What is 21-cm radiation? What (and who) produces it? What causes it, and what does it tell us about the universe? I discuss these questions and more in today’s Ask a Spaceman!

Support the show: http://www.patreon.com/pmsutter All episodes: http://www.AskASpaceman.com Watch on YouTube: http://www.youtube.com/PaulMSutter Read a book: https://www.pmsutter.com/books

Keep those questions about space, science, astronomy, astrophysics, physics, and cosmology coming to #AskASpaceman for COMPLETE KNOWLEDGE OF TIME AND SPACE!

Big thanks to my top Patreon supporters this month: Justin G, Chris L, Alberto M, Duncan M, Corey D, Michael P, Naila, Sam R, John S, Joshua, Scott M, Rob H, Scott M, Louis M, John W, Alexis, Gilbert M, Rob W, Jessica M, Jules R, Jim L, David S, Scott R, Heather, Mike S, Pete H, Steve S, wahtwahtbird, Lisa R, Couzy, Kevin B, Michael B, Aileen G, Toho Warrior, Steven W, Brian O, Mark R, Alan B, Craig B, Mark F, Richard K, Stace J, Stephen J, Joe R, David P, Robert B, Sean M, Tracy F, Sarah K, Ella F, Thomas K, James C, Syamkumar M, Homer V, Mark D, Bruce A, Bill E, Tim Z, Linda C, The Tired Jedi, Gary K, David W, dhr18, Lode D, Bob C, Red B, Stephen A, James R, Robert O, Lynn D, Allen E, Michael S, Reinaldo A, Sheryl, David W, Sue T, Josephine K, Chris, Michael S, Erlend A, James D, Larry D, Matt K, Charles, Karl W, Den K, George B, Tom B, Edward K, Catherine B, John M, Craig M, and Scott K!

Hosted by Paul M. Sutter.

AaS! 244: What’s the Most Important Wavelength in All Astronomy?