• Choose a category
• All
• Classic-Fiction

By Root 1132 0

did indeed produce small, dim sparks just after the transmitter. So there was a finite rate of propagation. Hertz also noticed a strange effect when he shone ultraviolet light on the secondary spark gap: it caused the spark to lengthen. He could find no explanation for this, and went back to general examination of the force. He treated it as if it were an optical phenomenon, and showed that though it travelled a straight line, it would be blocked by the bodies of his assistants. It was also polarised, since an electrified wire frame, rotated 90 degrees to its axis, cancelled it. It was reflected by the zinc sheets; it was refracted by a prism made of pitch; it took time to move from one place to another, all of which showed that it had to be moving through some kind of medium.

Once again the public first heard of this development only in connection with its application. It was used by Marconi, at the end of the century, to send radio waves across the Atlantic.

Meanwhile at Leyden in Holland an eminent Dutch physicist was giving the ether considerable thought. He was Henryk Lorentz, about whom Einstein was later to say, ‘He meant more than all the others I have met on my life’s journey.’Lorentz’s doctoral thesis had examined the light-wave theory in regard to Maxwell’s fields. The problem was that although Maxwell had postulated the wave in order to avoid the difficulty of explaining action at a distance, he had not freed it from association with ordinary matter. If the field went through glass it was necessary to calculate the effects of the resistance of the glass as if the ether went through the glass too.

Lorentz thought the unification of the electromagnetic phenomena would be simpler if ether were simply omnipresent and stationary, because he still wanted an absolute reference for all events and a stationary ether would retain something of Newton. The ether would also be imperceptible. In Lorentz’s view the force would move as elementary electric charges on the molecules of atoms in the ether, or on some smaller particles. The force would, in this way, create the field but remain distinct from it, and move, as a charge, from particle to particle. All that was required for this and for every other manifestation of the force was a stationary ether.

Marconi (left) watches an aerial being hoisted by kite in Newfoundland. A month later, after standing in sleet and rain for three hours, he received a signal from his transmitter in England. It was the first transatlantic wireless transmission.

The Michelson and Morley interferometer, showing the optical paths of two perpendicular light beams. Four mirrors at each end of both paths reflected the beams back and forth several times, thus significantly lengthening their route.

A young American began the search. He had originally gone to Germany to study under Hermann von Helmholtz, one of the great authorities on light and sound, and had been experimenting with the refraction of light in various translucent materials. Applications of his work would be found in the German dye industry, in carbide and natural gas illumination, and in quality-control in the expanding chemical industry. The young man, Albert Michelson, had noted: ‘Assuming that the aether is at rest and the Earth moving through it, the time required for light to pass from one point to another on the Earth’s surface would depend on the direction in which it travels.’

In 1887, the same year that Hertz was demonstrating that the force took time to propagate through space, Michelson and a colleague called Edward Morley set up equipment in the basement of the Case School of Applied Science, Cleveland, now Case-Western Reserve University. Michelson’s work on refraction had led him to invent an interferometer which could measure differences in the speed of light to one ten-billionth. The device made use of the phenomenon of the interaction of light waves, as shown by Thomas Young, to produce interference patterns made up of light and dark bands of varying sizes according to the extent to which two superimposed