Why Is Pluto No Longer a Planet

In 2006 the International Astronomical Union (IAU) demoted the much-loved Pluto from its position as the ninth planet from the Sun to one of five “dwarf planets.” The IAU had likely not anticipated the widespread outrage that followed the change in the solar system’s lineup. When the announcement was made (and even over 10 years later), people around the world objected to the planet’s demotion on principle, saying that it altered tradition and history, rather than engaging with the scientific reasoning. So, what was the IAU’s reason for demoting Pluto when it did? Why is Pluto no longer a planet?

The main event of the 2006 General Assembly of the IAU, the proposal that would come to demote Pluto, was a defining moment for the rest of the solar system as well. Fiercely debated by the members of the union, the resolution that was passed officially defined the term planet. What was once a loose word used to describe a large object within the solar system was now specific: planets are celestial objects large enough to be made rounded by their gravitational orbit around the Sun and to have shooed away neighboring planetary objects and debris. Pluto is now classified as a dwarf planet because, while it is large enough to have become spherical, it is not big enough to exert its orbital dominance and clear the neighborhood surrounding its orbit.

Before the resolution in 2006, the term planet had no working definition and was based on classification from before some of the major modern discoveries within the universe that were made possible by advances in technology. To many citizens of Earth, the demotion of Pluto felt like a break from tradition, and it was precisely that—a positive step forward into a new light, new knowledge, and changing perspectives of the universe.

Bats are idiosyncratic creatures, with habits that humans find incredibly odd—like occasional bloodsucking, sleeping upside down, and staying up all night. We characterize bats as supernatural, associating them with vampires and even superheroes. With their talent for echolocation, that’s no surprise. It’s for that ability to “see” with their ears that bats are perhaps most well known—that, and their supposed blindness, which (as the story goes) makes echolocation necessary for finding and feeding on fruits and insects and other small animals. But what if the most basic truth you’ve always been told about bats was false? What if being “as blind as a bat” just meant, well, being able to see perfectly well?

Contrary to what most people believe, bats are generally not blind at all and in fact are believed to have eyesight keener than that of most humans. The misconception that bats are blind comes from their nocturnal nature and enhanced hearing abilities. Because they hunt mostly in the dead of night, when lighting conditions are, of course, very dark, bats rely on echolocation to pinpoint exact locations of prey. This ability does not, however, require or have any connection to blindness. Instead, the genetic mutations that evolved the powers of echolocation in bats likely surfaced as they aided the animals in the darkness. A bat’s eyes, far from useless, are attuned to low-light conditions to better aid in finding prey and are enhanced by their super hearing power.

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