The Lorentz factorThe special theory of relativity
Lorentz set out the mathematical equations which governed the connection
between the distance and time when one frame of reference moves at a constant
speed v relative to another. These transformations are very similar to the ones
we have already worked out but involve a (Lorentz) factor depending on v and
the speed of light, c.
Enter Einstein
The way Einstein dealt with Michelson’s findings about the speed of light was
to adopt it as a postulate:
The speed of light is the same value for all observers and is independent
of direction.
If Jim Diamond flicked a torch on and off while passing through the station on
his speeding train, firing the light beam down the carriage in the direction the
train was moving, he would measure its speed as c. Einstein’s postulate says that
the watching stationmaster on the platform would also measure the beam’s
speed as c, not as c + 60 mph. Einstein also assumed a second principle:
One frame of reference moves with constant speed in relation to another.
The brilliance of Einstein’s 1905 paper was due in part to the way he
approached his work, being motivated by mathematical elegance. Sound waves
travel as vibrations of molecules in the medium through which the sound is being
carried. Other physicists had assumed light also needed some medium to travel
through. No one knew what it was, but they gave it a name – the luminiferous
aether.
Einstein felt no need to assume the existence of the aether as the medium for
transmitting light. Instead, he deduced the Lorentz transformations from the two