Here is my understanding based almost entirely on Brian Greene's book, The Elegant Universe.

For Quantum Mechanics and Relativity to be reconcilable there must be a graininess to the Universe, ie, at some small length and short time the Universe must be quantized so that no shorter length or time exists. If true, this would take away the problem of quantum foam - the frothing of time and space that should occur at small distances and
times due to the Uncertainty Principle. This quantum foam is totally inconsistent with Relativity which has no theoretical basis for any lumpiness. In Relativity theory space and time are smooth and continuous down to arbitrarily small dimensions.

This is why there is no good theoretical understanding of the Universe at a very early age - because Quantum Mechanics and Relativity can't agree and yet both are required. Both are required because the Universe was massive, requiring Relativity, and small, requiring Quantum Mechanics.

So the central assumption of String Theory is that there is a lower limit on the size of space and time. This eliminates quantum foam and allows, in principle, the reconciliation of Quantum Mechanics and Relativity. (No one has done it yet by a long stretch.)

So the finding of no such lower limit suggested by the article below is a blow to this hope for the reconciliation of the two.

Larry Edwards

On Monday, March 31, 2003, at 11:01 PM, Todd Duncan wrote:
> Does anyone have any insights about this recent Nature news update on
> observations related to the "graininess" of spacetime?
>
> "Sharp images blur universal picture - Hubble measurements suggests
> Universe isn't as lumpy as it should be."
>
> http://www.nature.com/nsu/030324/030324-13.html
>
> Are the results really as big a concern as they make it sound in the
> article?
>
> Thanks,
> Todd
>
> "We must be the change we wish to see in the world." - Gandhi
>
>
Larry Edwards larryedwards@access4less.net
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