So. Can we still do science?
Is theoretical physics still possible?
Oh yes, but I really would consider myself an applied mathematician. What I do is old-fashioned applied maths applied to problems: some physics, some engineering, a little bit of biology. Whatever happens to be interesting. Theoretical physics is part of that, and there's a lot to do. What's happened in the past 20 years is that there's a split between string theory, which has gone off into a world of its own, and everything else. The division between string theory and the rest of physics is now wider than the split between string theory and mathematics.
Physicists complain that they can't get funding unless there's a particular application for the work.
A lot of that is still being done. The recent Nobel Prize for the neutrino experiment pleases me very much. It's much more cost effective than building a big accelerator, and it's good to see that being recognised.
In one particular book review from 2004 [the NYRB essays are collected in The Scientist As Rebel], you expressed the reservation with string theory that it isn't measurable. What do you think today?
I would say it's just very good mathematics. Mathematicians love it. It isn't clear string theory applies to the real world, it may or may not. It's quite likely it may turn out to be useful for reasons nobody today can guess.
Well, I have a difficult time with things that aren't measurable or findable being science.
I would say those things aren't science. They don't belong in science. But you can still have interesting speculations that may be useful in unforeseen ways – but if it's not verifiable, it's not what I would consider science.
And it's quite convenient and handy to invent another universe ...
There's no reason other universes shouldn't exist; if they are unobservable, then they don't belong to science.
You have reminded us that science was actually a rebranding exercise for what was known as natural philosophy ...
Yes, William Whewell invented the word science.
Well then, if so much of "science" isn't science, should we go back to calling it "natural philosophy"?
OK, I'm being slightly facetious. Now for my space-mad children's question. They want to get to the stars. So how are we going to get there – what's the best prospect for interstellar travel?
The main point is to leave the energy source behind; don't carry it on the ship. What makes a huge difference if you really want to go fast is have a big laser in space, and ride the beam. The beam will supply the energy and you don't have to carry it with you. It's essentially a public highway system with the laser beam as the highway, and little ships with sails. That works and doesn't involve any new physics – it's just a question of engineering. And you could get up to half the speed of light, and that's much better than you can with any energy source you have with you.
That was proposed by Bob Forward, he worked out the details, and it certainly does work. He called it Starwisp. You're using the speed of light in your favour: you're borrowing the momentum from the light.
How about altering spacetime in front of the ship?
That's ... probably completely unreal.
Finally, what are your views on fusion? Do you see any real progress being made?
I think they made a terrible mistake 50 years ago when they stopped doing science and went to big engineering projects. These big engineering projects are not going to solve the problem, and they've become just a welfare programme for the engineers. You have these big projects, both national and international, that are really a dead end as far as I can see. Even if they're successful, they won't provide energy that's useful and cheap.
But it's not clear when you do science, whether you'll discover anything or not. But that's the only answer.
So with fusion, we should go back to the drawing board?
Yes, and it's not going to solve any problems for the near future.
But I don't think there is a problem in the near future anyway [laughs]. ®
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