Dr. Christopher Bird

At the request of a few viewers, today I am going to be writing about the phenomena of zero-point energy. I have always found this effect to be fascinating, because it seems like paranormal alternative science, but has not only got a solid explanation in quantum mechanics but has also been experimentally verified!

Consider a region of space which is completely empty. No air, no particles, not even light. It would be expected that this region has no energy in it, and in classical physics that is true. In fact the theory of general relativity essentially requires that empty space has no energy contained in it. But as so often happens in quantum mechanics, this obvious common-sense truth is proven false.

The reason is that in quantum mechanics, you cannot know the energy of a system precisely at any given moment (only average energy over a period of time). So in that region of empty space, on the subatomic level particles are constantly popping into existence and then disappearing again. And each of these 'virtual particles' carries a small amount of energy. But there are so many of them at any given time that the energies add up to be infinite!

At this point, some students (and readers) assume that this is a mathematical oddity with no real physical meaning. The energy in vacuum is clearly zero, no matter what some crazy theorists predict. Except that this effect has been measured experimentally!

If there are infinite quantities of virtual particles creating an infinite vacuum energy, then it should be possible to remove some of them and lower the energy of the vacuum. Specifically, if two metal plates are placed close together then virtual photons with wavelengths longer than the distance between the plates will not form. There isn't enough room for them. And since there are now fewer virtual particles in the region, the energy density between the plates is less than that of vacuum – essentially this is a region of negative energy. Physically, a region of negative energy (and hence negative pressure) will try to shrink, pulling the two plates together. This is called the Casimir effect, and has been observed in experiments.

Which then leads to the obvious question, if every region of space is filled with an infinite energy, is there any way to extract it? The short answer is that no one really knows. There has been a lot of research to find a configuration of metal plates so that the Casimir effect can run a generator, but as yet no one has found such a system. I suspect that it isn't possible, but as yet no laws of physics actually forbid it.

So there it is – zero point energy!