Quick Note:

In book three The Alchemist, Khalid demonstrates that when air is removed from the fused globe, the force that is holding the two halves together is so strong that it is impossible to pull apart. As described in the book when not even four horse running in the opposite direction were able to pull it apart, thus explaining the effects of objects in a Vacuum.

Vacuum

(From Wikipedia, the free encyclopedia)

A vacuum is a volume of space that is essentially empty of matter, so that gaseous pressure is much less than standard atmospheric pressure. The root of the word vacuum is the Latin adjective vacuus which means "empty," but space can never be perfectly empty. A perfect vacuum with a gaseous pressure of absolute zero is a philosophical concept that is never observed in practice, not least because quantum theory predicts that no volume of space is perfectly empty in this way. Physicists often use the term "vacuum" slightly differently. They discuss ideal test results that would occur in a perfect vacuum, which they simply call "vacuum" or "free space" in this context, and use the term partial vacuum to refer to the imperfect vacua realized in practice.
The quality of a vacuum is measured by how closely it approaches a perfect vacuum. The residual gas pressure is the primary indicator of quality, and it is most commonly measured in units of torr, even in metric contexts. Lower pressures indicate higher quality, although other variables must also be taken into account. Quantum mechanics sets limits on the best possible quality of vacuum. Outer space is a natural high quality vacuum, mostly of much higher quality than what can be created artificially with current technology. Low quality artificial vacuums have been used for suction for millennia.
Vacuum has been a common topic of philosophical debate since Ancient Greek times, but it was not studied empirically until the 17th century. Experimental techniques were developed following Evangelista Torricelli's theories of atmospheric pressure. Vacuum became a valuable industrial tool in the 20th century with the introduction of the light bulb and vacuum tube, and a wide array of vacuum technology has since become available. The recent development of human spaceflight has raised interest in the impact of vacuum on human health, and life forms in general.

Uses

Vacuum is useful in a variety of processes and devices. Its first common use was in Incandescent light bulbs to protect the tungsten filament from chemical degradation. Its chemical inertness is also useful for electron beam welding, for chemical vapor deposition and dry etching in semiconductor fabrication and optical coating fabrication, for cold welding, and for vacuum packing. The reduction of convection improves the thermal insulation of thermos bottles and double-paned windows. Deep vacuum promotes outgassing which is used in freeze drying, adhesive preparation, distillation, metallurgy, and process purging. The electrical properties of vacuum make electron microscopes and vacuum tubes possible, including cathode ray tubes. The removal of air friction is useful for flywheel energy storage and ultracentrifuges.
Suction is used for a very wide variety of applications. The Newcomen steam engine used vacuum instead of pressure to drive a piston. In the 19th century, vacuum was used for traction on Isambard Kingdom Brunel's experimental atmospheric railway.

Historical interpretation

Historically, there has been much dispute over whether such a thing as a vacuum can exist. Ancient Greek philosophers did not like to admit the existence of a vacuum, asking themselves "how can 'nothing' be something?". Plato found the idea of a vacuum inconceivable. He believed that all physical things were instantiations of an abstract Platonic ideal, and could not imagine an "ideal" form of a vacuum. Similarly, Aristotle considered the creation of a vacuum impossible—nothing could not be something. Later Greek philosophers thought that a vacuum 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 the vacuum whereby he investegated handheld plungers in water. [7][8]

In the Middle Ages, Christians held the idea of a vacuum 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 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 vacuum arising—that is, whether nature abhorred a vacuum. 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 vacuum if he so wished.[9]

Opposition to the idea of a vacuum 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 vacuum at the top of a mercury barometer. Some people believe that although Torricelli produced the first sustained vacuum in a laboratory, it was Blaise Pascal who recognized it for what it was. Robert Boyle later conducted experiments on the properties of vacuum. 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 vacuum then lapsed until 1855 when Heinrich Geissler invented the mercury displacement pump and achieved a record vacuum of about 10 Pa (0.1 Torr). A number of electrical properties become observable at this vacuum level, and this renewed interest in vacuum. This led to the development of the vacuum 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 vacuum, 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 vacuum 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 vacuum 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 vacuum 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 vacuum 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.

(From Wikipedia article "Vacuum", accessed 2/19/07, GNU Free Documentation License)