The Quest For Wonder Special Features – Episode 5
After hard day’s questing for Wonder with his puppet pal Professor Brian Cox, puppet Robin is left with a few questions. So after each episode he’s taking time to video chat with one of our Cosmic Genome scientists.
The Quest For Wonder Episode 5 Subscriber Exclusive
Telescopes and Astronomy with Professor Chris Lintott
Robin - Chris Lintott, it’s currently day so you don’t have to look at the sky, so, question one, are telescopes basically just giant microscopes in terms of how they work?
Chris - I think that’s right. Both microscopes and telescopes are just ways of collecting light, so really we think of telescopes as nothing more than a light bucket. What you do with it once you’ve got the light in your bucket is the interesting thing. You can pass it to a camera or put your eye to an eyepiece but all the telescope’s really doing is making sure you collect as much light as possible from the faint things you want to look at. And the same is true of microscopes.
Robin - Nasmyth’s telescope is massive but you can get really good ones in the shops that just, like, fit in a rucksack or even a little picnic box, so why was his so big?
Chris - When you get a big telescope, or when you get your bigger telescope, what you’re getting is two things. First of all you’re collecting more light and so with a bigger telescope you can see fainter stuff. But also because of the way the physics works out, the bigger the telescope, the finer the detail you can see in what you’re looking at. And so big telescopes are better but the telescope you buy now that you can fit in your rucksack will beat Nasmyth’s and that’s because the quality of the optics has got much better. With modern technology we can really cheaply make really good mirrors and really good lenses and so even a small modern telescope will show us things that the great astronomers of the past would’ve struggled to see.
Robin - What’s the biggest difference between his type of telescope and the ones we use now?
Chris - The basic designs of telescopes we use today are pretty much the same as those Nasmyth and others were using. You’d have a lens or a mirror that focuses the light that you’ve collected and then you do something with it. What has changed is what you do with it once you’ve collected the light. So, whereas people like Nasmyth probably would’ve been sketching what they could see through the telescope with a pencil and a pen, these days we have highly sensitive cameras and very specialised cameras that we can cool down so they’re very, very sensitive indeed, so we’re able to make much more of the light. When light from a telescope hits your eye, 99% of is wasted, but when it hits a modern camera 99% of it is recorded. So it’s really more what we do with the telescope that’s changed.
Robin - Nasmyth looked at the moon, which is kind of close, so what’s the furthest thing we can see with a telescope nowadays?
Chris - The furthest thing you can see with a telescope is kind of a difficult question. So, really, the way to measure it is to think about how long the light has taken to get to us. So from the moon that’s about a quarter of a second; the sun is about eight minutes away; the nearby stars that you see with the naked eye are a few tens or hundreds or thousands of years away. And with a really big telescope, and good conditions, we can see light from things that are so far away that their light has taken ten billion years to reach us. So we can look billions of light years away. If you want to see yourself, probably the furthest thing you can see with your own eyes, or with a small telescope, is The Andromeda Galaxy, the neighbouring system to our own Milky Way, and that’s 2.2 million light years away. So when you look at that, it’s like a faint smudge in the sky, but when you see that smudge you’re seeing it as it was a couple of million years ago.
Robin - What about sending a telescope into space?
Chris - For seeing faint stuff, being on Earth helps. What really matters there is the size of the telescope and it’s hard to send a big telescope into space. But when you want to see fine detail then the Earth gets in the way. From here on Earth the main problem is what’s happening to the Earth’s atmosphere, it’s moving around and it’s disrupting the image, that’s why stars twinkle. So going into space gets you away from that twinkling. it enables you to see with crystal clear precision the details that you’re looking at. So Hubble, by modern professional standards, is not a big telescope. It’s achieved its success because it’s got this very clear vision.
Robin - This all sounds brilliant, but if I go and buy a telescope, what will I be able to see?
