Relativity, Spacecraft and Electrons
Name: Ayed R. R.
if we have a spacecraft that has a stationary electron
inside it, and this spacecraft moving with an acceleration, according to
an observer inside it the electron is not moving so it will not radiate
electromagnetic wave, but according to an observer outside
this spacecraft will see the electron moving with acceleration so it will
radiate an electromagnetic wave.What will happen? Will it radiate or will not?
Notice that the spacecraft is accelerating, so to keep the
electron stationary in the spacecraft, it is necessary to exert a
force on the electron so it will accelerate at the same rate as
the spacecraft. Therefore, it will radiate due to being
accelerated, whether seen by a stationary observer external to
the spacecraft or seen by an observer in the spacecraft being
accelerated with the spacecraft (and the electron).
You ask a good question about a matter which has confused many
people. Just remember that for the electron not to be moving
relative to the spacecraft it must be accelerated at the same
rate as the spacecraft.
Best, Dick Plano, Professor of Physics emeritus, Rutgers U.
Relativity as commonly stated does not apply to accelerating frames of
reference. An "inertial reference frame" must have zero acceleration. This
is because an object can detect its own acceleration. When in a car driving
at constant speed and not turning, you can not tell very well whether you
are moving. If blindfolded, the only motion you detect for sure is the
jittering due to little bumps in the road. These jitters are accelerations.
At constant speed you cannot tell whether you are moving forward or
backward. On a smooth road, there is essentially no difference between
moving and idling the engine.
If the driver slams the brake, hits the accelerator, or makes a sharp turn,
you know it. The electron will radiate due to the acceleration for
everyone. Everyone senses the acceleration.
Dr. Ken Mellendorf
Illinois Central College
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Update: June 2012