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We shouldn鈥檛 be obsessed with finding a theory of everything, says Lisa Randall, one of the world鈥檚 most prominent theoretical physicists

Doesn鈥檛 every physicist dream of one neat theory of everything?
There are lots of physicists! I don鈥檛 think about a theory of everything when I do my research. And even if we knew the ultimate underlying theory, how are you going to explain the fact that we鈥檙e sitting here? Solving string theory won鈥檛 tell us how humanity was born.

So is a theory of everything a myth?
It鈥檚 not that it鈥檚 a fallacy. It鈥檚 one objective that will inspire progress. I just think the idea that we will ever get there is a little bit challenging.

But isn鈥檛 beautiful mathematics supposed to lead us to the truth?
You have to be careful when you use beauty as a guide. There are many theories people didn鈥檛 think were beautiful at the time, but did find beautiful later 鈥� and vice versa. I think simplicity is a good guide: the more economical a theory, the better.

Is it a problem, then, that our best theories of particle physics and cosmology are so messy?
We鈥檙e trying to describe the universe from 10²⁷ metres down to 10^-35 metres, so it鈥檚 not surprising there are lots of ingredients. The idea that the stuff we鈥檙e made of should be everything seems quite preposterous. Dark matter and dark energy 鈥� these are not crazy ingredients we鈥檙e adding.

Did the discovery of the Higgs boson 鈥� the 鈥渕issing ingredient鈥� of particle physics 鈥� take you by surprise last July?
I was surprised that the Large Hadron Collider experiments reached that landmark. I thought the teams would say something very affirming but the announcement of the discovery was amazing. It was a feat of engineering that they got the collision rate up to what it had to be, and the experiments did a better job at analysing the data.

Are you worried that the Higgs is the only discovery so far at the LHC?
I鈥檓 not worried that nothing else exists. But I am worried that the LHC might have too low an energy. Had the Superconducting Super Collider been built in Texas, it would have had almost three times the energy. There is a distinct possibility we鈥檒l discover things when the LHC鈥檚 energy is nearly doubled next year. But it鈥檚 too early to see signs of warped extra dimensions 鈥� they will take longer to find.

What would an extra dimension look like?
The best signature of the warped extra dimensions would be seeing a so-called Kaluza-Klein particle. These are partners of the particles that we know about but they get their momentum from extra dimensions. They would look to us like heavy particles with properties similar to the ones we know, but with bigger masses.

What if we don鈥檛 see one? Some argue that seeing nothing else at the LHC would be best, as it would motivate new ideas.
I don鈥檛 know what dream world they are living in. It would be very hard to make the argument to build a higher energy machine based on the fact that you didn鈥檛 see something.