On August 21, folks across the US will be able to see a total solar eclipse -- the first one visible coast-to-coast in nearly a century. The whole shebang will last about two minutes and 40 seconds at its longest, which is cool but kind of meh in the grand scope of solar eclipses throughout history. In 2009, for example, a solar eclipse visible in Southeast Asia set the record for the longest one of the century so far, lasting six minutes and 40 seconds.