Magazine article Science News

Oldest Pitch-Drop Experiment

Magazine article Science News

Oldest Pitch-Drop Experiment

Article excerpt

Grass grows quicker. Paint dries faster. Yet there's something irresistible about watching the glacial flow of pitch.

And now a long-forgotten experiment with pitch has come to light, probably the oldest known of its kind. In a small display case at Aberystwyth University in Wales sits a glass funnel filled with a heap of ultra-viscous pitch, dated April 23,1914. That's 13 years older than a similar setup at the University of Queensland in Australia, which Guinness World Records lists as the longest continually running laboratory experiment.

The allure of pitch--a black tarlike hydrocarbon by-product of distilling petroleum, wood or coal--comes from its split personality: It shatters from a quick hit with a hammer, but flows if set aside for long periods. For more than a century physicists have showcased that contradictory behavior with the pitch-drop and other experiments, in which a seemingly solid mass of pitch displays its liquid nature. At right is a sampling of multigenerational investigations of pitch.

Experiments in flowing pitch

1. Sinking bullets In an 1882 experiment, Scottish physicist Lord Kelvin put corks below and bullets above a block of pitch. Over time the corks floated to the surface and the bullets sank. Pitch was the only earthly material Kelvin knew of that could simultaneously behave as a solid and a fluid. He and other physicists of his era believed that a similar substance called the ether permeated the cosmos. …

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