I saw the Casimir effect in my head when I was a kid. Can't explain that!

"A vacuum is not really empty?!" *snort* , retorted the scientifically illiterate ignoramus.

Scar wrote:Could someone please explain this and the objections to it in simple terms?

I tried to explain it here.

The objections we were talking about are not that the effect itself doesn't exist, but that the explanation of it in terms of virtual particles is misleading. There are two schools of thought - one is that virtual particles exist as physical entities, the other is that they are only part of an approximation scheme which makes the mathematics of quantum field theory tractable. If you look up "virtual particle" on the physicsforums.com site, you will see the arguments raging over the years. The arguments are pretty difficult to settle because the virtual particles are, almost by definition, not directly measurable. But it keeps hobby physicists happy