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- [00:01]
A
Welcome to the rest of Science. I'm Hannah Fry.
- [00:03]
B
And I'm Michael Stevens. Today, Hannah, we are going to look into the past by looking up. But not in the usual way. We're not gonna be doing the whole like, whoa, when you see the stars, you're seeing them as they were years ago. No, no, no. We're gonna be looking at our own pasts in outer space.
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A
Am I. Hang on, Michael. Am I also gonna learn a mnemonic during this? But how many feet are in a mile? Cause I can feel one coming. That's not me looking into our past. That's me looking into our future.
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B
Believe it or not, Hannah, yes, you will. You've looked into our future. This is an episode where the research I did took me all over the place. And I'm not going to organize it. I'm gonna just blast it all over everyone's ears and eyes. Here we go.
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A
This episode is brought to you by Cancer Research uk.
- [00:52]
B
Here's something strange. Your DNA contains more ancient viral fragments than genes. The genes that build our cells make up only 2% of our DNA. And for years, that is what scientists focused on. They treated the rest, the ancient viruses and stuff, as junk.
- [01:13]
A
But now we know that that hidden majority, sometimes called the dark genome, influences how our biology works and how diseases like cancer behave.
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B
It's a remind. Progress rarely comes as a single breakthrough. It builds gradually. Cancer Research UK plays a central role in that progress, supporting decades of research into over 200 types of cancer, work that's helped double survival in the UK over the past 50 years.
- [01:42]
A
For more information about Cancer Research UK, their research breakthroughs and how you can support them, visit cancerresearchuk.org forward slash. The rest is science.
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B
I sold my car in Carvana last night.
- [01:56]
A
Well, that's cool.
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B
No, you don't understand. It went perfectly. Real offer down to the penny. They're picking it up tomorrow. Nothing went wrong. So what's the problem? That is the problem. Nothing in my life goes to smoothing. I'm waiting for the catch.
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A
Maybe there's no catch.
- [02:09]
B
That's exactly what a catch would want me to think. Wow. You need to relax. I need to knock on wood. Do we have. What is this? Table wood? I think it's laminate. Okay. Yeah, that's good. That's close enough. Car selling without a catch. Sell your car today on Carvana. Pick up fees may apply. Ready to soundtrack your summer with Red Bull. Summer all day play. You choose a playlist that fits your summer vibe the best. Are you a festival fanatic? A deep end dj, a road dog, or a trail mixer. Just add a song to your chosen playlist and put your summer on track. Red Bull Summer all day play. Red Bull gives you wings. Visit Red Bull.com BrightSummerAhead to learn more. See you this summer, By the way. Okay, here's. Here's another. This episode's going all over the place. Here's some other cool things I learned while I was doing this research. Yeah, when it comes to how many feet are in a mile, I've always found it hard to remember until I read a little mnemonic. Just remember five tomatoes. Five tomatoes. 5,000, 280. Oh, five, two 8 0s. 5, 8, 0. Five tomatoes. That's how many feet are in a mile. There you go. You're welcome.
- [03:26]
A
Or just as an alternative, you could just switch the metric system and not have to bother. I mean, that's just putting that one on the table for you, just as another option.
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Look, that's true. You can also remember that there's 1,000 meters in a kilometer. And you can remember 1,000 because it's easy to remember.
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A
Exactly.
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Do you know what's weird is that also the United States is on the metric system, they just have a conversion layer on top of it. Like, the inch is defined legally as 2.54 centimeters. No.
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A
Are you serious?
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Yeah, I'm serious. The inch is not described as the distance some, you know, Krypton atom vibrates or. No, it's just 2.54 centimeters. So we're tied to the metric system, but we add a layer of conversion to it.
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A
I also found out the other day that in America, instead of calling it the Imperial system, which is what we call it here in the uk, you guys call it the English system. And is that true?
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B
No, not for me, but maybe other Americans.
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A
What do people call it anyway? When someone said that, I was like, no, no, no, no, no, no, no, no, no, don't. No, you're not blaming that one on us, okay? We saw the light, we switched over. We've been on metric for a long time. No, have you also seen the flow diagram of what unit you should use to describe something if you're British? Because it is metric at all times. Unless you're talking about beer. Oh, yeah.
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B
Well, but also speeds on the motorways, right?
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A
Or speeds on the motorways or how much you weigh.
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B
Yeah. There you can use towels or you can use stones. Just a whole, like, total other direction. So a centimeter is less than an inch. And if you look At a ruler. I've got a measuring tape here. You can see I've got tick marks for inches and centimeters.
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A
Mm.
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B
Where is there a point where an integer number of centimeters lines up exactly with an integer number of inches? Like it must happen eventually, right?
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A
What did you say? One inch is 2.55 centimeters.
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B
So it's 2.54 centimeters.
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A
Five, four. Okay. 254 then.
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B
Yeah, but it actually happens sooner than you would think. Yeah. It happens at 50 inches.
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Does it?
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50 inches is exactly 127 centimeters. I can show it.
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That is satisfying.
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I can show you right here if you've. Gosh dang it. If you've got a measuring tape, you can hear how messy my office is.
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All the cans of soda.
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Come on.
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Dang it. Ding.
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50 inches.
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Oh, yeah.
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Is exactly 127 centimeters.
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That's satisfying.
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B
Guess what? So you've heard that. You've heard that phrase, give them an inch and they'll take a mile?
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A
Mm.
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Did you know that that is a corruption of the original phrase, which was.
