Heisenberg's uncertainty principle
Heisenberg's idea is that if something like an electron were shot into a big box with a certain speed and in a certain direction, then it would be possible to calculate a fairly accurate idea of what its path would be like in the future. However, if the box were made smaller then we would have a more certain idea of where it was located, and because of that we would have to have a less certain idea of how it was traveling. American physicist Brian Greene gave the analogy of a moth which flies placidly around in a large closet but who flies frantically back and forth and up and down when placed in a glass jar.p114 Another interesting uncertainty phenomenon, which makes possible many electronic devices, is called quantum tunneling. In our everyday life, people cannot move through walls. However, electrons can move through solid walls.p115 In the animation to the right, you can see a faint white puff on the right side of the wall after a big puff hits the wall from the left. That dim spot of light represents the photon or other atomic particle which tunnels through the wall.