It took 69 years, but at last we've seen the pitch drop. One of the world's longest-running experiments climaxed last week, when a finger-sized bulb of pitch (bitumen) separated from its parent bulk and dropped into a beaker. For the first time ever, this fleeting event has been recorded on video.
The pitch drop experiment was set up at Trinity College Dublin, Ireland, in 1944. The original version of the experiment, at the University of Queensland in Australia, has been running since 1930, but various glitches have prevented that team from actually seeing a drop separate.
"No one has ever seen a drop fall anywhere in the world," says Trinity'sShane Bergin, whose webcam recorded the event on 11 July. "It's one of the oldest experiments – an oddity, a curiosity."
Pitch shatters if hit with a hammer at room temperature. Physicist Thomas Parnell set up the Queensland experiment to illustrate that, although it appears solid, pitch is actually an incredibly viscous liquid. (Recent experiments showed that the same is true for "Gorilla Glass", used in smartphones and tablet screens.)
The world's longest-running scientific experiment is about to drop into the headlines. For over 80 years, two physicists at the University of Queensland have been standing guard over the Pitch Drop Experiment. Now, the decade-awaited moment of truth is bearing down: a drop is about to fall.
In 1927, the first physics professor at the University of Queensland, Thomas Parnell, sought to demonstrate that some materials exhibit seemingly contradictory properties. Once used to seal the bottom of boats, tar pitch feels solid at room temperature and shatters like glass under a hammer blow. But, as Parnell has undeniably demonstrated, pitch is actually a very, very viscous fluid.
So one day, Parnell placed a block of tar pitch in a sealed funnel. Three years later, the pitch had settled into the bottom of the funnel and in 1930 the bottom of the funnel stem was cut.
The first drop fell in December, 1938!
It is something of an overstatement to say that the pitch has been dripping ever since. In 86 years, a total of eight drops have dripped, with about a decade between drop falls. Now, the ninth is about to drop, probably in 2013. If you're lucky, you may see what no one has seen before—no one has ever witnessed the drop fall.
John Mainstone, a physics professor at the University of Queensland and the experiment's current custodian, missed the last two drops by pure bad luck.
Awaiting the eighth drip from a business trip, Mainstone secured a video surveillance system to trail the elusive drop. Alas, the video feed failed precisely during the fall of the eighth pitch-drop. Listen to John Mainstone tell the story of the missed adventure on last week's Radio Lab.