From Slackerpedia Galactica

In daily life, a vacuum is a device for instilling fear and dread in dogs and cats.

In science, a vacuum is hated by nature. A true vacuum is perfect nothing. Why we're able to talk about true vacuums if they aren't actually anything is a good philosophy question to bring up next time you're at a party. Scientists have decided that it is impossible to create a true vacuum. First, we can't seem to get rid of every single atom from a jar no matter how hard we try. The fact that energy and mass are equivalent doesn't help. Energy can still get into the best container, so even a jar that has no atoms or subatomic particles still isn't a vacuum because of all the energy flying through it. Quantum mechanics also won't allow a perfect vacuum, because the walls of a vacuum chamber emit blackbody radiation (energy) if they aren't at absolute zero and the uncertainty principle prevents any space from being without any sort of matter. Partial vacuums, which have some matter and energy and do exist in the real world, are often called vacuums though. For example, there is an interstellar medium between stars, but we can functionally call it a vacuum.

External Links

1. Here is an article where the good folks at Wikipedia talk about nothing