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A
Go on.
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Give them an inch and they'll take an L. Where's that from? An L, E L. L. Not like take an L, like lose, like loser, but taken L, E, L, L, which is a unit of measurement equal to a cubit. The distance from the. Of the forearm and the extended hand. That's an L because L used to mean arm. And that's why we call this an L bow, because it is the bend. The bow of the L, the bend of the arm, the elbow. So give them an inch and they'll take an L turned into give them an inch and they'll take a mile. Just because of people mishearing it.
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A
Right. And actually, you know, an inch and a mile. Give someone an inch, they'll take a mile. I mean, that's really taking the mickey a lot, but give them an inch and they'll take an L. You know, actually, the difference between an inch and an arm length is, you know, it's not that bad. So actually, people were not being as piss taking before. Right.
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B
And I like how today it has the added slang meaning of give them an inch and they'll take an L. Give them an. Give them an inch and they'll lose is what that. I don't know what that would actually mean, but. Okay, let's. Let's get. Let's. Let's get back to telescopes. Okay, so first things first. We are literally talking about looking into Earth's past, our personal pasts, by looking up into the sky. I would love to do this. And I have been thinking about doing this as a Vsauce episode for years, but it wasn't really until now that I got the pieces together. What do you know? It's time to record. So we're going to talk about it now. And I'm. I'm literally saying that we could use something like this idea to watch who assassinated jfk and how we could use this to lip read Albert Einstein's last words.
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Okay, let me ask you a question, though. Can I ask you a question to kick us off?
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Okay, yeah.
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This idea of looking out into the sky and then seeing ourselves, doesn't this require some sort of mirror?
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B
Yes, and I think we've briefly mentioned this on the podcast before, but we need a mirror. You know, if a mirror was 100 light years away and we looked at it through a telescope, we would see Earth as it. We would see ourselves as we were 200 years ago, because that's how long it would take the light to get to the mirror, bounce back and come back to us. As far as we know, there aren't any mirrors out there in outer space. Or are there? No, but kind of. You could watch how the pyramids were built. Exactly right. How many people were involved, see which aliens did them. Yeah, we could watch the aliens do it. Probably we would just see people doing it. But which exact technique they used would be resolved once and for all. Anyway, obviously, if we're going to be looking at our own pasts, we're going to be talking about light. So I wanted to show off my light. Nanosecond ruler. Look at that.
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A
Wait, hold on. Explain it. Is that how far?
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B
It's a ruler, like an architect's ruler. It's a triangular prism, it's got three faces, and it's just about 30 centimeters long, about a fifth of an inch shorter than a foot. So it's kind of the size of like a regular 12 inch ruler. For those of you who are not watching the video stream, this happens to be exactly how far light travels in 1 nanosecond.
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So that's 10 to the minus 9.
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10 to the minus 9 seconds. That's right. In a second, light travels a billion of these if you line them up in a long line. So because it's transparent, I can look through it and I can look at things like I can look at my computer screen where I see your face. And if I put my hand right up against one end and I look in the other, I can see my skin as it was a nanosecond in the past because that's how long it took the light that I'm seeing to reach my eyeball. So it gives you a sense of how, goodness gracious, like everything we see, we're seeing in the past, we only have one way to look and it's a go. And it's really trippy to think about what that means. It means that there is a sphere of light growing with me as the center at all times that contains photons that touched me sometime in the past. And once those hit some detector and are imaged, that image is me as I appeared at the moment that those photons touched me. So all this light that's hitting me, trillions of photons every second, they, they, they, they, they leave me and they go out into the world and they exist as this ever growing ghost of what I used to be, like what I used to be doing. And so for someone who's three feet away, they're seeing that photon ghost of me three nanoseconds ago, which is basically nothing. It's basically live. Face to face is live. But if I could see photons from that sphere of photons that left me a hundred years ago, well, I'd have to be 100 light years away to see them, but I would be able to see myself 100 years ago. Bad example. Cause I wasn't here 100 years ago. But you see what I mean, right?
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I don't know, Michael. That beard is starting to suggest otherwise.
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Yeah, I have to remind myself to not mention all the times I hung out with Silent Cal President Calvin Coolidge. Any of you who are more than a hundred years old are cracking up right now.
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A
So then if you're looking in the mirror, I mean, you are seeing an old version of yourself, essentially, you've never seen yourself as you are in that moment.
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That's right, yeah. For every 30 centimeters, for about every foot away, something is. You are that many times two. Because you gotta go there and back nanoseconds in the past. So what, like something a mile away, you're seeing that as it was 5280Ns
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ago, which is still a real sliver of time, like a really small amount of time. To be absolutely clear, you know, 5,000 out of a billion would be one second.
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Yes. A billion nanoseconds is. You're, you're finally at one second. But when you look at things that are light years away, you're literally seeing them as they were that many years ago. Because that's how long it took light information from them to reach us. So, yeah, not just the light, but their gravitational influence on us. Like, the sun is about, what, eight light minutes away. So if the sun does anything, like, if the sun decided to turn blue, we wouldn't know for about, you know, eight or nine minutes. And that brings up all kinds of big questions about, like, but when did the sun actually turn blue? I mean, does it. Does it make sense to say, oh, the sun actually turned blue eight minutes ago? Because there's no way to verify that. There's no way to have, like, go back in time.
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Well, yeah, because, I mean, I guess the question is for who? Like, the sun turned blue for who?
