The True Nature of the Force

One of the most amazing discoveries in all of science, let alone physics, is the discovery of the speed of light.

Yes, I did say "discovery", even though the speed of light had been known (approximately) for many years prior.

For many years, science thought it knew most of electricity and magnetism, that they were deeply related, etc.

So, we continued our research whilst the other guys were measuring the speed of light with varying degrees of accuracy. They usually got about 300,000 km per second.

Meanwhile, us lab physicists continued to study electricity and magnetism. We even discovered two numbers which seemed to be the same for empty space. That is, through our experiments, we got two constants referring to the properties of empty space, as witnessed by electricity and magnetism respectively. The electric one was called "epsilon-0" and the magnetic one "nu-0". In English, they are the "permittivity" and the "permeability" of free space. Once measured, with known values of the other numbers in the experiments, we could go ahead and calculate what would happen if we didn't know all the other numbers.

Meanwhile, the light-speed measuring people found that now, it was clear that the speed of light was a little LESS than 300,000 km per second, something like 299,000.

Then, in 1865, along came James Clerk Maxwell. He thought it might be a good idea to come up with THE set of equations which completely defined electricity and magnetism, or "electromagnetism", as he called it. He believed that they were just manifestations of the same thing. After the research, his equations seemed to lack something. They were not symmetrical. So, he made a correction (it is called "displacement current" now, but to us cynics, a "fudge" would perhaps be more appropriate - as any South Korean stem-cell research scientist would know).

Anyway, this "correction" made a whole, complete set of 4 symmetric equations, one of which (div B =0) predicted that magnetic monopoles did not exist.

A prediction of one of the other equations proved interesting as well. It predicted that under some circustances electric circuits will radiate self-propogating waves out into empty space in all directions, the speed of which was defined by those two constants mentioned earlier. More specifically, these waves would travel at a speed

s = 1/ SQRT(nu-0*epsilon-0)

Mr maxwell was excited. He plugged the known values of the permeability and permittivity into the above equation. as determned by electric and magnetic experiments, turned the handle, and came up with another constant, s, the speed of these new "waves".

He got this:

s = (approximately) 299,790 km per second.

Wait a minute minute! Isn't that the the latest figure for the speed of light our other chaps are trying to measure?

NOW we know what light is! It is simply an electromagnetic wave, of which many more have since been discovered. Radio, radar, microwaves, X-rays, gamma-rays, uv, infra-red, tv, all are part of what we now know to be the "electromagnetic spectrum", where the differents bits named above, differ only in wavelength. Oh, and there is the visible bit , too, that part which we see with our eyes, otherwise konwn as "light".

And all travel at one speed in empty space, 299,799 km per second, which we now call "c".

The implications that "c" was a derived quantity from other constants, and therefore a universal constant in itself, were not realised until Einstein started to address them in 1905, under Special Relativity, but that is another topic and post!