94 Years, 9 Drops World’s Longest Experiment Nears Century Mark

Scientific research can span years, but one experiment has been running for nearly a century. Known as the Pitch Drop Experiment, it began in 1927 and officially started in 1930. Australian physicist Thomas Parnell initiated the study to demonstrate the unexpected properties of everyday materials.

The experiment uses pitch, a tar-like substance that is 100 billion times more viscous than water and two million times thicker than honey. Despite appearing solid, pitch is actually a liquid that can shatter like glass when struck. Parnell heated the pitch, poured it into a glass funnel, and allowed it to cool for three years before cutting the funnel’s bottom in 1930, enabling the pitch to drip out at an excruciatingly slow pace.

The results have been staggeringly gradual, with only nine drops falling since the experiment began. Neither Parnell nor his successor, Professor John Mainstone, witnessed a drop fall. The first drop did not appear until 1938, and the drops have typically occurred every eight to nine years. However, the most recent drop took significantly longer, falling in April 2014—14 years after the eighth drop in 2000. The timing of the drops varies with temperature fluctuations.

Drop timeline:

• 1938: First drop
• 1946: Second drop
• 1954: Third drop
• 1962: Fourth drop
• 1970: Fifth drop
• 1979: Sixth drop
• 1988: Seventh drop
• 2000: Eighth drop
• 2014: Ninth drop

Recognized by Guinness World Records, the experiment holds the title of the longest-running laboratory study. As it approaches its 100th anniversary, visitors can observe the experiment at the Parnell Building, University of Queensland, Australia, or watch it via live stream.

During the ninth drop in 2014, 483 viewers witnessed the event online.