On 3/26/2019 6:14 AM, [email protected] wrote:
On Tuesday, March 26, 2019 at 6:28:18 AM UTC-6, John Clark wrote:
On Tue, Mar 26, 2019 at 4:40 AM <[email protected]
<javascript:>> wrote:
>>>Einstein never said everything is relative. Unlike
velocity there is such a thing as absolute
acceleration, if that were not true the Twin Paradox
could not be resolved.
/>> But in GR don't the field equations take the same form
in all frames, including accelerating frames, which if I
understand correctly,* IS* the Principle of Relativity?
TIA, AG/
*> Clark, how about an answer?*
*Sir yes sir!* Saying the field equations are the same form in all
reference frames is just another way of saying the fundamental
laws of physics are the same everywhere, and if they weren't the
same everywhere General Relativity would be a very bad theory. It
took Einstein 10 years to find equations that fit these invariant
requirements so that in every reference frame the spacetime
distance between 2 events is the same, and in every reference
frame absolute acceleration exists but absolute motion does not,
and every frame is accelerating except for one moving through flat
spacetime (aka a zero gravitational field) in a straight path, and
for every curved spacetime path there must be a force being
applied unless that particular spacetime curve happens to be a
geodesic.
John K Clark
*TY! But what still puzzles me is that, according to Brent, there is
no general transformation from one accelerating frame to another
accelerating frame (only a local LT). So, although the field equations
are claimed to be the same in all frames, accelerating or not, how
does one prove that without applying a general (non existent!)
transformation? TIA, AG
*
Look at Appendix C of this very nice paper arXiv:physics/9710036v1 It
derives the covariant equations for the field of an arbitrarily moving
charge.
Brent
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