The pitch drop experiment, started by Thomas Parnell of the University of Queensland in 1927, is probably the longest-running experiment of the 20th century. It was originally devised to demonstrate that pitch, a so-called viscoelastic polymer of which bitumen is a prime example, is not a solid but actually a viscous fluid. Even though it does appear solid at room temperature, and exhibits behaviours commonly associated with solids, like shattering on impact, when placed in a funnel pitch will slowly drip as if it were a very thick molasses—at an average rate of one drop every nine years. The viscosity of pitch, it has been calculated, is about 230 billion times that of water. Relegated to closets and then placed on display again only in 1975, this singular experiment can now be observed live via webcam: a scientific alternative to counting sheep. R. Edgeworth, B. J. Dalton and T. Parnell, “The Pitch Drop Experiment”
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The pitch drop experiment, started by Thomas Parnell of the University of Queensland in 1927, is probably the longest-running experiment of the 20th century. It was originally devised to demonstrate that pitch, a so-called viscoelastic polymer of which bitumen is a prime example, is not a solid but actually a viscous fluid. Even though it does appear solid at room temperature, and exhibits behaviours commonly associated with solids, like shattering on impact, when placed in a funnel pitch will slowly drip as if it were a very thick molasses—at an average rate of one drop every nine years. The viscosity of pitch, it has been calculated, is about 230 billion times that of water. Relegated to closets and then placed on display again only in 1975, this singular experiment can now be observed live via webcam: a scientific alternative to counting sheep.

R. Edgeworth, B. J. Dalton and T. Parnell, “The Pitch Drop Experiment”