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Hans de Vries
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SR transforms one reference frame into another. All effects observed inMeJennifer said:
a single reference frame can be explained from physics without SR !
Lorentz Contraction
It was found before Einstein (most generally around 1900 by Lienard &
Wiechert) theoretically that for instance the electric field of a moving
charge becomes flatter the faster it moves. It does so as it should do
according to the Lorentz contraction. They derived this from classical
physics. You might imagine that objects consisting out of atoms (where
interactions are dominated by EM fields) therefore also become Lorentz
contracted.
Time Dilation
You could see from the "bouncing photon clock" example a few post back
that this could be explained classically. It's also easy to see that the ticking
of this clock will slow down to zero when its speed approaches c.
Relativistic Mass
With Quantum Mechanics, where matter is described by de Broglie waves
and energy and momentum correspond to the frequency and wavelength
of these waves, one can show that the energy (= relativistic mass)
increases as an object moves faster and goes to infinite if the speed
approaches c. The de Broglie waves are the eigenfunctions of the
Klein Gordon equation which is very close to the classical wave equation.
Information goes with c in both the classical EM wave equation as well
as in the Quantum Mechanical Klein Gordon equation.
And then, as a miracle, all these physical effects disappear, if the observer
goes from the rest frame to the moving frame. This is what SR is all about.
SR = Lorentz transformations = what happens if the observer goes from one
reference frame to another. The way it works is mainly via non-simultaneity:
Lorentz Contraction
To see how Lorentz contraction disappears as a result of non-simultaneity
we can imagine that we instantaneously "freeze" a bypassing traveler.
Walking around him we can now see him "hanging in the air", indeed being
contracted in the direction in which he was moving. The traveler however
will complain that his front was stopped first, before his back was frozen in
time, and argues that this is the reason of his compressed state. You can give
him your "freezing device" and do the experiment the other way around.
This time you'll be the one who is Lorentz contracted.
Time Dilation
How can Time Dilation be undone via non-simultaneity? Since t’ depends
on both t and x we can say that a moving object is also ‘moving’ into the
future. Something which moves into the future will arrive there having aged
less. This is one way to look at Time dilation. Moving close to the speed of
light allows you to travel into the future without hardly aging at all.
In SR there is no special preferred (absolute) reference frame. That is, we
have not (yet?) been able to find one even though modern experiments are
extremely precise. As long as we don’t find such a preferred frame we should
consider the time coordinate as relative. Two distant events are unconnected
and saying they have the same t-coordinate is arbitrary in more or less the
same sense that saying that they have the same x-coordinate is arbitrary.
However, if, one day, we find such a preferred frame then we could consider
time absolute. It makes no difference at all for the effects of SR.
(Take another look at: The Twin brothers in an absolute reference frame)
https://www.physicsforums.com/showthread.php?p=1038957#post1038957
Relativistic Mass
Since energy (= relativistic mass) and momentum correspond to the frequency
and wavelength of the de Broglie waves, and, The Lorentz contraction and
Time dilation of these waves is undone, it follows simply that also the relativistic
mass increase is undone!
Regards, Hans.
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