The Slow Funnel

Usually when you use a funnel the fluid goes through quickly. Even if you’re filtering something you expect it do be done in 10 minutes or so. How about longer? How about over a year? Over a decade? How about almost 100 years?

One of the long running experiments is the Pitch Drop Experiment started at the University of Queensland in 1927. Pitch is another word for bitumen, or asphalt. It’s a very viscous liquid. Water has low viscosity. Honey flows slower, so it has a higher viscosity. Pitch has the somewhat higher viscosity of 2.3 × 1011. That’s 230,000,000,000 times slower than water.

To demonstrate this, in 1927 Thomas Parnell heated a sample of pitch and put it in a sealed funnel. 3 years later he cut the seal on the neck of the funnel to let the pitch start flowing. It took about a decade for the first drop to fall. The 8th drop fell on 28 November 2000. You can see the progress of the next drop in the experiment at this webcam.

This experiment is in the Guinness World Records as the longest continuously running lab experiment. There are other, longer running, experiments, but they have had interruptions.

Update 17 April 2014The 9th drop has collided with the 8th drop. Due to the amount of pitch at the bottom of the beaker, the 9th drop can’t fully detach from the funnel, so they are calling this the official 9th drop (or so I’ve heard). Onward to number 10!