Horace Heffner wrote:
On Jan 23, 2006, at 5:44 AM, Stephen A. Lawrence wrote:
Horace Heffner wrote:
I don't think it is generally accepted an more that m=m0*gamma is
a real effect. I definitely read that in some text.
I've also read that "m0*gamma" isn't "real" mass. I've also read
that time dilation is not "real". Both statements, as written, are
nonsensicle -- they are both meaningless.
To make them sensible statements you first must define "real".
Can you do that?
If you can, then you'll also be able to say definitively whether
either of those effects is "real".
But if you can't define "real" then any question about whether
something is "real" is meaningless.
Effects which are "real" are effects which can not be fully accounted
for by retardation. The effects which remain when clocks are brought
back together are therefore real. Any change in appearance, and that
includes locally observed forces as well as images, that is brought
back into balance upon return to the initial condition, is due to
retardation effects, delays in the communication of conditions. Real
effects are cumulative upon cyclical motion. Retardation effects do
not accumulate upon cyclical motion.
Sounds good to me. (And I bet it's a lot clearer than the notion of
what is "real" which was held by the authors who casually dismissed
relativistic mass increase as "unreal"...)
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.
Mass increase -- m ==> m0*gamma -- seems real too, though you might
disagree. 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.
Finally, just for fun, I put a resistor into a centrifuge, and spin it
up, and measure its resistance using a stationary meter....... WTF??
Horace Heffner
