FAQ 2 - Aren't there really only 3 (or 4) dimensions?

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2. Aren't there really only 3 (or 4) dimensions and the rest is unproven?

The traditional viewpoint has been that there are three dimensions of space, and that time is not a full dimension but rather a quality which gets overlaid upon our 3D space. Some accept that spacetime can be thought of as four dimensional but that is far as they will go, there are no dimensions beyond spacetime.

Books like Lee Smolin's "The Trouble With Physics" have stated that the study of string theory (and its extra dimensions) became so prevalent that it was at the expense of other avenues of study that didn't require the existence of higher dimensions. In the past year, with Smolin's book and Peter Woit's "Not Even Wrong" catching the imagination of the mainstream press, it became fashionable to dismiss any higher dimensional theories as being nothing more than mathematical self-indulgence. That pendulum is swinging more to the center where it should be now.

Which is not to say that the idea of extra dimensions being unnecessary has gone away, but rather that areas of research that do and do not require their existence are now being pursued somewhat more equitably. While thinking of spacetime as being fourth-dimensional has support within the scientific community, the hunt currently continues for incontrovertible proof of any extra dimensions beyond four. One of the more interesting possibilities is the recent discovery of a void 1 billion light years across that contains almost no stars, galaxies, or dark matter: some scientists are proposing this could be the evidence of our universe colliding with another, an event which could be proof of extra dimensions, which also ties to the string theory idea that there could be ten to the power of five hundred universes within the multiverse.

For the general public, it's easy to understand why extra dimensions are questioned - we can't see them, they don't affect us, why should we believe they exist? Here are some of the blog entries discussing extra dimensions and their possible existence:

What's Around the Corner?
Time is a Direction
Hypercubes and Plato's Cave
Why Do We Need More Than 3 Dimensions?
Dr. Mel's 4D Glasses
Information Equals Reality
Scrambled Eggs
Aren't There Really 11 Dimensions?
Are We a 3D Sphere on a 4D Hypersphere?
Strength of Gravity, Speed of Light
Finite But Unbounded?