On 9/15/2011 5:17 PM, meekerdb wrote:
On 9/15/2011 1:42 PM, Stephen P. King wrote:
On 9/14/2011 9:49 PM, meekerdb wrote:
Ummm, really? Let me see if I understand this claim, no
physicist believes that General Relativity (GR) is valid or no
physicists believe that there are solutions to the field equations of
GR that are invalid? What about Roger Penrose and Stephen Hawking?
They wrote the paper that showed a proof that the field equations of
GR generate singularities for relatively innocuous and plausible
conditions and yet they are still great proponents of GR. So... what
is the source of your opinion re "no physicist believes ..."?
On the contrary, the singularity is in the description. Which is
why no physicist believes the description (General Relativity) is
The importance of their paper was that it showed GR predicted a
singularity under very general conditions. Before that,it had been
widely assumed that the singularity prediction was just an artifact of
assuming perfectly spherical 3-geometry with no rotation. Of course I
can't really vouch for what every physicist ever believed. But I was
in graduate school at the time studying GR and nobody I knew,
including Penrose whom I met and my fellow students, drew any
conclusion except that GR breaks down and does not apply in those
circumstances. And no one was surprised by this. There was already
an active search for a quantum theory of gravity, which it was assumed
would avoid singularities.
AH! I understand and agree with you then. But we have to deal with
the observational evidence that space-time is smooth down below scales
that most forms of quantum gravity theories, loop quantum gravity for
example, predict a granularity or foam or some other form of
discontinuity. AFAIK the only way to fix the singularity problem of GR
is to introduce a cut-off scale/energy at which curvature (or the
source) can exist. I am aware of a few ideas that do this but none that
are widely studied.
It is my suspicion that GR is a theory that need to be examined as
to its tacit assumptions. While it is beautiful and amazingly
predictive, the singularity problem (and the hole problem, to mention
some others) point to a need for reconsideration of its fundamental
ontological assumptions. It seems to me that GR might be better
considered as a theory that relates the observations of multiple
observers with each other and not a theory of space-time per se.
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