“I think of it as the accumulated trace of everything”
Transcript of the telephone interview with Dr. John C. Mather immediately following the announcement of the 2006 Nobel Prize in Physics, on 3 October 2006. The interviewer is Adam Smith, Editor-in-Chief of Nobelprize.org.
[John Mather] – Good morning.
[Adam Smith] – Good morning, may I speak to Professor Mather please?
[JM] – This is John Mather, yes.
[AS] – Hello, my name is Adam Smith and I’m calling from the official website of the Nobel Foundation.
[JM] – Oh, yes.
[AS] – I know you’ve just been on the phone to the Royal Academy of Sciences but we have a tradition of recording very brief telephone interviews with Nobel Laureates immediately after they have been informed, so would you mind if I asked you a few, quick questions.
[JM] – No, please do, that’s fine.
[AS] – Thank you. It’s pretty early there, what were you doing when you actually heard the news?
[JM] – Well, I was asleep. I’m just barely waking up. So …
[AS] – I can imagine …
[JM] – I did receive a phone call from the Academy this morning.
[AS] – Must have been quite a surprise.
[JM] – Yes.
[AS] – You and George Smoot have been awarded the prize for your discovery, or rather for the satellite measurements of faint signatures of the early universe left behind in the form of background radiation. Why is it so important to observe this background radiation from space?
[JM] – Well, it really is very difficult to observe it well from the ground. The atmosphere of the earth absorbs the radiation somewhat, and even at wavelengths where the radiation does come through, the atmosphere emits its own radiation, which confuses matters quite a lot. So it really was important to get up into space where it’s cold and quiet.
[AS] – And I gather it took many, many years of work to get up into space with the COBE satellite?
[JM] – Yes, 15 years from proposal to launch and then we operated the satellite for 4 more years, and kept on analyzing data for another several years after that.
[AS] – So you need some considerable patience before you reach your Eureka moment?
[JM] – Yes. Well one suspects, in the beginning, but one doesn’t know, and so extreme care is required, especially for these kinds of things because there’s basically no other way to tell if the equipment got the right answer.
[AS] – And once the data did start flooding in the first key finding was that the cosmic background radiation did indeed display a perfect blackbody radiation spectrum. What does that tell us?
[JM] – Well, it says that the radiation really did come from the big bang. There really is not a good alternative explanation for having such a perfect blackbody spectrum. Many people looked, but no good explanation was found, and so the big bang theory is confirmed by that spectrum.
[AS] – Right. Now what are we actually seeing in the CMB? Is it a snapshot of a particular moment, or rather the accumulated trace of hundreds of thousands of years?
[JM] – Well, I think of it as the accumulated trace of everything. The history is roughly this; the early universe, in the first submicroseconds, was extremely [word inaudible] and all of the cosmic particles, protons, electrons, unstable nuclear particles, neutrinos and photons and background radiation were all hot and were all together. Then, as the universe expanded, progressively each kind either disappeared, because it was unstable, or annihilated some other kind of particle, or did not. But in any case they all cooled down and so the cosmic microwave background radiation is actually a remnant that traces back to those very earliest moments. But we see features of it that were finally set later. For instance, the spectrum that we observed to test the big bang theory could have been modified as late as, say a year after the big bang. And even in most recent times of course things in our own galaxy, and other galaxies, can emit small amounts of radiation that would confuse the measurements.
[AS] – Quite. So presumably all hot bodies are leaving their own, small background signatures?
[JM] – Absolutely. And similarly the spatial distribution, the map that we obtained, that shows the hot and cold spots, that shows the universe as it was approximately 389,000 years after the big bang.
[AS] – That’s very precise. And is there further information hidden in the CMB?
[JM] – Yes, we certainly think so. One of the continuing investigations is to get the polarization of this radiation. The polarization (is expected and some has been measured) tells us already that the first luminous objects after the big bang were quite early, when the universe was less than a 20th of its present size. So that’s already been measured with the WMAP satellite, and much more is thought to be lurking there in the radiation if we could measure even better. Traces from the gravitational waves of the earliest universe, for instance.
[AS] – Right. So increasing precision will yield more data.
[JM] – Yeah.
[AS] – What’s the main challenge to getting that increased precision?
[JM] – Well, it’s extremely carefully done because the signature is extremely faint. The radiation itself is called ‘faint’, but it’s not so faint; it’s about a microwatt per square meter coming to us, you can actually say that. But the spectrum measurement was made to a part in a hundred thousand accuracy and the hot and cold spots are about a part in a hundred thousand. Now this polarization is maybe a hundredth of that, so we’re getting down to signals that are measured in nanoKelvins.
[AS] – And COBE was a NASA project. Is it becoming more of an international effort as time goes on?
[JM] – Well, the European Space Agency is about to launch the Planck mission and maybe they will even make some progress with this polarization question. They certainly will have sensitivity to finer scale features on this guy.
[AS] – I suppose the last question that I wanted to ask was how you intend to celebrate the award of the prize with your team, which I know is very large?
[JM] – Good question. I think I will need to talk to them.
[AS] – That’s fair enough. OK, well many, many congratulations on the award and thank you very much for sparing the time to speak to us.
[JM] – Thank you.
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