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This is. This is the question of, like, what is happening in the Andromeda galaxy right now. If I could instantaneously teleport there, I would also move into its future relative to what it looks like to Earth.
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I'm just thinking about this, this 30 centimeters. So if you have a billion of those, I mean, if you are one light second away, the Artemis crew, when they were circling around the moon and looking back at Earth, the Earthshine photo that has now been, I mean, plastered everywhere. So this is the most incredible photo. They were having the same effect. Right. They were not looking at the Earth as to how it appeared in that moment, but how it appeared one second ago.
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Exactly.
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And that's enough to, like, feel a difference.
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Yeah, it is, it is. And by the way, that you feel it is mainly through communications, because we also are communicating with Artemis, or we did through radio waves, and those travel at the speed of light. And the Artemis crew became more than a billion of these away from Earth. So they were about 1.3 light seconds away from Earth at their maximum. So it took 1.3 seconds for their messages to get to us using radio waves, which means it took 1.3 seconds for light from us to reach them. So they were looking at Earth as it was 1.3 seconds ago. Now, from that distance, not much changes on Earth in 1.3 seconds that you can see. But you can even get more pedantic about it and say that the part of Earth that was. That was in the middle, like the equator or whatever, the point right below them that was closer to them than the. The edges of the Earth in the image, because the Earth curves away. So there's a larger light nanosecond difference between the middle of the Earth that they see and the edges.
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A
Right. I do feel like they missed an opportunity to set up a camera and very precise atomic clock. And then to sort of snap their photos. Synchronize the snap to a particular time. Right. One on the spaceship, one on Earth, I don't know, a dog or something. And then like demonstrate.
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Oh wow. They could have, yeah, they could have used atomic clocks and the known dilation caused by their travel speed and gravitational
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effects because time is not moving in the same speed. Right. On this extremely fast moving rocket.
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And on Earth, yeah, there would have been a difference. But they could have synchronized photos from their ship and from Earth and I think they could have brought themselves like a giant, you know, football field sized telescope and like watched someone pop a balloon. And the synchronized photos would be such that on Earth we would see the balloon exploding. And for them they would see like the pin not even touching the balloon yet. And we'd be like, whoa, who's right?
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When did the balloon get fought? Yeah, right. It's the same thing. It's the same paradox.
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I can't believe they got so distracted by the moon that they forgot to do this much cooler thing next time.
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Really they should, they should contact us before going up and we'll give them much better ideas of what kind of experiments they should be running.
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But this, this is going to be a slow walk towards an answer, by the way, because I'm going to keep getting distracted. I want to talk about the fact that because this is one light nanosecond, we've broken it down into light picoseconds. I can take this ruler and I can line up like my thumb and I can say wow, my thumb is about 210 light picoseconds long. So it takes light 210 trillionths of a second to get from that knuckle to the tip of my thumb. But don't worry, there's also, there's also even less useful measurements on this ruler because it's got all these sides. We've also got sound microseconds and my thumb is about 100, gosh, I'd say it's about 180 sound microseconds long. So that means it takes sound 280 microseconds to go from here to here across my thumb. That's a. What a. It's so much millionth of a second. Yeah, I can even measure how many micro Everests long my thumb is. So it's about, it's about seven millionths of Everest's height. So if you got 167,000 of my thumbs or just probably like human thumbs, roughly 167,000 human thumbs would be enough stacked on top of each other to be as tall as Everest. That's one of our most asked questions. So I had to address it.
- [18:15]
A
I always think it's a bit of a shame, you know, how people the sort of standard lengths of measurement. It's like, oh, as long as a blue whale or as big as a football field or you know, big two double decker buses. I always think that we could have much more imaginative examples than that. You know, I think the millionth of Everest is just that feels much more intuitive.
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It does, right? We all know what a millionth of Everest is. Scientists should be using that more in their, in their public announcements.
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I mean, hey, why not? The meter is 1/40,000th of the Earth's circumference. I mean, it's the same idea.
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Yeah, I know. And that, by the way, is like a whole really fun story. We should do a whole episode on the history of, of units because it explains why the earth's circumference is like almost such a round number of meters. It's not a coincidence. It's because of us.
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4,008. Yeah.
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40,008. Yeah, yeah, okay. But anyway, we're trying to talk about looking into the past. So let's now move on to things that we know can really affect light. Black holes. Right. So the idea here is that obviously a photon of light that has the wrong trajectory can fall into a black hole. Black hole's gravity is so strong, even light, the fastest thing possible, cannot escape from it. But if the light has a slightly different trajectory, it can just get deflected by the black hole. It can get bent. Right? Get bent. That's what a black hole says to light some light. Now that means that somewhere in between, there's a trajectory such that a photon will not fall into the black hole, but also will not get bent and escape along a different path. Instead, the photon will orbit the black hole. And these are called photon rings or photon spheres. This is a place where it's outside of the event horizon. So you could go there, you wouldn't be trapped in the black hole, but you could go there. And you could look off to the side and see the back of your head.
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A
You go there, the photon effectively bounces off your head, travels around in a circle, and then is there for you to see it effectively. I mean, this is like our donut universe where you can carry on looking all the way around. Like the Pac man universe, where you look around and then see the back of your own head. Okay, I'm with you.
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B
Exactly, exactly, but smaller, you know, just. Just the circumference of that particular photon sphere for the black hole. So there are also places where light will be bent 180 degrees. So it'll emanate from a place like my bedroom, circle around the black hole, and come straight back to my bedroom. So I could use a telescope to look at that particular part of space around the black hole. And I could see myself or I could see what was happening, you know, however long ago that light came from that spot.
