Carl%20Sagan%20-%20The%20Demon%20Haunted%20World

Maxwell and The Nerds
benefits of science and technology. We understand that there is a
downside. Circumstances today are much closer to what Maxwell
remembered from his childhood.
He made enormous contributions to astronomy and physics -
from the conclusive demonstration that the rings of Saturn are
composed of small particles, to the elastic properties of solids,
to the disciplines now called the kinetic theory of gases and
statistical mechanics. It was he who first showed that an
enormous number of tiny molecules, moving on their own and
incessantly colliding with each other and bouncing elastically,
leads not to confusion, but to precise statistical laws. The
properties of such a gas can be predicted and understood. (The
bell-shaped curve that describes the speeds of molecules in a
gas is now called the Maxwell-Boltzmann distribution.) He
invented a mythical being, now 'Maxwell's demon', whose
actions generated a paradox that took modern information
theory and quantum mechanics to resolve.
The nature of light had been a mystery since antiquity. There
were acrimonious learned debates on whether it was a particle
or a wave. Popular definitions ran to the style, 'Light is
darkness - lit up'. Maxwell's greatest contribution was his
discovery that electricity and magnetism, of all things, join
together to become light. The now conventional understanding
of the electromagnetic spectrum - running in wavelength from
gamma rays to X-rays to ultraviolet light to visible light to
infrared light to radio waves - is due to Maxwell. So is radio,
television and radar.
But Maxwell wasn't after any of this. He was interested in how
electricity makes magnetism and vice versa. I want to describe
what Maxwell did, but his historic accomplishment is highly
mathematical. In a few pages, I can at best give you only a flavour.
If you do not fully understand what I'm about to say, please bear
with me. There's no way we can get a feeling for what Maxwell did
without looking at a little mathematics.
Mesmer, the inventor of 'mesmerism', believed he had
discovered a magnetic fluid, 'almost the same thing as the
electric fluid', that permeated all things. On this matter as well,
he was mistaken. We now know that there is no special
361