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

Maxwell and The Nerds
butter knife comes to you when you pick it up, is a misconception.
What does it mean to have physical contact? What exactly is
happening when you pick up a knife, or push a swing, or make a
wave in a waterbed by pressing down on it periodically? When we
investigate deeply, we find that there is no physical contact.
Instead, the electrical charges on your hand are influencing the
electrical charges on the knife or swing or waterbed, and vice
versa. Despite everyday experience and common sense, even
here, there is only the interaction of electric fields. Nothing is
touching anything.
No physicist started out impatient with common-sense notions,
eager to replace them with some mathematical abstraction that
could be understood only by rarified theoretical physics. Instead,
they began, as we all do, with comfortable, standard, commonsense
notions. The trouble is that Nature does not comply. If we
no longer insist on our notions of how Nature ought to behave, but
instead stand before Nature with an open and receptive mind, we
find that common sense often doesn't work. Why not? Because
our notions, both hereditary and learned, of how Nature works
were forged in the millions of years our ancestors were hunters
and gatherers. In this case common sense is a faithless guide
because no hunter-gatherer's life ever depended on understanding
time-variable electric and magnetic fields. There were no evolutionary
penalties for ignorance of Maxwell's equations. In our
time it's different.
Maxwell's equations show that a rapidly varying electric field
(making large) ought to generate electromagnetic waves. In
1888 the German physicist Heinrich Hertz did the experiment and
found that he had generated a new kind of radiation, radio waves.
Seven years later, British scientists in Cambridge transmitted
radio signals over a distance of a kilometre. By 1901, Guglielmo
Marconi of Italy was using radio waves to communicate across the
Atlantic Ocean.
The linking-up of the modern world economically, culturally
and politically by broadcast towers, microwave relays and communication
satellites traces directly back to Maxwell's judgement to
include the displacement current in his vacuum equations. So does
television, which imperfectly instructs and entertains us; radar,
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