Chapter Three

Maxwell and the
Luminferous Aether

In 1847 a sixteen year old boy name James Clerk Maxwell was taken to see what was considered one of the “scientific wonders” of the age.  It was a special crystal from Iceland that had been cut into a prism.  The prism acted as any other prism would, letting light shine through it.  But when a second such transparent prism was held in front of it and turned just so, the light was completely blocked.

These crystals accomplish this feat through a then unknown process called polarization which acts much like a venetian blind controls sunlight through a window. Normally, a light source produces waves which go in all directions.  Polarization allows only light having a specific orientation to its oscillations to pass through.  By turning polarizing lenses so as to make them perpendicular to each other, all light is thereby blocked.

This demonstration fascinated the young James Clerk Maxwell and was to be the original motivation behind a lifetime of scientific experimentation and theorizing about the nature of light.

From the time of Sir Isaac Newton it had been accepted that light consisted of tiny particles which Newton labeled “corpuscles.”  But none of these strange behaviors of light lent themselves to any logical explanation using this approach.

If light could actually finally be understood it would unify the fields of mechanics and chemistry with those of electricity and magnetism.  This would represent the first coherent unified explanation of the world!

At Cambridge light became one of Maxwell’s central interests in research.  He turned his attention to the remarkable discoveries of another one of history’s great scientists, Michael Faraday who twenty years earlier had discovered that if one waved a magnet near a copper wire it would produce an electric current; a fact that nobody had any explanation for.  Maxwell began looking for a mathematical explanation for this phenomenon.   

He invented a new mathematical language which after years of work produced four equations that showed for the first time the exact relationship between magnetism and electricity.  Here are Maxwell’s equations which even today are commonly seen on the t-shirts of science geeks.

Maxwell’s Equations

I. Gauss’ law for electricity

II. Gauss’ law for magnetism

III. Faraday’s law of induction

IV. Ampere’s law

While the specific meanings of these equations is beyond the scope of this book, the speed with which waves travel within electromagnetic space is represented by the letter “C” in the last equation which is known as Ampere’s law.  It turned out that the speed these waves travelled at was exactly the same as the speed of light.  The “C” of Ampere’s law is the same “C” that Einstein later used to describe his special theory of relativity in the most famous formula ever developed, E=MC² .

Maxwell realized from this that light; electricity and magnetism must be the same kind of “thing.”  Light was in fact an electromagnetic wave.

This is considered one of the greatest insights into how the world works in the history of science and earned James Clerk Maxwell an honored position right between Isaac Newton and Albert Einstein.  Like those other two greats, Maxwell’s method of arriving at his astounding discovery remains shrouded in mystery. 

It was said of Maxwell by his scientific colleagues that Maxwell was always right, but you couldn’t see why.  Maxwell never made a mistake, but it was impossible to check exactly how he got from where he started to the startling ideas he produced.” 

Maxwell now understood that if light was electromagnetic waves, then color represented different frequencies of those waves.

Ultimately all the frequencies of electromagnetic radiation were discovered from radio waves at the slowest end to x-rays at the fastest.

But if light was an electromagnetic wave what was it that was waving?

The Luminiferous Aether

Although Maxwell was not the first to propose that light consisted of a wave rather than particles as per Newton’s analysis, his equations indicated that the speed of the wave was invariant.  In other words, it would not matter the speed of the reference frame in which the light was being emitted, light would always travel at the same speed “C.”

According to Galilean relativity, mentioned in chapter 2, this would only be possible if the light were travelling through some fixed in space medium.  If there was no such absolutely fixed, stationary medium, the speed of light would have to vary, and Maxwell’s equations wouldn’t work.

The name devised for this unseen medium that had to exist was the “Luminiferous Aether.” 

The mechanical qualities of the aether bordered on magical.  It had to be a fluid in order to fill space, but one that was millions of times more rigid than steel in order to support the high frequencies of light waves. It also had to be massless and without viscosity, otherwise it would visibly affect the orbits of planets. Additionally it appeared it had to be completely transparent, non-dispersive, and incompressible.

The apparent absurdity of these supposed qualities of the aether, though disturbing, could not dissuade the physics community from believing in it.  After all, what other alternative was there?  Maxwell’s equations had been tested and proven beyond a doubt to be correct.  There was no doubt that light consisted of waves.  The aether simply had to exist!

Maxwell noted in the late 1870s that detecting motion relative to this aether should be easy enough—light traveling along with the motion of the Earth should have a different speed than light traveling backward, as they would both be moving against the unmoving aether.

Numerous experiments were carried out in the late 1800s to test for this “aether wind” effect, but most were open to dispute due to low accuracy. Measurements on the speed of propagation were so inaccurate that comparing two speeds to look for a difference was essentially impossible.

Michelson–Morley experiment

Performed in 1887 by Albert Michelson and Edward Morley at what is now Case Western Reserve University, its results are generally considered to be the first strong evidence against the theory of a luminiferous aether.

Earth travels a tremendous distance in its orbit around the sun, at a speed of around 30 km/s or over 108,000 km per hour. The sun itself is travelling about the Galactic Center at even greater speeds, and there are other motions at higher levels of the structure of the universe.

Since the Earth is in motion, it was expected that the flow of aether across the Earth should produce a detectable “aether wind”. Although it would be possible, in theory, for the Earth’s motion to match that of the aether at one moment in time, it was not possible for the Earth to remain at rest with respect to the aether at all times, because of the variation in both the direction and the speed of its motion.

At any given point on the Earth’s surface, the magnitude and direction of the wind would vary with time of day and season. By analyzing the return speed of light in different directions at various different times, it was thought to be possible to measure the motion of the Earth relative to the aether. 

Michelson had a solution to the problem of how to construct a device sufficiently accurate to detect aether flow. The device he designed, later known as an interferometer, sent a single source of white light through a half-silvered mirror which split it into two beams travelling at right angles to one another.

After leaving the splitter, the beams travelled out to the ends of long arms where they were reflected back into the middle on small mirrors. They then recombined on the far side of the splitter producing a pattern of constructive and destructive interference based on any possible time difference between the reflected light waves.

If the Earth is traveling through an aether medium, a beam reflecting back and forth parallel to the flow of ether would take longer than a beam reflecting perpendicular to the ether. The result would be a delay in one of the light beams that could be detected when the beams were recombined. The slightest change in the time spent would be observed as a shift in the positions of the interference fringes.

The experiment, instead of providing insight into the properties of the aether, proved that the luminiferous aether simply wasn’t there.

The Lorentz–FitzGerald contraction hypothesis attempted to explain away the negative result of the Michelson–Morley experiment and to hang on to the luminiferous aether.

The hypothesis held that there was a decrease in length detected by an observer in objects that traveled relative to that observer.  This contraction is usually only noticeable at a substantial fraction of the speed of light, and is only in the direction parallel to the direction in which the observed body is travelling.

This hypothesis shows the ridiculous lengths to which scientists were willing to go to preserve their long established belief in the aether.  No explanation was offered as to why objects should appear to contract at speeds relative to the observer, only that if they did it would explain the null results of the Michelson–Morley experiment while still allowing for the existence of the aether.

Ironically, the Lorenz-Fitzgerald contraction actually turned out to be essentially correct for reasons they never could have guessed. 

A 26 year old patent clerk in Bern, Switzerland published a paper in 1905 entitled, On the Electrodynamics of Moving Bodies.  That young man was named Albert Einstein and his paper became the basis for the theory that did more to alter our view of reality than any other theory in the history of mankind.  That theory is known to us as the Theory of Special Relativity.