Chapter 1: What is the main topic discussed in this episode?
Welcome to the Rest of Science. I'm Hannah Fry.
And I'm Michael Stevens. Today, Hannah, we are going to look into the past by looking up, but not in the usual way.
Chapter 2: What unique perspective does the podcast offer on viewing the past?
We're not going to 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 going to be looking at our own pasts in outer space.
Am I... Hang on, Michael. Am I also going to learn a mnemonic during this about how many feet are in a mile? Because... I can feel one coming. That's not me looking into our past. That's me looking into our future.
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 going to just blast it all over everyone's ears and eyes. Here we go. This episode is brought to you by Cancer Research UK. 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.
But now we know that that hidden majority, sometimes called the dark genome, influences how our biology works and how diseases like cancer behave.
It's a reminder that 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.
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.
By the way, okay, 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. 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, 5,280 feet. 5-2-8-0s. 5-2-8-0. Five tomatoes. That's how many feet are in a mile.
There you go. You're welcome.
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Chapter 3: How does our DNA relate to the concept of time and memory?
Yeah, I'm serious. The inch is not described as the distance some, you know, krypton atom vibrates. No, it's just 2.54 centimeters. So we're tied to the metric system, but we add a layer of conversion to it.
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? No, not for me, but maybe other Americans do that. 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.
Well, but also speeds on the motorways.
Right. Or speeds on the motorways. Or how much you weigh. Yeah, there you can use pounds 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. 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?
What did you say? One inch is 2.55 centimeters.
2.54 centimeters.
5'4". Okay, 254 then.
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Chapter 4: How does light travel impact our perception of time?
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.
Than the solar system. Amazing.
Yeah. And we could, we 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.
I mean, look, you just really, really, really want to know what Genghis Khan looked like. And I understand that ambition.
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.
Yeah. Yeah. Yeah. I mean, what you're saying is it's technically possible, just difficult.
It's technically possible. Yeah.
Well, hold on. Before we get to that, should we take a little break?
Yes.
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Chapter 5: What role do mirrors play in observing our past through space?
Everything that has mass bends light, even you and me a little bit. But the sun is big enough that 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.
Yeah, no, that's exactly right.
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 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. Right. 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 550 AU away 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.
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 travelled, including those that have left our solar system.
That's right. Yeah, it's like in excess of 80 billion kilometers away. And 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 a slingshot around the sun to get out there within you and I's lifetime.
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