On 7/31/2014 11:27 AM, John Clark wrote:
On Wed, Jul 30, 2014 at 7:57 PM, LizR <[email protected]
<mailto:[email protected]>> wrote:
> if space-time isn't an infinitely divisible continuum, it presumably has
some sort
of granularity,
Our quantum theories may need work. Quantum theories of Physics insist that space is
quantized just like everything else,
I don't think that's true. In fact all quantum field theories assume a
continous spacetime.
that is to say space can not be continuous but must be grainy and the lumps in space
must be as large or larger than the Planck Length of 1.62*10^-35 of a meter because size
is meaningless in quantum theories if things are smaller than that.
It is the smallest size that could in principle be measured *assuming a classical theory
of gravity*. To measure something smaller would take a photon of such short wavelength it
would form a black hole - but all this is assuming that the formation of such small black
holes still obeys the classical equations of GR. And it's significance is not clear,
since QM already assumes a continuum with no such limit.
But now to everybody's surprise there is experimental evidence that seems to say that if
space is quantized at all then the lumps must be smaller than 10^-48 of a meter; that's
at least ten thousand billion times smaller than the Planck Length, the smallest size
previously thought to exist and it makes one wonder if the smallest possible size is
actually zero.
The paper I cited, arXiv:1109.5191v2 [astro-ph.CO] 18 Apr 2012, says
"In the context of quantum gravity, our bounds set M1c2 greater than 525 times the Planck
mass,
suggesting that spacetime is smooth at energies near and slightly above the Planck mass."
Which corresponds to the granularity being smaller than the Planck length by a factor of
1/525.
The 10^-13 factor comes from a paper testing for birefringence, i.e. chiral asymmetry,
which is different from spatial granularity.
http://journals.aps.org.proxy.library.ucsb.edu:2048/prd/pdf/10.1103/PhysRevD.83.121301
Brent
For more see:
http://www.physorg.com/news/2011-06-physics-einstein.html
John K Clark
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