One of the most important science experiments of all time was a complete and utter failure.
In 1887, Albert Michelson and Edward Morley set up their project in the dormitory basement at a university in Cleveland, Ohio. The idea was to bounce light beams off mirrors in different directions and measure their speeds. The two researchers thought their hoped-for result—capturing light moving at different velocity—would help to prove the existence of aether.
The aether was the invisible material thought to permeate all the empty space in the universe, used by famous thinkers from Aristotle to Isaac Newton to explain the mysteries of the natural world. The much-heralded Michelson-Morley experiment, as the 1887 event would go down in history, sought to detect the existence of this undetectable substance.
Instead, it found nothing.
The experiment would go down as a faceplant, a failure that marked the end for a theory that had dominated physics for 2,000 years. But the fallout of the Michelson-Morley experiment led to the idea of the universal speed of light, inspired Einstein’s breakthroughs in relativity, and opened the door to much of modern physics. Sometimes it takes failure to move forward.
The Stuff of Gods
Aether meant many things to many people. Ancient Greeks saw aether as the god of light and the fifth element of the universe. To the medieval alchemists, it was the fabled philosopher’s stone that could turn lead into gold and prolong life. Centuries later, early modern scientists like René Descartes and Nikola Tesla were still pointing to aether to explain fundamental natural phenomena like gravity and light. Yet aether does not exist, and it never did. It may be the most enduring imaginary concept in scientific history.
Aether was invented by the ancients. In Greek mythology it described the pure air that the gods breathed in the heavens as opposed to the normal air breathed by mortals on Earth.
The word “aether” comes from the Greek aithêr, meaning “upper air.” The Greeks’ mythology described the pure air that the gods breathed in the heavens as opposed to the normal air breathed by mortals on Earth, and went further than that. Aether was also a Greek god, one of the first-born deities in the pantheon, the primordial god of light and the sky. This bright, divine Aether was the classical philosophers’ version of our upper atmosphere. In Plato’s theory of the cosmos, he writes that there are different kinds of air and “the brightest part is called the aether.”
In the 4th century BCE, Aristotle brought this concept of heavenly air into the world of physics. His philosophy saw aether as the fifth element, after earth, air, fire, and water. He believed the four terrestrial elements were changeable and transient, but the planets and stars were eternal and thus must be made of a different substance that transcended the earthly four. He called it aether.
Centuries later, the classical fifth element would inspire another epic but influential scientific misfire: alchemy.
The Alchemist’s Cookbook
Alchemy, the magical medieval proto-science, came into vogue in the Western world in the 12th and 13th centuries, when the texts of the Greek and Arab philosophers were translated into Latin and European scholars finally got wind of these ancient ideas.
Alchemists dusted off the antique concept of aether and put a new spin on it. To them, it described the most pristine and perfect essence found in nature, which they called “quintessence.” They too saw quintessence (so named from the Latin phrase qüinta essentia, meaning “fifth essence”) as divine, but believed it was found on Earth as well as in the heavens. A bit of godly essence was hidden in all things, whether animal, plant, or mineral. The trick was freeing it.
Aristotle believed the four physical elements were changeable, and alchemists took this idea and ran with it. The underlying belief was that metals were alive and growing, and could change into other substances. Metals were all composed of the four elements, but were in different stages of maturity on their way to spiritual perfection.
The theory, then, was that by distilling a substance down to its elemental form and creating the perfect balance and proportions of the different elements, you could purify matter and transmute one substance into another. The ultimate goal was to turn immature base metals like lead into higher metals like gold by releasing their perfect state, or quintessence.
But what exactly was quintessence? That depends on which alchemist you ask. Alchemy was a secretive and enigmatic art with endless interpretations. To some, quintessence was a subtle substance found in some degree in each of the other four elements. Others thought it contained all the other elements within it. One of the best-known European alchemists, the 16th-century Swiss physician Philippus Aureolus Paracelsus, called the aether element “the substance of stars and souls.” Isaac Newton, a passionate alchemist, described it as “the perfect Elixir ... our gold ... red virginal milk most fragrant and healthy.” In essence, it was a pure and perfect spirit concealed in all things—both chemically and spiritually.
The Philosopher’s Stone
The alchemists’ quest for gold wasn’t just about metallurgy, though. This was Christian Europe, after all, and alchemy’s aims were spiritual as much as chemical. Metals and mortals could both be made more pure by freeing that little bit of divine spirit hidden in nature. Purification represented humans striving to perfect the soul. Achieving gold was like knowing God.
