Some experiments finish in an afternoon. A few have been running longer than anyone looking after them has been alive. In a glass funnel in Brisbane, Australia, a blob of tar has dripped nine times since 1930, and no one has ever watched a drop fall there. In Oxford, a bell has rung on the same pair of batteries since 1840. In a California fire station, a light bulb has glowed since 1901. Here is how these slow-motion marathons work, why they keep going, and what they actually teach.
Tar that is secretly a liquid
Pitch is a black, tar-like substance made from oil or coal. Sailors once used it to waterproof wooden ships. At room temperature it feels solid. Hit a lump with a hammer and it shatters like glass.
In 1927, Thomas Parnell, the first physics professor at the University of Queensland, wanted to show his students that this feeling was misleading. He heated some pitch, poured it into a glass funnel with a sealed stem, and let it settle for three years. In October 1930 he cut the stem open. Then he waited.
The pitch started to flow, very slowly. The first drop fell in December 1938. The second fell in February 1947. New drops kept coming roughly every eight years, each one stretching out like a slow black tear before it lets go.
The word scientists use here is viscosity, which simply means how thick and slow a liquid is. Water has very low viscosity. Honey has much more. From the timing of the drops, researchers estimate this pitch is about 100 billion times more viscous than water. It is a liquid. You just need decades to see it behave like one.
Nine drops, and nobody saw one land
The strangest part of the story is how often people missed the moment. John Mainstone looked after the experiment from 1961 until 2013. In July 1988, the seventh drop fell while the funnel was on display at Brisbane’s World Expo, and Mainstone had stepped out for a drink. In November 2000, a webcam was watching, but it failed at the key moment, so the eighth drop went unrecorded too.
Mainstone died in August 2013, aged 78, without ever seeing a drop fall. Physicist Andrew White took over. In April 2014, the ninth drop touched the pile of earlier drops in the beaker while it was still hanging from the funnel. When the team swapped in a fresh beaker a few days later, the wooden base wobbled and the drop snapped off. Not exactly a triumphant finish.
After the seventh drop, the building got air conditioning. Cooler air makes the pitch thicker, so drops now stretch longer and take 12 to 13 years instead of about eight. The tenth drop has been forming since 2014, and as of 2026 it still has not fallen. A live camera watches it, and the university says it expects the drop sometime in the 2020s.
Guinness World Records lists it as the longest continuously running laboratory experiment. In 2005, Parnell, long after his death, and Mainstone shared an Ig Nobel Prize, a tongue-in-cheek award for research that makes people laugh and then think.
The drop someone finally caught
Queensland’s funnel is the famous one, but it is not the only one. At Trinity College Dublin, someone in the physics department set up a pitch funnel in October 1944. It sat on a shelf for decades, gathering dust. In 2013, physicists noticed a new drop forming and pointed a webcam at it. On July 11, 2013, the drop fell on camera, the first time anyone had recorded a pitch drop as it happened.
Other funnels are slower still. One at Aberystwyth University in Wales dates to 1914 and has not produced a single drop. At its pace, the first may be more than a thousand years away.
A bell that has been ringing since 1840
In a corridor near the entrance of the Clarendon Laboratory at the University of Oxford, two small brass bells sit under glass. A tiny metal ball, about 4 millimeters across, swings between them roughly twice a second. It has been doing that, with only brief pauses, since 1840.
The power comes from two dry piles, an early kind of battery made from stacked discs. Each bell hangs under one pile, and the two bells carry opposite electric charges. The little ball touches one bell, picks up its charge, gets pushed away, and is pulled toward the other bell. Then the whole thing runs in reverse.
The trick is that each swing moves only a tiny amount of electricity. The piles need high voltage to push the ball, but they spend almost nothing per ring, so they drain incredibly slowly. The bell has rung an estimated 10 billion times, and Guinness lists it as the world’s most durable battery. Behind two layers of glass, you cannot hear it.
Nobody knows exactly what is inside the piles, which are sealed in sulfur. It is not perpetual motion, either. One day the charges will even out, or the ball will wear out, and the ringing will stop. Nobody can say when.
A clock that winds itself with the weather
In Dunedin, New Zealand, a clock in the physics department at the University of Otago has been running since 1864 without anyone ever winding it. It was built by Arthur Beverly, a local watchmaker.
Its fuel is the daily rise and fall of temperature, plus a little help from changes in air pressure. Inside is an airtight box holding about a cubic foot of air. As the room warms, the air expands. As it cools, the air shrinks. That push and pull moves a flexible diaphragm, which slowly lifts the weight that drives the clock. A daily swing of about 6 degrees Fahrenheit (3.3 degrees Celsius) is enough to raise a one-pound weight by about an inch, and that is all the clock needs.
It has stopped now and then for cleaning, repairs, and a building move. It also stalls when the temperature stays too steady, then restarts once the days begin to swing again.
The light bulb that will not burn out
At Fire Station 6 in Livermore, California, a hand-blown light bulb has hung from the ceiling since 1901. The Centennial Light was made by the Shelby Electric Company of Shelby, Ohio, in the late 1890s and donated to the local fire department. When it moved to the current station in 1976, it was unplugged for only 22 minutes and rode in a special box with a fire-truck escort.
It started life as a 60-watt bulb. Today it glows about as brightly as a 4-watt nightlight. Its long life likely comes down to a thick carbon filament (the glowing thread inside the glass), very low power, and almost never being switched off. Turning a bulb on and off heats and cools the filament over and over, and that stress is what usually kills it.
It has had one big scare. On May 20, 2013, webcam viewers saw it go dark. The next morning an electrician found the bulb was fine. Its power supply had failed, and the light was back after under ten hours.
Experiments built to outlive their makers
Some long experiments are slow on purpose. In 1988, the biologist Richard Lenski started 12 flasks of E. coli bacteria, all descended from one ancestor. Every day since, someone moves 1 percent of each population into a fresh flask of food. This Long-Term Evolution Experiment has now passed more than 82,000 generations. Around generation 31,000, one population evolved the ability to eat citrate, a food E. coli normally cannot use. The flasks moved to Texas in 2022 under Jeffrey Barrick, then followed him back to Michigan State University in 2025.
Then there is the 500-year experiment. In 2014, scientists at the University of Edinburgh sealed dried microbes in 800 small glass vials. Some get opened every two years for the first 24 years, then once every 25 years, all the way to 2514. The question is simple: how long can a dormant microbe stay alive? Future caretakers are asked to rewrite the instructions every 25 years so they still make sense.
Why slow science still matters
None of these setups is likely to win a Nobel Prize. Most started as classroom demonstrations or curiosities. But they show that some things in nature happen on time scales longer than a research grant, a career, or a lifetime. A substance can be a liquid and still look solid for your whole life. A battery can last nearly two centuries if you ask very little of it. Evolution can be watched in a flask if someone is willing to keep going for decades.
They also depend on people more than equipment. Each has survived because someone kept caring for it and handed it on. Mainstone waited more than fifty years and never saw a drop fall. Whoever sees the tenth one, if anyone does, will probably be watching a screen.
If you want to join the watch, the University of Queensland keeps its pitch drop camera online. Just do not expect anything to happen today.
Further reading
Liquid Rules: The Delightful and Dangerous Substances That Flow Through Our Lives — Mark Miodownik’s lively tour of the liquids around us, including a chapter on tar that tells the Queensland pitch drop story and explains why roads can heal their own cracks.
The Clock of the Long Now: Time and Responsibility — Stewart Brand on thinking in centuries instead of quarters, built around a clock designed to tick for 10,000 years — a natural companion to experiments meant to outlive their makers.