How do we measure the expansion history of the universe? Why are supernovae so dang useful? Come on, what's with this "dark energy" business? I discuss these questions and more in today's Ask a Spaceman!

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Music by Jason Grady and Nick Bain. Thanks to WCBE Radio for hosting the recording session, Greg Mobius for producing, and Cathy Rinella for editing.

Hosted by Paul M. Sutter, astrophysicist at The Ohio State University, Chief Scientist at COSI Science Center, and the one and only Agent to the Stars (http://www.pmsutter.com).