The Life and Death of the Aether (Part II)

Might the Key to the Future Rust in the Past?

The failure of relativity and quantum mechanics to unify our physical conception of reality in the 20th and 21st centuries is a clear call to action.  New ways of thinking about the problem are absolutely mandatory for further progress.  In the words of former editor at Science and Nature magazines, and author of The Dream Universe, Dr. David Lindley, “We need a new Einstein.”  

 If Dr. Lindley is correct, that next Einstein, or Einsteins, had better have a good grip on the history of the search for explanation of light, gravity, and magnetism, which led to the present situation.  This blog series, which started here, serves to summarize that history for you future Einsteins, using the original words of the venerable predecessors wherever possible. 

 Einstein himself was well aware of the detailed investigations that preceded him and in light of the current stagnation, we will all prove wise to return to square one and check our premises.  In the forward to Max Jammar’s book on the history of the concept of space, Einstein wrote:

“The scientist makes use of a whole arsenal of concepts which he imbibed practically with his mother's milk; and seldom if ever is he aware of the eternally problematic character of his concepts…And yet in the interests of science it is necessary over and over again to engage in the critique of these fundamental concepts, in order that we may not unconsciously be ruled by them.”

 It is my sincere hope that by digging deeply into the history of the science of invisible phenomena I will unearth gaps, which our brightest minds can capitalize on in the development of future theory.  One thing is absolutely clear — the thinkers up until Einstein, by and large, conceived of a physical mediator of these phenomena.  Even Newton, the first to publish a gravitational theory devoid of mediation, was reluctant to specify the cause of the motions he described (and described with great accuracy).  Scientists gave their mediator of invisible phenomena the title, aether, after Plato’s fifth element. 

Today, we pick up the story in France, at the turn of the 17th century with the birth of Rene Descartes and follow his early work into the mechanics of light.  

“Give me matter and motion, and I will construct the universe.”

 Descartes provided the first mechanistic examinations of light.  He used his aether model explain magnetism and gravity as well, and thinkers entertained these ideas off and on until Faraday and Maxwell introduced the modern conception of the “field” in the 19th century.  

 For Descartes, material existence was not qualified by touch or other observational sensory means, but rather through the concept of extension.  He considered space itself, categorized for the first time in the coordinate system that bears his name, a particular form of matter.  Where there was extension there was matter.  Because he was fully committed to mechanical explanations for physical reality, distance between objects implied invisible material between them.  Invisible attractions like gravity, or magnetism required contact mechanisms, no matter how much they lacked the lacked empirical evidence.  He was in no way interested in what he considered the irrational conceptions of action-at-a-distance.  

Descartes developed a vortex model of the motions of bodies, based upon the swirling of the luminiferous aether.  Fascinatingly, scientists revered his model for several hundred years, even after Newton had lost faith in the aethereal medium and published his widely accepted, yet mediator-less, action-at-a-distance work on gravitation in at the turn of the 18th century.  Luminaries as far-reaching as Euler and the Bernoulli brothers continued to develop Descartes’ vortex model throughout the following century.  So, what exactly was Descartes’ aether, and how did it address the phenomena in a way that was so appealing at the time?  

The distance that extended between ordinary objects was allegedly filled with transparent matter of a most exquisite form.  Descartes reasoned that the aether is comprised of tiny, yet discrete, spherical fibers, which can be divided further and perhaps indefinitely.  This allows the fibers unlimited degrees of freedom for independent motion.  Most presciently, he was the first to indicate that light reflected an occurrence between worldly objects, within the aether, an idea that would see development up until our presently accepted conception of light as a self-propagating electromagnetic field.  You can learn more about the development of the modern fields here.  

Descartes ascribed the sensation of light to in-situ pressures within the aether affecting the eye through touch.  In an essay entitled, Dioptrique, he wrote:

“I would have you think that light is nothing other, in bodies that we call luminous, than a certain movement, or a very quick and strong action which moves towards our eyes through the medium of the air and other transparent bodies in the same fashion as the movement or the resistance of bodies encountered by this blind person, passing to his hand by the intermediary of the walking stick.”

 The idea of a highly rigid, yet composite, mediator made sense to Descartes because it could convey the action of a luminous body, like the sun, nearly instantaneously to an observer on Earth.  Even colors could be envisioned as different pressures:

“Nor will you find it strange that, by means of it, we can see all sorts of colors; and perhaps you will even believe that these colors are nothing other in the bodies that we call colored than the different ways in which these bodies receive light and send it back to our eyes: if you consider that the differences that a blind person notices between trees, stones, water, and other things, by the intermediary of his stick, seem no more the same to him than the differences we see between red, yellow, green, and all the other colors; and nonetheless these differences are nothing other than the different ways of moving, or resisting the movements of, this stick.”

