On Sunday, November 11, 2018 at 12:43:27 PM UTC-7, Quadibloc wrote:

On Sunday, November 11, 2018 at 8:36:43 AM UTC-7, Gary Harnagel wrote:

Astronomy and meteorology allow observation under many different
conditions and as time passes, the data mount up. Astronomy is also
aided by controlled physics and chemistry experiments in laboratories
and then ASSUMING that those conditions apply elsewhere. We know
that relativity applies throughout the solar system because we have
actually performed experiments with spacecraft. We ASSUME SR and GR
work all the way back to the Big Bang, but maybe they don't.

Well, for one thing, we can analyze the spectra of light from the stars.
We assume that the same pattern of lines stands for the same element in
a distant star, so we can tell what is in those stars - but the fact
that we _are_ seeing the same patterns of lines indicates that some of
our laws of physics must be working out there.

The fine-structure constant, which got its name from some characteristics
of spectral lines, is a ratio involving the speed of light, the inertial
mass of the electron, and the force exerted by its charge. So those
spectral lines are the result of physics.

So it appears that quantum mechanics is universal. I was referring to
relativity, general specifically. String theorists and Seth Lloyd as
well have shown that the GR field equations can be derived from QM
making certain assumptions. What happens under different assumptions?

And, of course, absent evidence to the contrary, that the laws of physics
are the same elsewhere and in the past is the most reasonable starting
assumption. It can be re-evaluated when we run into trouble.

John Savard

We seem to have run into trouble. We have not found either dark matter or
dark energy in spite of intense efforts in those directions.