Studying The Universe
Studying The Universe
Chris Lintott (Astronomer) gives expert video advice on: What intrigued you most about astronomy?; What would your advice be to anyone interested in getting involved in astronomy?; What is the most mindblowing thing about astronomy? and more...
What intrigued you most about astronomy?
Well, I dabble in a whole range of things, but the thing that really intrigues me is the star formation. This is because we know the basics. We know that clouds of gas and dust, that we call nebulae, collapse to form stars, just under their own gravity, but beyond that the details are far from clear. It amazes me that I can't tell you why the sun is the size that it is, I can't tell you why it's the mass it is, I can't tell you why it has planets. So trying to understand those questions is the main thrust of my research.
What would your advice be to anyone interested in getting involved in astronomy?
Go out and look up. Even if you're in the city, just noticing the phases of the moon, and seeing Venus. I saw Venus hanging above Euston Station the other day, and actually that was one of the most beautiful things I've seen. To see that from the middle of London is fantastic. Get a magazine or join an astronomical society, and take some notice of what you can see in the sky from wherever you are, and follow wherever that leads you. Some people get into taking pictures, some people just like to look up. Maybe you want to read up on the science behind it, but most of all, just notice what's in the night sky. You can tell an astronomer, because they step out and do that, look up straight away, and there's something nice about knowing where we are in the universe.
What is the most mindblowing thing about astronomy?
I was in Hawaii on top of an extinct volcano called Molocchea, using a radio-telescope to look at a nearby star-forming region. You set the telescope up. What professional astronomers actually do is look at computer screens all day. They set the telescope up, and set it recording the information it was receiving for half an hour. What do you do for the next twenty minutes? I wandered outside with my binoculars, and looked up at the darkest night sky I have ever seen. At that point you realize that we're on a very small, insignificant, boring little planet, and yet somehow we've evolved, that we can look up, and I can ask questions like how stars form, how old is the universe, how did we get here, how likely it is that we can get here? Even just attempting to answer some of those questions blows my mind whenever I think about it. It's just incredible that we can get anywhere close to understanding the universe.
If the universe is infinite and expanding what's it expanding into?
What's happening is that space itself is expanding. So, for now, we'll leave this open if this is true or not. Imagine a universe which is closed. By that I mean, if I head off in that direction, I'm sitting in Salzburg. I then go past Chitchgur, and keep going for billions and billions of light years, it's possible that the universe's shape is such that I'll just come back 'round and end up sitting back here talking to you'. It might take a huge amount of time to do that but it's possible that the universe has that sort of geometry. Now if that's true, wherever you go in the universe, you're never going to hit an edge. You're within space and it's all connected and it can expand because the distance from here to the next galaxy can get bigger as space expands. You never hit an edge. So the question of what it's expanding into doesn't really apply. The problem is that our brain's want it to and it's hard to comprehend, apart from in mathematics, exactly what that means.
What is a worm hole?
A worm hole is something is general relativity. Einstein's great theory of gravity, says worm holes can exist but that we have no evidence that it exists. Let's start with the idea of a black hole. If you have a lot of stuff in a small space, and then it has a very strong gravitational field and that field can get so strong that even light which is the fastest thing in the universe can't escape the black hole and we know these exists. We see small one's, which are caused by the death of massive stars and we see really big ones several million times the size of the sun at the center of galaxies. There is one at the center of our Milky Way and we know that because we've seen stuff falling into it, and disappearing from our universe. No information will ever escape the black hole, except if there's a way out. The theory of relativity says that it's just possible that these black holes aren't holes at all, but tunnels which connect maybe to another black hole, and maybe to some other region of space. So it's possible that if you fall into a black hole, you might just come out the other side somewhere in the distant regions of the universe. Now there's absolutely no evidence beyond Star Trek that those actually exist but the theory says they could be there.
What is dark matter?
Dark matter is one of the biggest mysteries in what we understand about the universe. The great progress in the last ten years has meant that we know how much stuff there is. We know that because we can see how the universe is expanding and that expansion changes with time because of the gravity of all the stuff that is within the universe. So if you have lots of stuff you have strong gravity and the universe gets pulled together, if you have not much stuff then the universe expands without really being affected by the matter within it. Now, we can count up all the stuff we can see, we can weigh galaxies by looking at their stars, adding up the gas, the stars, all the matter that we know about and its not enough to match the measurements of the universe's expansion. In fact, all normal matter, everything that you and I are made of, everything the earth and solar system are made of adds up to a sixth of the total matter in the universe. So the question, what's the rest of it? Well we don't know so we call it dark matter. We see its effects by its gravity but that's it, it doesn't seem to interact with the rest of the universe and there is some around you right now, wherever you are sitting. The theory tells us that there is something like a hundred thousand dark matter particles passing through your body every second, but they don't interact, they have gravity but they don't interact with normal matter in any other way.
