Bryan Gaensler – TRANSCRIPT
Good morning, everybody.
400 years ago, Galileo pointed his telescope at the sky, and ever since then, we’ve built bigger and more powerful telescopes to look at the sky in increasingly more detail. And though we’ve learned a lot, there are some problems that we still can’t answer.
Today I’m going to describe to you the things we still don’t understand about the universe and how we, in Australia, are going to take a new approach to try and answer them. I’m going to start by putting the entire history of the universe on one slide.
So, here it is. Pretty amazing that we can do this. The Big Bang at the top and us, 13.7 billion years later, at the bottom. So we know the universe began in this huge explosion, a Βig Βang. We know that for a long period after that not much happened. The universe was dark. Gas was floating around in that darkness. We call that period the Dark Ages. Then after about a billion years or so, these clouds of gas collapsed under gravity and formed stars and galaxies. “Let there be light,” as someone once said; the stars turned on. You might call this the Cosmic Renaissance.
We now have stars and galaxies and for billions of years; they have evolved, collided, aged, and eventually giving birth to the Sun, the solar system, and us. And we now look at the sky and try to understand it. And while we know a lot about the beginning, we actually know quite a lot about the Big Bang, except the minor detail of why it happened in the first place – and we know a lot about the universe now, but there’s that big gap in between the Dark Ages and the Cosmic Renaissance. We don’t know how we got from the Big Bang to us.
So, we have a problem: we don’t understand how the universe has evolved. There’s a second problem. The universe is changing, and it’s changing quite quickly. In December 2004, a little star, about 50,000 light-years away, gave off a sudden flash. For a quarter of a second, this star was brighter than the Milky Way by a factor of a 1,000. This intense radiation hurdled across space and crashed into the Earth’s atmosphere, lighting up the ionosphere and knocking out satellites all over the world.
Now, luckily we happened to see that when it happened. A quarter of a second it was on, and then it was gone. But it turns out, there are explosions like this happening all over the sky every day. We don’t understand what they are and what they’re telling us. And unless we’re looking at the right place at the right time, we normally miss them. The universe is dynamic. Not only do we not understand it, but we’re not even seeing the whole story.
And there’s a third problem, a very minor problem that we don’t actually know what the universe is made of. Now, the stuff we think about when we look at the sky –galaxies, stars, planets, trees, people– they’re all made of atoms. We think we understand atoms. But atoms are only 5 percent of the universe. There is a lot of other stuff out there. Stuff that we can’t see and we don’t understand. About 23 percent of the universe is something we have no idea what it is, so we just call it dark matter.
But if that’s not bad enough, 72 percent of the universe is filled with something even less understandable, some sort of mysterious anti-gravity force called dark energy. So, 95 percent of the universe is completely mysterious. Or as my colleague Bob Kirschner likes to say, “The universe is like Los Angeles. It’s only 5 percent substance and 95 percent energy.”
So, the universe evolves, and we don’t understand that. The universe changes; we don’t understand that. The universe is dark, and we don’t understand that either. We haven’t really done much in the last 400 years. So, why don’t we understand these problems? We’ve got these amazing telescopes.
What is the problem? The problem is that the answers to these questions are not buried in individual objects that we can study in great detail. Here is a typical picture from the Hubble Space Telescope, the most powerful telescope ever built. You’ve seen breathtaking images of incredibly distant stars. But the answers to these questions are not in individual objects, but they’re written on the whole sky. They have subtle imprints that you need to look at the whole sky at once to get the answers for.
To show you the contrast between the Hubble Space Telescope and the whole sky, here it is what Hubble sees, and let’s just see how much of the sky we see every time we take a picture with Hubble. There’s a nice galaxy. There are some stars. But we’re still going, we’re still going, and this is about a quarter of the sky. So, you can see Hubble is only telling you a tiny, tiny part of the story. You need to take this new approach of all-sky astronomy if you really want to see what’s going on.
So, why don’t we do that? Why don’t we just point Hubble all over the whole sky? Well, there are three problems. There are three reasons why we can’t do this all-sky astronomy just yet. The first is that our telescopes simply can’t see that much of the sky at once. So, as I said, the Hubble Space Telescope, best telescope ever built –billions of dollars; let’s ask it to take a picture of the Moon. That’s a bit embarrassing. You don’t ask something as amazing as Hubble to take a picture of the Moon. Surely that’s way beneath its capabilities.
Well, it turns out Hubble can’t take a picture of the Moon, because it has too small field of view. In fact, they tried to make a picture of the Moon. It took them many, many days; and this is how much of the Moon they were able to cover. Because Hubble has a tiny field of view, and we know Hubble’s great. So, that’s what Hubble saw. A beautiful picture of a tiny part of the Moon. But you can see that if you want to take image of the whole moon, let alone the whole sky, you would need to build an entirely different type of camera than ones we’re used to building. So, that’s problem number one.
So, OK, let’s suppose you’ve built some amazing camera that can do a lot better than Hubble, and it can see the whole moon. So, if you’ve done that, you’ve got a new problem. And that’s that you are going to be generating a lot of data. So data isn’t such a big deal anymore. We’re pretty blasé about data. I’m sure many of you have iPods. And a 160-gig iPod, the biggest one you can get right now, well, 160 gigs is an insane amount of data – thousands and thousands and thousands of songs. Not many people have a music collection big enough to fill up an iPod.
But let’s consider if you’ve built one of these cameras that can look at the whole sky, how much data you would generate. Well, let’s consider how much data you would generate in the first second. OK, well, you’d certainly fill up one iPod in the first second. You would easily fill up 10 iPods. Well, it turns out that in the first second you would fill up 500 160GB iPods. That’s after one second. Imagine how much data you would accrue if you used this telescope to look at the sky all night or maybe all year.
So, even if you could build a telescope to look at the whole sky, we simply don’t have hard drives that are big enough or fast enough to store the data. We have to have a new way of dealing with this incredible torrent of information that would be coming in from the whole sky relentlessly before we even had time to even think about what to do with it. So, let’s suppose you’ve solved this problem too. You’ve got your amazing telescope, and you’ve somehow dealt with the endless iPod problem, and you’re somehow saving all the data somewhere. So, now you have this incredible dataset.
So, how does a scientist look at this data and make sense of it? This is the ultimate needle in the haystack problem. Somewhere in your dataset is the answer you’re seeking. Unless you know where to look, you’re simply not got going to find it. Here’s a sort of simulated dataset that we might get from one of these new telescopes, and there is some subtle answer buried in it. But unless you know where to look, you’re not even going to know where to start. So, these are three questions about astronomy and three big problems that we need to solve if we want to build the telescopes. But what’s really exciting is that here in Australia, we are about to turn on telescopes that can solve all of these problems, and that can answer all these questions. For example, I talked about this problem of needing new cameras that can look at the whole sky.