In a later essay within the same series, he also took a crack at explaining the particular motion responsible for colors and came very close to our present conception.  For instance, he wrote that colors resulted from various spinning motions within the substances, which combined in proportions:

“the movement of the parts of the bodies which we call colored, can compete in various ways with light, to increase or decrease the whirling of the parts of the subtle matter (aether).”

What is astounding, is that Descartes correctly imagined each color to have different energies, much like we do today with the concept of frequencies, but had the assignment backwards, presuming red to be the fastest and violet the slowest.  Yet it would be the Englishmen across the channel in the following century, that really tightened up our understanding of the nature of color.

Despite the extraordinary steps he took in conceiving of light, gravity, and magnetism, Descartes is primarily remembered for his invention of our modern coordinate system of geometry.  Perhaps it is this invention that ultimately allowed Einstein to formulate his relativistic theories in the 20th century.  In Einstein’s words, 

“These schematic considerations concern the nature of space from the geometric and from the kinematic point of view, respectively. They are in a sense reconciled with each other by Descartes' introduction of the coordinate system.”

Thanks Descartes!

Catching a Wave

 In 1665, Robert Hooke dropped a serious science bomb with his book, Micrographia.  It is an all-encompassing work, and the first full-length publication of the Royal Society. It stemmed from Hooke’s own experimentation with the newly innovated technology of microscopy.  Micrographia contains the first use of the term “cell,” among other gems.  

Hooke also sets up the idea of light as a vibration for the first time.  He departs from Descartes notion of light as a static pressure and sees the phenomenon instead as a motion of aethereal fibers themselves:

“this motion is propagated every way with equal velocity, whence necessarily every pulse or vibration of the luminous body will generate a Sphere, which will continually increase, and grow bigger, just after the same manner (though indefinitely swifter) as the waves or rings on the surface of the water do swell into bigger and bigger circles about a point of it, where by the sinking of a Stone the motion was begun, whence it necessarily follows, that all the parts of these Spheres undulated through a Homogeneous medium cut the Rays at right angles.”

In this conception, Hooke brings forth the “wave surface” — a notion preserved up to the present in the idea of a wavefront.  He also improved upon Descartes explanation of snell’s law.  While Descartes understood that refraction was the result of impeded forward motion by light, his lack of a vibratory theory ultimately hampered progress beyond this.

 Hooke, on the other hand, suggested that the properties of the refracting medium affected ability of the material to transmit aethereal pulsations.  This pulsating theory led him to a bizarre theory of colors.  He wrote, 

“precise hypothesis regarding the different colours was that Blue is an impression on the Retina of an oblique and confus'd pulse of light, whose weakest part precedes, and whose strongest follows. And, that red is an impression on the Retina of an oblique and confus'd pulse of light, whose strongest part precedes, and whose weakest follows." 

The theory was not measurably an improvement over Descartes’ notion, and yet both were immediately overturned in 1671, when a young fellow at Trinity College named Isaac Newton published his work with a prism during the plague of 1666.  Newton definitively explained that white light is an assembly of all colors, along an indefinite continuum.  He wrote,
  
“Colours are not Qualifications of light derived from Refractions, or Reflections of natural Bodies (as 'tis generally believed), but Original and connate properties, which in divers Rays are divers. Some Rays are disposed to exhibit a red colour and no other: some a yellow and no other, some a green and no other, and so of the rest. Nor are there only Rays proper and particular to the more eminent colours, but even to all their intermediate gradations.”

 For a brief moment there was a calm on the old continent, but it would not hold for long.  Newton, despite his great victory in establishing a theory of color, could not be persuaded to embrace the vibratory theory of Hooke.  A long bloody intellectual war would ensue in the coming century, fought all throughout the west to determine if light was a wave in the aether or a particle of aether in flight.  In some sense, quantum mechanics issued a ceasefire in the 20th century.  And yet at the same time, much confusion abounds as to the physical interpretation of the apparent paradox.

Next time, we’ll jump into the front lines of the particle-wave civil war between the venerable Newton and his myriad opponents, including Jean Fresnel, Christiaan Huygens, and Thomas Young.