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Expanding Universe

Margaret Warner speaks with cosmologist Adam Riess about a new information report which states that the universe is expanding more rapidly now than in past years. By using exploding stars as a tool indicating distance, the discovery was made. The results and what they mean to us is discussed.

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  • ELIZABETH FARNSWORTH:

    Today's issue of the Journal Science reports new information about the evolution of the universe. It is apparently expanding faster now than it did in the past. That's the conclusion of new studies carried out by an international group of astronomers. A lead author of one of the studies was cosmologist Adam Riess of the University of California at Berkeley. And he joins us now. Thanks for being with us.

    ADAM RIESS, University of California, Berkeley: Thank you.

  • ELIZABETH FARNSWORTH:

    What is it that you learned?

  • ADAM RIESS:

    Well, we've been using supernovae, which are exploding stars, and we've been using them as tools, as cosmological indicators of distance.

  • ELIZABETH FARNSWORTH:

    What do you mean, using them?

  • ADAM RIESS:

    Well, we would like to map out the universe. We would like to see how fast it's expanding, but the universe is very dark. And occasionally a supernovae explodes and illuminates a piece of the universe. And while it's lit up, we can use that supernova to measure how fast that piece of the universe is rushing away from us.

  • ELIZABETH FARNSWORTH:

    And so you're looking through the Hubble and other telescopes, right?

  • ADAM RIESS:

    Right.

  • ELIZABETH FARNSWORTH:

    These stars that are exploding billions of light years away.

  • ADAM RIESS:

    That's right.

  • ELIZABETH FARNSWORTH:

    And then what do you do?

  • ADAM RIESS:

    So what we've done is we've used the supernovae to measure how fast the universe is expanding today, and then we found some very distant supernovae, which are about 5 billion light years away, and it's taken the light so long to reach us, that when it does reach us, it tells us how fast the universe was expanding when the light left the supernovae. So, we can use this information to compare the expansion rate of the universe today to the expansion rate about 5 billion years ago.

  • ELIZABETH FARNSWORTH:

    And we should just remind people, a supernovae, it's actually a star that is–it's a huge mass of stars exploding?

  • ADAM RIESS:

    It's a star which has reached the end of its life cycle and can no longer hold itself up under pressure and explodes.

  • ELIZABETH FARNSWORTH:

    Okay. So what are the conclusions you've drawn after looking at this information?

  • ADAM RIESS:

    So, our expectation was that the universe would continue to slow down after expanding. You see, there's gravity in the universe, and everything is pulling on everything else, all the stuff in there, the planets, the stars, and the galaxies. And we thought that this expansion would slow down. What we've actually found is a very strange result, that it's speeding up.

  • ELIZABETH FARNSWORTH:

    And this is–we should just go back to the beginning–this is all–the expansion originated with what people refer to as the "big bang."

  • ADAM RIESS:

    That's right.

  • ELIZABETH FARNSWORTH:

    Right?

  • ADAM RIESS:

    That's right.

  • ELIZABETH FARNSWORTH:

    And so you're finding it's speeding up, and why?

  • ADAM RIESS:

    That's a very good question. As I said, our naive expectation is gravity would cause it to slow down. And the less gravity we have, the less it would slow down. And yet, it should never really speed up unless there's some other force, or some other sort of energy out there, which is acting in the opposite direction of gravity. Now, Albert Einstein had suggested even back in the 1920's that there might be such a force. He called his cosmological constant and described it as a repulsive force, something that goes in the opposite direction of gravity. So, we're trying very hard to figure out what's going on with this data. But the implication seems to be that this cosmological constant, this repulsive force might exist and might actually be pushing the universe out faster, overcoming gravity.

  • ELIZABETH FARNSWORTH:

    Why did some scientists react with what one called amazement and horror to these conclusions? Why was it such a shock to them, or to you?

  • ADAM RIESS:

    Oh, well, it's a very desperate scientist which relies on such outlandish sort of mechanisms to explain their data, so we were hoping we'd find a more simple explanation, something mundane, but–

  • ELIZABETH FARNSWORTH:

    But instead you found a new force in the universe?

