Watched in isolation, the video doesn't look like much. A drop of tar slowly detaches from the beaker above it, settling gently atop the tar below it. You might not realize what the big deal is—until you notice the clock furiously spinning behind it, and realize that even this glacial movement is sped up to a ridiculous degree. And the moment becomes downright exciting when you realize that scientists have been waiting to see it for 69 years.
Trinity College in Dublin set up its tar pitch-drop experiment in 1944, Nature explains, to demonstrate the concept that tar is actually a high-viscosity substance, meaning it appears solid but is actually slowly flowing. A similar experiment has been running in Brisbane since 1929. Drops fall in each place every seven to 13 years, but the moment has never before been captured. "I have been examining the video over and over again," says the man who's headed the Brisbane experiment since 1961 without ever seeing it drop. (Read more science experiment stories.)