Timeline of the pitch drop experiment. The experiment was not originally carried out under any special controlled atmospheric conditions, meaning that the viscosity could vary throughout the year with fluctuations in temperature. However, sometime after the seventh drop fell in 1988, air conditioning was added to the location where the experiment resided. The temperature stability has lengthened the interval between each drop. The pitch drop experiment is recorded in the Guinness Book of Records as the world’s longest continuously running laboratory experiment, but it isn’t the only pitch drop experiment in the world. A pitch drop experiment was recently discovered at Aberystwyth University in Wales, that actually predates the famous Queensland experiment by 13 years. But the pitch used is stiffer and has never yielded a single drop.