Where is the nearest black hole and do we need to worry about it?
Well you don't need to worry about it, I know that. The nearest, really big one, is in the center of our galaxy. It's an amazing object, because we can watch stars which are in orbit around it and they whiz around every ten years or so. Telescopes are now good enough that we can watch this, and that allows us to weigh the black hole in the center. It's a few million times the mass of the sun and its still eating material, and you see flares coming out of it as materials drops in. But, its no threat to us. We're in a perfectly stable orbit, we're going to keep going around our galaxy, the sun goes around the center of the galaxy every 225 million years, and we're going to be doing that for a long while yet. There are probably some nearer, small black holes. Most small black holes form when stars bigger than eight times the mass of the sun reach the end of their lives. They explode, and their outer layers fly off and the center collapses to a black hole. They're out there, and they're perfectly happy, but they're no threat to anyone and the odds of one coming through the solar system is very low indeed.
How do stars form?
Well, we know the basics. If you look up in the night sky in the winter, you can see a constellation called Orion. With Orion's belt: 3 stars in a diagonal line. Just below that hangs Orion's sword. And even with the naked eye, from a city, you can see that one of those stars is odd: it's fuzzy. If you look in binoculars or a telescope, you can see it's what we call a nebula. It's a vast region of gas and dust. Now within that dust, there are some very cold places, just 10 degrees above absolute zero. And at those temperatures, the gas is able to collapse under its own gravity. What happens is this collapse goes on, and at the center, the density goes up. And atoms begin to hit each other. And then there's a point where you reach a critical density. Atoms can then hit each other often. And when they do, they merge, and they start turning hydrogen into helium. And that's the ignition that starts the star. The young star then blows off the rest of the material and comes out into the big, wide world. So, we know the very basics of how stars form. The details are complicated and not well understood, but they form from gas clouds that are collapsing.
How are galaxies formed?
Galaxies, if you look right back to the time just after the Big Bang, we can image the universe as it was three hundred thousand years after the Big Bang. You don't see a smooth surface, we can see ripples. There are areas that are dense, and areas that are less dense. Like everywhere else in life, the rich get richer and the poor get poorer, so you have a dense area. It's got a stronger gravity than its neighbor. It pulls in more material. It gains more gravitational attraction. More material falls in. These small differences that we see then become exaggerated. The big one, the dense regions, go on to form galaxies, which are just clumps of gas isolated from the other clumps. You get these isolated blobs, and within them the stars form. You have this blob of gas that we call a proto-galaxy first.
What size is the Universe?
I can only tell you what size our observable universe is. The one thing we've learned is that where you seem to be looking is only a tiny portion of the whole universe. If you think about it, if we know the expansion of the universe when we measure the distance, from this direction I can see light which has been travelling towards us for 13.7 billion years. If I look this way, I can see light that's been travelling towards us for 13.7 billion years, but that's it. There hasn't been time for any light beyond that to reach us. The universe carries on, but we haven't seen an edge yet. Maybe we're about to see one, but it's at least that big. At least one theory that's accepted by most people, the theory of inflation, says that it's indescribably more massive than that, and that we're only seeing a tiny portion of it.
What are the chances of a large asteroid crashing into earth?
High probability that it could happen. The last large one crashed into Siberia in 1908. It flattend a few hundred miles. There is not much to be done about them. It has been suggested to blow them up, but that would only result in more scattered and smaller bits of radio activity. Targeting them with rocket motors could possibly veer them off course, but that would only be effective if the astorid is detected early enough. Another economically viable method would be to paint them a color that deflects or repels pressure from the sun which also controls their movement. There is a European mission, Don Quixote, that is studying this problem, however limited funds might bog this study down.
Is the static on your TV something to do with the Big Bang?
If you've still got an analog television, and you switch it away from the channel, you get that black and white fuzz across the screen. One percent of that fuzz is light that was emitted three hundred thousand years after the Big Bang. Before that, the universe was opaque, so light couldn't get further than a centimeter before hitting something. But the universe expanded, it cooled, and there was this transition. Suddenly light could travel across the whole universe. From that point, we're still receiving light from those very early days. It interferes with your television, but it also tells us a huge amount about three hundred thousand years after the Big Bang. We can actually make a picture of the universe as it was back then. Not a simulation, not a drawing, not an artist's impression, but an actual, honest-to-God picture of the universe as it was, almost 13.7 billion years ago.