Actually, our 'space-time' continuum has 4 dimensions which are the 3- dimensions of normal space plus the 1-dimension of time taken together.
There is no evidence for a 4th spatial dimension in the universe at-large, although some theories in physics suggest that at the quantum-scale, 20 powers of 10 smaller than the nucleus of an atom, space-time might have up to 6 more dimensions, but these are not really like space or time.
Some theories actually say that these extra dimensions could be bigger than atoms. The search for them is now continuing, by looking at how gravity behaves as you look at smaller and smaller scales under laboratory conditions. The results state we do not live in a universe with 4 large space dimensions, but we could live in one with 5 large ones. These other two would only be about a millimeter in size and hard to detect gravitationally.
Copyright 1997 Dr. Sten Odenwald
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