A century of patience. The world's longest-running experiment unfolds
Pitch, or high-temperature coal tar, looks like black stone, though it is a liquid with very high viscosity. But how can we prove that this "stone" is actually a dense fluid? Prof. Thomas Parnell aimed to demonstrate this experimentally, leading to what is still the longest ongoing scientific experiment in the world.
The experiment commenced at the University of Queensland in Australia in 1927. Prof. Thomas Parnell intended to illustrate that pitch (a type of tar), which appears to be stone-like, hard, and crumbles upon impact, is contrary to the appearance of a liquid.
To achieve this, he placed a sample of pitch in a sealed glass funnel, waited several years for the funnel's outflow to be completely filled, then opened the outflow and encased everything under a glass dome. And waited.
The Pitch Drop Experiment
The wait lasted until 1938, when, 11 years after the experiment began, the first drop detached from the funnel. The scientist also witnessed the fall of a second drop in 1947, after which he passed away, but his experiment was not halted.
As a result, the funnel with a pitch sample has been under observation since 1927. In that time, some conditions have changed—the room with the funnel has been air-conditioned since the mid-80s, and a stable and slightly lower temperature has noticeably slowed the separation of subsequent drops.
- 1927 - Start of the experiment
- 1938 - Fall of the first drop
- 1947 - Fall of the second drop
- 1954 - Fall of the third drop
- 1962 - Fall of the fourth drop
- 1970 - Fall of the fifth drop
- 1979 - Fall of the sixth drop
- 1988 - Fall of the seventh drop
- 2000 - Fall of the eighth drop
- 2014 - Fall of the ninth drop
Nearly a century has passed since the experiment began. During this time, nine drops of pitch have detached. Prof. John Mainstone, the experiment's caretaker (who passed away in 2013), could talk about extraordinary bad luck.
In 1988, the funnel with pitch was displayed during the World Expo 88 exhibition, during which, after 111 months of waiting, the seventh drop detached. Despite such a prominent placement, no one saw it live. Prof. Mainstone had just gone out for a drink, and the fall of the drop was recorded after the fact.
Live Stream
Since 2000, such mishaps are no longer possible. The world's longest experiment is under constant camera surveillance, and the University of Queensland has made the footage available online.
The Pitch Drop experiment can be observed by anyone today, although the probable fall of the next, tenth drop will not occur for a few more years. Despite this, people around the world continuously monitor the transmission – at the time of writing, it was being watched by 31 people.
