The University of Queensland is home to the world's longest-running laboratory experiments. It had been in operation for so long that two of his administrators died before seeing results.
The experiment was started in 1927 by Thomas Parnell, the university's first physics professor. For the purpose of demonstrating highly viscous substances, Parnell heated pitch, the residue obtained from the distillation of coal tar, and placed it in a closed glass funnel, which he waited for three years until it settled into the shape of a container. That may seem like a long time to wait for the experiment to begin, but considering the length of the planned demonstration, it was just a long blink of an eye.
In 1930, Parnell cut the shaft of the funnel, allowing the highly viscous liquid to slowly flow out the bottom. Since then, experiments have continued to run incredibly slowly. The first decrease occurred 8 years after the start of the experiment, and then another 5 decreases over the next 40 years. This experiment spans his nearly 100 years and is under the responsibility of several different administrators. Both Mr Parnell and his successor, Professor John Mainstone, died without seeing the fall, and its current custodian is Professor Andrew White.
But now the experiment is being monitored by a webcam, meaning someone could witness the next experiment. The last drop (until the next one) occurred in 2014 and can be seen here in significantly sped-up footage.
So, can we learn anything interesting from this experiment?
Despite the experiment being less controlled than ideal (it is affected by room temperature fluctuations and the inner diameter of the stem cannot be precisely measured without risking damage to the experiment), there were some surprises for us. had.
Considering many factors, a reasonable estimate of pitch viscosity can be made.
“Pitch viscosity is calculated as q = (2.3 +0.5) x 10.8 “This is very large compared to the viscosity of common liquids,” a paper describing the experiment explains. “The viscosity of water at 20℃ is 1.0 x 10-3 path. However, it should be noted that (ignoring superfluidity) it is close to the geometric mean of the range of values considered by physicists. The Earth's effective viscosity is on the order of 10.20 path. ”
This is not very consistent with previous predictions.
“Viscosity results from pitch drop experiments do not agree well with predictions based on: [previous] “The measurements take into account the huge variations in viscosity with temperature, as well as the rather unknown temperature history of the experiment. The likely explanation lies in the differences in viscosity of samples with different pitches. “The proportion of volatile substances may differ,” the researchers wrote. The presence of hydrocarbons can affect viscosity. ”
If you would like to watch the experiment live, you can do so. There is currently a fairly large chunk forming, but the next decline is expected to be sometime in the 2020s, and we don't recommend watching it for too long as there are still plenty of years left.