Vacuum

For other uses, see vacuum cleaner and Vacuum (musical group).

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.

Related Topics:
Ancient Greek - Philosophers - Plato - Platonic ideal - Aristotle - Cosmos

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In the Middle Ages, the idea of a vacuum was thought 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 vacuum considered whether a vacuum 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 William Burley whether a 'celestial agent' prevented the vacuum arising—that is, whether nature abhorred a vacuum. This speculation became irrelevant after the Paris condemnations of Bishop 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.

Related Topics:
Middle Ages - God - Genesis - William Burley - Bishop Tempier

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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 vacuum, it was Blaise Pascal who recognized it for what it was. Robert Boyle later conducted experiments on the effects of a vacuum. For example, a canary exposed to vacuum would become unconscious, but would revive when air was reintroduced. 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.

Related Topics:
Galileo - Evangelista Torricelli - Mercury - Barometer - Blaise Pascal - Robert Boyle - Canary - Air - 1654 - Otto von Guericke - Magdeburg hemispheres

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Concurrently, theories of the nature of light had proposed the idea of a 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 idea of the 19th century, but it was known to have significant shortcomings. 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. (Of course, if the aether were the medium in which light waves traveled and electromagnetic and gravitational fields manifest, then it would be exceedingly difficult to distinguish the characteristics of such medium from those of the field or fields one was in. It would no more be possible to show that the Earth moved in relation to such an aether than it would be to illustrate that it moved in relation to its own electromagnetic and gravitational fields.)

Related Topics:
Light - Aethereal medium - Newton - Luminiferous aether - Michelson-Morley experiment - Interferometer - Speed of light - Earth

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