Macroscopically, it has 4 very large dimensions which we perceive as 3-space and 1-time. These are bent around in a topology appropriate to the type of universe we live in...either flat, hyperbolic or closed like a sphere. There MAY be a second component to the topology of our universe that enters are the quantum scale. Each point in 4-d space-time is accompanied by a complete 6-dimensional 'thing' which has a topology in these 6 dimensions that is closed or 'compact. The shape of the 6-dimensional subspace is not known, however, physicists seem to think that the symmetries in these subspaces are related to physical relationships that underlie how forces and particles behave, and why they have the properties they do.
Another possibility is provided by 'brane theory' in 1999-2000 suggests that the additional dimensions may be large. With 4 space dimensions, gravity will behave differently at 100 million kilometers. This isn't observed, so we don't live in one of those universes. With two extra, large dimensions to space, gravity looks differently at about one millimeter scale. Physicists are testing for this possibility in 1999-2001. With even more 'large' dimensions, the departures shrink to atom size, then eventually Planck size at 10^-33 centimeters.
Copyright 1997 Dr. Sten Odenwald
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