| Topic: |
Science > Physics |
| User: |
"The Ghost In The Machine" |
| Date: |
04 Sep 2005 03:00:04 PM |
| Object: |
Is c really constant in a strong grav field? |
First, a clarification. c is of course always constant in SR.
This is a GR question, and is more of a measurement artifact
than anything else, since one cannot measure speed without
a nonzero distance.
In SR, one can take a rod and timer arrangement, assume space
isotropy, and simply measure lightspeed from any source (a
stationary one is easiest to set up but any source will do if
the detectors can detect it). The arrangement is as follows:
L A B
* --> []-------------[]
\======C======/
A clock C is positioned equally far from A and B, which are two
detectors along a long straight path. The light source L fires
off a ray going through A, then B. The signal path goes LAC and
LABC; this is a strange variant of a two-way light measurement if
one uses light pipes between AC and BC. Since it turns out space
is isotropic anyway this isn't a big issue.
Now assume not SR, but *GR*, and distort local space by
placing the rod vertically in a gravitational field such
as Earth's. For simplicity assume B is sitting on the
ground and AB is pointing straight up at a light source.
The ticks near B will be shorter, as I understand it,
although the calculations are far less straightforward,
especially since the Earth is rotating.
How much of an error is induced by the differences in
tick lengths if one has, say, an AB distance of 100 m?
(Say, along the side of the Empire State building, or
even the Harvard tower.)
Bear in mind that AFAIK instantaneous lightspeed in GR is
still considered a constant c; the problem is similar to
the slope of a tangent along a smooth curve in differential
calculus, versus the slope of a secant.
Also, has anyone measured this error, and how would one easily
calculate it? I'm not all that well-versed in tensors. :-)
TIA
--
#191,
It's still legal to go .sigless.
.
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| User: "tj Frazir" |
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| Title: Re: Is c really constant in a strong grav field? |
04 Sep 2005 05:17:38 PM |
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1 ,, no object is ever moving when it ejects a photon and that point
wount move.
2,,gravity bends light because light remains at c .
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| User: "The Ghost In The Machine" |
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| Title: Re: Is c really constant in a strong grav field? |
04 Sep 2005 07:00:06 PM |
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In sci.physics, tj Frazir
<GravityPhysics@webtv.net>
wrote
on Sun, 4 Sep 2005 18:17:38 -0400
<21095-431B7282-127@storefull-3218.bay.webtv.net>:
1 ,, no object is ever moving when it ejects a photon and that point
wount move.
2,,gravity bends light because light remains at c .
Sorry, not quite the answer I was looking for. :-)
Mind you, since I now know that lambda/lambda_0 = sqrt(1-2GM/(c^2r)),
I might be able to answer my own question.
Or not.
:-)
--
#191,
It's still legal to go .sigless.
.
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| User: "tj Frazir" |
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| Title: Re: Is c really constant in a strong grav field? |
05 Sep 2005 10:24:42 PM |
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Photons fall into the atoms gravity and orbit down to mass at c.
To get out of the exchange with the electron , some of the electrons
energy changes direction because it cant go faster.
The neutron has too much mass at c in orbit .
Th electron can cut accross the nutron orbit and allmost hit the center
of the atom wile in orbit . wile the nuteron as a more round orbit .
The orbits shapes and the mass in orbit ..
like an eliptical orbit between 2 masses due gravity . The orbits are
eliptical and the center of mass is ot at the same point of the atom
that the center of gravity is .
.
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