Pluto isn’t a planet for the same reason whales aren’t fish
History plays a role in demarcating natural categories, from biological species to mineral kinds to planetary classification.

Michael L. Wong is an astrobiologist, planetary scientist, and science communicator at Carnegie Science's Earth & Planets Laboratory.
History plays a role in demarcating natural categories, from biological species to mineral kinds to planetary classification.
Three potential satellite projects may change our night sky forever. Beyond the environmental and scientific problems, the proposals are an ethical nightmare.