According to ancient and medieval science, aether, also spelled æther or ether, also
called quintessence, is the material that fills the region of the universe above the
terrestrial sphere.
The concept of aether was used in several theories to explain several natural phenomena,
such as the traveling of light and gravity.
In the late 19th century, physicists postulated that aether permeated all throughout space,
providing a medium through which light could travel in a vacuum, but evidence for the presence
of such a medium was not found in the Michelson-Morley experiment.
Mythological origins
The word αἰθήρ in Homeric Greek means "pure, fresh air" or "clear sky."
In Greek mythology, it was thought to be the pure essence that the gods breathed, filling
the space where they lived, analogous to the air breathed by mortals.
It is also personified as a deity, Aether, the son of Erebus and Nyx in traditional Greek
mythology.
Aether is related to αἴθω "to incinerate", and intransitive "to burn, to shine", meaning
"people with a burnt visage").
See also Empyrean.
Fifth element
In Plato's Timaeus speaking about air, Plato mentions that "there is the most translucent
kind which is called by the name of aether".
Aristotle, who had been Plato's student at the Akademia, disagreed with his former mentor
and added aether to the system of the classical elements of Ionian philosophy as the "fifth
element", He noted that the four terrestrial classical elements were subject to change
and naturally moved linearly.
Aether however, located in the celestial regions and heavenly bodies, moved circularly.
In Aristotle's system of classical elements, aether had none of the qualities the terrestrial
classical elements had.
Aether was neither hot nor cold, neither wet nor dry.
Aether did not follow Aristotelian physics either.
Aether was also incapable of motion of quality or motion of quantity.
Aether was only capable of local motion.
Aether naturally moved in circles, and had no contrary, or unnatural, motion.
Aristotle also noted that crystalline spheres made of aether held the celestial bodies.
The idea of crystalline spheres and natural circular motion of aether led to Aristotle's
explanation of the observed orbits of stars and planets in perfectly circular motion in
crystalline aether.
Medieval scholastic philosophers granted aether changes of density, in which the bodies of
the planets were considered to be more dense than the medium which filled the rest of the
universe.
Robert Fludd stated that the aether was of the character that it was "subtler than light".
Fludd cites the 3rd-century view of Plotinus, concerning the aether as penetrative and non-material.
See also Arche.
Quintessence Quintessence is the Latinate name of the fifth
element used by medieval alchemists for a medium similar or identical to that thought
to make up the heavenly bodies.
It was noted that there was very little presence of quintessence within the terrestrial sphere.
Due to the low presence of quintessence, earth could be affected by what takes place within
the heavenly bodies.
This theory was developed in the 14th century text “The testament of Lullius”, attributed
to Raymond Lull.
The use of quintessence became popular within medieval alchemy.
Quintessence stemmed from the medieval elemental system, which consisted of the four classical
elements, and aether, or quintessence, in addition to two chemical elements representing
metals: sulphur, 'the stone which burns', which characterized the principle of combustibility,
and mercury, which contained the idealized principle of metallic properties.
This elemental system spread rapidly throughout all of Europe and became popular with alchemists,
especially in medicinal alchemy.
Medicinal alchemy then sought to isolate quintessence and incorporate it within medicine and elixirs.
Due to quintessence's pure and heavenly quality, it was thought that through consumption one
may rid oneself of any impurities or illnesses.
In “The book of Quintessence”, a 15th-century English translation of a continental text,
quintessence was used as a medicine for many of man’s illnesses.
A process given for the creation of quintessence is distillation of alcohol seven times.
Over the years, the term quintessence, has become synonymous with elixirs, medicinal
alchemy, and the philosopher’s stone itself.
Legacy
With the 18th century physics developments physical models known as "aether theories"
made use of a similar concept for the explanation of the propagation of electromagnetic and
gravitational forces.
As early as the 1670s, Newton used the idea of aether to help match observations to strict
mechanical rules of his physics.
However, the early modern aether had little in common with the aether of classical elements
from which the name was borrowed.
These aether theories are considered to be scientifically obsolete, as the development
of special relativity showed that Maxwell's equations do not require the aether for the
transmission of these forces.
However, Einstein himself noted that his own model which replaced these theories could
itself be thought of as an aether, as it implied that the empty space between objects had its
own physical properties.
Despite the early modern aether models being superseded by general relativity, occasionally
some physicists have attempted to reintroduce the concept of aether in an attempt to address
perceived deficiencies in current physical models.
One proposed model of dark energy has been named "quintessence" by its proponents, in
honor of the classical element.
This idea relates to the hypothecial form of dark energy postulated as an explanation
of observations of an accelerating universe.
It has also been called a fifth fundamental force.
This quintessence however differs from the cosmological constant, in that it is changing
over time unlike the constant and unchanging quintessence of the medieval and ancient Greek
period.
Aether and light The motion of light was a long standing investigation
in physics for hundreds of years before the 20th century.
The use of aether to describe this motion was popular during the 17th and 18th centuries,
including a theory proposed by the less well-known Johann Bernoulli, who was recognized in 1736
with the prize of the French Academy.
In his theory, all space is permeated by aether containing "excessively small whirlpools."
These whirlpools allow for aether to have a certain elasticity, transmitting vibrations
from the corpuscular packets of light as they travel through.
This theory of luminiferous aether would influence the wave theory of light proposed by Christiaan
Huygens, in which light traveled in the form of longitudinal waves via an "omnipresent,
perfectly elastic medium having zero density, called aether".
At the time, it was thought that in order for light to travel through a vacuum, there
must have been a medium filling the void through which it could propagate, as sound through
air or ripples in a pool.
Later, when it was proved that the nature of light wave is transverse instead of longitudinal,
Huygens' theory was replaced by subsequent theories proposed by Maxwell, Einstein and
de Broglie, which rejected the existence and necessity of aether to explain the various
optical phenomena.
These theories were supported by the results of the Michelson-Morley experiment in which
evidence for the presence of aether was conclusively absent.
The results of the experiment influenced many physicists of the time and contributed to
the eventual development of Einstein's theory of special relativity.
Aether and gravitation
Aether has been used in various gravitational theories as a medium to help explain gravitation
and what causes it.
It was used in one of Sir Isaac Newton's first published theories of gravitation, Philosophiæ
Naturalis Principia Mathematica.
He based the whole description of planetary motions on a theoretical law of dynamic interactions.
He renounced standing attempts at accounting for this particular form of interaction between
distant bodies by introducing a mechanism of propagation through an intervening medium.
He calls this intervening medium aether.
In his aether model, Newton describes aether as a medium that "flows" continually downward
toward the Earth's surface and is partially absorbed and partially diffused.
This "circulation" of aether is what he associated the force of gravity with to help explain
the action of gravity in a non-mechanical fashion.
This theory described different aether densities, creating an aether density gradient.
His theory also explains that aether was dense within objects and rare without them.
As particles of denser aether interacted with the rare aether they were attracted back to
the dense aether much like cooling vapors of water are attracted back to each other
to form water.
In the Principia he attempts to explain the elasticity and movement of aether by relating
aether to his static model of fluids.
This elastic interaction is what caused the pull of gravity to take place, according to
this early theory, and allowed an explanation for action at a distance instead of action
through direct contact.
Newton also explained this changing rarity and density of aether in his letter to Robert
Boyle in 1679.
He illustrated aether and its field around objects in this letter as well and used this
as a way to inform Robert Boyle about his theory.
Although Newton eventually changed his theory of gravitation to one involving force and
the laws of motion, his starting point for the modern understanding and explanation of
gravity came from his original aether model on gravitation.
See also Akasha
Celestial spheres Life energy
Light energy Plane
References