Re: I'm sure this is a silly question

In article <1140313394@xxxxxxxxx>, throopw@xxxxxxxxx (Wayne Throop)
wrote:

:: David Mitchell <david@xxxxxxxxxxxxxxxxxxxx>
:: Given that it's canon that particles appear and disappear from the
:: "quantum foam", all the time, (with a nod to Heisenberg so that they
:: Don't Really Count), and that gravity is always positive.
:: What happens to the mass of all those particles? IOW, pick a point,
:: any point, draw a line in any direction to the edge of the universe.
:: Along that line there are particles appearing and disappearing all
:: the time.
:: So why don't we notice the mass of all those particles? Is it that
:: they cancel out? Or that they are only around for so short a time
:: that they don't count? Or am I missing the point?

: Aaron Bergman <abergman@xxxxxxxxxxxxxxxxxx>
: You've basically discovered the cosmological constant problem.

Are you sure you don't mean he discovered the "where's the
mass of all the zero point energy" problem? Or something?
Or are they the same problem?

I'm interpreting somewhat loosely, but pretty much, they're the same
thing. Energy is what gravitation (more properly, stress-energy), so
that's the real issue.

it's not clear
it'd produce a gravitational interaction at all; we're down at the
planck scale, so we're not talking the classical approximation
of general relativity.

Well, that's certainly part of the problem. We don't have a fully worked
out theory of quantum gravity, so the answer could be hiding somewhere
in there. The problem is that that should only matter up at the planck
scale and it looks like there is plenty of stuff happening at
intermediate scales that contribute to the vacuum energy. In other
words, your theory of quantum gravity either has to do a fine tuning to
an amazing degree of accuracy to get the small but nonzero value we
observe, or it has to violate the idea that we can understand long
distance things independent of what happens at very short distances.

Aaron
.

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