Forecasting The Fate Of Mysteries

The LHC is part of an international effort to unlock the secrets of the universe. It cost about $10 billion over four years, which sounds a lot, but which is only 0.005 percent of the world gross domestic product for that period. Can't we afford two hundredths of a percent to understand the universe?

And it is absolutely safe. There has been a scare story that it might create a tiny black hole that would swallow up the Earth. But if the collisions in the LHC produced a micro black hole, and this is unlikely, it would just evaporate away again, producing a characteristic pattern of particles. Collisions at these and greater energies occur millions of times a day in the Earth's atmosphere, and nothing terrible happens. The world will not come to an end when the LHC turns on. The LHC is feeble compared with what goes on in the universe. If a disaster was going to happen, it would have happened already.

Pointing to a future path for physics
Alan Guth, MIT, cosmologist
What we're trying to understand is the first fraction of a second of the history of the universe, and how the evolution that took place then put the universe on the path to become what it is today. Inflationary theory is a twist on the conventional big-bang picture. What changes is our understanding of the history of the universe for a very short period during the first minute. The theory modifies the evolution to include a brief period during which gravity is turned on its head and becomes repulsive instead of attractive. If inflation is right, this short period of repulsive gravity is the actual bang of the big bang, in the sense that it is what propelled the universe into its enormous expansion, which we're still seeing today.

I think many physicists, including me, feel that the direction of physics in the coming years is very uncertain. I'm talking about the actual science, not just the funding. The key shocker for many of us was the discovery about 10 years ago that the universe is accelerating. It was not expected theoretically, at least not by most of us, and it is very hard to understand in the context of the theories that we have been using all these years. The LHC is likely to play a major role in telling us the direction in which we should be moving.

Think of it like the Hubble telescope
Edward Witten, Institute for Advanced Study, string theorist
There's a chance that something would be discovered that wouldn't fit well with any of our ideas. The chance of finding higher dimensions—it's possible, but just barely possible. If everything is lined up exactly right, it's conceivable the LHC could do that. Energy would seem to disappear because the idea is that, when particles have a sufficiently high energy, they can escape into a higher dimensional world. If it's a long shot to get direct evidence for extra dimensions, it's even more of a long shot to get a clear black-hole signature at the LHC.

What the LHC really does is explore the energies at which the nature of the weak interactions can be understood. The important forces of nature are gravity, the nuclear force—also called the strong interactions—electromagnetism and weak interactions, which is probably the least familiar force to those who aren't physicists, responsible for certain forms of atomic radioactivity. The weak interactions are a big piece of the puzzle. They're the least understood because they're so weak. It's very mysterious.

We've already discovered the W and Z particles, which are two important ingredients in weak interactions. Putting together what we already know, we know the energy scale at which the weak-interaction symmetry is broken. And it's definitely in reach of the LHC. In fact, the LHC goes beyond that. That's the big question which I'm sure the LHC will answer.

You should think of the LHC as being something like the Hubble space telescope: it's built to explore the universe and understand it better.

© 2008