Eighty-three years ago, Professor Thomas Parnell of the University of Queensland cut the stem on a (formerly) sealed funnel of tar pitch. The pitch-drop funnel—an experiment in measuring the viscosity of an ultra-high viscosity substance—has been on display ever since, with only eight drops of pitch passing through the funnel in as many decades.

This year, the ninth drop is finally expected to fall.

As a continually (and still) running experiment, the Pitch-Drop Experiment is the longest-lived in history. A few experimental devices (an electric bell and a thermodynamically-powered clock) are older than the Pitch-Drop funnel, but both stop working periodically, while the pitch marches ever-so-slowly on.

Professor Parnell started the project eight decades ago to illustrate for his students that some "solids" are actually just very, very, very high-viscosity liquids. And pitch is a very, very, very high-viscosity liquid . . . 230 billion times more viscous than water—a factoid for which we are indebted to Professor Parnell.

Roughly 230 billion times more viscous, anyway. The experiment is hardly precise, with no controls for temperature, humidity or vibration. Air conditioning was installed in the room between the 7th and 8th drops (which has evened things out a bit) but all things considered, it's entirely possible that pitch is only 229 billion times more viscous than water. It's a maddening uncertainty, but one we must somehow find the strength to endure.

Curiously, no person has actually seen any of the eight previous drops at the moment they dropped. Each time, the pitch-drops have stealthily avoided any and all attempts at observation or recording. The last drop, in 2000, coincidentally fell while the webcam trained on it was malfunctioning. The drop before that snuck past an otherwise dedicated observer when he stepped out to grab a cup of coffee.

(It's been 25 years since that observer's coffee cost him his shot to see drop #7 . . . and at 73 years old he's still waiting to see one.)

This time around, there's three separate webcams trained on the drop, so perhaps finally someone will get to see it happen. One of those webcams is live, so it could even be you. But if you miss this one, don't worry . . . drops are only about a decade apart, and there's enough pitch left in the funnel for this experiment to run another hundred years.

Note: the 10-second video at the top is a time-lapse recording of a year's worth of pitch falling. It's that slow.