Physics Banter - View Single Post - Empirically Confirmed Superluminal Velocities?

EL

(J?rgen Clade) wrote in message . com...
Hello holog,

Why do people think if you go faster than light you can immediately go
back in time?
i.e. if you could travel at twice the speed of light it would still take
two years to get to alpha centuri, right?

That´s from the earth´s point of view. If you could travel to alpha
centauri at twice the speed of ligtht, the events "departure from
earth" and "arrival at alpha centauri" would be spacelike seperated
events. This means that their temporal sequence depends on the frame
of reference you choose. The violation of causality becomes obvious if
you immediately travel back from alpha centauri to earth, again at
twice the speed of light: Then your arrival on earth would be *before*
your departure from earth. SR avoids such violations of causality by
limiting the maximum speed at which you possibly can travel to the
speed of light.

regards,
Jürgen

[EL]
Hi Jürgen,
I hope that you do not seriously believe in this chicken poop.
The distance between Earth and Alpha Centauri is a quantified
dimension of length that exists at once.
It is rather ridiculous to talk about a distance that shrinks in its
physical nature if an observer perceives it as shrunk.
Your perception may shrink indeed but the distance may not shrink and
if you do believe that poop then you do certainly need a shrink.

If the minimum distance is taken as a physical invariant then with a
constant velocity quantified in distance over time must take time by
simple division.

That time is a positive quantity that does not give a **** to who is
assigning a sign to it and who is observing it.
SR takes no credit for the constancy of electromagnetic waves in
vacuum but Maxwell does.
SR takes credit to the waste of time and bandwidth and the chicken
poop you posted.

EL