Maxwell: In the Field 3

[Monte Davis]

Worse was to come. In 1855, young Maxwell began to extend
Faraday's ideas in a ten-year campaign. "I was at first almost
frightened when I saw such mathematical force made to bear upon
the subject," Faraday admitted, "and then wondered to see that
the subject stood it so well." Maxwell modeled not just lines of
force, but sheets and surfaces of it, rotating tubes of invisible
fluids, particles of electricity spinning between the tubes,
wheels within wheels that put Ptolemy and Descartes to shame. Yet
it worked.

And Maxwell didn't believe it for a minute. He borrowed from
mechanics, he said, "to allow the mind at every step to lay hold
of a clear physical conception, without being committed to any
theory rounded on the physical science from which that conception
is borrowed." By 1865, in A Dynamical Theory of the
Electromagnetic Field, he abandoned the gears and the plumbing.

What remained was the field. It needed no properties that were
not in his beautifully symmetric equations. It accounted for all
known phenomena of electrical charges, magnets, and their
motions. It carried waves at a speed he could calculate.

********

Hertz understood, and a few others. Most were like C.J. Monro,
who wrote to Maxwell: "The coincidence between the observed
velocity of light and your calculated velocity of a transverse
vibration in your medium seems a brilliant result. But I must
say, I think a few such results are wanted before you can get
people to think that, every time an electric current is produced,
a little file of particles is squeezed along between rows of
wheels..."

There was no need to think that. The Cheshire Cat vanishes once it has
smiled.

Where did the cat go?

Into the field. The electromagnetic field. Maxwell's field.

After a pigeon?

After a transverse undulation in the luminiferous ether.

Oh.

*********

We all know about the ether, the supposed medium for electromagnetic 
waves. One of those weird substances people used to believe in, like 
phlogiston or caloric, right? It had to be infinitely rigid yet
infinitely tenuous. Michelson and Morley mounted their instruments 
on a stone slab, set the slab afloat in mercury, and took their readings 
on tiptoe, after midnight (no fluid waves, no sound waves, no seismic 
waves, please). All the world of physics held its breath, and... no ether. 
Nothing but light itself.

Too bad about Maxwell. After all, he had written right there for all to see
in 
the Britannica --- hell, he and Huxley were the science editors, ninth
edition, 1878! 
--- "there can be no doubt that the interplanetary and interstellar spaces
are not 
empty, but are occupied by a material substance..."

It's a good thing Michelson and Morley set us straight, right?


**********

FitzGerald, 1878: "If the Maxwell theory induced us to emancipate ourselves
from 
the thralldom of a material ether, it might possibly lead to most important
results in 
the theoretic interpretation of nature."

Einstein, 1938: "It was, indeed, a long time before the full content of
Maxwell's 
theory was recognized. The field was at first considered as something which 
might later be interpreted mechanically with the help of ether. By the time
it 
was realized that this program could not be carried out, the achievements of

the field theory had already become too striking and important for it to be 
exchanged for a mechanical dogma..."

Feinberg, 1968: "The notion that light is fundamentally just another kind of
matter 
is likely to persist in any future theory."

You can still read in textbooks that Einstein created special relativity to
account for the Michelson-Morley results. In fact, he was not thinking of
that at all. He was thinking instead that the most important property of
Maxwell's equations was their symmetry. What would happen to the
symmetry if you could ride on a wave of light?

While the others were trying to explain where the cat had gone, Einstein was
looking very hard at that smile.

***********