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Hendrik Lorentz
Hendrik Lorentz was a physicist who supported the then current belief that light required the existence of a medium, through which it travelled. This medium was called the luminiferous aether (or ether).
In 1892 he sought to explain the results of the Michelson-Morley experiment by suggesting that the apparatus was moving with respect to the aether, but the effect on the measurement of the velocity of light was being masked by another effect, which was known as the Lorentz contraction.
The Lorentz contraction was thought to affect the dimensions of the measuring equipment, due to its motion with respect to the aether. However, Einstein's Special Theory of Relativity made the idea of a light medium redundant. Instead, Einstein used the Lorentz contraction to describe the effect of relative velocities on the dimensions of spacetime itself. Hence it is now known as the Lorentz transformation.
The Lorentz Transformation
The Lorentz transformation (for time) is:
In this equation:
t is the time elapsed in the rest frame of the observer.
T is the time elapsed in the rest frame of the object.
The only other variable is v (the velocity) and it is:
- Squared, so the sign of the velocity is lost.
- Divided by the square of the velocity of light, so the effect is infinitessimally small except for velocities close to that of light.
- Subtracted from 1, so the result is always positive and less than 1.
- Square rooted, which further reduces the impact of small velocities.
- Inverted, so the result is always larger than 1 (i.e. time is always dilated irrespective of the direction of motion).
So the Lorentz transformation explains why the passage of time is dilated and distances contract at high velocities. However, these effects depend solely on the magnitude of the relative velocity. This constraint is important, and needs to borne in mind when we discuss some of the myths that have grown up around the theory.
Further information on the Lorentz contraction may be found here
Further information on Lorentz's life and works may be found here.
