"Enkidu" wrote in message
...
"Mark K. Bilbo" wrote in newsklck5-ofd.ln1@75-104-
203-5.cust.wildblue.net:

But no matter how big a fraction of c you're moving away from me, any
light you emit in my direction is traveling at c. Even we're both
moving
away from each other at a healthy fraction of c, the light we emit is
going to be moving at c when we (or anybody else) measures it.

Think about it in a different way, say throwing mables off a train at
pedestrians. If the train has a velicity of 10 m/s, and you can throw the
.01 kg marbles at 5 m/s, the marbles would hit pedestrians ahead of the
train with a kinetic energy of 1.125 kgm^2/s^2. Marbles thrown at
pedestrians behind the train would have a kinetic energy of
0.125 kgm^2/s^2.

I'm not certain of this, but if you throw the marble forwards (wrt the
direction of the train) it's initial velocity (wrt the ground) will be +10 +
5 m/s =15 m/s forwards. If you throw the marble backwards (wrt the direction
of the train) it's initial velocity (wrt the ground) will be +10 - 5 m/s =5
m/s forwards. Therefore no marble could ever hit a pedestrian who was
*behind* the train at the moment you threw it (ignoring ricochet, etc.),
given those parameters. To hit a pedestrian behind the train wouldn't you
have to throw the marble (backwards) with a velocity greater than the
train's forward speed.

Smiler,
The godless one
a.a.# 2279