James Peebles


“Wonderful – Yes! Fascinating – Yes! Eager to know more – Absolutely!”

Telephone interview with James Peebles following the announcement of the 2019 Nobel Prize in Physics, 8 October 2019. The interviewer is Adam Smith, Chief Scientific Officer of Nobel Media.

James Peebles’ romantic dream is that we will be surprised once again in our search for the missing mass of the universe. He reflects on cosmologists’ connection with explorers and the constant interplay between observation and theory. He spoke to Adam Smith by telephone, early on the morning of 8 October , having just heard the news that he had been awarded the 2019 Nobel Prize in Physics.

Interview transcript

James Peebles: Hello.

Adam Smith: Hello, my name is Adam Smith. Many congratulations on the award.

JP: Thank you.

AS: You are of course a cosmologist, but I suppose you are also an explorer, an explorer of the universe. Does it feel as if you’re an explorer with your mind?

JP: Oh yes. We think, we ask ourselves questions, some of us start computing, others start measuring. It is an exploration of course. Very different from exploring far reaches of the Earth, but explore in so many ways.

AS: You mention that interplay between observation and theory. That is very important, isn’t it?

JP: It certainly is. We must always bear that in mind. It’s so easy … well, I will make a small sermon … it is so easy for us theorists who build wonderful castles, beautiful ideas. Sometimes, it is remarkable, sometimes these beautiful ideas prove to be close to what the observations tell us. But often and also they turn out to be wrong. No great surprise, but time will tell, and it is the measurements that tell us. Of course we must bear in mind that measurements without theory are equally empty. It’s stamp collecting.

AS: It’s a great joint enterprise.

JP: That is the whole point.

AS: And of course you’ve been instrumental, as the committee said, in changing cosmology from, in their words, speculation to science. One of the results has been your discovery that we don’t know what most of the universe is made of.

JP: Yes.

AS: May I ask, would you hazard a guess as to when, how, or indeed if, we’ll know what it is made of?

JP: One of the wonderful things about this exploration is that of course we don’t know what we will see. And it is true here. I hope that we will be surprised by what is found to be the nature of the dark matter. It might be something that has already been considered seriously. If so, the demonstration will be a detection, perhaps in the laboratory. There are remarkably sensitive experiments now hoping to detect the interaction of dark matter with ordinary matter. It might be through its annihilation that releases energy that can be detected as radiation. But my romantic dream – I guess I am romantic about these things – my romantic dream is that we will be surprised yet once again. I’m hoping that will be the case. And so I cannot tell you at all how it will be discovered that we know what the dark matter is. It will have to appear.

AS: That was beautifully said, yes, and I like the idea that one doesn’t know where one needs to look. It could be in the laboratory, it could be out in space. One just has to keep looking.

JP: That is very appropriate, you don’t know where to look. It means that these beautiful experiments to detect dark matter must decide on a direction and then work exceedingly hard over many years to explore in that direction. It takes a tough mind to do that because you consider that they might be looking in the wrong place. I mean that in no way to be a negative statement – I deeply admire the people who are doing these experiments to detect, one way or another, to detect the dark matter – but they know, and they are resigned to the fact, that they don’t know where to look. So they choose a direction, you make that tough decision and you work hard at it.

AS: Do you ever find it overwhelming, all this mystery?

JP: No, no, no. Overwhelming? No, no, that has never come to my mind. Wonderful? Yes. Fascinating? Yes. Eager to know more? Absolutely.

AS: I so much look forward to speaking more when you come to Stockholm in December. It’s very exciting news.

JP: [Laughs] It is indeed, we are excited.

AS: Thank you, thank you very much indeed. It was a huge pleasure speaking to you and we look forward to meeting you in December.

JP: You’re very welcome.

AS: Thank you, bye bye.

JP: Goodbye.


To cite this section
MLA style: James Peebles – Interview. NobelPrize.org. Nobel Media AB 2019. Mon. 21 Oct 2019. <https://www.nobelprize.org/prizes/physics/2019/peebles/interview/>

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