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Vendredi, 07 Octobre 2011 22:07

How a Physicist Sees the Universe: Messy and Sublime

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How a Physicist Sees the Universe: Messy and Sublime

Theoretical physicist Lisa Randall thinks about many things. Not just particle physics and cosmology, which are her forte, but also about the process of science, the nature of risk and uncertainty and even the approach that art and religion take to understanding the world.

In her latest book, Knocking on Heaven’s Door: How Physics and Scientific Thinking Illuminate the Universe and the Modern World, Randall writes about some of the most important scientific quests of today: the search for the Higgs boson, unraveling the mystery of dark matter and dark energy, and the possibility of discovering new physics at CERN’s Large Hadron Collider. Expanding beyond this scope, though, she also presents a scientists’ take on topics ranging from the recent financial crisis to the role of asymmetry in art.

Wired recently sat down with Randall to talk about her view of the universe.

Wired: Your book seems to be mainly about two things: the current state of particle physics and the process of science. Why did you choose to write on these two topics together?

Lisa Randall: Firstly, I didn’t want to just do what I had done in my previous book, Warped Passages: Unraveling the Mysteries of the Universe’s Hidden Dimensions; I wanted to do something interesting that was different.

So really the seed for the book was to go into this idea of the nature of science. I think it’s an interesting story just how science is done, and I think that process tends to get oversimplified and overstated a lot of the time.

Having decided to do that, I thought I should round it with actual science. So I also write about the current state of particle physics and the Large Hadron Collider. People can get so caught up in thinking, you know, this is all so abstract but I think it’s important to understand that there are concrete testable results.

Wired: You write that the process of science can be complicated and messy. Why do you think it’s important for readers to know that?

Randall: There can sometimes be this fear among laypeople: I don’t understand everything in science perfectly so I just can’t say anything about it. I think it’s good to know that we scientists are also confused some of the time. This way we can invite others in. They can participate in understanding, and apply scientific methods to other contexts in their lives.

The process of science is difficult and challenging. It involves always being aware that your ideas might be right or they might be wrong. I think it’s that kind of balance that makes science so interesting. I mean, if we had all the answers already, that would be a lot less exciting as a research field.

Wired: Speaking of challenges, there was coincidentally a large news story the week your book came out about faster-than-light neutrinos.

Randall: I think it was a really great example of how the process of science works. You have this solid ground that you really understand but then sometimes you find these little holes that might actually reveal whole new worlds that lie underneath. I mean, for various reasons I think this [faster-than-light neutrino] result will go away. But I don’t think it was wrong to present it, and it wasn’t wrong to try and find out if it was right.

And what’s really important to remember is that new results don’t always make the old theory wrong. This is a really important and basic concept that’s often misunderstood. A lot of people are very critical here. They say, “Why are you doing science if you’re just going to find out it’s all wrong anyway?” But that’s just not how it works.

Even if the results turn out to be true, it would tell us that Einstein’s theory is still right over a large regime. But we would then know that there are some deeper underlying differences that apply when you do these extremely precise measurements. Usually, when a new theory is shown to be right, it simply underlies the old one, which is now an approximation. It doesn’t mean we need to throw away the old theory.

Wired: You write about risk and uncertainty from a scientific perspective: How can people apply these ideas in their lives?

Randall: One example from the recent financial crisis was when bankers and economists were evaluating risk. They allowed for some variation in how the economy would grow, and maybe they even thought it could go down a little bit. But they didn’t account for the possibility that it could go down by as much as it did. Now I would say it was clear that the previous decade was a bit anomalous. So you might want to allow for this variation, account for your uncertainties and then evaluate your risk within that context.

Another point to look at is scale. When we evaluate risk, why do so many people get so many different answers? Well, Goldman-Sachs might be evaluating risk for them, while the US government might want to know what is the risk to the economy as a whole. And I might want to know what is the risk to my pension fund. Those are different questions and they are over different timescales. I think for these problems it can help to understand how a scientist would approach them, looking at them with rational critical reasoning over different scales.

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