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The 365 Days of AstronomyAuthor: 365DaysOfAstronomy.org
The 365 Days of Astronomy podcast launched in 2009 as part of the International Year of Astronomy. This community podcast continues to bring you day after day of content across the years. Everyday, a new voice, helping you see the universe we share in a new way. This show is managed by Avivah Yamani, edited by Richard Drumm. This podcast is funded through Patreon.com/CosmoQuestX and produced out of the Planetary Science Institute. Language: en Contact email: Get it Feed URL: Get it iTunes ID: Get it |
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Cheap Astronomy - Dear CA # 133: Why It's Always C
Wednesday, 15 April, 2026
Cheap Astronomy investigates why light moves at light speed in a vacuum. Hosted by Steve Nerlich. Shining a light! Dear Cheap Astronomy – Why does a photon travel at speed c, part1 It may sound a bit strange to ask why light travels at the speed of light, but that's because c isn't really the speed of light – it's really a measure of the relationship between distance (or space) and time. It's become customary to call c the speed of light, but in reality light moves at different and slower speeds through air, water or glass, it only moves at c in a vacuum. Dear Cheap Astronomy – Why does a photon travel at speed c, part1 Last week we grappled with the issue of why light is able to move at the speed c, which is around 300,000 km/sec in a vacuum. Some key points we landed were that c is actually the fastest speed that anything can move and that light isn't the only thing that moves at c, gravity does too. The constant c is perhaps better thought of as defining the fundamental relationship between space (or distance) and time, where it must take at least one second to cross 300,000 kilometers – meaning it must take at least 0.000000033 second to cross one meter, and you can add even more zeros to cross centimeters and then nanometers. We've added a new way to donate to 365 Days of Astronomy to support editing, hosting, and production costs. Just visit: https://www.patreon.com/365DaysOfAstronomy and donate as much as you can! Share the podcast with your friends and send the Patreon link to them too! Every bit helps! Thank you! ------------------------------------ Do go visit http://www.redbubble.com/people/CosmoQuestX/shop for cool Astronomy Cast and CosmoQuest t-shirts, coffee mugs and other awesomeness! http://cosmoquest.org/Donate This show is made possible through your donations. Thank you! (Haven't donated? It's not too late! Just click!) ------------------------------------ The 365 Days of Astronomy Podcast is produced by the Planetary Science Institute. http://www.psi.edu Visit us on the web at 365DaysOfAstronomy.org or email us at info@365DaysOfAstronomy.org.
