Yes, the question of what makes a planet a "planet" is back in the news after a team of planetary scientists published a new paper challenging the status quo and arguing that Pluto should be a planet again. You may have thought this issue was settled back in 2006 but many problems exist with the current definition. We explain what's wrong with the current version, what this new paper proposes instead and the consequences of the change if it were to be accepted. ::More about this Video:: ► Runyon et al. (2017), "A Geophysical Planet Definition": http://www.lpi.usra.edu/meetings/lpsc2017/pdf/1448.pdf ► IAU 26th General Assembly Resolution 5A, "Definition of ‘planet' ": https://www.iau.org/news/pressreleases/detail/iau0603/ ► Chen & Kipping (2016), "Probabilistic Forecasting of the Masses and Radii of Other Worlds": https://arxiv.org/abs/1603.08614 ► Background music by Thomas Bergersen "Final Frontier": http://www.thomasbergersen.com ::Playlists For Channel:: Latest Cool Worlds Videos ► http://bit.ly/NewCoolWorlds Cool Worlds Research ► http://bit.ly/CoolWorldsResearch Guest Videos ► http://bit.ly/CoolWorldsGuests Q&A Videos ► http://bit.ly/CoolWorldsQA Science of TV/Film ► http://bit.ly/ScienceMovies ::Follow us:: SUBSCRIBE to the channel http://bit.ly/CoolWorldsSubscribe Cool Worlds Lab http://coolworlds.astro.columbia.edu Twitter https://twitter.com/david_kipping Instagram https://www.instagram.com/cool.worlds THANKS FOR WATCHING!!