Pitch Drop Experiment Began in 1927

pitch drop

The longest running experiment listed in the Guinness Book of World Records is the Pitch Drop Experiment which began back in 1927. The physics professor at the University of Queensland in Australia at the time was Thomas Parnell. He wanted to show his students that tar pitch, which can be shattered by a hard impact, is actually fluid that will flow at room temperature. Tar pitch is a brittle coal derivative which has an extremely high viscosity.

To begin the experiment, Parnell took tar pitch, melted it, poured it into a glass funnel with a sealed stem, placed it under a bell jar, and then let it cool for three years. At the end of the cooling period, he hung the glass funnel over a beaker, cut the stem seal, and waited for the pitch to drop. It took eight years for the first drop of pitch to fall from the bottom of the funnel and an additional nine years for the second drop. Parnell did not live to note the third drop fall from the bottom of the funnel which did not occur until 1954. Although the experiment was still running, it had, at this point, been relegated to a dusty corner in the physics department.

Luckily for the experiment, a gentleman by the name of John Mainstone joined the Queensland physics department in 1961. While Mainstone wanted to display the experiment for the edification of the engineering and science students, he was unable to secure approval. It wasn’t until 1975 that Mainstone talked the physics department into displaying the long-running pitch drop experiment which began back in 1927. Mainstone, the long-time custodian of the experiment, passed away last September.

The pitch drop experiment is currently broadcast via live web cam. Andrew White, a quantum physicist at the university and current custodian, admits that the experiment is not that exciting to watch. In fact, he has said that a far more interesting pursuit would be to watch paint dry. He goes on to state that the continental drift of Australia at six centimeters a year is 10 times faster than the pitch drop.

The last time a drop fell was in the year 2000. Another drop is due to fall at any time now. Perhaps the next drop will fall soon, or in the next six months, or in the next year. The next drop will be the ninth drop of pitch to fall since the inception of the experiment. While the experiment has been recorded for quite some time, no one has ever been able to witness the moment when the pitch drop has actually detached and fallen. The eighth drop, on Nov. 28, 2000, occurred during a camera malfunction.

Between the introduction of air conditioning at the school during the 1980s and the fact that the weight of the pitch in the funnel decreases with each drop, each subsequent drop will take longer to fall. It has taken 14 years for this ninth drop to near its point of detachment. It is the hope of many researchers and public viewers that this time, someone, somewhere, will actually get to see the drop fall.

The pitch drop experiment which began in 1927 and is the longest and slowest running experiment is now broadcast live over the internet. At this point there is not just one but three web cameras trained on it. Each web cam has its own, individual power source, and each camera sends video to the internet 24 hours a day, seven days a week. The webcast, of which there are approximately 18,000 subscribers, is called the Ninth Watch webcast. Generally, there is an average of about 200 people viewing the experiment at any given time.

By Dee Mueller

University of Queensland
Popular Science
The Star