On 5/27/2025 1:22 PM, Alan Grayson wrote:
On Tuesday, May 27, 2025 at 12:37:00 PM UTC-6 Brent Meeker wrote:
On 5/26/2025 10:16 PM, Alan Grayson wrote:
On Monday, May 26, 2025 at 11:07:03 PM UTC-6 Brent Meeker wrote:
On 5/26/2025 9:29 PM, Alan Grayson wrote:
On Monday, May 26, 2025 at 7:44:59 PM UTC-6 Brent Meeker wrote:
On 5/26/2025 2:51 PM, Alan Grayson wrote:
On Monday, May 26, 2025 at 5:57:36 AM UTC-6 John Clark
wrote:
On Sun, May 25, 2025 at 3:33 PM Alan Grayson
<[email protected]> wrote:
/> I'm disagreeing with anyone, including you,
who thinks the EP is an absolute, when in fact
it's a relative, an approximation./
The Equivalence Principle, which is the foundation
of General Relativity, states that at sufficiently
small scales there is no way to tell the difference
between a gravitational field and a simple
acceleration. And it is not an approximation. But
is it always correct? That is not certain because
General Relativity does not take Quantum Mechanics
into account, nevertheless so far at least the
Equivalence Principle has easily passed every
experimental test put to it.
*Since the EP depends on measurement accuracy, it's
mischaracterized as some absolute principle. That's
pretty obvious regardless of contrary opinions,
including Einstein's. AG
*
It was just an inspiring idea that Einstein had. It
didn't need to have three digit accuracy.
Brent
*Sure, but inspiring how, in what way? No one seems able to
put some beef on this. AG
*
He saw that gravity didn't need to be treated as a force, it
could be treated as force-free motion in non-flat spacetime.
This explained why all objects, whatever the material, fall
with the same acceleration, something already determined
experimentally by Baron von Etvos. It's sometimes referred
to as inertial mass = gravitational mass.
Brent
*Interesting, TY, but does GR explain the acceleration? AG*
I just wrote, "This explained why all objects, whatever the
material, fall with the same acceleration,.."
Brent
*Change in position must occur because (I conjecture) geodesic motion
depends on time, which is always incrementing. Doesn't this imply that
every test particle has its own clock, *
Right
*or there's a universal clock which every particle can read? *
One uses a t coordinate which is just to label events, as do x, y, and
z But it's not necessarily anyone's time.
*And why does acceleration exist; because the velocity vector changes
direction due to the curvature of spacetime? TY, AG*
Following a geodesic, /force-free/ motion, is not acceleration in
general relativity. It is an extremal path, one of maximum proper
time. The four-velocity changes both direction and magnitude, due the
curvature of spacetime.
Brent
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