Is Pluto a planet? Why do we care? Why did we ever call it a planet in the first place? How has our definition of "planet" changed over the millennia, and how might it change in the future? I discuss these questions and more in today's Ask a Spaceman! 

Keep those questions about space, science, astronomy, astrophysics, and cosmology coming to #AskASpaceman, Twitter@PaulMattSutter,, and for COMPLETE KNOWLEDGE OF TIME AND SPACE! Music by Jason Grady and Nick Bain.