The holy grail of alchemy was the legendary philosopher’s stone, which wasn’t a stone at all but an elusive substance that could isolate the pure essence of a material and transmute it into something else, namely gold. In the medicinal corners of alchemy, it was also known as the elixir of life, a universal cure that could bring eternal life. In a sense, the Stone was the physical representation of the concept of perfection, or quintessence itself. In fact it was sometimes called the lapis aethereus, Latin for “aethereal stone.”
Discovering this magical substance was the magnum opus of any alchemist. Newton devised a secret recipe for the philosopher’s stone, though like most of his alchemy work, it wasn’t published until long after his death. The key ingredient of his recipe was mercury, which was likely also a key ingredient in the nervous breakdown he suffered in 1693 during his time experimenting with toxic chemicals.
A more happy side effect of the quest for the elusive stone was the accidental discovery of phosphorus, first made by boiling copious amounts of human pee. In 1669, a German hobby alchemist named Hennig Brand got his hands on a recipe for turning lead into gold using concentrated urine.
Brand somehow gathered more than 50 buckets of the golden liquid (he reportedly preferred the urine of beer drinkers), and after a likely gruesome period of experimentation in his basement laboratory, wound up with a bright, white liquid that would burst into flame when exposed to oxygen. Brand was certain had found the philosopher’s stone. In fact, he had discovered the 15th element on the periodic table, still used in the tips of matches today. He named it phosphorus, meaning “bringer of light.”
Aether 2.0
Alchemy would not survive the Age of Reason in the West. By the late 18th century it had morphed into the modern field of chemistry or else was relegated to the occult. Yet the theory of aether endured. In the 17th and 18th centuries, thinkers dusted off, revised, and reintroduced the concept of aether in another influential but ultimately flawed attempt to explain the natural world. This aether 2.0 was a subtle, invisible substance that existed everywhere, filling the “empty” vacuum of all space.
In 1644, when he developed his mechanical theory of gravity, French philosopher René Descartes (who thought, therefore he was) reasoned that empty space must not be empty at all and must be filled with something. He believed that something was aether. He envisioned a dense, fluid medium comprising colliding particles that could transmit forces, including the mysterious force of gravity. His theory said that as objects moved through the aether fluid, the displaced particles created vortices that pushed planets into orbit. Earth was an immense aether vortex, circling around the sun.
Descartes’ mechanical gravitation was less of a true scientific theory and more of a thought exercise. And while his vortex notion would be disproved, he got people thinking about the mechanics of the universe. In particular, he got Isaac Newton thinking about it just as the man under the apocryphal apple tree was about to change the world.
Aether played a major role in Newton’s early theories of gravity and light in the mid-1600s. He defined it as an elastic, invisible, strong, and subtle matter that existed everywhere in different forms. “It is not a single uniform substance,” he wrote, “but just as the air contains aqueous vapours, so the aether may contain various aetherial spirits adapted to produce the phenomena of electricity, magnetism and gravitation.”
Early in his career, Newton described gravity as the pressure caused by aether flowing downward toward Earth. But then he changed his mind, thanks to a nagging, unanswered question: If the mechanics of gravity were explained by particles of aether pushing celestial bodies toward Earth, then what was pushing the particles of aether?
Instead, in his monumental 1687 book Principia, Newton didn’t bother with the aether. He theorized that the forces of attraction and repulsion are acting on each other from a distance and proved many of the motions of the cosmos mathematically. But Newton admitted he couldn’t explain the cause of gravity itself, and famously declared he would not “feign hypothesis.” Some say he quietly speculated the aether had something to do it, but without any experiments to back it up, he did not publish the theory.
With the aether–gravity question shelved, attention turned to the nature of light—and yet another aether theory entered the stage.
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Invented for the Planets to Swim In
In the 18th and 19th centuries, as physicists grappled with light, there was some debate over whether it was a wave or a particle. (Trick question—we now know it has properties of both.) Scientists thought that if light were a wave, then it needed a medium to travel through. Waves, after all, aren’t objects themselves, but the effects of movement on a substance like air or water. And so, once again minds turned toward aether.
Dutch scientist Christiaan Huygens first proposed the “luminiferous” or light-bearing aether as a medium for the propagation of light. It was a popular theory. Nikola Tesla held onto it well into the 20th century, writing in 1938 that all attempts to explain the workings of the universe without recognizing the existence of a light-bearing aether are futile.
