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The search for extra dimensions
Feature: November 2000
The idea that the universe is trapped on a membrane in some high-dimensional space-time may explain why gravity is so weak, and could be tested at high-energy particle accelerators.
The possibility of extra dimensions, beyond the three dimensions of space of our everyday experience, sometimes crops up as a convenient, if rather vague, plot in science fiction. In science, however, the idea of extra dimensions has a rich history, dating back at least as far as the 1920s. Recently there has been a remarkable renaissance in this area due to the work of a number of theoretical physicists. It now seems possible that we, the Earth and, indeed, the entire visible universe are stuck on a membrane in a higher-dimensional space, like dust particles that are trapped on a soap bubble.
In this article we look at the major issues behind this new development. Why, for example, don't we see these extra dimensions? If they exist, how can we detect them? And perhaps the trickiest question of all: how did this fanciful idea come to be considered in the first place?
http://physicsweb.org/articles/world/13/11/9
Some physicists speculate not only that these extra dimensions exist, but also that the number of dimensions could change in time. Perhaps all 10 or 11 dimensions of string theory existed on an equal footing at the time of the big bang; then three spatial dimensions expanded, while 6 shrank. To answer your question, it seems more likely, to physicists, that there were more dimensions than we know of now, at the time of the Big Bang, rather than fewer dimensions.
http://www.fnal.gov/pub/inquiring/quest ... sions.html