Posted on behalf of Brian Owens.

John Mainstone, who for 52 years tended to one of the world’s longest-running laboratory experiments but never saw it bear fruit with his own eyes, died on 23 August after suffering a stroke. He was 78.

Mainstone had been looking after the pitch-drop experiment at the University of Queensland in Brisbane, Australia since he arrived at the university as a physics professor in 1961. The experiment, set up in 1927 by the university’s first head of the physics department, Thomas Parnell, consists of a sample of tar pitch slowly running through a funnel (see ‘Long-term research: Slow science‘).

The pitch forms a drop that falls into a waiting beaker about once every decade or so. In the 52 years that Mainstone spent watching the pitch, he never managed to see a drop fall. In 2000, when the eighth drop fell, the webcam set up to capture it failed at the critical moment. With three cameras trained on it now, Mainstone had been looking forward to finally seeing the experiment in action later this year, when the ninth drop is expected to fall. But sadly the pitch proved too slow-moving for him in the end.

Mainstone did, however, get to see video of a drop falling from a similar experiment in Ireland earlier this summer. “I have been examining the video over and over again,” he told Nature at the time, “and there were a number of things about it that were really quite tantalizing for a very long-time pitch-drop observer like myself.”

The pitch drop had become famous in the past few decades, thanks in no small part to Mainstone’s years-long campaign to get the university to put it on public display. It is listed as the worlds longest-running laboratory experiment in the Guinness Book of World Records, and in 2005 Mainstone shared an Ig Nobel Prize in physics with Parnell for their work on it.

Mainstone was always happy to talk about the experiment, and would explain enthusiastically (and at some length) what it meant not just for science, but for the wider culture, to have something that enables us to think more deeply about the passage of time, and our place in the universe. “It’s going about its business while the world is going though all sorts of turmoil,” he told Nature in January.

This is not the end for the pitch drop experiment. Mainstone lined up his successor years ago, in anticipation of the time when he would no longer be able to take care of the apparatus, which has enough pitch in it to keep going for another 150 years. And so Andrew White, a physicist at the university and one of Mainstone’s former students, will now take over the vigil.