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A
So this is your mirror, essentially.
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This is our mirror that there are
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some photos that are being sent back.
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That's right. Now, the closest black hole to Earth is like a thousand light years away. More than that. Let me see. I wrote down my. The best contenders we know of so far. Yeah.
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A
So thousand's not bad, you know, A thousand's not bad.
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B
A thousand, not bad.
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A
We've missed the crucifixion of Jesus. Unfortunately, we've missed the birth and death of Jesus Christ.
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B
So to be specific, Gaia BH1, which was discovered in September of 2022 by Karim El Badry. By the way, we're discovering a lot of black holes now. This one is only 1,560 light years away.
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A
Hang on, I got it wrong. Because you've got to double it, haven't you?
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B
You've got to double it.
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A
We can look at 3,000 years ago. Okay.
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B
That's right.
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A
We haven't missed. We haven't missed the birth and death of Jesus.
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B
We'd have to keep watching for a thousand years. Yeah, and there might be black holes that are closer, but Gaia BH1 is, what, 3120 light year, total travel distance there and back. So if we could look at the light that had slingshot it around it, or boomerang back, I guess that's the right word to use. Boomerang back. We would see Earth as it was 3,120 years ago. Was there any cool stuff happening back then?
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A
Okay, let's think. I mean, Pythagoras is around. Then there is this tree, this olive tree in Crete. That would have been sort of the oldest tree in the world. And that would have been. That would have been a little sapling.
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That's cute. I'm looking up the Wikipedia page for the year 1094 B.C.
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A
right. The pyramids are already, you know, 1500 years old by this point.
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B
Wow. You could watch tomb robbers in the Valley of Kings.
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A
You could. You could. I think there's Something about Israel.
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B
King David in Israel, Maybe Ramses the 11th was the Egyptian Pharaoh during the 12th Dynasty. We could check out what he was up to.
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A
This is around the time of the, the invention of cavalry.
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B
Oh, interesting.
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A
In Eurasia, you know, breeding horses that are large enough to be, to be ridden into battle. That's quite fun.
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B
Yeah, it keep us busy. And every day we would see one more day in the future. So we could like, follow these stories. The problem though is can you really do this?
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A
Can you really do this, Michael?
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B
And the answer is no. But the answer is also yes. Um, obviously when light travels that far away from Earth, there's a lot of light extinction. All right? It's going to run into gas and dust and it's going to spread out and there's going to be way fewer photons that reach that black hole than originally emanated in all directions from the tomb robbers in the Valley of the Kings. Right. Trillions of photons are falling off of them, but only some of them make it to this black hole. And an even smaller percentage actually have just the right trajectory to go around. But if you get a big enough telescope, you can capture these photons and if you're willing to sacrifice some resolution, you can take some time lapses, put a lot of photos together and you can make some things out. So I've been trying to figure out how big of a telescope you would need. And here's what I came up with. So to make out a detail such that one pixel of your image represents just one centimeter. One square centimeter of area.
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A
Well, of Earth originally.
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B
Of Earth originally. Of Earth, Yeah.
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A
You are ambitious. Go on.
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B
Oh, yeah. I'm not gonna, I'm, I'm, I'm starting with a lot of ambition here. So we're trying to, we're, we're trying to take a picture such that each pixel is just 1cm.
- [25:15]
A
I remember growing up and there being a new satellite image which could. You could distinguish sheep essentially. Right? You could distinguish a sheep in an image. And everyone was very excited about it. And that is, you know, that's probably like two or three pixels, but a sheep is way bigger than two or three centimeters.
- [25:39]
B
Okay, I've got my answer. Now. What did you find?
- [25:45]
A
I found that the commercial satellites have about 30 centimeters per pixel. You want something that's 30, we're going
- [25:56]
B
to be better than them. I want to be able to like read a large print book.
- [25:59]
A
Okay. Okay. And then the spy satellites, the sort of top secret ones, they are about 10 centimeters per pixel?
- [26:08]
B
10. Only 10? Well, you know, obviously, I'm. I'm glossing over you.
- [26:14]
A
You don't just want to be able to. You. You want to be able to tell what time it is on someone's wristwatch. That's sort of like the resolution you.
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B
That would be awesome. Yeah. I want to be able to see the expressions on people's faces. I want to be able to see what, like, you know, Genghis Khan looked like. Sure, Genghis Khan. I said Kong, like King Kong. But so, I mean, there's things I need to learn that don't require telescopes. But also, yeah, I'm looking for this great resolution. But to do this, to get a resolution of 1cm per pixel from a distance of 3,120 light years, you would need to have a telescope whose primary mirror was.18 light years wide.
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A
Okay.
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B
That's more than. That's more than one and a half trillion kilometers wide. For reference, Pluto is only about 6 billion kilometers away from the sun. So we need a telescope that is orders of magnitude larger than our own solar system.
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A
Than the solar system. Amazing.
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B
Yeah. And we could. It wouldn't have to be one big piece. It could be an array of smaller, more manageable to build pieces. But I think that we're limited by the amount of matter in our own solar system. We'd have to destroy the entire solar system, build a whole new thing that's even bigger. And then we could watch tears fall from the eyes of Achilles.
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A
I mean, look, you just really, really, really want to know what Genghis Khan looked like, and I understand that ambition.
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B
I really want to know, and I really want to be able to, you know, watch. Not a movie about history, but literally watch history.
