David,

The formula for time dilation is a function of velocity. If I am moving
at a
given velocity with respect to you, then you are moving at the exact
same
velocity with respect to me.

Not quite correct.

In that case, if I am moving at 10kph with respect to you, at what velocity
will you be moving, with respect to me? Greater, or less?

Stephen


(formerly)" dlzc1.cox@net wrote in message
news:sy0ob.123157$gv5.53477@fed1read05...
Dear Stephen Bint:

"Stephen Bint" wrote in message
.. .
Dear David Smith:

You have said,

If both frames are moving the same speed, but different directions,
they
will both age the same.

So, like the person who wrote the account of the twin paradox in the
FAQ,
you do believe that time dilation affects the rate of aging.

Let me say yes, this way: If I travel between here and the store in my
car
in different ways, do I show different mileage on my car for each trip?
Yes, the path you travel racks up different "mileage".

The formula for time dilation is a function of velocity. If I am moving
at a
given velocity with respect to you, then you are moving at the exact
same
velocity with respect to me.

Not quite correct.

To whatever extent there is time dilation and a
reduction of aging, it is predicted to be the same for you as for me,
because v is the same, and the formula is a function of v.

Not necessarily true. Since one frame does not see time or length the
same
as the other, inferred velocities are bumfuzzled. For example a moving
triplet and a stationary triplet will not agree how fast the moving
triplet
is moving. (I added a third twin, to merge with your gedanken. I hope
their mom doesn't mind.)

You see me in
slow motion and I see you in slow motion, so both our ages are reduced
by
the same amount.

Not the same amount, no. The sign is correct ("slowed"), but the
magnitude
is not.

Is that not the case?

Answered. Look at the FAQ again.

David A. Smith