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Posted by Tim on April 25, 2003 16:36:24 UTC

supposedly everything is in motion according to physics textbooks.

the rub is since Einstein that:

the laws of physics are the same in all inertial frames of referance.
the speed of light in free space has the same value for all observers, regardless of their state of motion.

these two "facts of life" force us to revise what we at first may intuitively believe about motion.
it becomes apparent that no observer can move as fast or faster than the speed of light. there is an upper limit on the speed of which an observer can attain. this would be counter intuitive since the time of Newton up until Einstein. we can no longer just add velocities without taking into account the fact that the speed of light is going to be the same for the the various observers involved in those velocities. this is also a new wrinkle since the time of Newton up until Einstein. we are forced to use Lorentz coordinate transformation with respect to the more intuitive Galilean transformation.
if we want to get it right from the perspective of special relativity we are forced to "do the math" and that math is allways going to have the value for the speed of light in it.

i think that you are correct when postulating that "actual" speed is a meaningless term unless we define them being measured as from some particular perspective. there is no absolute frame of referance.

from the point of view of your previous posting with respect to the "apparent" velocities question you just need to realise that if your thinking leads you to believe that something (other than a massless particle) has equaled or exceeded the speed of light then there is a problem with the validity of your understanding of what is really happening in a physical sense.

regards, tim

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