Re: Simple question

Dear Ali:

"Ali" <akousari@xxxxxxxxxx> wrote in message
news:1193693371.813714.205500@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
It appears to me that the time for any other frame of
reference can be slowed down but not speeded up.

No.

That is true wether the other frame of reference is
moving relative to ours or is in a gravitational field.

No, the GPS satellites are "aging" very slightly faster that a
similar clock down here on Earth.

I wonder if some one can kindly explain the
following puzzle for me.

You have a good answer from PD.

Suppose that you are traveling in a space craft
looking at you twin sister on earth. For both of
you time for the other one is running slower.

Travelling away, they each see the other agning more slowly than
themselves. They just don't agree on the difference in aging.
And when travelling towards the other one, they each seem to age
very much faster than their twin. And again they do not agree on
how much faster.

You see your sister staying younger than you
and she sees you staying younger.

Only true on the outbound leg.

Now, when you come back to the earth, slow
down, and stop (decelarating as if being in a
gravitational field) still your sister sees your
time running slower ( as you see hers) and not
faster.

No.

But you should see her time run faster if she
has to grow older to catch up with you (of
course the same is true otherway round).

Not quite.

Is there anyway that way that we can see the
other clock run faster?

Yes, on the return trip, or by understanding "relativistic
doppler shift".
http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/reldop2.html
http://www.astro.cornell.edu/academics/courses/astro201/doppler_rel.htm
http://adsabs.harvard.edu/abs/1985PhRvL..54..255K
http://www.phys.ufl.edu/~rfield/PHY3063/images/Chapter1_19.pdf

David A. Smith


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