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Each year, the Nobel Prize in physics is awarded to “ the person who shall have made the most important discovery or invention within the field of physics.” To ensure validity, said discovery is tested with time, that is, the winner is not selected until a number of years after the discovery. While in other more subjective and politically-influenced fields the Nobel Prize has been made laughable and the butt of jokes, the award in physics is still the pinnacle. If we review the winners, their achievements are breathtaking. In 1932, for example, German Werner Heisenberg was awarded the Prize for creating quantum mechanics. In 1935, English physicist James Chadwick for the discovery of the neutron. In 1969, it was Murray Gell-Mann for identification and classification of the elementary particles that include the quark, the basic constituent of protons and neutrons (and all other baryons and mesons). In 2006, John Mather and George Smoot shared the prize for their discovery of the cosmic background radiation, a measurement that virtually assures the Big Bang creation. The list goes on with unquestionable awards.
But, in 1907, the Nobel Prize was awarded for the biggest nothing in the entire history of physics.
It happened like this …
Forty years prior, 1867, two professors conducted an experiment at what is, today, Case Western Reserve (Cleveland, Ohio). The problem they were trying to solve was this. How does light travel to us from outer space (or from anywhere for that matter)? It was well established that light was a wave. Diffraction experiments clearly showed its wave property. But, what was the transport mechanism? What carried the wave?
For example, sound waves travel in air. A massive tree falls in the forest. The falling giant swiftly pushes air out of its way as it accelerates to the ground. Branches break, timber snaps, and all of these actions rapidly push atmospheric air out of their way. The air rushes back in to fill the void (like the wake behind a boat) and the pulsating air waves travel across the woods to where you stand. The pulsating air waves vibrate a tiny membrane at the base of your ear canal, shaking an attached little bone and sending an impulse to your brain. You hear the tree crash because the vibrating air carries the sound waves.
(Don’t even think it. Don’t ask about the tree falling in the forest with no one there to hear it. You could just as easily pose the question, “If a tree falls in the forest and all the loggers are deaf, will they still be able to see it?” There is, decidedly, such a thing as a dumb question.)
Now, if you slept on the moon and put your windup alarm clock on the moon-rock beside you, you would slumber on in tranquility. Oh, the alarm would go off, all right, but there is no atmosphere to carry the sound. You will not hear the sound because there is no air there to carry the sound. Sound waves must have a transport mechanism. That mechanism does not have to be air, but it has to be something. For example, sound waves can also travel through solid objects like a railroad rail. (Haven’t you seen the old westerns where the Cheyenne Indians put their ears to the rail to warn the painted warriors that the Iron Horse of the white man is only 100 arrow-shots distant?) Thus, sound waves need some medium of transport.
Water waves travel in water. Drop a pebble in the water and you see the waves spreading out in concentric circles. Waves form behind the motor boat for reasons we discussed above. Ocean waves are disturbances in the water, mostly caused by wind blowing across the water and creating a disturbance that gets transferred by the wave.
The story of waves goes on and on. (Ha. Ha. Little joke.)
The problem is. then, what carries light waves? Surely, there must be something.
For the ignorant, nomenclature is the first line of defense. (We don’t know what it is, where it is, or how it works, so let’s give it a name and look like we know something.)
So, in 1887, a name it had. “Luminiferous aether,” the medium that transports light waves. The name quickly was shortened to just “ether,” without the “luminiferous” and without the beginning “a” in “aether.”
So it is that Albert Michelson (1852-1931), a professor at Case School, and Edward Morley (1838-1923), a professor at the contiguous campus of Western Reserve, decided to find the ether. They built a simple device consisting of a coherent light source (a laser), two mirrors, one half-mirror (like the spy half-mirrors at the convenience stores) and a detector (a piece of paper will work). The initial light beam is split by the half-mirror and the resulting beams are reunited like old lovers. But, like old lovers, the
reunited beams are out of phase and interfere with each other to produce an interference pattern. The interference pattern is a series of light and dark fringes that you see on the piece of paper. The whole device is called an interferometer, which means a device to measure the interference (pattern) of the two converging light beams.
I bought some mirrors and lasers once and set the experiment up in my garage. The real problem is vibrations. I used a big sand table, but the vibrations from the street were too great and my little interference pattern wiggled around like a worm. Michelson and Morley used a one foot thick slab of stone about 5 feet square. They didn’t have automobiles and tractor-trailers rumbling down their streets, nor air conditioners vibrating their walls, nor refrigerators humming, nor washing machines sloshing. Furthermore, to dampen all vibrations, they floated the entire stone slab on a bed of liquid mercury. (The EPA was three-quarters of a century away.) They controlled thermal variations by conducting the experiment in the basement of a large stone dormitory, keeping the temperature as constant as possible. (I, myself, relied on the Texas summer remaining a constant 100 degrees Fahrenheit, 21 hours a day.
Anyway, with this apparatus, they investigated the alternating light and dark fringes formed by the intersecting light beams, measured the distance between them, measured the distances between everything else and, knowing the wavelength of light, they calculated the speed of light. The concept is straightforward and easily understood. Implementation, to the accuracy required, is extremely difficult.
So, they measured the speed of light, rotated the stone slab floating on the pool of mercury, and measured the speed again. (Yes, this giant slab of stone could float in liquid mercury. Review Archimedes’ principle.) They kept rotating the slab around and measuring the speed of light. Why? Because, if the earth is moving through the ether, that would give the ether an apparent velocity relative to the earth (like air swishing by you when you swing at the playground). With the ether swishing past the earth, the speed of light should be more in one direction than the other. In other words, the light beam should travel faster upstream than downstream, which seemed obvious at the time.
It is to the great credit of Albert Michelson that he was one of the greatest experimental physicists ever. No government grant or special-interest funding to chisel away at his integrity. No “fudging” because he knew the direction of the earth’s rotation (west to east). His experimental skills and integrity remain in a select class. When he published his data, no one seriously questioned the data, only the conclusion.
The conclusion was that no matter which way the slab was turned, the speed he measured was always the same. Michelson and Morley worked for months on this experiment, accumulating more and more data. There was no change. They could detect no difference whatsoever in the speed of light, no matter which direction the slab was rotated. The experiment was null. They found no direction for the ether. They could not detect even the slightest movement of the ether. They found nothing.
This result perplexed every physicist for the next 35 years. All sorts of weird explanations were concocted to explain why the mysterious ether went undetected. (It was dragged along by the earth; it had vortices, etc.) It was not until 1905 that a young Albert Einstein offered the correct (but not really the most obvious) answer. Michelson and Morley did not find the ether, because there is no ether. The speed of light is a constant of the universe. Forget about the comparison with sound and water waves. That connection is bogus. Light does not require a medium of transport. There is no ether and never was.
So, thus, it turns out that in 1907, the Nobel Prize in physics went to Albert Michelson for finding nothing.
P.S. Purists will argue that Albert Michelson had many other significant achievements and this was only one of them, citing that the Nobel was “for his optical precision instruments and the spectroscopic and metrological investigations carried out with their aid.” Posh. No one remembers what those were. The truth is that without the null ether experiment, Michelson would be just another name in physics and not the winner of the 1907 Nobel Prize.
P.S.S. Purists will also argue that light does indeed have a medium of transport. That medium is the fabric of spacetime, itself. To which I say, “Jolly, Good,” and reserve the right to discuss that on another day.