Chris - I think the best thing to look at, the first thing you should look at, with a small telescope is the moon. Because the thing that surprised Galileo is still surprising now when you see it for the first time, which is that the moon is a world. It’s got mountains, it’s got the craters that we know about, but it’s got a landscape, and if you look at the moon night after night as the sun rises and sets over that landscape you see those features change, and on different nights you see different parts of the moon’s surface well lit up. So I would always look at the moon. But through a small telescope, the planets will be good. Saturn’s rings will be there, you’ll see Titan, Saturn’s biggest moon, Jupiter and its four large moons which you can watch dancing around the planet. And you’ll see the Great Red Spot, the enormous storm on Jupiter that’s been there for a few hundred years as well. And then looking beyond that gets a bit more difficult but you’re able to see the colour of stars and even some of what we call deep sky objects, things like star clusters and the nebula where stars are born. So, really, once you start off you get to explore the universe, but start close to home. Look at the moon, look at the planets and see how they change over time.
Now, the sun’s really bright and a telescope is designed for looking at faint stuff and so what happens when you look at the sun through a telescope is that the telescope does a very good job of collecting lots of the sun’s light and if you’re lucky the telescope will melt, and if you’re not lucky the much more likely outcome is that it will melt your own eyeball and so it’s a very, very bad idea to collect that much light. Everything else is OK! The full moon is fine and anything else from there on down, but you don’t need a telescope to look at the sun, so don’t try!
My advice is go and find your local astronomical society. There are a few hundred of these just in the UK and most of them will have public observing nights where you can go and try lots of people’s telescopes or you can bring yours along and get somebody to help you set it up. So, I think you do need help. Lots of telescopes sit in the attic because people aren’t quite sure where to look or what to look for so do get some help. But it’s not difficult! I think owning a telescope, or even just paying attention to the sky, gives you the sense of where we are in the universe. It doesn’t take much to learn the sky and to notice where the planets are from night to night. So it’s quite easy once you get started but an astronomical society will give you that first boost.
Robin - Seems like every day someone is finding something new or some telescope or other, so what’s the most exciting thing that we’ve seen lately?
Chris - The most exciting thing that I’ve seen through a telescope in recent years is something called Hanny’s Voorwerp which is a strange green cloud of gas - looks a bit like an evil version of Kermit the Frog - hanging in space. It was discovered by a Dutch schoolteacher, Hanny van Arkel, who was looking at images from a large survey online and said, ‘There’s something interesting in this image’. And the voorwerp is a huge cloud of gas, it’s hot, it’s been heated to about fifty thousand degrees, so ten times the surface of the sun in temperature. And it’s been heated because it’s been hit by a jet of material coming from a black hole in a nearby galaxy. So it’s got this wonderful story, but it’s been great fun using all the telescopes we can get our hands on to try and work out what this thing is and to work out whether there are other things like it out there. It’s just about visible in, sort of, back garden telescopes as well. So, I have gone looking for it myself, I haven’t found it yet, you need a very clear night, but seeing pictures of that and realising no one had ever seen it, or very few people had ever seen it before, was really exciting.
Robin - Brian’s always just looking up at the stars and going ooh and aah, so why do you think people are more fascinated by looking up more than looking down?
Chris - I think that when you look up, you’re confronted really obviously with things that we don’t understand. Even questions like, ‘Why is the sky dark at night?’ or ‘What are the stars?’ or ‘What happens if I just keep going into space?’, those are actual research questions. Those are questions that are very close to the things that real astronomers, professional astronomers, work on. So I think the looking up - amateur astronomy - is a way of getting very close to saying, ‘I don’t know the answer to that question’ and I think a lot of science…the people that get inspired by science, are the people who get inspired by an answer that begins, ‘I don’t know’ rather than people who are looking for solid facts. And I think you get there faster in space.
Also, I think what’s most fascinating about the moon is that it’s right on the edge of being visitable. It’s right there and yet only a handful of people have ever been there. It is a world. It has these mountains and these landscapes but no one you know, and no one I know, in fact, nobody on Earth has ever seen them, so I think the idea that it’s just out of reach really intrigues and interests people. As a scientist, what’s interesting about the moon is that it has a record of what’s happened in this bit of space for the last four billion years. On Earth our history has been covered by all this biology. What you see when you look at the Earth are plants which get in the way. Whereas you look at the moon, which is blissfully free of these things, you see a record of every crater, or every impact that’s hit the surface in the last few billion years, and so we learn more about the Earth by going to the moon. But it’s a pretty good holiday destination as well.
Watch all episodes of The Quest For Wonder here.