Ether theory, or aether theories, is an idea in physics which proposes the existence of a medium that can transmit gravitational or electromagnetic forces. “Aether” is the Greek word for air, a reference to either heavenly or fresh air, and it is believed that this medium must be a space-filling substance for the transmission to occur.
There are several different ether theories that have been proposed over the years, but most have fallen out of favor by modern physicists because of the development of rules regarding special relativity. Although modern physics does look at non-standard interpretations, the presence of the ether theory still holds relevance.
General Relativity and the Ether Theory
When Albert Einstein proposed the theory of general relativity, he referred to the gravitational field within the theory as “aether.” His terminology never gained real support, but the concept still remains. “This aether,” Einstein wrote, “may not be thought of as endowed with the quality characteristic of ponderable media, as consisting of parts which may be tracked through time.”
“The idea of motion may not be applied to it.” This means the aether could potentially stand alone, outside of the rules of relativity that Einstein proposed.
The reasoning behind Einstein’s thinking is known really only to him, but may be based on the ideas of luminiferous aether and mechanical gravitational aether.
It was Isaac Newton who suggested the idea that an aether could exist in 1718. He wrote that although spaces may have seemed empty, they could be filled with compact and dense bodies that could not be distinguished through mere perception. If that was the case on our planet, then what could the aether be like when considering celestial bodies or the vastness of the universe?
Over the next century, several solutions that attempting to explain the propagation of light or the movement of gravity were all proposed as various ether theories. For light to exist, ether theory suggests that a medium must exist. The goal of the ether theories was to describe that medium.
Lorentz and Fitzgerald offered a framework that could explain motion of absolute aether while being undetectable. In 1905, when the special theory of relativity was introduced by Einstein, the mathematics of both ideas were the same. This event led to the eventual dismissal by most physicists of luminiferous aether and would be the final nail in the coffin for ideas of mechanical gravitational aether.
How a Quantum Vacuum Fits into Ether Theory
In the world of quantum mechanics, spacetime is non-empty unless being evaluated at an extremely small scale. Particle pairs can appear and disappear quickly, which creates the foundation of a particulate ether theory being possible.
The theory of relativity does not suggest or attempt to eliminate the idea that matter pervades the universe. It only suggests that matter in our universe is symmetrical in its construction. When considering the vacuum of space, therefore, an interesting question persists: is there a medium within the vacuum of space that is similar in structure to the orange juice that sits in your glass?
As experiments using particle acceleration have discovered in recent years, the vacuum of space is like looking through a transparent piece of glass. You may not see that it is there, but if you walk into it, you’ll have evidence of its existence. And, if you hit a piece of glass hard enough, it will either splinter, shatter, or break in some other way.
That means, for all practical purposes, the airless void of space is a relativistic ether. It may not be called that because of the negative connotation that science has applied to this term, but that does not exclude it from being potentially correct.
What We Can Take from the Ether Theory
Ether theory is an attempt to explain how forces move in the universe. There must be some level of substance to the empty spaces that we encounter for electromagnetic and gravitational forces to work. We can see gravity working in something as basic as the orbit of our planet around the sun or a satellite around the Earth, which means there must be some level of substance that fills the void.
As we learn more about what this substance may be, whether it ends up being dark matter or some exotic particle we’ve never encountered before, we will also know more about the basic structures of the universe and how that relates to human life. Hidden or in plain sight and just not recognizable with current technologies, with that kind of knowledge, the future’s potential is virtually unlimited.