How do we see far off galaxies, discover new planets and stars, and study the secrets hidden in space? Master rigger Sean Riley goes to Chile to visit the world's largest, most advanced optical combined telescope, which provides astrophysicists with some of the answers to questions about the Big Bang, the nature of matter, and the origins of the universe. But at the moment the results are not so clear-the mirror that focuses on stars from millions of light years away needs cleaning. This 23-ton mirror shaped like a contact lens is loaded, transported, polished, given a new coating, and reinstalled in its home. The surface has to be totally flawless-the kind of flawless that's non-negotiable. If anything goes wrong on this fix, it's going to bring a whole lot more than seven years of bad luck!

Encoded with permission for digital streaming by Infobase on May 18, 2013. Learn360 is distributed by Infobase for Films for the Humanities & Sciences, Cambridge Educational, Meridian Education, and Shopware.

European Southern Observatory (2:21) -- How the Mirror Will Be Moved (4:29) -- Protecting the Mirror (3:58) -- Capturing Light (2:41) -- Light-Collecting Instrument (3:43) -- Big Bang (3:04) -- Putting the Mirror in Place (2:54) -- Steps to Clean the Mirror (2:49) -- Pump Malfunction (4:03) -- Troubleshooting (4:35) -- Images from Telescopes (3:11) -- Mishaps and Success (3:45) -- Recoating the Mirror (2:49) -- Successful Project (4:30) -- Credits: 20-Ton Telescope: World's Toughest Fixes (0:13).