Re: GPS CLOCK PARADOX

In sci.physics.relativity, Jeckyl
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wrote
on Wed, 30 Jan 2008 21:28:28 +1100
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"Ockham" <my@xxxxxxxxxxxxxxxxxx> wrote in message
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"snapdragon31" <snapdragon31@xxxxxxxxx> wrote in message
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On Jan 29, 8:54 pm, Randy Poe <poespam-t...@xxxxxxxxx> wrote:
On Jan 29, 8:14 pm, HW@....(Dr. Henri Wilson) wrote:

According to relativists, GPS clocks GAIN 38us per day on the ground
clock.
That is due to two components, 45us for gravity and -7us for relative
speed.

Accordingly, an observer (OO) in GPS orbit would see the GC LOSING 52us
per
day.

After one year, the OO would calculate that the OC was about 19ms ahead
of the
GC.
However, the GO would calculate that his GC was only 13ms behind.

What happens when the clocks are reunited?
Who is right?

Two people drive different routes from city A to
city B. When they are reunited, one odometer reads
220 km and the other reads 230 km. Which one is
right?

- Randy

| According to relativity, both odometer readings are wrong. They do
| not represent the true distance of the routes travelled because of the
| length contraction effect.
| According to Newton's law, both odometer readings are right.

| The GPS clock paradox is a variation of the twin paradox, so no valid
| solution.

The paradox resides in the third postulate.

Androcles .. we've told you .. there is no third postulate

Yes there is; it's not usually expressed as a postulate, but
it is a simple one:

- If a TWLS be conducted between a source and a moving mirror,
then the time taken (as observed by the source) of the
light beam from source to mirror and back to source is
exactly twice that of the time taken from source to
mirror. In other words, t_AB = t_BA.

There's no elegant method by which to verify this postulate
experimentally, as the source cannot directly observe the
light returning without the light returning, which takes
the rest of the time, and the moving mirror cannot observe
the source emission at all, until t_AB is already past.
Therefore, this is an assumption, albeit a very reasonable
one.

Besides, as Ockham should well know by now, if the light
goes c+v in one direction and c-v in the other, the average
speed thereby is less than c because of a variant of the
"headwind/tailwind" effect; the MMX was designed to measure
that effect (and failed to show any variance).

Also, various other measurable effects are well-documented.
For example, SR postulates changes in wavelength and frequency;
Newton merely postulates changes in frequency.

It is all paradoxical, to be sure -- but there's no real contradiction.


'the "time" required by light to travel from A to B equals
the "time" it requires to travel from B to A' -- Albert Einstein

The time for a signal to get from the satellite to the receiver
does not equal the time for an uplink because the satellite has
moved, obviously.

Indeed .. SR and Einstein agrees with that. Time from A to B for light is
only the same as the time from B to A when A and B both at rest in some
frame of reference (ie they are not moving relative to each other)


B does not have to be at rest. Of course the actual time
at which the ray of light impacts B (and the position
of B at the point of impact) might be a little hard to
specify unless one has an alternate "infinite speed"
particle, which is currently (and probably forever will
be) impossible.

--
#191, ewill3@xxxxxxxxxxxxx
Useless C/C++ Programming Idea #11823822:
signal(SIGKILL, catchkill);

--
Posted via a free Usenet account from http://www.teranews.com

.

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