Title: We’re expanding – and accelerating!
Podcaster: Brains Matter
Organization: Brains Matter http://www.brainsmatter.com
Description: There have been multiple theories of the ongoing evolution of the universe. Solid state, the big crunch – but hardly anyone expected the universe to not only expand, but to accelerate in it’s expansion. The Ordinary Guy talks to Dr Brian Schmidt, who explains the discovery, and what this means.
Bio: The Brains Matter podcast has been producing and communicating science stories and interviews since September 2006. The show is based out of Melbourne, Australia, and takes an everyday person’s perspective of science in easy-to-understand language.
Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by the Physics Department at Eastern Illinois University: “Caring faculty guiding students through teaching and research” at www.eiu.edu/~physics/.
G’day everyone – I’m the Ordinary Guy from the Brains Matter podcast. Today is special for two reasons. This podcast is being released on the 24th of May North American Eastern Time, which means that if you’re listening to this more than 6 or so hours after it’s released, it’s the 25th of May Australian Eastern Time. Why is this special? Because it’s my birthday!
The other reason why this podcast is special is because you’re about to find out that not only is the universe expanding, but accelerating in its expansion – I talk to one of the primary researchers who discovered this – Dr Brian Schmidt from the Australian National University.
OG: Firstly, can you tell us a bit about your discovery, and what it means.
Dr Schmidt: Well, the discovery was I think particularly interesting, because it was so unexpected. So I think people had preconceived notions about what the universe might do. I personally aesthetically liked the idea of a universe continually renewing itself through a big bang and a big crunch. But of course, we as scientists need to go out and measure these things. And so the discovery that the universe is speeding up in its expansion, as I say, was a big surprise and I have to admit I personally was in denial when I first saw the results because I figured I must have done something wrong. It is like throwing a ball up into the air and having it take off, and go into outer space. That’s tantamount to what the universe is doing, and that’s why it was so unexpected.
OG: How did you make the discovery?
Dr Schmidt: Starting in 1994, a group – large group of people from around the world, and myself, started a program to observe distant exploding stars. We used distant exploding stars because we can sort of calibrate how many watts they put out just like you have a hundred watt light bulb, you can read the 100 watts on the side of the light bulb – you know how bright it’s going to be – well, we read off the ‘wattage’ of supernovae – these exploding stars we look at, by how fast they rise in brightness and fade. And so that allows us to essentially calibrate how bright they are intrinsically and of course the further away a lightbulb is away from your eye, the fainter it appears. The further away a supernova is away from the Earth, the fainter it appears. So by seeing how bright these things are, knowing how bright they are intrinsically – knowing how many watts they produce, we can gauge how far away they are. Now it turns out, if you see how far away something is, the universe is expanding and so we can see how much the universe has stretched between us and that object so as the object’s light comes towards us, the light gets stretched, and so it becomes redder, so we measure how much the universe stretches – we measure how far away that is, and that tells us the rate of expansion of the universe. It essentially tells us how much the universe is stretching over its time, and so you can imagine it’s like seeing a rubber band being stretched, and we know how far away the ends of the rubber band are, and we can run it backwards and see, you know, how big the universe was in the past – or we can guess what it is.
OG: What could be causing this acceleration?
Dr Schmidt: So, as you said, we expected the universe to be full of matter, and that matter to slow the universe down over time, just like when I throw a ball up into the air, gravity of the Earth slows the ball down. So, seeing the ball take off, or or the universe take off means there has to be something that’s really pushing on the universe – that’s acting the opposite way to the way we think gravity normally works. Well it turns out that Einstein back in 1917 invented what we needed. Einstein seems to have invented a lot of things people need, and this is another example! He invented something he calls “The Cosmological Constant” That’s energy tied to space itself. So as the universe expands, more and more of this “dark energy” as we call it now, the cosmological constant, is created with the expanding space. At any given piece of space, there’s a constant amount of energy so as space gets larger, there’s more energy. Now, according to Einstein’s equations of General Relativity, which he had sort of finished off in 1916, if you solve for the effect of gravity on this dark energy, that is energy tied to space itself, gravity does not attract this stuff – it pushes it away! So the existence of this stuff would cause the universe to be pushed away from itself and lead to it’s acceleration. So Einstein invented that in 1917 because he looked at his equations for General Relativity and he said “Geez, the universe should be contracting or expanding according to my equations – it’s clearly not doing that – I need to invent something” and he said “ah my equations are incomplete – I can add this energy to space and it fixes all my problems” In 1929 when it was realised by Hubble that the universe was expanding, he said that was a mistake. It was claimed by Gamow to say that was his biggest blunder of his life time. Well, Einstein’s biggest blunders are my biggest discoveries!
OG: How do we know it is THAT related to the Cosmological Constant?
Dr Schmidt: So Dark Energy is problematic because it’s whacko right? Making up energy tied to space, and the only easy effect we can see in our universe ’cause it’s very thinly spread – but the universe is a big place so there’s a lot of it – but here in this office for example, there is very little of it, and so very difficult to get your hands on directly. The difficulty we have is the only direct effect that we’ve so far come up with that dark energy has in the observable universe is the acceleration. So that means we need to have a theory that somehow takes this ‘stuff’ and explains it in the bigger picture, and that hasn’t happened yet. So it’s been a problem.
OG: We now know that the universe is expanding at an accelerating rate, what’s that going to mean for us as humans over the next few million years, so as the universe continues to expand at an accelerating rate.
Dr Schmidt: The universe is speeding up and so philosophically, I mean, in terms of what it’s going to do to us as humans – it’s, you know – the effects are measured in billions of years, not millions of years. However, it does provide some interesting food for thought. The universe that we see -it turns out as the universe expands faster and faster. The universe, when we say the universe is expanding, it’s the creation of space and that’s why earlier I was reluctant to use the word Doppler Shift. It’s the actual creation of space. Space can get separated, because there’s no motion involved, faster than the speed of light. So light from galaxies that we observe right now; when we look back at a very distant galaxy we’re looking back in time. And so the most distant galaxies we see right now were – we’re looking back at the universe when it was less than a billion years old – or about 12 and a half billion years in the past. Those galaxies’ light, because of this acceleration, can no longer reach us. So the information from the universe is becoming smaller. Galaxies over time are literally going to fade out from existence, from our ability to see them..
OG: So they’re still there, it’s just that we have no…
Dr Schmidt: They’re beyond the horizon that we can see and that’s because the universe is accelerating – that expansion between two points is faster than the ability of light to go from point A to point B and so things we can see in the past, we will not be able to see in the future. The horizon – the part of space that we can see..
OG: … gets smaller…
Dr Schmidt: … is shrinking right now. As we look forward to time, we will see fewer and fewer galaxies over time. So we always say – I’m a cosmologist – someone that studies the universe, well, now is the time – now is the time to work on cosmology because in the future there will be nothing left to study. All the galaxies that we see will have been pushed beyond our ability to see them, and we’ll be looking into a very, very dark universe.
Thanks for listening – if you’d like to hear more episodes of Brains Matter, please go to http://www.brainsmatter.com.
So it’s goodbye from me, and goodbye from the universe.
Bye for now!
End of podcast:
365 Days of Astronomy
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