We talked about the
concept of Galilean transformation in the previous section. Here we talk about
inconsistencies of the transformation with the theory of electricity and
magnetism.
In between the time
period of the 18th and 19th
century there was a significant development in the field of mechanics due to
remarkable contribution of Sir Isaac Newton and many other following the path
laid down by him. Mechanics was then already both very analytical and abstract.
Classical mechanics was at its height of serene beauty.
However, there were
other new generation of scientists doing the study on the newly discovered
phenomenon so called Electric and Magnetic field. Michael Faraday followed the
lead on the very subject matter. Although Faraday’s work on the electricity and
magnetism was highly insightful, electric and magnetic field were considered to
be entirely different concept. Maxwell from his analysis on the Ampere’s
contribution found a loop hole, this led him to develop a set of equation
which we now call the Maxwell’s Equation.
What’s more interesting
is that he found a wave equation associated with the electric and magnetic
theory which propagated with the speed$(c)$, which was a pure constant.
But since Galilean transformation points us to the fact that that
velocity is a relative concept. We could state in principle that the light should have different speeds in different frame due to
the velocity addition rule. We have just found that the light had a constant speed with no indication to any particular frames of reference. How could that be? Was there a universal frame of reference that light moved on??
To put it in plain words, we found that Velocity of light was a constant $c$, but the question remained, to whom? Someone sitting inside the bus, or someone standing still on the surface of the earth. Trying to figure out a way out of it, scientists began speculating about illusive substance permeating all over space called aether. The detailed history can be found here.
To put it in plain words, we found that Velocity of light was a constant $c$, but the question remained, to whom? Someone sitting inside the bus, or someone standing still on the surface of the earth. Trying to figure out a way out of it, scientists began speculating about illusive substance permeating all over space called aether. The detailed history can be found here.
In this point of time physicists had apparently three possible direction;
- The first one was that there was an absolute standard of rest. Galilean relativity in mechanics was just a coincidence. The “relativity” coincidences in electrodynamics are nothing deep. Or
- There was no absolute standard of rest. Galilean relativity applies to all of physics. Maxwell's equations are wrong. Seek new laws of electrodynamics consistent with Galilean relativity.
- There was no absolute standard of rest. There exists a relativity principle that applies to all of physics, but it's not Galilean relativity. Laws of mechanics must be revised. Perhaps laws of electrodynamics can survive intact.
Which path did
Einstein follow? The third one..
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