Proton decay experiment to determine the ultimate stability of matter..Mine workers passing the entrance to the Kolar proton decay experiment, 6,000 feet underground in a gold mine in India. The experiment consists of 150 tons of iron tube arranged in a cubic layout. Each tube is converted to act like a large Geiger counter, and is designed to detect the products from the decay of a proton. The half-life of the proton is estimated at 10 to the power 34 years, so the experiment has to contain as many protons as possible for the probability of an event occurring to be realistic. India. (1985)