Simran Joshi
The world’s longest-running scientific experiment, the Pitch Drop Experiment, has been captivating scientists and enthusiasts for nearly a century. Initiated in 1927 by Australian physicist Thomas Parnell, this experiment demonstrates the surprising behavior of pitch, a substance that appears solid but flows like a liquid over time.
Since its official start in 1930, only nine drops of pitch have fallen from a glass funnel, with the most recent drop descending in 2014. This Guinness World Record-holding experiment, housed at the University of Queensland, offers a unique glimpse into the slow and fascinating nature of high-viscosity materials.
The World’s Longest Experiment: A Century of Waiting
Started in 1927 and officially in 1930, the Pitch Drop Experiment is considered to be the world’s longest-running laboratory experiment and has even been placed in the Guinness World Records.
The researcher behind this experiment was Australian physicist Thomas Parnell, who could reveal such sensational properties of a highly viscous substance called pitch, which acts sometimes like a liquid and sometimes like a solid.
He demonstrated its fluidity by heating the pitch, allowing it to cool over three years, and then letting it drip slowly from a funnel. Since its formation, only nine drops have dropped, the first in 1938 which took eight years to make it to the ground. Interestingly, neither Parnell nor his successor, Professor John Mainstone never witnessed a drop fall. The ninth drop fell in April 2014 after 14 years since the last drop, and was witnessed by 483 people through a live webcam organized by the University of Queensland.
A Century of Patience: The Drop-Time Interval Timeline of Drops
The time span of the experiment tells a lot about the pitch’s extreme viscosity. The drops fell in 1938 (1st drop), 1946 (2nd drop), 1954 (3rd drop), and so on, every 8–9 years. However, the flow rate was increasing and in the 9th drop in 2014 was still after 14 years as it took down due to temperature changes.
It is “100 billion times more viscous than water and two million times more viscous than honey,” yet it looks solid.
But it flows under gravitational pull. On the other hand, if hit with a hammer, it can shatter like glass. Now, visitors in Australia can see the experiment in the Parnell Building of the University of Queensland or follow it through live streaming as the world waits for the 10th drop.
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