Lisa Randall on extra dimensions, the Large Hadron Collider, and weird physics

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Harvard physicist Lisa Randall, author of the mind-bending 2006 book Warped Passages: Unraveling the Mysteries of the Universe's Hidden Dimensions, has a new book out. Knocking on Heaven's Door sounds like an entertaining way to knock you right out of your existing reality tunnel. Smithsonian interviewed Randall:

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There are a lot of bizarre ideas here, from string theory to a "brane" of extra dimensions right next to our own. Why should we regard these ideas as more than fanciful constructs?

I'm certainly not asking anyone to take on faith any of the ideas that I present. That's part of the point of the book: science proceeds, and we systematically end up with new ideas and explanations, going from the human scales we're very familiar with to scales that are so remote it's hard to have intuition about them. Science is a self-correcting process, too, something that I expect will happen with the recent announcement of neutrinos that may move faster than the speed of light.

Can you describe the essence of your idea about extra dimensions?
There could be more to the universe than the three dimensions we are familiar with. They are hidden from us in some way, perhaps because they're tiny or warped. But even if they're invisible, they could affect what we actually observe in the universe. There are lots of things we cannot see with the naked eye that turn out to be based in reality.

Extra dimensions could be relevant to one of the questions we're trying to answer at the (Large Hadron Collider): how particles get their mass, and why they have the masses that they do, which are far smaller than physicists would expect them to be. So our idea is there's an extra dimension that's so warped, the masses would be big in one place and small in another. In other words, gravity could be weaker in one place and stronger in another. If so, it could be a natural explanation both for why particles masses are what they are, and why gravity is so much weaker than the other elementary forces we observe.

This extra dimension could be separated from ours by a million trillion trillionth of a centimeter. Is this a parallel yet inaccessible universe?

It interacts with our dimensions only via gravity. And gravity is extremely weak. An elementary particle at ordinary energies exerts negligible gravitational force. But at the LHC, if this idea is right, we would see evidence of this extra dimension. Particles could carry momentum into the extra dimension, and that could actually be observable.

"Opening Strange Portals in Physics"

Knocking on Heaven's Door: How Physics and Scientific Thinking Illuminate the Universe and the Modern World (Amazon)