What Is the World's Longest-Running Laboratory Experiment?

The Answer: The University of Queensland Pitch Drop Experiment

The world’s longest-running laboratory experiment is the University of Queensland Pitch Drop Experiment, started in 1927 by Professor Thomas Parnell, which has been slowly dripping pitch for nearly a century and holds the official Guinness World Record.

What Is the Pitch Drop Experiment?

In 1927, Professor Thomas Parnell — the University of Queensland’s very first physics professor — set up a simple but profound demonstration. He heated a sample of pitch and poured it into a sealed glass funnel. After allowing it to settle for three years, he cut the stem of the funnel open in 1930 and let gravity do the rest.

Pitch looks and behaves like a solid at first glance. You can shatter it with a hammer. It appears to be rock. But it is actually a liquid — just an extraordinarily slow-moving one. Pitch is approximately 230 billion times more viscous than water, making it one of the most viscous substances ever observed flowing under natural conditions.

How Slow Is a Pitch Drop?

Because pitch flows so slowly, a single drop takes roughly a decade to form and fall. In the nearly 100 years since the funnel’s stem was opened, only nine drops have fallen. That glacial pace is what makes this experiment both scientifically remarkable and almost comedically difficult to observe.

The timing of each drop is unpredictable enough that even dedicated observers have missed every single one — for decades. Professor Parnell himself never saw a drop fall. Neither did his successor, Professor John Mainstone, who watched over the experiment for 52 years and missed every drop during his tenure, sometimes by minutes.

The Incredible Run of Bad Luck

The experiment’s history reads like a comedy of near-misses. Drop after drop fell when no one was looking — during lunch breaks, over weekends, in the middle of the night. Professor Mainstone famously stepped away from the experiment on multiple occasions only to return and find a fresh drop had just fallen.

In 2000, a camera was finally set up to watch the funnel continuously. It malfunctioned just as the eighth drop fell. The bad luck was almost statistically impossible.

When Was a Drop Finally Recorded?

It wasn’t until 2014 that a webcam — streaming the experiment live online — successfully caught the ninth drop falling on camera. It was the first time in 87 years that a drop had been recorded. Yet even then, no human being was watching the live stream at the exact moment it happened. The event was confirmed only after the fact by reviewing the footage.

The experiment remains active today. A tenth drop is currently forming, and the webcam continues to stream live. Anyone in the world can watch it online and potentially become the first person to witness a pitch drop fall in real time.

Why Does the Experiment Matter?

Beyond the record-breaking duration, the pitch drop experiment is a genuine scientific tool. It provides a measurable, real-world demonstration of viscoelastic materials — substances that behave as both solids and liquids depending on the timescale of observation. It also serves as a humbling reminder that some of the most important scientific observations require extraordinary patience.

The experiment has outlived both the professor who started it and the one who spent his career watching it. It is science on a timescale that dwarfs human attention spans — and it’s still going.