Professor John Mainstone with the eighth drop in late 1990, about 2-1/2 years after the seventh drop fell.

Story highlights

The "pitch drop" is the world's oldest scientific experiment

It is designed to show that the brittle pitch is in fact, a liquid.

Progress is so slow that now, 86 years later, only the ninth drop is forming

No-one has witnessed the drop including the scientist in charge of the study since 1961

Hong Kong CNN  — 

At some point in the next few months, a tendril of black tar-like substance will drop from a glass funnel and land in a beaker under a bell jar in what is thought to be the world’s oldest scientific experiment.

The “pitch drop” at the University of Queensland in Australia began in 1927 and is designed to show that the brittle pitch – which was once used to waterproof boats and can be shattered by a hammer – is in fact, a liquid.

But the progress of the pitch through the funnel stem is so slow that now, 86 years later, only the ninth drop is forming.

Even if you stare at the experiment for hours, which you can do on the university’s web cam, nothing appears to happen at all – making watching paint dry or grass grow action packed by comparison.

At room temperatures pitch appears to be a brittle solid, but the experiment demonstrates otherwise

No-one has witnessed the once-in-a-decade drop, including Professor John Mainstone, the scientist in charge of the study since 1961.

“It’s looking like things will happen in a matter of months but for all I know it might be a matter of weeks,” Mainstone tells CNN.

“People think I have got in the habit of sitting alongside it day and night but I do need some sleep,” adding that he normally checks on it five or six times a day and keeps an eye on the web feed from his computer.

In 1979, Mainstone missed the key moment after skipping his usual Sunday campus visit and, in 1988 he missed it by just five minutes as he stepped out “to get a refreshment.”

The last drop – in 2000 – he thought was captured on camera only to find a glitch and nothing on film.

“We were defeated again.”

But he is philosophical, saying that he could miss the drop – which takes a tenth of a second – in a blink of the eye.

With three web cams trained at the bell jar, kept inside a glass cabinet at the entrance to two lecture theaters, Mainstone is confident this time the flash of action will be captured electronically if not by eye.

The experiment was conceived by Thomas Parnell, a professor of physics at the university, as a class demonstration.

He heated a sample of pitch and poured it into a glass funnel with a sealed stem. Three years later he cut the glass stem and began waiting for the pitch to drip out.

As well as shedding light on the properties of everyday materials like pitch, the experiment also contributes to a deeper understanding of the passage of time and has caught the imagination of amateur scientists and philosophers, says Mainstone.

He says and an “astounding number” like to watch the live feed and others make the pilgrimage in person.

“People say to me, it is a fluid or is solid and I say you have to put and in there because it’s manifesting two aspects of nature.”