Galaxies in Hubble Deep Field credit: NASA, ESA, S. Beckwith (STScI) and the HUDF Team
You hear distances all the time in astronomy. This star is 10 light-years away; that galaxy is 50 million light-years away; that Big Bang over there happened 13.7 billion years ago. But how did astronomers actually figure out how far away everything is? It's not a single measuring stick. Instead, astronomers have built up a series of overlapping measuring tools (yes, we're calling supernovae and variable stars "tools"), which take us from right around the corner to very ends of the Universe. Get out your ruler… no, the bigger one… never mind… just listen.
Welcome to Astronomy Cast, the most popular astronomy-related podcast. Just look at what listeners have to say about it:
Astronomy Cast is out of this world! It's hard to believe that it's free! This is an absolute must for any amateur astronomer or anyone interested in astronomy or cosmology. The hosts, Pamela and Fraser, are fun to listen to, extremely knowledgeable, and are able to explain difficult subject matter with great analogies. Bravo!
"Very interesting and almost "easy" for amateurs to listen and understand"