- [27:51]
A
Yeah, yeah, yeah. I mean, what you're saying is it's technically possible, just difficult.
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B
It's technically possible, yeah.
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A
Well, hold on. Before you get to that, should we take a little break?
- [28:01]
B
Yes.
- [28:09]
A
Foreign. This episode is brought to you by Cancer Research uk.
- [28:19]
B
We often think of beating cancer as treatment, but imagine stopping it before it begins. After years of work, Cancer Research UK scientists are launching a clinical trial of lungvax, the first vaccine designed to prevent lung cancer.
- [28:35]
A
It builds on TracerX, the world's largest cancer evolution study, which tracked lung cancer cells over many years to uncover the disease's earliest warning signs. Lungvax is designed to train the immune system to spot these signs early on, destroying faulty cells before cancer develops.
- [28:53]
B
So it's not treatment, but preventative, with the potential to stop lung cancer before it starts. The first stage of the trial starts this year. Focusing on people at higher risk.
- [29:05]
A
It shows what long term research makes possible.
- [29:08]
B
For more information about Cancer Research uk, their research breakthroughs and how you can support them, visit cancerresearchuk.org thereest Issac are
- [29:20]
C
you looking for support in your weight management journey? Zepbound Tirzepatide may be able to help. Zepbound is a prescription medicine used with a reduced calorie diet and increased physical activity to help adults with obesity or some adults with overweight who also have weight related medical problems to lose excess body weight and keep the weight off. Zepbound is Approved as a 2.5, 5, 7.5, 10, 12.5 or 15mg injection. Zepbound contains Tirzepatide and should not be used with other Tirzepatide containing products or any GLP1 receptor agonist medicines. It is not known if Zepbound is safe and effective for use in children. Don't share needles or pens or reuse needles. Don't take if allergic to it or if you or someone in your family had medullary thyroid cancer or if you've had multiple endocrine neoplasia Syndrome Type 2. Tell your doctor if you get a lump or swelling in your neck. Stop Zepbound and call your doctor if you have severe stomach pain or a serious allergic reaction. Severe side effects may include inflamed pancreas or gallbladder problems. Tell your doctor if you experience vision changes before scheduled procedures with anesthesia. If you're nursing pregnant, plan to be or taking birth control control pills. Taking Zepbound with a sulfonylurea or insulin may cause low blood sugar. Side effects include nausea, diarrhea and vomiting, which can cause dehydration and worsen kidney problems. Talk to your doctor, call 1-800-545-5979 or
- [30:46]
B
visit zepbound Lilly.com no one goes to Hank's for spreadsheets. They go for a darn good pizza. Lately, though, the shop's been quiet, so Hank decides to bring back the $1 slice. He asks Copilot in Microsoft Excel to look at his sales and costs and help him see if he can afford it. Copilot shows Hank where the money's going and which little extras make the dollar slice work. Now Hanks has a line out the door. Hank makes the pizza, Copilot handles the spreadsheets. Learn more@m365copilot.com. Here's a different idea. Instead of building really big telescopes. We can take advantage of the fact that our solar system already contains some accidental telescopes.
- [31:39]
A
Go on.
- [31:40]
B
Okay, let's talk about the sun. So one of Einstein's big predictions was that a massive body can bend light. Doesn't have to be a black hole. Everything that has mass bends light, even you and me a little bit. But the sun is big enough that it's, it's, it's very noticeable. And this was confirmed years later after his prediction. During a solar eclipse, stars that should have been behind the sun were visible at the edge of the sun.
- [32:08]
A
Yeah, no, that's exactly right.
- [32:10]
B
So what was happening is that imagine my fist is the Sun. Here's a star behind it, that light that's coming off the star and it should go this way and miss the Earth. It gets bigger, bent by the gravity of the sun and it comes right towards the Earth. And so we're able to see things that we shouldn't otherwise see. And this had to be done during an eclipse because of course the sun is too bright otherwise. Well, that's just what a lens does. A lens takes light and it bends it and then that light focuses somewhere else to produce an image for the Sun. Its focal length is about 550au away from, from the sun, where an au is an astronomical unit. That's the distance from the sun to the earth. So 550 times further from the sun there's a focal point. So you can put a telescope there and you can use the sun to capture an enormous amount of light and send it all to a little telescope just like a meter in diameter. And this is an actual real proposal. In fact, there's something called focal, which, oh man, I didn't write down what it stands for, but there are projects that have been proposed to the European Space Agency and to NASA to do this.
- [33:25]
A
Okay, but this is an enormous distance, 500 times the distance between the Earth and the sun. I mean this is by some order of magnitude way further than any human made object has ever traveled. Including those that have left our solar system.
- [33:42]
B
That's right. Yeah. It's like in excess of 80 billion kilometers away. And the, the, the furthest human made thing from Earth is the Voyager 1 probe. And it's not even that far yet, not even close. And it's been traveling since the 70s. However, it wasn't built to go really far. It was built to look at planets. We could use solar sails and, and a slingshot around the sun to get out there within you and I's lifetime.
- [34:13]
A
But Then when you get there, how are you transmitting any of that data? I mean, all very good if you can, you can sit in the focal point, have a mirror that's, that's like a meter wide, get this incredible image of the universe that you otherwise wouldn't have access to. You know, really amp up the sort of the power of your, your telescope. But what are you going to do then? How are you going to get it back?
- [34:36]
B
Well, I mean, you send it back. You send back the data from the telescope. Just like Voyager sent back photos of Jupiter.
