Vacuum

Vacuum is commonly taken to mean pressures below, and often considerably below, atmospheric pressure. It refer to an actual imperfect vacuum as one might have in a laboratory or in space. Vacuum can be created by removing air from a space using a vacuum pump or by reducing the pressure using a fast flow of fluid. It refers to how closely it approaches a perfect vacuum. Other things equal, lower gas pressure means higher-quality vacuum. The recent development of human spaceflight has raised interest in the impact of vacuum on human health, and on life forms in general.