Quantum mechanics is the theory used to provide an understanding of the behavior of microscopic particles such as electrons and atoms. However, it is more than just a collection of formulae used by physicists and chemists to calculate, for example, where an electron might be. The quantum theory also introduced an entirely new way of thinking about very small objects that is strangely different from the way we think about macroscopic objects.

An example of a macroscopic object is a baseball. Whenever we throw a ball into the air it is a good idea to know where it will fall and how fast it will be traveling when it hits something. The most exact way to describe the ball's motion is by using classical mechanics, which predicts the position and velocity of the ball at every instant during its flight. This approach fits our everyday experience...