The world’s oldest laboratory experiment is currently being broadcast live

At the University of Queensland there is an exhibition featuring the world’s oldest laboratory experiment. It has been around so long that two of its guardians died before seeing any results.

The experiment was initiated in 1927 by Thomas Parnell, the university’s first professor of physics. Intended as a demonstration of highly viscous materials, Parnell took pitch – a residue from the distillation of coal tars – heated it, placed it in a sealed glass funnel, then waited three years for it to takes the shape of the container. This may seem like a long time to wait before an experiment even begins, but given the expected duration of the demonstration, it was only a long shot.

In 1930, Parnell cut the stem of the funnel, allowing the highly viscous liquid to flow slowly from the bottom. Since then, the experiment has been moving incredibly slowly. The first drop occurred eight years after the experiment began, and five more over the next 40 years. The experiment has now been going on for almost 100 years and is under the care of several different caretakers. Parnell and his successor, Professor John Mainstone, both died without seeing the straw fall for themselves, Professor Andrew White being the current guardian.

But now the experiment is under constant webcam surveillance, meaning someone could witness the next one. The last fall (until another one occurred) took place in 2014, seen here in highly time-lapse footage.

So, can experience teach us anything interesting?

Although the experiment is less controlled than ideal (it is subject to ambient temperature fluctuations and the internal diameter of the rod cannot be measured precisely without risking damage to the experiment), it has some surprises in store.

By taking into account a number of factors, it is possible to make a reasonable estimate of pitch viscosity.

“The viscosity of the pitch is then calculated as q = (2.3 +0.5) x 10⁸ Pa s, which is enormous compared to that of common liquids,” explains an article about the experiment. “Water at 20°C has a viscosity of 1.0 x 10^-3 Not. It should be noted, however, that (disregarding superfluidity) it is close to the geometric mean of the range of values ​​considered by physicists – the effective viscosity of the Earth is of the order of 10²⁰ Not.”

This does not match well with previous predictions.

“The viscosity result from the height drop experiment does not agree well with predictions based on (previous) measurements, even accounting for the enormous variation in viscosity with temperature and the temperature history rather unknown to the experiment,” the team writes. “The likely explanation lies in the different viscosities of the different pitch samples – these could have different proportions of trapped volatile hydrocarbons, which would affect the viscosity.”

If you want to watch the experience live, you can. Currently, a pretty big drop is forming – but we don’t recommend looking too long as the next drop is expected to fall sometime in the 2020s, and there’s still a good part of a decade to go.