Re: Imagine



chronos wrote:
> so you mean that S3 would save fuel on a way
> back to his mother S1 at a speed of only 0.8c?

Ah, you see, you think speed is an absolute number, defined with
respect to some absolute benchmark. That's just the point. There is no
such *physical* thing as zero velocity.

Let me pose it to you a different way. Suppose you are driving from
Quito to Nueva Loja in Ecuador and back again, traveling at highway
speed the whole way. Do you use more gas going at 1060 mph from Quito
to Nueva Loja, compared to going at 940 mph from Nueva Loja to Quito?
(In case you're confused, note that you are probably measuring speed
with respect to the highway. I was measuring speed from a point
suspended over the Earth, and the surface of the earth is moving at
1000 mph under me, due to the planet's rotation.)
If you puzzle on this for a little while, you'll start to ask yourself
the right questions.

PD

.