String Theory

The theory holds that reality ultimately consists of sub-microscopic strings whose different possible ways of vibrating are the hidden mechanism behind the many types of particles that make up the universe. But the model works only if one assumes the strings have several extra dimensions of space in which to vibrate, beyond the three familiar dimensions. Thus space itself would contain extra dimensions.

Theorists have traditionally explained the invisibility of the extra dimensions through the rather stupefying idea they are crumpled into tiny balls at each point in space, big enough to affect the strings but not to reveal themselves to us.

String theory has drawbacks, the biggest probably being that many physicists believe it can't be verified by any test. But its explanatory power has kept it alive anyway. It has in fact blossomed into a range of different versions. Complicating the story further, some of these variants have turned out to be alternative ways of saying the same thing.

Of the different variants of string theory under consideration today, some reduce the need for tiny dimensions by providing a new explanation of why some dimensions are invisible. In this proposal, everything we see is trapped in a three-dimensional space, other dimensions being outside this zone.

Our universe is related to the "extra" dimensions much as a two-dimensional surface, or membrane, would be related to a three-dimensional region within which it existed. For this reason, our visible universe in this scenario is called a "brane" (for membrane).

Branes are in fact the counterparts, in higher dimensions, of the "strings."

Clash of the branes

Listen to Richard Dawkins
String theory: From Newton to Einstein and beyond by David Berman
String theory - Physics - From Wikipedia, the free encyclopedia

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