sci.physics.relativity

On Sep 7, 9:35 pm, bz wrote:
> "Sue..." wrote innews: @ :
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> > On Sep 6, 11:02 am, bz wrote:
> >> meda wrote in news:
> >> @ :
>
> >> > Not true.
> >> > In gravitational time dilation calculations no velocity is involved,
> >> > so the free space does very well constitute an absolute rest frame
> >> > and an absolute time.
>
> >> No. It just means that the formula was derived under conditions of zero
> >> relative velocity.
> >> There are separate formula for time dilation due to relative motion.
> >> If you want the total time dilation, you sum the effects (and must take
> >> into account any changes in g due to the motion, which limits the easy
> >> summation to circular orbits, or those very close thereto).
>
> > If we put a planet near an atomic clock, the clock will slow down.
>
> > If the planet is spinning, are you saying the spin will slow the
> > clock more, or less than, just the presence of the planet?
>
> Depends on how the clock is suspended 'near the planet'.
>
> If you put a planet near an atomic clock, absent a very tall tower or a
> balloon (and a very deep atmosphere), the clock must orbit the planet to
> maintain a constant distance from the planet.
>
> In order to orbit, it must (as far as I know) be in motion.
> Preferably in free fall in a circular orbit.
>
> That implies the clock is moving.
>
> Not only moving but moving in a 'non inertial way' per SR but perhaps
> approximating inertial per PoR of GR.
>
> Moving clocks, especially those undergoing acceleration due to gravity,
> tick at a different rate than they would if they were NOT moving [and/or
> undergoing acceleration].
>
> When we put a clock in orbit, it ticks FASTER (less slowly) than a similar
> clock would tick on the ground, because it is further away from the planet.
> Then, when it is in orbit, it ticks slower(less fast) than a similar clock
> would, if suspended by magic at the same altitude but undergoing no
> acceleration around the center of the earth.
>
> So, if the earth stopped spinning and the clock were suspended from a tall
> tower, it would run faster than if the earth were spinning and it were
> suspended from the same tall tower.

You *seem* to be making some distinction between a clock
orbiting a planet, and a planet spinning beneath a clock.

I am not sure I understand what point of reference you
are using to make such a distinction.


Sue...

>
> --
> bz
>
> please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
> infinite set.
>
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