Jonathan,
> To me the coolest part of relativity is its axiom - that the speed of
> light is a constant!
same here! it was a great insight from Einstein to postulate this and by
recognizing this value in Maxwell's equation, this constant even apply to
all electromagnetic waves speed in vaccum.
> The speed of light APPEARS constant when we measure it within the same
> frame of reference. If the observer and observed are in different frames
> of reference, the speed of light appears to be different.
This would be true in Galileo's relativity. In special relativity however,
the light appears to have the same speed regardless of your reference
frame. For instance, one is still (v=0) and watch a photon pasing by, and
can measure it's speed to be c; if another observer is traveling with a
velocity v, he/she will measure the same speed when observing the photon!
(eventhough he/she has already some speed). This is in violation with our
insight and Galileo's relativity (exemple of simple car case when one
double the other one and one can calculate the relative speed between the
two cars) that we can experience in daily life. Although it doesn't make
sense to us intuitively, the way Einstein get away with it is by using
Lorentz transformation, which will predicts that to explain this
paradoxial situation, time has to be related to space and contradcted or
expanded accordingly for the speed of light to be constant in all
reference frames.
Actualy Lorentz had it all mathematically before Einstein, but the latter
was the he one who gave a physical interpretation of it.
However,
> rather than accepting that it is the speed of light that differs,
> Einstein's axiom assumes the speed of light to be constant, and
> consequently, the flow of time must be different in different frames of
> reference. The point is not that Einstein's view is more "correct". It
> is that Einstein's explanation turns out to be a lot simpler, and led to
> his simple equation relating matter and energy. In classical physics the
> dimensions of mass, time and distance are treated as entirely separate
> (hence the 3 basic units of the SI system: the kilogramme, second and
> metre). In relativity, the interrelationships between three become much
> clearer.
However, E=mc^2is only a particular case (which is the rest mass energy),
and should really be written Eo=mc^2. And particle physicists even drop
the c in their calculation (for simplicity). However, one has to be very
careful when associating the concept of mass to the energy (I believe)
because in the above equation we left off the momentum. so for particle
moving, this simple relationship doesn't hold anymore.
Aloha
-rv,
> Have a good weekend everyone,
> Jonathan
>
>
>
>
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