The moving pitch drop falls...


When University of Queensland physics Professor John Mainstone died at the age of 78 following a stroke last month, it made me wonder at the dedication that must drive good scientists. For the last 52 years, Mainstone was custodian of the pitch drop experiment, the longest running scientific experiment in the world. And yet, in all his time as custodian, Mainstone never actually saw a pitch drop fall.

It’s not often that zen meets science in life, but you’d have to say that the pitch drop experiment, which has been running since 1927 when the university itself was an adolescent, has become the most zen-like science imaginable. Originally designed by the university’s first head of physics Professor Thomas Parnell, the experiment demonstrates that something which feels solid may still act like a fluid.  Even pitch, hard as rock, will eventually drip.


Parnell heated a little bowl of pitch and then, instead of, say, waterproofing his boat with it, he poured it into a funnel sealed at the bottom. After the pitch settled – three years later – Parnell cut off the seal. It started to form a drop, proving his point. Because it’s in a funnel and at room temperature, the pitch acts like a fluid, albeit a very viscous one, 230 billion times more viscous than water. In fact, it flows so slowly that a pitch drop has fallen only eight times in the 86 years since the experiment was set up. And no one has actually seen a drop fall in all that time. The one forming right now is expected to fall any day. Watch out!

One of the zen aspects of the pitch drop experiment relates to time. It outlived the experimenter Parnell, and captured other imaginations. Mainstone joined the university as a young physicist in 1961. When a technician showed him the experiment – which is, as you’d expect, a glass funnel filled with hard black gunk with a big drop hanging down, over a beaker in which sits a drippy pile of the black gunk – it was stored in a cupboard where it had languished since Parnell’s death in 1948. Mainstone brought it out of the cupboard. Interested in both the history of his discipline and the history of the university, he became its champion.

The experiment has been relocated, once when the university moved from its original Gardens Point site to St Lucia, and once it even crossed the river. While Brisbane was coming of age as a big city during Expo 88, the pitch was getting ready to drop, so the experiment was taken to the Expo site on the river’s south bank for all to see. Mainstone was there watching over his charge, but he went out for a few minutes and while he was out, you guessed it, the pitch dropped. In 2000, when the next  drop had formed, Mainstone, who was overseas, rigged up a camera so he wouldn’t miss it. But the night the drop fell, a power outage meant the camera stopped working. Which brings me to the other zen aspect of the pitch drop, the existential nature of the experiment. If no one is watching when the pitch drop falls, does it actually happen?

Mainstone continued his dedication to the pitch drop experiment after he retired. Largely because of his efforts, thousands have seen it in the foyer of the Parnell building at St Lucia. In 2005, it was awarded the prestigious Ig Nobel prize for physics. Now hooked up to the internet, there are three cameras peering at the drop, to catch it when it falls. Following Mainstone’s passing, stewardship has been handed on to Professor Andrew White, a quantum physicist. I hope he’s patient.

I love science for the same reasons I am in awe of zen, its cool stare at the world in which we live, so carefully but never cruelly eschewing sentimentality, its gentle but firm discipline, its soothing principles and rules. But all the same, I wish the scientist who’d cared for the pitch drop experiment for over half a century had lived to see the drop fall. Vale John Mainstone. I never knew you but I do love your work.



Based on the column published in The Courier-Mail Qweekend  on 14 September 2013. I write mainly about writing, education, birth, health and the thrill of parenting. You can Get in touch,  tick the box to receive emails, Like Writer Mary-Rose MacColl on Facebook or follow MaryRoseMacColl on Twitter. Have a great day!