Quantum Mechanics

A theory of physics that is applicable to systems of extremely small scales (ie. the size of an atom). QM quantifies the "fuzzyness" of the universe. This means that it is a probabilistic theory, which tells you the chances of something happening. For example, in classical mechanics, if you throw a ball in the air, it will follow a projectile motion path. On the other hand, if you throw a particle up in the air, it might come back down, or it might "tunnel" out of the earth's gravitational barrier, and become free. QM tells you the chances of each scenario ocurring.