Editing Zero-point energy (section)

=== Early aether theories ===
[[File:James Clerk Maxwell.png|thumb|upright|James Clerk Maxwell]]
Zero-point energy evolved from historical ideas about the [[vacuum]]. To [[Aristotle]] the vacuum was {{lang|grc|τὸ κενόν}}, "the empty"; i.e., space independent of body. He believed this concept violated basic physical principles and asserted that [[Classical element#Greece|the elements]] of [[Fire (classical element)|fire]], [[Air (classical element)|air]], [[Earth (classical element)|earth]], and [[Water (classical element)|water]] were not made of atoms, but were continuous. To the [[atomists]] the concept of emptiness had absolute character: it was the distinction between existence and nonexistence.{{sfnp|Saunders|Brown|1991|p=1}} Debate about the characteristics of the vacuum were largely confined to the realm of [[philosophy]], it was not until much later on with the beginning of [[Renaissance|the renaissance]], that [[Otto von Guericke]] invented the first vacuum pump and the first testable scientific ideas began to emerge. It was thought that a totally empty volume of space could be created by simply removing all gases. This was the first generally accepted concept of the vacuum.{{sfnp|Conlon|2011|p=225}}

Late in the 19th century, however, it became apparent that the evacuated region still contained [[thermal radiation]]. The existence of the [[Luminiferous aether|aether]] as a substitute for a true void was the most prevalent theory of the time. According to the successful [[Electromagnetism|electromagnetic]] aether theory based upon [[James Clerk Maxwell|Maxwell's]] [[electrodynamics]], this all-encompassing aether was endowed with energy and hence very different from nothingness. The fact that electromagnetic and gravitational phenomena were transmitted in empty space was considered evidence that their associated aethers were part of the fabric of space itself. However Maxwell noted that for the most part these aethers were ''ad hoc'':

{{Blockquote|To those who maintained the existence of a plenum as a philosophical principle, nature's abhorrence of a vacuum was a sufficient reason for imagining an all-surrounding aether&nbsp;... 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, till a space had been filled three or four times with aethers.{{sfnp|Kragh|Overduin|2014|p=7}}}}

Moreever, the results of the [[Michelson–Morley experiment]] in 1887 were the first strong evidence that the then-prevalent aether theories were seriously flawed, and initiated a line of research that eventually led to [[special relativity]], which ruled out the idea of a stationary aether altogether. To scientists of the period, it seemed that a true vacuum in space might be created by cooling and thus eliminating all radiation or energy. From this idea evolved the second concept of achieving a real vacuum: cool a region of space down to absolute zero temperature after evacuation. Absolute zero was technically impossible to achieve in the 19th century, so the debate remained unsolved.