In 1927, Thomas Parnell, a physics professor at the University of Queensland, in Australia, designed an experiment ot show his students how viscous a fluid could be. He poured hot pitch into a glass funnel, let it cool, and then waited. Eight years later, the first drop fell. After another nine years, the second drop fell The Pitch Drop Experiment is now the world's longest running lab experiment. There have been a total of eight drops, occurring at an average interval of ten years. The drop takes about a tenth of a second. No one has ever actually seen a drop fall.
--Nick Paumgarten in the New Yorker