On Jan 23, 2006, at 9:56 AM, Stephen A. Lawrence wrote:
Time dilation is clearly real, then. I send a clock out to Pluto
and back via a fast rocket, and check its time, and now it is
slow. I do it again, and it's slower.
Well the time difference is the result of a real effect. hat effect
is not necessarily time dilation, because time dilation (observed
time differences) is at least in part due to retardation.
Mass increase -- m ==> m0*gamma -- seems real too, though you might
disagree.
Yes, it seems that way to me. This effect can explain at least a
portion of the "real" nature of the final time difference for the
twins - depending on what kind of clock is used. If mass is used in
the clock, then certainly real time differences can be expected. I am
not sure there will be a real difference if the clocks used consist
only of photons bouncing between mirrors. Which then brings up the
"reality" of the Fitzgerald contraction. Is length contraction
real? Certainly some of it is not real, because it is due at least
in part to retardation.
I accelerate a clock to gamma=10, and let it collide with a clock
which is "stationary". The energy given up by the traveling clock
is consistent with its mass being m0*gamma; it makes a very real
"bang", which involves locally observed forces that are far larger
than those we would have observed had its mass been merely m0, at
the speed at which it was traveling.
I put a centrifuge into a (closed!!) box, and start it going. As
it spins up I weigh it. It gets heavier, which again involves
local measurement of a force. Once again, m ==> m0*gamma seems to
me to be quite "real".
Length contraction is far more dubious. As far as I know there is
no way to observe it which doesn't involve making "simultaneous"
measurements at separate locations which opens us up to all kinds
of problems, though the "cracking spinning disk" experiment still
bothers me.
I wonder if it is possible to make an accurate clock which doesn't
depend on mass?
Finally, just for fun, I put a resistor into a centrifuge, and spin
it up, and measure its resistance using a stationary meter.......
WTF??
Nothing like trying to iron out experimental artifacts! 8^)
Horace Heffner
