Pitch Drop Experiment Record in Trinity

18 July 2013

After decades of waiting, physicists at Trinity College Dublin have beaten their Australian counterparts by capturing on camera the result of one of the world's oldest continuously running experiments.

The aim of the experiment is to demonstrate that some substances that appear solid are in fact high-viscosity liquids.
It was begun by a colleague of Nobel Prize winner Ernest Walton in the physics department of Trinity in 1944 and involved placing several lumps of pitch into a funnel and placing the funnel in a jar. 

The jar was placed in a dusty cupboard, first in a store room and then in a lecture theatre and left. Over several decades a number of drips did form in the funnel and fall into the jar, giving credence to the hypothesis that pitch is indeed viscous.

A similar experiment began in the 1920s in Queensland in Australia. It is considered to be the world's longest running laboratory experiment and has dripped eight times. However, despite close monitoring, technical glitches have meant that the Australian experiment has never been caught dripping on camera and the ninth drop is expected any day now.

A number of weeks ago, Trinity physicists noticed that a drip had formed. They set up a webcam to video the experiment around the clock. Last Thursday, the drip finally dropped into the jar, and was captured on camera.

The Trinity College physicists have estimated that based on the results from the experiment, the viscosity of pitch is calculated to be 230 billion times that of water or 230,000 times the viscosity of honey. The findings are due to be published in Nature.