> I was just talking to someone in chat about this
> sorta stuff, then i found this post... I
>thought maybe Dave or someone could explain to me
> how this works... This being why you have to be
> moving relative to the earth, and it can't be
>moving relative to you...

It's called the "Twin Paradox", and it's not a
paradox. Basically, it goes like this: One twin
flies away at near light speed while the other
stays on Earth. The Earthbound observer sees the
space-travelling twin as younger than himself, due
to time dilation. However, as you (or whoever it
was) so eloquently pointed out, if everything were
"relative", the space-travelling twin could just
as easily say "I am sitting still, and my twin and
all the Earth is flying away from *me* at near
light-speed". And in fact, these two statements
are functionally identical. And it *is* true that
the space-travelling twin would look back at his
twin on Earth and see *him* as younger. Paradox?
Nope. It's relativity.

The argument is "well, what if the twin in the
shipt comes back? They can't *both* be younger,
can they?" But, in order to come back, the
space-travelling twin must undergo an
acceleration--and that makes the two reference
frames non-equivalent. So the paradox breaks
down, and the twin in the ship sees his twin on
Earth as being older than he on the return trip.

Don't ask me to explain much more than that, I
freely admit to not getting a lot of this myself.
I'm terrible at math, and you really *need* to
understand the math to *really* understand relativity.

Anyway, here's a link. You know, you guys could
do google searches just as easily as I can.

-- Dave