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Re: [Phys-l] The behavior of light



On 05/04/2008 12:43 PM, Fink Trevor M wrote:
So, then, true or false. If the man traveling near the speed of
light lived 100 years, and traveled at that speed for his entire
existence, he would perceive to have lived 100 years (assuming dead
people now have the ability to perceive). However the stationary
observer would have long since passed, but also would have perceived
to have lived 100 years. Each of them lived out their full 100 years,
both defining 100 years as the same amount of time and experiencing
it as the same amount of time, but in actuality the stationary
observer died first.


*) Let's assume _uniform_ motion. No acceleration. That is,
let's not get this mixed up with the infamous twins, one of
whom is _accelerated_.
http://www.av8n.com/physics/twins.htm

*) 100 years of proper time is 100 years of proper time. The
modern (post-1908) viewpoint is to think of each clock's
proper time as "the" time for that clock.

*) Stop trying to explain what happens to the clocks. Nothing
happens to the clocks.

*) There is no such thing as "the" stationary observer. Each
guy is stationary in his own frame.

The situation is completely symmetric. Each guy observes
that the other guy is moving. That is, relative to the blue
guy the green guy is moving and vice versa. This symmetry
is easy to see if you draw the spacetime diagram. It is
also easy to see in the math: The space/time rotation matrix

[ cosh sinh ]
[ ]
[ sinh cosh ]

has a rather obvious symmetry

*) I won't say anybody's clock "is" slow. The /projection/ of
each guys clock onto the other guy's frame is slow. That's a
property of the projection, not a property of the clocks.

By way of analogy, consider a flagpole whose length (proper
length!) does not change. However the length of the shadow
of the flagpole does change during the course of the day.
I don't have a problem with that. The shadow is a perfectly
real thing, and sometimes has direct physical significance.
But don't think that the shadow "is" the flagpole.

You must keep track of the distinction between "thing" and
"projection of thing".
http://www.av8n.com/physics/odometer.pdf

*) The Subject: line needs to be changed, but I'll let it slide
for now. There's nothing special about the behavior of light.
This has to do with the geometry and trigonometry of spacetime,
which affects all reference frames equally, whether it involves
the presence of light, and/or something else, or nothing at all.