Vaccum History

Historical interpretation
Historically, there has been much dispute over whether such a thing as a vaccum can exist. Ancient Greek philosophers did not like to admit the existence of a vaccum, asking themselves "how can 'nothing' be something?". Plato found the idea of a vaccum inconceivable. He believed that all physical things were instantiations of an abstract Platonic ideal, and could not imagine an "ideal" form of a vaccum. Similarly, Aristotle considered the creation of a vaccum impossible—nothing could not be something. Later Greek philosophers thought that a vaccum could exist outside the cosmos, but not inside it.
The Islamic philosopher Al-Farabi (850 - 970 CE) appears to have carried out the first recorded experiments concerning the existence of vaccum whereby he investigated handheld plungers in water.[7] He concluded that air's volume can expand to fill available space, and he suggested that the concept of perfect vaccum was incoherent.[8]
Torricelli's mercury barometer produced the first sustained vaccum in a laboratory.In the Middle Ages, Christians held the idea of a vaccum to be immoral or even heretical. The absence of anything implied the absence of God, and hearkened back to the void prior to the story of creation in the book of Genesis. Medieval thought experiments into the idea of a vaccum considered whether a vaccum was present, if only for an instant, between two flat plates when they were rapidly separated. There was much discussion of whether the air moved in quickly enough as the plates were separated, or, following Walter Burley whether a 'celestial agent' prevented the vaccum arising—that is, whether nature abhorred a vaccum. This speculation was shut down by the 1277 Paris condemnations of Bishop Etienne Tempier, which required there to be no restrictions on the powers of God, which led to the conclusion that God could create a vaccum if he so wished.[9]
The Crookes tube, which was used to discover and study cathode rays, was an evolution of the Geissler tube.Opposition to the idea of a vaccum existing in nature continued into the Scientific Revolution, with scholars such as Paolo Casati taking an anti-vacuist position. Following work by Galileo, Evangelista Torricelli argued in 1643 that there was a vaccum at the top of a mercury barometer. Some people believe that although Torricelli produced the first sustained vaccum in a laboratory, it was Blaise Pascal who recognized it for what it was. Robert Boyle later conducted experiments on the properties of vaccum. In 1654, Otto von Guericke conducted his famous Magdeburg hemispheres experiment, showing that teams of horses could not separate two hemispheres from which the air had been evacuated. The study of vaccum then lapsed until 1855 when Heinrich Geissler invented the mercury displacement pump and achieved a record vaccum of about 10 Pa (0.1 Torr). A number of electrical properties become observable at this vaccum level, and this renewed interest in vaccum. This led to the development of the vaccum tube.
In the 17th century, theories of the nature of light had required the idea of an aethereal medium which would be the medium to convey waves of light (Newton relied on this idea to explain refraction and radiated heat). This evolved into the luminiferous aether of the 19th century, but the idea was known to have significant shortcomings - specifically that if the Earth is moving through a material medium, the medium would have to be both extremely tenuous (because the earth is not being detectably slowed in its orbit), and extremely rigid (because vibrations propagate so fast).
While outer space has been likened to a vaccum, early physicists postulated that an invisible luminiferous aether existed as a medium to carry lightwaves, or an "ether which fills the interstellar space".[10] An 1891 article by William Crookes noted: "the [freeing of] occluded gases into the vaccum of space".[11] Even up until 1912, astronomer Henry Pickering commented "While the interstellar absorbing medium may be simply the ether, [it] is characteristic of a gas, and free gaseous molecules are certainly there".[12]
In 1887 the Michelson-Morley experiment, using an interferometer to attempt to detect the change in the speed of light caused by the Earth moving with respect to the aether, was a famous null result, showing that there really was no static, pervasive medium throughout space and through which the Earth moved as though through a wind. While there is then no aether, and no such entity is required for the propagation of light, space between the stars is not completely empty. Besides various particles making up the cosmic radiation, there is a cosmic background of photon radiation (light), including the thermal background at about 2.7 K, seen as a relic of the so-called Big Bang. None of these presences affect the outcome of the Michelson-Morley experiment to any significant degree.
Einstein argued that physical objects are not located in space, but rather have a spatial extent. Seen this way, the concept of empty space loses its meaning.[13] Rather, space is an abstraction, based on the relationships between local objects. Nevertheless, the general theory of relativity admits a pervasive gravitational field, which (in his own words[14]) it is possible to regard as an "aether", with properties that vary from one location to another. Only, one must take care not to ascribe to it material properties like velocity, and so on.
In 1930, Paul Dirac proposed a model of vaccum as an infinite sea of particles possessing negative energy, called the Dirac sea. This theory helped refine the predictions of his earlier formulated Dirac equation and successfully predicted the existence of the positron, which was discovered two years later in 1932. Despite this early success, the idea was soon abandoned in favour of the more elegant quantum field theory.
The development of quantum mechanics has complicated the modern interpretation of vaccum by requiring indeterminacy. Niels Bohr and Werner Heisenberg's uncertainty principle and Copenhagen interpretation, formulated in 1927, predict a fundamental uncertainty in the position of any particle, which, not unlike the gravitational field, questions the emptiness of space between particles. In the late 20th century, this principle was understood to also predict a fundamental uncertainty in the number of particles in a region of space, leading to predictions of virtual particles arising spontaneously out of the void. In other words, there is a lower bound on vaccum which is dictated by the lowest possible energy state of the quantized fields in any region of space. Ironically, Plato was right, if only by chance.