The original string theory by Max Green and John Schwarz required 26 dimemsional spacetime, rather than the 4-d spacetime we seemingly exist in, in order for the equations of string theory to not have infinities.

Besides the obnoxiousness of 26 dimensions, what ever happened to the othe 22, that string theory also had vibrations on each string that could travel faster than the speed of light called tachyons.

So finally Green, Schwarz and Witten, who is like the Einstein of our time, developed a 10-d theory using supersymmetry, but which did not have either tachyos or infinities, but which had particles that have never been observed. Some think these supersymmetric partilces are what constitute dark matter. Since then 9-d and 11-d and even 13-d theories have been developed by a host of string physicists.

They use a word, compactification, to explain where all these extra dimensions went to. The shrink to close to planck scale sizes that cannot be observed.

But string theory is not the latest theory or the most fundamental theory.

A more fundamental theory called Loop Quantum Gravity(LQG) removes the assumption that spacetime exists. It merely assumes that something called loops exist and from appropriate mathematical constructions of these loops, loop physicists can derive first spacetime, and then geometry, and now the big bang and inflation of the universe. Presumably it may someday derive even string theory and therefore tell us what all these extra dimensions are about and what the unified field is, and if so, most important how the extra dimensions become invisible.

Richard

• I think they came up with that from hair. - sound1 - October 2, 2003 - 19:19 UTC
  • Hindu scripture says there are 46 million hairs - yanniru - October 3, 2003 - 02:00 UTC
    • Please give the reference. - sound1 - October 3, 2003 - 05:27 UTC
      • Reference - yanniru - October 3, 2003 - 12:54 UTC