Is it possible to make a perfect vacuum?
Asked by: Dan Klingensmith
Answer
Practically, it is impossible to make a perfect vacuum. A perfect vacuum is defined as a region in space without any particles.
The problem is that to maintain a vacuum in a region you have to shield it from the environment. It is not difficult to make a container that would prevent atoms from entering the region.
The first problem is that the container itself will radiate photons (which in turn can create electron positron pairs in the vacuum) if it is not kept at a temperature of 0°K. Note that a perfect vacuum has by definition a temperature of 0°K. reaching 0 °K is practically impossible.
The second problem is that there are weakly interacting particles that could enter the region. No matter how thick the walls of the container are, there is always a finite probability that, say, a neutrino would enter the region.
Answered by: Saibal Mitra, M.S., Physics Grad Student, UVA Amsterdam
http://www.physlink.com/education/askexperts/ae290.cfm
Basically no matter how thick his scull is and how cold and unfeeling he is, he still does not approach a perfect vacuum. There is always a chance of a photon or some other sub atomic particle bouncing around inside his empty vacuous head.
