69-year experiment captures pitch-tar drop

Begun in 1944, an Irish attempt to witness apparently solid pitch tar dripping from a funnel finally bears fruit.

Tim Hornyak
Crave freelancer Tim Hornyak is the author of "Loving the Machine: The Art and Science of Japanese Robots." He has been writing about Japanese culture and technology for a decade. E-mail Tim.
Tim Hornyak
2 min read
Pitch drop experiment
The moment on July 11 when a drop of pitch fell into a beaker at Trinity College in Dublin. Screenshot by Tim Hornyak/CNET

It took seven decades, but the pitch has finally been caught in the act.

Since 1944, physicists at Trinity College in Dublin have been trying to measure the viscosity of pitch tar, a polymer seemingly solid at room temperature, and witness it dripping from a funnel.

A drop forms only rarely, but last week a Webcam was on hand to witness the magic moment.

"The viscosity of pitch-tar is calculated to be 230 billion times that of water or 230,000 times the viscosity of honey," the college's School of Physics says on the experiment page.

"Nobody has ever witnessed a drop fall in such an experiment -- they happen roughly only once in a decade!"

The experiment is one of the oldest in the world, but a similar attempt at the University of Queensland in Australia has been going since 1927. It has only yielded eight drops.

A Webcam that was poised to record a drop of the Australian pitch in November 2000 malfunctioned, but another drop could fall this year: see the live view here. It could take another century for all the pitch to flow through the funnel.

The ostensible purpose of these trials is to measure pitch viscosity and to demonstrate how apparently solid materials can flow. When pitch is hit with a hammer, it fragments into shards.

It may sound like something fit for an Ig Nobel Prize, but the Trinity experiment was originally set up by a colleague of Nobel laureate Ernest Walton, who split the atom. Trinity physicists plan to publish their findings in the scientific journal Nature.

"For me, it summed up why I like being a scientist," Professor Shane Bergin of Trinity's School of Physics told RTE News.

"It acts as a catalyst for curiosity, and that's, for me, what the driving force of science is."

Check out the vid below showing the moment when the pitch drop was caught on video. Was it worth the 70-year wait?