- [34:43]
A
Yeah, but then, I mean, isn't it too far?
- [34:45]
B
It's not, it's not too far. I mean, look, look, look, look. I'm not the engineer who's building the thing. I'm the, I'm the boss giving them okrs. I'm saying figure it out. And I mean, you're right to bring these concerns up because in order to. Here's something really cool we could do with it. We could position it such that an exoplanet that was a hundred light years away was exactly behind the sun. And then we could look at the light that came around the edge of the sun. It's all bent around. It's actually, it's called an Einstein ring. The planet wouldn't appear like a planet. It would appear like a ring of light that was all warped around the sun. And then we could piece that back together into an image of the exoplanet. In order to make that work, we would need to have a precision of, of aiming accuracy that's about a hundred times what we currently can do. And it would take a long time for us to send and receive instructions from this telescope. Of course, you know, but listen to this. Using the sun as a telescope would allow a brightness factor of 1 trillion times. So things become a trillion times brighter than they are to the naked eye and a magnification of 100 billion times.
- [36:08]
A
Wait, what do we get from James Webb? What does that give us? Because comparing to the naked eyes, like. Well, I mean, you can't see very much from the naked eye at all.
- [36:15]
B
No, I mean, magnification is kind of the wrong word to use for like James Webb. It doesn't zoom, doesn't have a zoom. Right. It just is like focused at infinity and it takes in what it can. Its optical resolution is about a tenth of an arc second. So that's what a pixel is going to be for the James Webb telescope.
- [36:34]
A
Okay. It's quite far away from a centimeter, isn't it?
- [36:37]
B
Yes. Well, so let's talk about, like, what an arc second is. It's a way of describing how large the apparent size of something is. Right. Like, if you're really close to me, you know, your head will take up a lot of my field of view. But if you move further away, your head becomes small. Like right now, I can crush your head between my fingers. Because its apparent size is very small, it takes up a very small part of my field of view. We can divide up the field of view into degrees. Right. 360 degrees would be the whole thing. And then you can divide a degree into what are called arc minutes. And there are 60 arc minutes in each degree. And you can divide an arc minute into 60 arc seconds. Now, to put this into perspective, if you hold out your pinky at arm's length, it covers about 1 degree of space around you. So 360 of your pinkies could completely surround you. Three fingers like this held at arm's length, that's about 5 degrees. One of these little, little, like, hang loose symbols. This is about 25 degrees. So when we're talking about 0.1 arc seconds, we're talking about the distance subtended by my pinky at arm's length divided by 60, divided by 60 again, and then a tenth of that.
- [37:54]
A
And that's what you get for a pixel.
- [37:57]
B
That's what you get for a pixel
- [37:58]
A
from James Webb, which is incredible compared to everything we've had before, it's absolutely incredible. It's important to say, actually, the reason why they use arcseconds rather than a distance metric, like centimeters. You don't know how far away this stuff is.
- [38:12]
B
Right.
- [38:12]
A
All you have is your field of vision. That's the most sensible way to split up. Split up the, you know, the size of the image that you can possibly see.
- [38:20]
B
So James Webb has a resolution of a tenth of an arc second, but this proposed solar gravitational lens would have a resolution of a 10 billionth of an arc second.
- [38:33]
A
Whoa. Yeah.
- [38:36]
B
So like a billion times better.
- [38:38]
A
You are seeing way more. Wow.
- [38:42]
B
So, to put it another way, if we found an exoplanet that was 100 light years away, we could, with this telescope, that's, what, 80 billion kilometers away, use the sun to see that exoplanet 100 light years away with a resolution of about 25 kilometers per pixel.
- [39:03]
A
Right. Okay. This is a lot better. That's a lot better.
- [39:07]
B
That's not bad. That means we can see cloud cover, we can see oceans, coastlines, mountain ranges. You could see lights from cities. If you Want to. If you want to see what 25 kilometer per pixel resolution looks like, just check out photographs from the Discover satellite, which is taking photos of Earth all the time. If you look at them, they just look like Earth. Obviously you can't see buildings, but you can see that that's the planet Earth. It's a globe.
- [39:36]
A
Oh, yeah, yeah. I mean, you can see the outline of the coasts. Yeah, I mean, that's incredible. You can see. I mean, you can literally distinguish then between, well, day and night, between, between water and land. I mean, you can even really probably tell mountain ranges on that. Yeah, the atmospheric, you know, you can see clouds, you can see. There's incredible. That's absolutely incredible. Yeah, you'd get a proper image of what exoplanets look like, and that's for
- [40:06]
B
an exoplanet a hundred light years away. It would look like that except with its own terrain and weather. But, you know, the closest exoplanet is like, you know, Proxima Centauri B. That's only a handful of light years away. Like, give me a break. That'd be amazing. There's a lot of problems with this. I mean, one is that it's a long distance, 550 AU, more than 80 billion kilometers away. Yeah, it's about 10 times further away than Pluto.
- [40:37]
A
Okay, that's actually, when you put it that way, that doesn't feel quite so bad. But maybe that's because I'm just forgetting how much closer the Earth is to the sun than it is to Pluto.
