Schrödinger’s Planet
Updated at 4:15 p.m. ET on August 27, 2021.In 2006, astronomers gathered in Prague to consider a very basic question: How many planets are in our solar system? Was it nine, or was it actually eight, or perhaps as many as 12? By the end of the conference, after several polite debates and “lots of heated hallway discussions,” the verdict was in. Under the new rules of planethood, the solar system had eight planets, and Pluto wasn’t one of them.