What is the difference?

1) A perfect vacuum;
2) An absolute vacuum;
3) An ultra-high vacuum;
and,
4) A hard vacuum.

Thanks :cool:

A perfect vacuum is defined as a region in space without any particles.

An absolute vacuum is defined as space with the absence of particles at a temperature of zero Kelvin.

Ultra-high vacuum is a controlled environment created to take pressures down past 1x10^10 Torr. Pressure range.

A hard vacuum is used to describe a controlled environment of low pressures where extreme forces are involved.

Thanks (Q).

Re. the 'perfect' vacuum: Does 'no particles' mean no EMR?

Curious :cool:

I thought there was no such thing as a "Perfect Vacuum" because of "Zero-point" :D

wouldnt zero point just behave better in a perfect vacuum?

I have to disagree a little with (Q) on this.

A "perfect vacuum" and an "absolute vacuum" are, in my opinion, different terms for the same thing - a space devoid of any matter.

"Ultra-high vacuum" is a technical term referring to an atmosphere with a pressure of less than about 10^-8 Torr.

"Hard vacuum" is a loose term usually used to refer to the conditions in outer space.

zero point refers to EM energy which has no mass. a vacuum is determined by measuring pressure, which requires mass. therefore, ZPE does not affect vacuum definitions.

But EM radiation has relavistic mass and curves space like matter does. Given that, shouldn't ZPE demonstrate that a perfect vacuum is impossible?