- [40:48]
B
Yeah, Pluto is far away. I mean, this thing would be far away. Personally, I think that a lot of these issues can be resolved within our lifetimes. And because of the new solar cell technology that it used to be an idea, now we're actually using it, where you actually have like a big sail that unfolds and it's pushed by the light pressure of the sun. And that push just keeps happening, so you get acceleration. It just gets faster and faster and faster and faster. We could get them out there. And when I say them, I say them because we might need more than one. It'd be nice to have multiples that are like chained up so that one gets into position, it does its thing, it tries to take the pictures, and then we learn from any mistakes it makes. And then we just wait for the next one. This, this is a very specific idea. And if you want more information, there's a PBS spacetime episode about them. And they call this proposal, the String of Pearls proposal, where you've got A string of these little telescopes that are all moving back into position one after the other, trying their best to capture whatever it is we have put on the other side of the sun for them to see lensed and magnified and embrightened by the sun's gravity.
- [42:06]
A
Wait, tell me again what this project is called. Focal.
- [42:09]
B
Yeah, look up. Solar Gravitational Lens. There's a specific proposal called focal. Although it's a difficult task, it's still better than the alternative, which is we never see what these exoplanets look like, especially within our lifetime, 100 light years. It's going to take 100 years just to get a spacecraft there. If it traveled at the speed of light, which it can't now, we could get it. We could get it using, I don't know, solar sails and maybe some kind of plasma radioactive propulsion system that would still be developed to get there within, you know, 500 years. But I don't care about that. I don't care what my great, great, great grandkids experience. No, I take that back. I do. And if that's all we could do, I would do that for them. But I'd like to see these planets.
- [43:00]
A
I'd like to see it, too. I think it's also. It's also worth saying, I mean, look so much that we are incredibly biased towards vision, right? As, as, like humans, it's us, our primary sense, it's the. It's the way that we explore. And so this is a way to really accelerate the. The. The power that we already have. I mean, exploring the universe as you described, we can't go out there. But. But if we could only see it, think about how much more we would understand about answering the question of whether we're really alone. Even answering the question about, I don't know, like, all of the things that come up in this podcast so often. What are the edges of the universe? What happened before the Big Bang? All of these questions. I've done a complete 180. From thinking it was completely ridiculous science fiction and just scientists looking for funding for outlandish, crazy, wild ideas, I've done a 180. I'm now the biggest proponent for it of all.
- [43:56]
B
You've done a 180? Just like the light around the black hole, that's gonna let me see my path. Yeah, I completely agree, because at the moment, our images of exoplanets are actually data showing a wobble in a point of light, which is that planet, star like we have. We can't even resolve a star to be anything More than a point of light. We can learn what the star is made of by looking at the spectrum emitted from the star. But like we can't see an exoplanet if you look, look up information about them. There's a lot of artist renderings, but I'm talking about a feasible way. I mean feasible is kind of in quotes, but a feasible way to image them, just like the images we see of Earth. And it would allow us to tell what's, what kind of atmosphere they have, find signs of life. We couldn't communicate with any intelligent life there within our lifetimes because it would take, you know, 100 years. What's, what's the, what's the best candidate? I feel like the best candidate for an Earth like exoplanet 30, 40, 50 light years away. There are some good candidates for Earth like exoplanets, and we could look at them. I wanted to bring up one more celestial body telescope idea that's even easier than a solar telescope. And that is one that's been pushed pretty hard by David Kipping. He has a YouTube channel where he explains his papers about this on his YouTube channel, Cool Worlds. And his like thesis, I believe, was about using Earth as a telescope. Now, Earth doesn't have nearly as much gravity as the sun, but Earth does have something else that bends light. An atmosphere.
- [45:38]
A
Right.
- [45:39]
B
So light is refracted by Earth's atmosphere. And that effect is much more dramatic than the gravitational deflection. He's calculated out and shown that we could put a telescope four times as far away from Earth as the Moon.
- [45:58]
A
Not far at all. Get there in a few days.
- [46:00]
B
Okay. So obviously there are some problems with using the atmosphere as a lens. One is that the atmosphere scatters light. The biggest one is that it's full of things called clouds which just block the light. However, about 14km up, there's enough air to refract light. There's few enough clouds that only about 8% of starlight or just light from outer space is going to get lost. For light refracted 14 km above the surface of the Earth all the way around the planet, the focal point is about four times as far away as the Moon, about 1 1/2 million kilometers, which is where the James Webb telescope is. Okay. We can put things there. And the, the, the amplification power, like theoretically of such a telescope would be 45,000 times. I think more realistically, Kipping has said it's more like 22,500.
- [46:57]
A
Amazing.
- [46:58]
B
That would effectively mean that a meter wide telescope would act like it would have the power of. Because of assistance from Earth's atmosphere. The power of a 150 meter telescope. To put that in perspective, the James Webb telescope. Six and a half meters. Wow.
- [47:17]
A
Wow. Why aren't we doing this? This is great.
- [47:21]
B
Well, I don't know. I. I think, I honestly, I think that we will do it.
- [47:25]
A
I've switched. Forget the focal project.
- [47:29]
B
I want this one because this is our, this is our, our only access to these things that are so far away it's going to be through light. And we're going to need to use telescopes that already accidentally exist, AKA celestial bodies. Like the universe provided us with the tools to look across these vast distances and it provided us with a mind to appreciate them. But the mind can't build them fast enough. That's okay. The universe gave them to us.
- [48:03]
A
Yeah. At least not fast enough to satisfy our curiosity within our given lifetimes. I think there's something quite nice about that though, you know that we're talking now about exploration that covers such vast distances, that uses such gigantic celestial objects to assist them, that this has to be multi generational endeavors. Right. This is not something that you can just, I don't know, have satellites launching in World War II and then land on the moon in the course of a single generation. This is something that's going to take many, many generations in order to be able to successfully do.