But as scientists learned more about the true nature of light, the properties of aether became increasingly magical. To be consistent with the laws of physics, aether had to be fluid, so it could fill all space, but also solid enough to support light waves. It existed everywhere, yet was invisible, weightless, undetectable, and had no effect on physical objects—almost as if it didn’t exist at all.
And still, the aether theory survived another major breakthrough in the understanding of light. Scottish physicist James Clerk Maxwell discovered that electromagnetic waves travel at the speed of light because in fact they are one and the same. In other words, radio waves and X-rays and visible light were all part of the same electromagnetic spectrum. Scientists were thrilled: This meant that the different kinds of waves didn’t need their own aethers, but all traveled through the same luminiferous aether.
A luminiferous aether became entrenched in physics, even as the aethers of yesteryear were considered fallacies, and theories about the nature of aether abounded. Maxwell himself summed up the state of affairs in his definition of aether for the Encyclopedia Britannica in 1878:
“Aethers were invented for the planets to swim in, to constitute electric atmospheres and magnetic effluvia, to convey sensations from one part of our bodies to another, and so on, until all space had been filled three or four times over with aethers … The only aether which has survived is that which was invented by Huygens to explain the propagation of light.”
And then, the aether died in a basement.
The Fail That Wasn’t
Michelson and Morley hypothesized that light would travel at different speeds as it moved in different directions through the aether. The goal of their famed experiment, conducted less than a decade after Maxwell’s formal definition of aether, was to record the effect of the “aether wind,” the idea that the rotating Earth moving through the aether should create a wind of sorts, and light beams moving through it would have a measurable drag.
Of course, they found no difference in speed. Experiments capable of more exact measurements followed, all with the same null result. After all these centuries, it seemed aether didn’t exist after all, a humbling revelation that Albert Einstein described as “very perplexing to physicists.” It seemed light traveled through a vacuum, not a luminiferous material.
Today we accept this fact as textbook science. In the 19th century, though, it required a radical realignment in thinking. Scientists started to abandon aether theory, and in its wake, an alternative model was proposed: Einstein’s theory of special relativity.
The theory of relativity didn’t disprove aether, but it provided a simpler explanation that didn’t require an absolute omnipresent medium for the motion of light. Einstein proposed that light traveled at a constant speed through a vacuum, and that everything is moving relative to everything else. An aether wasn’t needed as a fixed reference framework for the universe because time and space were relative, part of one continuum. Spacetime was the new aether.
In that sense, the Michelson–Morley experiment wasn’t a failure at all, but a titanic turning point in the way scientists considered the very nature of time and space. Twenty years later, Michelson became the first American scientist to win the Nobel Prize in Physics, for developing instruments used to accurately measure the speed of light.
Soon after special relativity, French physicist Louis de Broglie proposed another revolutionary theory. He found that electron particles may also have the properties of a wave, and matter on an atomic scale has the same dual nature as light. This groundbreaking hypothesis led to the theory of quantum mechanics, which also had no need for aether.
Quantum mechanics sealed the coffin. By the end of the 1920s, aether was discarded, archaic. And yet it didn’t disappear.
Dark Aether?
The term “aether” (or “ether”) lives on as a colloquial expression in the West, an abstract idea of the intangible void. Certain traditional cultures still consider aether the fifth element, and it plays prominently in the esoteric worlds of magic, mysticism, and the supernatural.
More recently, the spirit of aether has even come back into the discussion of the cosmos, thanks to the mysterious discoveries of dark matter and dark energy, the elusive force believed to be the cause of the accelerating expansion of the universe. It’s not hard to see the parallels between the aether of yore used to fill in the gaps of understanding and this new invisible, imponderable energy. In fact, a form of dark energy proposed by physicists in the 1980s was dubbed “quintessence” after the fifth element of antiquity.
The new quintessence has been described as a fifth fundamental force, after the four conventional forces of nature known to physics: gravitational, electromagnetic, strong nuclear, and weak nuclear forces. Dark matter and dark energy can’t be readily explained by any known theories of physics, which is leading scientists to consider whether there is another, yet-unknown force. Might as well call it aether.
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Meg is a writer and editor living in Brooklyn. She’s had the pleasure of nerding out about history and tech for Atlas Obscura, Motherboard, and Gizmodo.
