Electromagnetic waves

Strong support for this view came from an unexpected source - electricity
and magnetism. We saw in the last chapter that there are some strong
connections between electricity and magnetism: electric currents give
rise to magnetic fields, and changing magnetic fields induce currents.
These effects are summarized by what are known as **Maxwell's equations**,
which are a set of mathematical relations which, given any source of
charges and/or currents, allow one to solve in principle for the resulting
electric and magnetic fields. These equations are a great
triumph in science, and are extremely well verified experimentally.
Now, if one examines these equations in a vacuum (i. e., in the
absence of any source of charge and current), one finds a non-trivial
solution emerges. This solution mathematically is a simple wave, just like
the type we have been considering, and has a speed given
completely in terms of the parameters arising in Maxwell's equations.
This speed turns out to be numerically equal to the speed of light
in a vacuum:

What this means is that light is interpreted as a set of
oscillating electric and magnetic fields, which can and do exist
in a vacuum.

1999-09-29