- [48:38]
B
Yeah. And I think that we, in a way, I think we owe it to future people to start these projects now. I think that we should start solar lens telescopes and Earth atmospheric lens telescopes now for us. But at the same time, we should launch things that in 500 years will reach, you know, an exoplanet and, and then 500 years later, send its data will finally be received on Earth. And those people a thousand years from now will say thank you. This is the most incredible gift you guys could have left us. Because there's a lot of things we're leaving the future that aren't good. The least we can do is balance
- [49:17]
A
it out with an incredible gift to future generations. One other incredible gift though, I mean we could, rather than relying on celestial mirrors, you know, black holes and Einstein rings and so on, we could just do a second project which was launching just a massive mirror that just hangs out about five light years away, you know, so that from that moment on you get to rewind 10 years whenever you like. I think, I think I'd like to see that project suggested, you know.
- [49:48]
B
Yeah, I guess the way to do it would be Would it just be a mirror or would it be better to send a telescope that then uses some massive object to create a high resolution image and then it sends that back at light speed to Earth so we can all tune into a television channel or a live stream on Twitch of Earth five years ago, and we can zoom in close enough to make out our bodies, our facial expressions. Give me a break. Why would you not do that?
- [50:19]
A
I mean, that would be pretty fun. Fun.
- [50:21]
B
Obviously there's a. There's a lot of problems. Our, Our, our atmosphere is going to scramble up that light. It's going to be really hard to get crisp, clean pictures of faces doing things quickly. But you can see, you know, vaguely where people are maybe. I don't know. It's like, there's a lot of details here that would need to be figured out.
- [50:43]
A
A new form of cctv, but it's like celestial. What could the other c be? Celestial circuit television.
- [50:53]
B
Wow. Do you think there's going to be privacy concerns? Of course there will be.
- [50:59]
A
Yeah, I think there definitely would be. Gosh, you need to get every single person on Earth to sign a waiver.
- [51:04]
B
You would, yeah, you would. Or maybe there could be a team in charge of the feed and they, like, randomly insert feedback, fake events so that you never know if something's real or not. That way we're protected. And yet you can kind of believe.
- [51:21]
A
Michael, have you not just reinvented the era of smartphones and deep fakes? Is that.
- [51:27]
B
Yeah. Okay, I'm, I'm, I'm. I'm saying a lot of things that I'm taking back right after I say them, but there's something here that's very beautiful and important.
- [51:37]
A
You know, I think that feels like a very lovely place to, to stop. So we should say thank you for, for watching and listening to the rest of science. Make sure you're following wherever you get your podcasts. Make sure that you like and subscribe on YouTube. Can you tell that I just read that from a script? Because it feels like words that never naturally leave my mouth.
- [51:53]
B
No, it sounded great to me.
- [51:55]
A
Did it, did it sound really authentic?
- [51:57]
B
Here, I'll. To make it sound better, I will do a worse version. And if you'd like to ask us a question which we might just answer in our Thursday episodes, you can send that to the rest is science. Goal hanger.com.
- [52:09]
A
that didn't sound like you were reading at all, Micha. Cool. You know, when I, when I first started presenting science shows at the BBC, they sent me into this presenter training thing. I told you this before, I don't think I have everyone when they, when they first start, they sound a bit like that when they're reading. They sound really robotic. And what they do is they get you to read some Winnie the Pooh and imagine you're reading it to like a really small child. Then you read the script in that same voice. And if you'd like to ask a question, which we might just answer in our Thursday episodes, you can send it into the rest is scienceolehanger.com and that's basically how you practice changing your tone so that you're not just stuck between two levels.
- [52:55]
B
It like slows you down and you wind up reading a bit ahead. So you can do the voice, but so in the training, you're having to do this for Winnie the Pooh but then like actual news stories.
- [53:05]
A
Exactly. Anyway, you can hear more of our robotic greeting when you join us on future episodes of the Rest of Science. We'll see you next time. Yep.
- [53:15]
B
Hold on, let me just look at the script. Bye.
- [53:30]
A
Some follow the noise. Bloomberg follows the money because behind every
- [53:36]
B
headline is a bottom line.
- [53:38]
A
Whether it's the funds fueling AI or crypto's trillion dollar swings, there's a money side to every story.
- [53:45]
B
And when you see the money side,
- [53:47]
A
you understand what others miss.
- [53:50]
B
Get the money side of the story. Subscribe now@bloomberg.com the right window treatments change everything. Your sleep, your privacy, the way every room looks and feels. @blinds.com, we've spent 30 years making it surprisingly simple to get ex exactly what your home needs. We've covered over 25 million windows and have 50,000 five star reviews to prove we deliver. Whether you DIY it or want a pro to handle everything from measure to install, we have you covered. Real design professionals, free samples, zero pressure right now. Get up to 50% off with minimum purchase. Plus get a free professional measure@blinds.com rules and restrictions apply. Ryan Reynolds here from Mint Mobile with a message for everyone paying big wireless way too much. Please, for the love of everything good in this world, stop with Mint. You can get premium wireless for just $15 a month. Of course, if you enjoy overpaying. No judgments. But that's weird. Okay, one judgment anyway. Give it a try@mintmobile.com Switch upfront payment of $45 for three month plan equivalent to $15 per month required intro rate first three months only, then full price plan options available, taxes and fees extra. See full terms@mintmobile.com.