Dediscovery: My new essay for a new section of the New York Times

In the late 1800s, prominent astronomers declared that Mars was criss-crossed by canals–evidence, they declared, of an advanced civilization. But in the early 1900s, astronomers gazed through more powerful telescopes and discovered that the canals were mirages.

The astronomer Percival Lowell, who had become the leading champion of the canals, scoffed at the new findings He declared that the criticism came "solely from those who without experience find it hard to believe or from lack of suitable conditions find it impossible to see."

Although the new evidence led many astronomers to abandon Lowell's position, he never retracted his claim. It wasn't until five decades after his death in 1916 that space probes finally went into orbit around Mars and sent back close-up pictures of a canal-free Red Planet.

I've always been fascinated by the way science casts aside bad ideas. For most of us, it's easy to assume that science shakes them off quickly, but the truth is that it can take quite a while for the process to play out. Recently I was invited to contribute a piece to the new "Sunday Review" section of the New York Times, which ...