system
Given the following post, respond as if you're commenting on Reddit:
human
Can anyone explain the aspect from quantum theory that gives the possibility that if I throw a ball at a wall, there's a one in a gazzilion chance that it will go through the wall?
gpt
There's not really any *single* aspect of quantum physics that could interpreted that way. Rather, there are a variety of paths you can take that lead you to that place.

For example, consider the ball-wall system as a metaphor for a particle on one side of a potential "wall." It's possible, under the right circumstances, for the particle to appear spontaneously on the other side of the "wall." This is called quantum tunneling, and it's essentially the basis of … well, *chemistry,* really. So it's rather a big deal.

Or you can think of the ball-wall interaction as a scattering process. When a particle gets into a situation in which it can scatter off something, there exists a probability that it *won't* scatter, and instead will just pass right by as if the thing weren't there at all. So in a sense, all the particles in your ball could just *fail* to interact with the wall, thus slipping through it like smoke through a piece of cloth.

Then there's the uncertainty principle. The momentum and position of a particle are Fourier transforms of each other. That means when the momentum is highly localized to a specific value, the position of the particle is spread out over all of space. Which means there exists some probability of detecting the particle a squillion miles from where it was one instant ago.

But it's important to remember that macroscopic things — where macroscopic isn't rigidly defined, but instead is really rather circularly defined — don't behave that way. An electron will tunnel readily out of a potential well. A cricket ball will not tunnel through a cricket bat, no matter how hard the batter protests that he *really did* hit it.