“One creates from nothing. If you try to create from something you’re just changing something. So in order to create something you first have to be able to create nothing.” –Werner Erhard
One of the oldest adages in existence is you can’t get something for nothing, as over a million websites will tell you, including not-so-subtly, cartoonstock.
(Image credit: chaospet.)
Well, let’s take this question as seriously as our knowledge allows us to. (And by that, I mean physically, rather than philosophically or theologically.) In physics, can you get something for nothing? And if so, what can you and can’t you get?
In many ways, yes, you can. In fact, in many ways, getting something when you have nothing is unavoidable! (Although you can’t necessarily get anything you want.)
For example, take a box and empty it, so that all you’ve got is some totally empty space, like above. An ideal, perfect, empty vacuum. Now, what’s in that box?
Did you guess nothing? Well, it turns out that empty space isn’t so empty.
One of the consequences of Heisenberg’s Uncertainty Principle — that you can’t know a quantum state‘s energy exactly for a finite duration of time — means that when you’re talking about very short time intervals, there are large uncertainties in the energy of a system. Over short enough timescales, the energies are large enough that particle-antiparticle pairs wink in-and-out of existence all the time!
“That’s crazy talk,” you say. Prove it!
And they did.
Take two identical, uncharged, parallel metal plates, and put them close to one another. The vacuum fluctuations in between the plates cause there to be a pressure pushing the plates together. This isn’t the gravitational force or an electromagnetic force, but a force due to empty space itself.
Researchers have uncovered a fundamental link between the two defining properties of quantum physics. The result is being heralded as a dramatic breakthrough in our basic understanding of quantum mechanics and provides new clues to researchers seeking to understand the foundations of quantum theory. The result addresses the question of why quantum behaviour is as weird as it is — but no weirder.