? asked in 科學及數學其他 - 科學 · 1 decade ago

What is vacuum?

In Physics, what is the meaning of vacuum?

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  • 1 decade ago
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    From Wikipedia, the free encyclopedia

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    Look up Vacuum in

    Wiktionary, the free dictionary.

    For other uses, see Vacuum (disambiguation).

    A vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than standard atmospheric pressure. The Latin term in vacuo is used to describe an object as being in what would otherwise be a vacuum. 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, partly because quantum theory predicts that no volume of space can be 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 in relation to how closely it approaches a perfect vacuum. The residual gas pressure is the primary indicator of quality, and is most commonly measured in units called 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 frequent topic of philosophical debate since Ancient Greek times, but was not studied empirically until the 17th century. Evangelista Torricelli produced the first artificial vacuum in 1643, and other experimental techniques were developed as a result of his theories of atmospheric pressure. Vacuum became a valuable industrial tool in the 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.



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    粗略真空 (Rough Vacuum) 760 ~ 1 Torr

    中度真空 (Medium Vacuum) 1 ~ 10-3 Torr

    高真空 (High Vacuum) 10-3 ~ 10-7 Torr

    超高真空 (Ultra-High Vacuum) 10-7 Torr以下

    Source(s): wiki
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