Re: mass increase due to speed

Dear robert:

"robert" <roberto_ruggeri_@xxxxxxxxxxx> wrote in message
news:Dte_g.40951$6C2.20416@xxxxxxxxxxxxxxxxxxxxxxx

"Brian Kennelly" <bwkennelly@xxxxxxx> wrote in message
news:pke_g.5969$gM1.4604@xxxxxxxxxxxxx
robert wrote:
If you were in a spaceship with absolutely nothing in your
visual range, and another identical spaceship moving in a
straight line flew passed you, SR tells us that it would be
impossible to know who's moving and who's stationary.
But wouldn't measuring the mass of both spaceships tell us
who's moving as their spaceship would have a
greater mass due to the effect of movement through
spacetime?

How do you propose to measure the mass? Whatever
method you propose, you will find that each would
measure the other as having the greater mass.

Say you were in your ship and measured the mass of a
basketball. You were then accelerated (say to 99%
speed of light). If you now measured the mass of the
basketball would you find it 'heavier' or would it appear
the same?

All mass measurements in your frame are with respect to other
masses in your frame. The basketball in your ship will weigh the
same as a basketball, no matter how fast you are moving.

Now, you observe a basketball in the other ship, on on the Earth.
How do you propose to measure its mass from your frame?

Let's make this easier. Let's say you are observing the Moon
orbiting the Earth as you fly by at 0.99c. Will the Earth-Moon
system curve your path more or less than it would at 0.0001c?
Will the Moon suddenly fall into the Earth, will its period
suddenly alter beyond what your gamma accounts for?

David A. Smith


.

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