Conspiracies are sometimes real. The Watergate break-in is a good example of a political conspiracy that actually happened. But thanks to the social-media algorithms that push users toward ever-more-emotional, conspiratorial content, it's probably never been easier for false conspiracy theories to spread.

All conspiracy theories must have certain necessary elements: a conspiracy between two or more people, a secret action, and a motive, said Karen Douglas, a professor of social psychology at the University of Kent in the U.K. But the ones that take off usually have something extra.