Pitch is a very tough substance, used to waterproof boats and traditional burning torches. At room temperature you can shatter it with a hammer. The black substance, so dark that it is the source of the term ‘pitch-black’, seemed to be a solid at room temperature; Professor Thomas Parnell disagreed, and set up one of the longest science experiments ever, to prove his point. This became known a the ‘Pitch Drop Experiment.’
The preparation itself took years, in 1927 he prepared a sample in a sealed funnel, then heated it. Three years later it had cooled and settled down. In 1930 the bottom of the funnel was cut, giving the pitch free sway to plummet downwards under the effects of gravity. So began one of the slowest drips the world has ever witnessed. Each drop takes between eight and nine years to form, but form and fall they did. Professor Thomas Parnell only ever lived past two drops of pitch before his death in 1948. The experiment continued without him.
As of 2011 eight drops of pitch have fallen, the ninth drop is currently forming. Thanks to odd circumstances though, no-one has ever actually seen the pitch drop. Few people have the patience to watch something day and night for months on end, and with the previous drop a webcam was set up, but technical difficulties scuppered those hopes. Perhaps we shall catch the next one. By the way, pitch is a fluid, a very viscous or thick liquid, but a liquid nonetheless. Compared to water, calculations show that pitch is 230 billion times more viscous than water. Calculations also show that it may outlive us all, it is listed as the longest running experiment in the Guinness Book of World Records, and there is enough tar to keep the experiment going for 100 years. Albeit rather slowly.
The experiment is to be found in Queensland University, Brisbane, Australia.