In Shelf Life Episode 5 we get to learn how astronomers collect baseline data over time, and collate it into a meaningful picture about how stellar phenomena change in periods as short as generations. The common belief in scientific circles used to be that stellar events either happened overnight, like supernovas, or took tens of thousands to millions of years to evolve to the next stage. Recently some museums have been compiling the images of the night skies taken on photographic plates as far back as the 1890s into a huge database, and then processed the results to show small pieces of sky over that 130 year span. What they discovered was that lots of stars fluctuate over a decade or two much more than anyone suspected, rather than remaining unchanged for the lifetimes of civilizations. I can’t wait to find out what new insights we gain with this as a baseline supposition as we process still more collections of data that we were never able to put together before computers made it easy.