Re: Re: C S Lewis


"al" <almond@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:dq2tc4$dqb$1@xxxxxxxxxxxxxxxxxxxxxxx
>
> "Dave" <Nospam@xxxxxxxxxxxxxxxxxxxx> wrote in message
> news:dq1dq9$fou$1@xxxxxxxxxxxxxxxxxxxx
> >

<Snip old history>

> >
> > Your source linked upthread leaves a fair bit to be desired. First off,
> the
> > clock differential between GPS satelites and earth is due to
Gravitational
> > time dialation, not Special Relativistic dialtion, which is what your
page
> > calculates. Secondly, I am curious where that site gets the relative
> > velocity between the earth bound observer and the GPS sattelite, as my
> > understanding is GPS statelites are in geosychronous orbit. Third, even
> by
> > his calculation (which given his other errors, I place no stock in), he
> > finds a microsecond per day difference, which he then handwaves away.
> > However, according to:
> > http://science.nasa.gov/headlines/y2002/08apr_atomicclock.htm a one part
> in
> > 10^12 change is responsible for the 3 meter uncertanty in current GPS
> > systems. One microsecond per day is one part in 10^11, so would result
in
> a
> > 30 meter error! Thats some handwave. Finally, take a good look at that
> > link, when judgeing sources, if my choice is between an organization of
> > scientists responsible for our spaceflight program and some anonymous
> fellow
> > with a msn group and a pet theory, Ill stick with NASA, thank you very
> much.
> >
> > As I recall (and it's been a while) the thought experiment to prove time
> dilation was with a long rod with a light source and reflector at each
end.
> The rod and attachments were travelling at relativistic speeds towards
their
> destination end on. The light flashed at one end and was detected timed
and
> returned by the other. In this way it was inferred that the shortening of
> the rod due to velocity would alter the time.


First, this seems somewhat confused as, as I understand what you are
describing, an observer at one end of the rod would not see time dilation at
the other end of the rod as since the rod is a fixed length, neither end has
a relative velocity with respect to the other. If you want a refresher on
Relativity, both special and general, I highly reccomend the following
collections of links: http://math.ucr.edu/home/baez/relativity.html.

To provide some background from my own understanding: What you are
describing (I believe poorly, but I may be missing what you are saying) is
the Special Relativistic effect. This is the effect that most people have
encounterd in popular books and physics 101 classes. There is also a
General Relativistic effect. Special relativity predicts that inertial
observers travelling with some relative velocity between them will
experience time at different rates. General Relativity predicts that time
progresses slower inside a gravity well.

Both of these effects are in play with GPS. I was wrong above, GPS
satellites are not in geosychonous orbit, so there is a relative velocity
between the observer (reciever) and the clock (satellite), and a StR effect
comes into play. The StR results in the GPS clock running slower than an
earthbound clock. However, the GtR results in the GPS clock running faster,
and is 7 times larger than the StR effect. The net result is that the GPS
clock is running faster than an earthbound clock, and the signal broadcast
from the satellite is configured to adjust for that. The obeserved speed of
the GPS clock agrees with the predictions of Relativity to within the limits
of accuracy of the clock.



.

Relevant Pages

  • Re: Short pulser.
    ... The operation of the GPS sat is set by the DIGITAL DIVIDER in it for the atomic clocks, ... Now lets see how long before this is confirmed, could show up as a change in spectral width from an atomic clock. ... The kinematic correction wins out in this case. ... If you own any relativity books, ...
    (sci.electronics.design)
  • Re: C S Lewis
    ... >>> velocity between the earth bound observer and the GPS sattelite, ... >> dilation was with a long rod with a light source and reflector at each ... Special relativity predicts that inertial ... > between the observer and the clock, ...
    (talk.origins)
  • Re: About the length of the standard meter in Paris on 1 July 1905
    ... Relativity Theory, longer by a very small amount than its length just ... of section 4 he applies it to a clock at the equator and another ... For ANY rod at any place in the ... similar rod at rest in an Earth’s pole, ...
    (sci.physics.relativity)
  • Re: About the length of the standard meter in Paris on 1 July 1905
    ... (just a day after the publication of his first Relativity paper). ... of section 4 he applies it to a clock at the equator and another ... similar rod at rest in an Earth?s pole, ...
    (sci.physics.relativity)
  • Re: C S Lewis
    ... >>> velocity between the earth bound observer and the GPS sattelite, ... >> dilation was with a long rod with a light source and reflector at each ... Special relativity predicts that inertial ... > between the observer and the clock, ...
    (talk.origins)