LESSON TEN. THE ETHER AND THE ELECTROMAGNETIC THEORY OF LIGHT.
All space is filled with a weightless, invisible medium called Ether. It is the substance with which the universe is filled, it reaches to the stars and through the very earth itself.
It has been known for some time that light consists of vibrations or motions in the ether. In 1867, Clerk Maxwell offered the theory that these light waves are not merely mechanical motions of the ether, but are electrical undulations. According to this theory, the phenomena of electro-magnetism and the phenomena of light are all due to certain modes of motion in the ether.
Twenty years later, Heinrich Hertz discovered convincing proofs of Maxwell’s theory and succeeded in producing electro-magnetic waves in such a manner that they possessed the same properties, traveled at the same speed, and were capable of being reflected, refracted, polarized, etc.
FIG. 25. Hertzian Oscillator and Resonator.
Hertz employed an apparatus consisting of two metallic balls connected by metal rods to two metal sheets. The two balls were also connected to the secondary terminals of an induction coil. This apparatus comprised the oscillator and served to create the electro-magnetic waves.
In order to detect the waves, he employed a resonator consisting of a circle of wire having in it a minute spark gap capable of fine adjustment.
As soon as the coil is set in operation a spark snaps across the gap and sets up a temporary conducting path for the surgings that follow. Each spark sent by the coil across the gap consists of a dozen or so oscillations, each lasting less than a millionth of a second.
Then if the resonator is placed a few feet away from the oscillator and turned broadside on to the oscillator, it will be found that small sparks jump across the gap. Hertz employed various arrangements for reflecting and polarizing the waves and definitely proved that their nature is the same as that of light.