Re: How can the Planck length be claimed to be the smallest length?

On 8 Mai, 17:44, "Chris H. Fleming" <chris_h_flem...@xxxxxxxxx> wrote:

If gravity quantizes around the planck scale, then below that scale
one does not have the convenience of a classical metric. Without a
metric, how do you define length?

If one takes 10^24 atoms of silicon in a single
crystal (around 1 kg)
it is undisputed that the whole object has a
measureable gravitational length.
The crystal bends space-time around it and attracts
other masses;
that is easy to measure. And there is a definite
metric in our environment.

It is also undisputed that all atom masses
in the crystal essentially add up
(the crystal binding energy can be neglected here).
Since the gravitational length of the silicon
crystal is defined as R=2GM/c^2,
it is very hard to avoid saying that every silicon atom
has a gravitational length given by the
same formula, this time using the atomic mass.

However, the gravitational length calculated
in this way for one atom is much smaller
than the Planck length. (about 10^18 times smaller).

So it does seem that much smaller lengths than a Planck
length have a physical meaning...

John


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