofa was four days old. You should have ordered from Wayfair. With Wayfair, there's no what if. Just style you love and quality you can trust. Visit wayfair.ca.

Wayfair, every style, every home.