Re: Echo time in Schwarzschild coordinates/metric

Edward Green wrote:
A very simple question:

Suppose, static at a partcular r in Schwarzschild coordinates (in the
Schwarzschild metric, of course) I sent a laser pulse radially inward
to a mirror 1 meter away (as measured by my meter stick). How do I
calculate the time to return by my local clock?

Since I use local clocks and meter sticks, I'm tempted so say "2/c".
But are any subtleties introduced by the fact that I am using
non-inertial coordinates and measuring in the direction of
acceleration? What is the order of the correction, if any?

xxein: Suppose r was 2M!

Yes, there are subtleties involved exactly because the light will
travel through many different inertial frames that are the local limits
only derived from the larger dynamic. Each one is slightly different
wrt OWLS --- but taken as inertial, TWLS allows a correspondence such
as Lorentz and Einstein speculate to great accuracy.

Iow , the frames have to be infinitesimal in size to exactly mimic the
coordinate transform. But we allow a sloppiness of our measurements to
follow the universe's act. Yet, and still, we use a different brand of
thinking to realise a gravity (why it is there and how it affects).

Our physics is sad until it finds out what gravity exactly is.

Yes, we have a supposed metric that is supposed to describe motion wrt
mass, but even that runs across limits where the crossing is undefined.
All one has to imagine is the variable value of c across different
FORs with a moving gravity (non-linear background). Again - if r was
2M?

I don't like to say this but I have to. Even with two fairly simple
ingredients (mass and energy), there is no predictable outcome for a
final product - ever. Nor is there a beginning set. If you would like
to imagine no end to existence, why would there have to be a beginning
of one?

Our universe runs the scope of infinitesimal to infinity - even from
our viewpoint. Yet we self-impose a coarseness to this structure to
comply to only what we can and have observed. Why? Because that is
all we have to work with. We supply limits where there might not be
and disallow extensions where there could be. Why? Because we don't
think the way the universe operates.

Why does gravity exist in the sense of the universe operation? Until
you get a good handle on that, all is just human contrivance. Just the
way we make a test-theory of how things work.

I don't think this was posted. Please forgive a repeat.

.

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