  • ADAM RIESS:

    Well, it would appear that way. We've gone down a long laundry list of other possibilities. And, one by one, we've checked them off. And from what we can see, there's really not too much left, besides the possibility of this repulsive force.

  • ELIZABETH FARNSWORTH:

    Okay. Now, put this–give us this in a little bit broader picture so that somebody who has no astronomical knowledge could understand it. How could you explain this in terms that would be easy for me to understand? Is there an analogy that you could use?

  • ADAM RIESS:

    Well, I think the hardest thing for people to understand is what it's like when the universe expands. And I guess a useful analogy would be if you had a loaf of raisin bread and it was rising in the oven and it was getting bigger and doubling every so often, and you were just a raisin in the middle of the raisin bread. And that's us, sitting in the Milky Way Galaxy. All the other galaxies are the other raisins, and as the loaf of bread expands, all the other raisins appear to be rushing away from us. And it's interesting to try to measure at what rate this loaf is doubling in size. That's the expansion rate. You might expect it to just keep expanding at some certain rate, but what we found is the loaf is suddenly getting bigger and bigger at a great speed.

  • ELIZABETH FARNSWORTH:

    And does that mean that the universe could just keep on expanding forever?

  • ADAM RIESS:

    Well, if you take this result at face value, if this is really true, the implication is yes, that the universe would expand forever. And it also allows us to make a pretty good estimate of how old the universe is. We estimate, using this technique, the universe is about 14 billion years old.

  • ELIZABETH FARNSWORTH:

    And that's older than had been thought, right?

  • ADAM RIESS:

    That's right. And if this turns out to be true, it may be a relief to some cosmologists. There was a problem in cosmology known as the age crisis.

  • ELIZABETH FARNSWORTH:

    Remind us what cosmology is.

  • ADAM RIESS:

    Cosmology is the study of the shape, structure, and dynamics of the universe. And there are some stars in the universe which are thought to be about 12 billion years old. And at one time we thought the universe might only be eight or ten billion years old. So it was this kind of strange situation where it's like you're actually older than your mother, and that doesn't seem possible. If this cosmological constant exists, it will also represent a correction to the age of the universe and allow it to be older than some of the oldest objects in it, which doesn't mean this is true, doesn't mean it's right, but it sure would be a relief.

  • ELIZABETH FARNSWORTH:

    Is there a lot of skepticism still about these findings among scientists?

  • ADAM RIESS:

    Oh, yes, I would say so, and I would say that we're very skeptical too. As I said, we'd like to find a more mundane explanation for it. But I think if this isn't right, it's probably something equally as interesting.

  • ELIZABETH FARNSWORTH:

    What do you say to somebody who says, why should I care about this, you know, I'm sitting here, I can see the stars, they look great, why do I care about whether it's expanding quicker now, or whether it's going to end with a bang or a whimper?

  • ADAM RIESS:

    Well, I think people have always been very curious about space and the universe. I think our everyday experience is we look up, we see all the stars, and they just look frozen there, and we would expect the universe is just static, but to learn the universe is actually dynamic, it has a history, it has a start, it has a future, and I think once we come to understand that, we want to know the answers to these questions: When did it start? Why did it start? Where's it going? What's the ultimate fate?

  • ELIZABETH FARNSWORTH:

    And finally, in the few seconds we have left, what kind of studies will end some of the skepticism? Do you have studies underway now?

  • ADAM RIESS:

    There are other groups which have worked to confirm this result, and they have actually confirmed it from this experiment. But, as we often find in science, it may take a completely different experiment, something which has a whole other set of assumptions to confirm this. Probably in about 10 years scientists are going to be studying the cosmic microwave background, which is the radiation left over from the "big bang." And there may be clues in that as to whether there really is this repulsive force.

  • ELIZABETH FARNSWORTH:

    Okay. Well, Adam Riess, thank you very much.

  • ADAM RIESS:

    Thank you.

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