On 7/11/2020 9:00 PM, Alan Grayson wrote:
On Saturday, July 11, 2020 at 9:49:31 PM UTC-6, Brent wrote:
On 7/11/2020 8:07 PM, Alan Grayson wrote:
On Saturday, July 11, 2020 at 8:41:21 PM UTC-6, Brent wrote:
On 7/11/2020 4:29 PM, Alan Grayson wrote:
On Saturday, July 11, 2020 at 5:05:02 PM UTC-6, Brent wrote:
On 7/11/2020 12:54 AM, Alan Grayson wrote:
On Tuesday, July 7, 2020 at 10:06:44 PM UTC-6, Alan
Grayson wrote:
On Tuesday, July 7, 2020 at 8:50:50 PM UTC-6, Alan
Grayson wrote:
On Tuesday, July 7, 2020 at 8:05:28 PM UTC-6,
Bruce wrote:
On Wed, Jul 1, 2020 at 4:18 PM Alan Grayson
<[email protected]> wrote:
How, exactly, is the Principle of
Equivalence used by Einstein to develop
GR? TIA, AG
This lecture by Sean Carroll should answer
all your questions:
URL: https://wp.me/p2WMeM-3vl
Bruce
I'll watch it tonight, but I think I've figured
it out; specifically, the EP implies space-time
is curved by the presence of mass/energy (and
this is independent of the need to express the
laws of physics in a coordinate independent way
via tensors). AG
Here's my reasoning regarding the EP; if an
observer is in a box subject to uniform
acceleration, a beam of light starting on the
extreme left side (moving transverse or
perpendicular to the acceleration vector), will hit
a lower point on the right side, showing that
uniform acceleration results in curved paths in
space-time. But if this result is identical to
gravity, locally, it means that curved paths in
space-time are produced by, or are equivalent to
gravity.
That makes no sense. You're saying that because curved
paths can be produced two different ways then they must
always be produced the second way.
BUT gravity is only observed in the presence of
mass/energy. ERGO, the EP implies mass/energy
curves space-time. AG
And that's not even true. Gravitational waves can
propagate thru the vacuum. The Schwarzschild solution
is for empty space. De Sitter space is an empty cosmos.
Light can propagate through empty space, but it can't arise
from nothing. Same presumably for gravitational waves. AG
Are you going to say the same thing about matter? electric
charge?
Brent
I'm not sure what your point is. All I was saying above is that
mass/energy causes curvature of space-time as per the EP. A
gravitational wave moving through empty space seems no different
in principle than light moving through empty space. In both cases
there is a mathematical solution for the wave motion, with the
source of the wave left undefined. But every wave motion must has
a source. AG
And every source must have an origin? There is nothing in the
equations that says there must be a source.
Brent
Can EM waves exist if there are no charges and currents? If you
affirm, has this ever been observed? This result, if it is a result,
is likely an artifact of the mathematics which has no basis in
physical reality. Anyway, are you claiming that spacetime curvature
can exist in the absence of matter/energy? Is this what the EP says? AG
It's what the equations say. So if waves only exist due to matter
sources that's a separate fact, not part of the theory. It seems just
as plausible to me that fields existed first and "stuff" appeared as
quantized waves in the fields.
Brent
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