Nestled in quiet laboratories at opposite ends of the globe, two unassuming funnels hold a substance that challenges our fundamental understanding of matter. These funnels contain pitch, a material that behaves like both a solid and a liquid, and form the centerpiece of the world’s longest-running laboratory experiments. What began as simple demonstrations of an unusual material property has evolved into scientific odysseys spanning generations, capturing the imagination of scientists and laypeople alike, and offering profound insights into the nature of time, matter, and scientific patience.
The Substance That Defies Classification
Pitch, or bitumen or asphalt, appears solid at room temperature. You can strike it with a hammer and it will shatter like glass. Yet this seemingly solid material harbors a remarkable secret: it flows like a liquid, albeit at an extraordinarily slow rate. This paradoxical behavior places pitch in a fascinating gray area between states of matter, challenging our everyday understanding of solids and liquids.
Pitch has an estimated viscosity of approximately 230 billion times that of water. For comparison, honey is only about 10,000 times more viscous than water. This extreme viscosity means that while pitch is technically a liquid, it appears completely solid in human timeframes, creating the perfect subject to demonstrate extreme patience.
The material belongs to a class known as amorphous solids, which lack the ordered crystalline structure of true solids. Other examples include glass and certain plastics. These materials exist in what scientists call a “supercooled liquid state,” where they maintain many properties of liquids while appearing solid to casual observation. This state challenges the traditional classification of matter into distinct solid, liquid, and gas phases that most of us learned in school.
The unique properties of pitch have made it historically valuable for waterproofing and as an adhesive. Ancient civilizations from Mesopotamia to Egypt used natural bitumen for construction, shipbuilding, and even mummification. The Bible mentions pitch being used to seal Noah’s Ark, and archaeological evidence shows pitch was used to waterproof boats in ancient Babylon. This practical material with extraordinary properties has been hiding in plain sight throughout human history, waiting for modern science to reveal its most peculiar characteristics.
The Queensland Experiment: A Century of Waiting
In 1927, Professor Thomas Parnell at the University of Queensland in Australia set up the longest-running laboratory experiment in history. He heated a pitch sample, poured it into a sealed funnel, and allowed it to settle for three years. In 1930, he cut the seal on the funnel stem, allowing the pitch to begin its glacial flow.
The first drop fell in December 1938, eight years after the experiment began. The second drop fell in February 1947, and subsequent drops have fallen in 1954, 1962, 1970, 1979, 1988, and 2000. The ninth drop formed in April 2014 and remains attached to the funnel as of 2023.
Perhaps the most frustrating aspect of this experiment is that, despite its 96-year duration, no one has ever witnessed a drop falling. The eighth drop fell during Easter weekend in 2000, when no cameras monitored the experiment. In 2013, webcams were installed to capture the ninth drop, but technical issues caused the cameras to be offline during the critical moment.
The experiment has survived world wars, funding cuts, and multiple generations of custodians. Professor John Mainstone oversaw the experiment for 52 years until he died in 2013, never witnessing a drop fall despite his half-century of vigilance. The current custodian, Professor Andrew White, continues the tradition of monitoring and maintaining this scientific marathon.
The Queensland experiment exists in a glass display case in the foyer of the physics building, where thousands of visitors come each year to observe a substance that appears completely static but is actually in constant, imperceptible motion. The experiment has become a powerful metaphor for processes that occur beyond the threshold of human perception, reminding us that our senses provide only a limited window into physical reality.
The Dublin Experiment: A Forgotten Treasure
While the Queensland experiment is widely known as the world’s longest-running laboratory experiment, another pitch drop experiment at Trinity College Dublin has an equally fascinating history. Established in 1944 by a colleague of Nobel laureate Ernest Walton, this experiment was forgotten for decades before being rediscovered in the 1990s in a storage cabinet.
What makes the Dublin experiment particularly notable is that in July 2013, it became the first pitch drop experiment to capture the fall of a drop on camera. This historic moment occurred on a weekend when no one was in the laboratory. Still, thankfully, the webcam was functioning correctly, capturing what had eluded scientists for nearly a century.
The Dublin experiment has yielded more drops than its Queensland counterpart, likely due to differences in the pitch composition and the funnel design. By 2023, it had produced at least 11 drops, falling approximately once every decade.
The rediscovery of the Dublin experiment highlights another fascinating aspect of these long-term studies: they often outlive their creators and original purpose, becoming scientific artifacts that connect us to previous generations of researchers. The experiment had been maintained by laboratory technicians who dutifully cared for it even after its original significance had been forgotten. This continuity of scientific stewardship represents one of the most admirable aspects of the scientific enterprise—the willingness to preserve knowledge and experiments for future generations.
Scientific Significance and Modern Applications
Beyond their value as curiosities, pitch drop experiments provide essential insights into non-Newtonian fluids and the nature of extremely high-viscosity materials. The experiments have helped scientists better understand the behavior of materials at the boundary between solid and liquid states.
Modern applications of this research extend to fields such as polymer science, geology, and materials engineering. Studying materials with extreme viscosity has practical applications in understanding geological processes like glacier movement and mantle convection, which occur over similarly extended timeframes.
Additionally, these experiments serve as powerful demonstrations of the scientific method and the value of long-term observation. In an era of rapid scientific advancement and pressure for immediate results, the pitch drop experiments stand as monuments to scientific patience and the importance of maintaining experiments across generations of researchers.
In 2005, the Queensland experiment was awarded the Ig Nobel Prize in Physics. This humorous award celebrates unusual or trivial scientific achievements that “first make people laugh, and then make them think.” This recognition highlights how these seemingly simple experiments continue to captivate scientists and the public, bridging the gap between specialized research and popular science.
The Legacy of Extreme Patience
The pitch drop experiments remind us that some phenomena in our universe operate on timescales vastly different from human experience. They serve as humbling reminders of our place in the cosmos and the limitations of our perception. In a world of instant gratification and rapid technological change, these experiments testify to the value of patience, persistence, and long-term thinking.
As global challenges unfold over decades or centuries, such as climate change or space exploration, the pitch drop experiments offer an important lesson: some problems and phenomena require sustained attention across generations. The scientific insights gained from watching pitch drop are modest compared to the philosophical perspective they provide—a perspective that encourages us to think beyond our immediate horizons and consider processes that unfold over decades, centuries, or even millennia.
The next time a drop falls in Queensland or Dublin, a new generation of scientists and observers will be watching. They will continue a scientific tradition that connects us across time and reminds us that sometimes the most profound discoveries require not just brilliance but patience.