Theories of the Universe: The Experiment That Failed

The Experiment That Failed

Now that the speed of light had been accurately measured, the question of the existence of ether still needed to be addressed. In 1887, a famous experiment was set up to determine if the presence of ether could be found. It was called the Michelson-Morley experiment, named after the two scientists who set it up. The reasoning behind the experiment went something like this. If ether is motionless in space, then any object moving through it, like the Earth, would encounter an ether wind blowing in the opposite direction. The Earth moves through space as it orbits the Sun. Physicists thought that the ether wind was blowing past the Earth at the same speed that the Earth orbited the sun.

The speed of this ether wind could be measured by using a light beam, since the speed of light is always constant. (I'll cover how they knew that in “Cracks in a Newtonian World.”) The idea was to measure the motion of the Earth with respect to the fixed ether by measuring the speed of light as it moved back and forth in different directions on the surface of the Earth. The ether wind would affect the speed of light waves, just like wind affects the speed of sound waves in the air. According to this theory, the speed of light would increase in some directions and decrease in other directions. When the various speeds were compared, it would be easy to calculate the speed of the Earth. Since the speed of light is a fixed velocity, any fluctuations in its speed would be accounted for by the ether wind.

The experiment was set up very precisely, and carried out a number of times, but it was an utter failure. There was no ether wind discovered. But this failure ended up changing the face of physics. It forced physicists to rethink their ideas about the structure of the universe and this long-held cosmological belief was soon regarded as a quaint superstition. However, even though this particular experiment didn't show any sign of ether, it didn't stop some scientists from still believing in its existence. And an important point to remember is that any experiment is designed so that certain outcomes, within particular parameters, may or may not be found. Just because this particular experiment didn't show any signs of its existence, doesn't mean that another theory or experiment couldn't. The existence of ether still has yet to be solidly proved or disproved. It's just fallen to the side, because its existence isn't necessary for the many theories and mathematics of today's cosmology.

Waves Come in All Shapes and Sizes

Once it was discovered that light was an electromagnetic wave, a number of other scientists and experimenters found more types of electromagnetic radiation. They established the terminology that helped to define the properties of electromagnetic waves. Here is a summary of some of the most significant discoveries:

• Joseph Henry, an unsung American scientist, produced and detected electromagnetic waves when Maxwell was only eleven years old. He built an electric circuit in which an oscillating electric current produced electromagnetic radiation. The more rapid the oscillation the more radiation it produced.
• Heinrich Rudolf Hertz (1857-1894) helped to clarify the content of Maxwell's theories and formulas by showing through experimentation how oscillating electric currents produced electromagnetic radiation. By pushing the design of Henry's circuit, he was able to find both the frequency and wavelength of the electromagnetic wave. From this he was able to figure out the speed with which the waves traveled. He found that although the frequency and wavelength change, all electromagnetic waves travel at the same speed: the speed of light.
• Wilhelm Conrad Rntgen (1845-1923) discovered x-rays in 1895. While performing experiments with very high-frequency radiation, he found that these electromagnetic waves passed through many substances. With a leap of insight, he directed these rays at his wife's hand that he placed in front of a photographic plate. After developing the negative, he saw that he had a photograph of the skeletal structure of her hand. Within months, x-rays were used in medical diagnosis.
• Ernest Rutherford (1871-1937) and his students studied the rays that come out of naturally radioactive substances such as uranium, and discovered that there are three kinds, which he named alpha, beta, and gamma. In reality the alpha rays were really helium atoms without their electrons (although no one even knew that atoms had electrons yet), and the beta rays were electrons.

So there you have a brief list of the early discoveries that were made regarding some of the more common forms of electromagnetic radiation.