Heisenberg uncertainty principle

The Heisenberg uncertainty principle is one of the counterintuitive ideas that arises from early twentieth century quantum mechanics. In episode 11 of Subatomic Stories, Fermilab scientist Don Lincoln explains what the principle is, how many people get it wrong and how to understand it properly.

We might be able to predict the path of a baseball based on the motion of the bat, but even the tiniest adjustment in the swing could make a large difference in the ball's flight. Photo: Zach Putnam

In the 19th century some scientists thought that if we could know, at any given time, the position and velocity of every atom, we could in principle calculate the future. They believed the past determines the present, and the present determines the future.