Pic by smlp.co.uk - CC BY 2.0

The longest experiment

Science can be a rather slow process. Sometimes the technology needed to confirm a hypothesis is not there yet, and has to be invented by subsequent generations. Sometimes repeated trials are necessary to make sure the conclusion is correct. It can take several generations of scientists building upon each other’s work to come to a new discovery.

And sometimes science just goes all quirky and decides to see how slow you can go.

There is an experiment that has been running for 83 years. It is located at the University of Queensland, and involves a beaker, a glass funnel and some tar pitch. Now, pitch is the black stuff traditionally used for waterproofing wooden boats. It is derived from tar, which emerges from pine wood and roots when they are heated at a particularly high temperature, leaving behind charcoal (a process known as ‘destructive distillation’). Pitch can also be created from petroleum products in a similar process, and the resulting material we commonly recognise as bitumen or asphalt.

If you think “asphalt,” you imagine a solid substance. Pitch is seemingly solid at room temperature and shatters if smashed with a hammer.  However, pitch is actually a viscoelastic polymer, which means that it also exhibits the properties of a fluid — except it does so incredibly slowly.

Pitch drop experiment at UQ // Picture from UQ Physics Museum website
Pitch drop experiment // UQ Physics Museum website

To showcase the surprising properties that such everyday materials as pitch can have, in 1927 Professor Thomas Parnell of UQ heated some pitch and poured it into a sealed glass funnel. Three years later, after the pitch settled, the sealed stem of the funnel was cut. Ever since that day, the pitch has been slowly dripping out of the funnel. How slowly does it drip?

The first drop touched down eight years after the beginning of the experiment. Since then a World War has taken place, the Soviet Union has risen and collapsed. Microwave ovens, colour televisions, mobile phones and the Internet have entered our homes. The United States has changed 14 presidents. A new millennium has arrived.

And only seven more drops have landed from the funnel. The material is about 230 billion times thicker than water1.

What’s more, over all these years, nobody has actually witnessed a pitch drop fall. Eight drips, eight misses. A long-term custodian of the experiment, Professor John Mainstone, has been monitoring the pitch for 52 years. A technical camera mishap, a badly timed dash for a can of soda, a misjudged weekend off is all it takes to miss the magical moment.

And here’s where it gets exciting. Today, anyone can witness this moment, as the ninth drop is predicted to fall any second now. Well, any day. Definitely this year. Very soon.

There is a live online webcam feed showcasing the experiment for anyone interested around the world. Take a look and you too can witness historical science in slow action.

Show 1 footnote

  1. http://www.physics.uq.edu.au/physics_museum/pitchdrop.shtml
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