What?
We create and maintain vacuum wherever it is needed.
Why?
Without a good vacuum, particle physics experiments would be impossible. Accelerated particles must not slow down; and when their speed is 3/4 the speed of light, collisions with slow-moving particles like those found in the air reduce the speed dramatically. To ensure that the particles don't slow down by the time they arrive at their target, a good vacuum is necessary. A list of articles about vacuums can be found at http://www.vacuumlab.com/articles.htm
How?
Vacuum pumps are the tools of the trade. There are two principles upon which they can operate. The first type physically removes some fixed volume of gas, pushing it outside. The second makes gas stick to a cold surface, thereby reducing the pressure but not removing the gas from the chamber. We call this cryopumping.
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