Changes

==Etymology==

==Etymology==

[[Latin]], from neuter of vacuus empty, from vacare to be empty

[[Latin]], from neuter of vacuus empty, from vacare to be empty

*Date: [http://en.wikipedia.org/wiki/16th_Century 1550]

*Date: [https://en.wikipedia.org/wiki/16th_Century 1550]

==Definitions==

==Definitions==

*1 : [[Absence|emptiness]] of [[space]]

*1 : [[Absence|emptiness]] of [[space]]

:b : a space partially exhausted (as to the highest [[degree]] possible) by artificial means (as an air pump)  

:b : a space partially exhausted (as to the highest [[degree]] possible) by artificial means (as an air pump)  

:c : a degree of rarefaction below atmospheric pressure

:c : a degree of rarefaction below atmospheric pressure

*3 a : a [[state]] or condition resembling a vacuum : void <the power vacuum in Indochina after the departure of the French — [http://en.wikipedia.org/wiki/Norman_Cousins Norman Cousins]>  

*3 a : a [[state]] or condition resembling a vacuum : void <the power vacuum in Indochina after the departure of the French — [https://en.wikipedia.org/wiki/Norman_Cousins Norman Cousins]>  

:b : a state of [[isolation]] from outside [[influences]] <people who live in a vacuum…so that the world outside them is of no [[moment]] — [http://en.wikipedia.org/wiki/W.S._Maugham W. S. Maugham]>

:b : a state of [[isolation]] from outside [[influences]] <people who live in a vacuum…so that the world outside them is of no [[moment]] — [https://en.wikipedia.org/wiki/W.S._Maugham W. S. Maugham]>

*4 : a device [[creating]] or utilizing a partial vacuum; especially : vacuum cleaner

*4 : a device [[creating]] or utilizing a partial vacuum; especially : vacuum cleaner

==Description==

==Description==

In everyday usage, '''vacuum''' is a volume of [[space]] that is essentially empty of [[matter]], such that its gaseous pressure is much less than atmospheric pressure. The [[word]] comes from the Latin term for "empty". Even putting aside the [[complexities]] of the [[quantum]] vacuum, the [[classical]] notion of a [[perfect]] vacuum with gaseous pressure of exactly zero is only a [[philosophical]] [[concept]] and never is [[observed]] in [[practice]]. [[Physicists]] often discuss [[ideal]] test results that would occur in a perfect vacuum, which they simply call "vacuum" or "free space", and use the term partial vacuum to refer to real vacuum. The [[Latin]] term in vacuo is also used to describe an object as being in what would otherwise be a vacuum.

In everyday usage, '''vacuum''' is a volume of [[space]] that is essentially empty of [[matter]], such that its gaseous pressure is much less than atmospheric pressure. The [[word]] comes from the Latin term for "empty". Even putting aside the [[complexities]] of the [[quantum]] vacuum, the [[classical]] notion of a [[perfect]] vacuum with gaseous pressure of exactly zero is only a [[philosophical]] [[concept]] and never is [[observed]] in [[practice]]. [[Physicists]] often discuss [[ideal]] test results that would occur in a perfect vacuum, which they simply call "vacuum" or "free space", and use the term partial vacuum to refer to real vacuum. The [[Latin]] term in vacuo is also used to describe an object as being in what would otherwise be a vacuum.

The [[quality]] of a vacuum refers to how closely it approaches a perfect vacuum. Residual gas pressure is a primary indicator of quality, and is most commonly [[measured]] in units called [http://en.wikipedia.org/wiki/Torr torr], even in metric [[contexts]]. Lower pressures indicate higher quality, although other variables must also be taken into account. [[Quantum theory]] sets limits for the best possible quality of vacuum, predicting that no volume of space can be perfectly empty. Outer space and interstellar space are naturally occurring high quality vacuums, mostly of much higher quality than can be created artificially with current [[technology]]. Low quality artificial vacuums have been used for suction for many years.

The [[quality]] of a vacuum refers to how closely it approaches a perfect vacuum. Residual gas pressure is a primary indicator of quality, and is most commonly [[measured]] in units called [https://en.wikipedia.org/wiki/Torr torr], even in metric [[contexts]]. Lower pressures indicate higher quality, although other variables must also be taken into account. [[Quantum theory]] sets limits for the best possible quality of vacuum, predicting that no volume of space can be perfectly empty. Outer space and interstellar space are naturally occurring high quality vacuums, mostly of much higher quality than can be created artificially with current [[technology]]. Low quality artificial vacuums have been used for suction for many years.

Vacuum has been a frequent [[topic]] of philosophical debate since Ancient [[Greek]] times, but was not [[studied]] empirically until the [http://en.wikipedia.org/wiki/17th_Century 17th century]]. [http://en.wikipedia.org/wiki/Evangelista_Torricelli Evangelista Torricelli] produced the first laboratory vacuum in 1643, and other [[experimental]] [[techniques]] were [[developed]] as a result of his [[theories]] of atmospheric pressure. A torricellian vacuum is created by filling a tall glass container closed at one end with mercury and then inverting the container into a bowl to contain the mercury.[2]

Vacuum has been a frequent [[topic]] of philosophical debate since Ancient [[Greek]] times, but was not [[studied]] empirically until the [https://en.wikipedia.org/wiki/17th_Century 17th century]]. [https://en.wikipedia.org/wiki/Evangelista_Torricelli Evangelista Torricelli] produced the first laboratory vacuum in 1643, and other [[experimental]] [[techniques]] were [[developed]] as a result of his [[theories]] of atmospheric pressure. A torricellian vacuum is created by filling a tall glass container closed at one end with mercury and then inverting the container into a bowl to contain the mercury.[2]

 

Vacuum became a valuable industrial tool in the [http://en.wikipedia.org/wiki/20th_Century 20th century] with the introduction of incandescent light bulbs and vacuum tubes, 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 on life forms in general.[http://en.wikipedia.org/wiki/Vacuum]

[[Category: Physics]]

[[Category: Physics]]