U.S. Scientists’ Research on Universe Expansion Earns Nobel Nod
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GWEN IFILL: Now our changing understanding of the cosmos and what it has to do with the Nobel Prize in physics.
The prize was awarded to three U.S. scientists today: Brian Schmidt, of Australian National University, Adam Riess of Johns Hopkins University and Saul Perlmutter of the University of California, Berkeley. That research found the universe is expanding at an accelerating rate.
Perlmutter was recently profiled on “Quest,” a science program produced by KQED San Francisco. Here’s part of that story. It’s narrated by Andrea Kissack.
SAUL PERLMUTTER, Lawrence Berkeley National Laboratory: I was one of those kids who always thought that we should know how the world works around us. That — here we live on this Earth and we don’t fall through the floor. And somebody should have given us an owner’s manual about how the whole thing fits together and how you use it.
ANDREA KISSACK: In 1998, Perlmutter was part of one of two teams that discovered the expansion of the universe had started to accelerate seven billion years ago. But what exactly does it mean that the expansion is accelerating?
First, you have to understand the universe is infinite, not an easy concept to grasp.
SAUL PERLMUTTER: Look, you’re not going to be able to picture this very well, but just imagine that you are living here on a galaxy and there’s galaxies forever going that way, and there are galaxies forever going that way, and there are galaxies forever going that way, in all directions. Nothing but galaxies, no end. You can go as far as you want, and you’ll find more and more galaxies.
And just imagine that there’s sort of a typical distance between those galaxies. And the only thing I mean when I’m saying that the universe is expanding is that we’re sort of pumping extra space between the galaxies. And when we say it’s accelerating, we just mean that that extra pumping is happening faster and faster, and the distances are growing bigger and bigger, more and more quickly.
ANDREA KISSACK: So, how did Perlmutter’s team figure out the history of the universe? They did so by looking at the light from supernovae, stars that exploded billions of years ago.
HANNAH SWIFT, physics student: Hey.
SAUL PERLMUTTER: How’s it looking?
HANNAH SWIFT: It’s looking good. We’ve — the weather is good. The telescope has been released and ….
ANDREA KISSACK: Sitting in a room at the Berkeley lab, Perlmutter and physics student Hannah Swift are connected to one of the world’s largest telescopes, the Keck II in Hawaii. The other half of their team is actually in Hawaii.
SAUL PERLMUTTER: What do the odds look like tonight for the weather?
MAN: I think it looks good. I think we’re definitely going to get data.
ANDREA KISSACK: Their plan for the night is to confirm that five supernovae previously identified through another telescope are the Type 1a supernovae they need for their research.
SAUL PERLMUTTER: The Type 1a supernovae explode in a very similar way every time. And so they brighten like fireworks and then fade away, but they reach the same peak brightness.
ANDREA KISSACK: Their predictability makes these exploding stars what researchers call standard candles. Their initial brightness is constant, and it grows fainter with distance. And since researchers know light always travels at 186,000 miles per second, they’re able to calculate how long ago these supernovae exploded.
SAUL PERLMUTTER: When a supernovae explodes, the light starts spreading out in all directions much like the ripples on the water spread out when you drop a pebble into the lake. The, you know, range in which we were studying the supernovae to see the acceleration was so far away that the light was coming towards us from a time where the clouds of gas were coalescing into what became our solar system.
WOMAN: As the star moves away from us, one other thing happens to its light. Because the universe is expanding, the light waves stretch.
SAUL PERLMUTTER: While the light is traveling to us through the universe, the universe is expanding. And everything in the universe that’s not nailed down expands with the universe. And that includes the very wavelengths of the photons of light that are traveling to us from the supernova.
WOMAN: If the object is moving away from the observer, it will appear red. In astronomy, this phenomenon is known as “red shift.” One way to visualize these stretching wavelengths is to look at how waves of sound, which are similar to waves of light, change. Can you hear how the pitch of the honk changed as the sound source moved away from you? This is because its wavelength is stretching. The same happens with supernovae’s light.
SAUL PERLMUTTER: Now with these two ingredients, the brightness of the supernova and how much the light has been shifted towards the red in its appearance, you now can just read off the history of the expansion of the universe because the brightness tells you how far back in time any given supernova event occurred. The red shift, as we call it, tells us how much the universe has expanded since that time.
MAN: (INAUDIBLE) following. I think a little (ph) star (ph) matter explosion when this is complete and look and see what it looks like, and then I’ll abort it, well, depending on what it looks like.
ANDREA KISSACK: But even though astronomers have become the historians of the universe, they can only speculate about what’s causing this stretching.
SAUL PERLMUTTER: One example of a slightly more exotic explanation could be that there’s extra dimensions in the universe beyond the three dimensions that we’re aware of space and the one dimension of time. It’s possible that there are other dimensions that we just don’t usually experience.
Perhaps in some way, we’re limited to the dimensions that we experience, but that other things, like perhaps gravity, could not be limited, and maybe it can seep into one of these extra dimensions. And that would make it look to us as if it was becoming diluted, that you’re having less effective gravity. And perhaps that’s one of the reasons the universe could be accelerating.
ANDREA KISSACK: Or the accelerated expansion could actually be caused by a new form of energy. This dark energy might be the missing force that sheds light on how gravity, the force that works on a large scale, fits in with the forces that bind atomic particles together. Could this undiscovered form of energy be the key to a unified theory of everything?
SAUL PERLMUTTER: You can try out, you know, almost any crazy idea, and that doesn’t mean that any crazy idea will be the right one but it allows you to play a little bit. And then we’re hoping that we’ll get actual measurements that will pin down the theorists to some set of answers that could be possible.
ANDREA KISSACK: Researchers say that the only way to discard the inaccurate hypotheses is to come up with an ever more precise history. This will require observing more supernovae up closer. To do this, Perlmutter’s team designed a satellite that would carry a telescope more powerful than the Hubble into space.
SAUL PERLMUTTER: You can see, you know, hundreds of times more sky at a time. And it’s also designed for just the wavelength range, just the colors where we need to study the supernovae and the other galaxies in order to study dark energy.
ANDREA KISSACK: The design of the supernova accelerator probe — SNAP for short — inspired NASA and the Department of Energy to join in a joint dark energy mission, incorporating ideas from SNAP and other proposals. Scientists expect to have the mission’s final design soon.
So long as dark energy continues to be a mystery, it’s unclear what the future of the universe might be. It could well be that in billions of years, the universe will stretch into nothingness, or the whole thing could reverse and contract into a big collapse.
SAUL PERLMUTTER: In some sense, we may have found just the right spot to come to, so we are at just the right scale to be able to enjoy looking out at the infinite space above us and down into the microscopic world beneath us.
We’re, I think, at just about the right time in history to be able to look back at the early hot, fiery, Big Bang period and project into the future of what we might get to see. In some sense, we’re in a very cozy medium, and I think it’s a nice place to be.