A "Pitch Drop" Experiment has finally revealed...a pitch drop.
Tar pitch has extreme viscosity (something like 230 billion times that of water) and takes a very, very long time to drop. In fact, its drop rate is about one drop per decade so it's extremely easy to miss the vital moment.
The best-known experiment designed to observe a pitch drop was set up in Australia in 1927, but with no recording technology, observers had to carry out a long term vigil. A more recent experiment started in 1944 in Trinity College, Dublin.
There were a number of near-misses, perhaps the most frustrating being for Professor John Mainstone in Queensland, who broke-off his observation to make a cup of tea...and missed the drop in the 15 minutes he was away. In 2000, with video equipment installed, the pitch dropped again, only for the video camera to malfunction and fail to record the drop.
Finally, on the 18th July 2013, thanks to the introduction of webcam technology, a pitch drop was finally filmed. Exciting? You be the judge.