杏吧原创

Imagining the fourth, fifth and higher dimensions has amused mathematicians
since at least the 19th century. It became a popular pursuit after 1884, when
Edwin A. Abbott wrote his bestseller Flatland. The protagonist, A. Square, is
taken from his two-dimensional world by a passing sphere, and shown the wonders
of 鈥渢hree-space鈥� and the poverty of one and zero-dimensional universes. He goes
on to imagine spaces of even higher dimension, as strange to us as three-space
is to Flatlanders.

For A. Square, these higher planes remained pure speculation, but we might
just be luckier. Physicists commonly use extra dimensions in their theories,
even if they haven鈥檛 always been a very appealing playground. One leading
attempt to unify the forces of nature is string theory, which has six or seven
extra space dimensions. But they are unimaginably tiny. Where鈥檚 the fun in
exploring a territory that鈥檚 only 10^-35 metres across?

Then in 1998, three physicists found a more promising kind of hyperspace.
They suggested that two or more of string theory鈥檚 extra dimensions might be far
larger鈥攋ust so long as these dimensions are barred to every force except
gravity. They could even be infinitely large.

This opening up of hyperspace has prompted a gold rush in theoretical
physics. The glittering prizes on offer are the origin of planets and the birth
of universes; dark matter, antigravity and the power to create black holes.

If you鈥檙e ready to join in, just set your course at a right angle to reality . . .