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 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 0ï¿½K. Note that a perfect vacuum has by definition a temperature of 0ï¿½K.
reaching 0 ï¿½K 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
'The strength and weakness of physicists is that we believe in what we can measure. And if we can't measure it, then we say it probably doesn't exist. And that closes us off to an enormous amount of phenomena that we may not be able to measure because they only happened once. For example, the Big Bang. ... That's one reason why they scoffed at higher dimensions for so many years. Now we realize that there's no alternative... '