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You know what a planet is, right? A big round thing that orbits a star. Uh, not so fast. The surprisingly vicious debate over the planetary status of Pluto has given us a fascinating glimpse into what a scientific definition really is. And perhaps the word planet is too vague to be used as a scientific definition at all.

Hosted by Matt O'Dowd
Written by Drew Rosen and Matt O'Dowd
Graphics by Leonardo Scholzer
Directed by: Andrew Kornhaber
Produced By: Kornhaber Brown

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We love to classify things. Labels help us keep stuff organized in our heads. In science, categorization provides a fast and easy way to know the properties of a member of the group just by knowing what group it belongs to. Chemists group elements on the periodic table, those groups exhibit similar chemical behavior that reflect outer-shell electron number. Biologists group organisms by similar physical characteristics, and this taxonomy reflects genetic relationships. Astronomers are all about space taxonomy. We classify galaxies based on their shape, black holes based on how they feed, stars based on their colour and brightness, and planets by… well, by a set of criteria that has caused more tension and heartbreak than any made-up grouping scheme really should. Because a change in that scheme demoted Pluto from planet to not-planet. Today we’re going to settle whether this was reasonable, and whether we should keep the word “planet” at all.

Big Bang Supporters:
Alexander Tamas
Anton Lifshits
David Barnholdt
David Boyer
David Nicklas
Fabrice Eap
Juan Benet
Justin Lloyd
Matt Miller
Morgan Hough

Quasar Supporters:
Mark Heising
Mark Rosenthal
Vinnie Falco

Hypernova Supporters:
Chuck Zegar
Danton Spivey
Donal Botkin
Edmund Fokschaner
Hank S
John Hofmann
John R. Slavik
Jordan Young
Joseph Salomone
Matthew
Matthew O'Connor
Syed Ansar

Gamma Ray Burst Supporters:
Adrian Molyneux
Alec Zero
Andreas Nautsch
Bradley Jenkins
Brandon Labonte
Brian
Dan Warren
Daniel Lyons
David Behtala
DFaulk
Dustan Jones
Geoffrey Short
James Flowers
James Quintero
Jason
John Funai
John Michael Kerr
John Pollock
Jonah
Jonathan Nesfeder
Joseph Dillman
Josh Thomas
Kevin Lee
Kevin Warne
Kyle Hofer
Malte Ubl
Mark Vasile
Nick Virtue
Nick Wright
Paul Rose
Scott Gossett
Steve Bradshaw
Sigurd Ruud Frivik
Tim Stephani
Yurii Konovaliuk