An enormous hole is being dug in the bottom of a salt mine in Ohio to conduct a federally funded experiment that could prove that the entire universe will disappear someday in an enormous fireball.

The experiment, backed by $2 million from the Department of Energy, involves excavating a chamber 70 feet high 2,000 feet down in a salt mine on the shores of Lake Erie, filling the hole with 10,000 tons of the purest water and surrounding the water with 2,000 photoelectric cells. If there is a sudden flash of light at any time in the next year that the photoelectric cells pick up, it means the world will come to an end someday.

"A flash of light will mean a proton has decayed and has released energy in its decay," Dr. Frederick Reines of the University of California at Irvine yesterday told the annual meeting of the American Physical Society. "It will mean that the notion that protons live forever is not the correct one."

An unstable proton means that all matter as we know it in the universe ultimately will decay. Decay of the proton means that at some distant point in time the protons that make up the heart of the universe will suddenly lose a tiny fraction of their mass and become electrons, an act that will release enough energy to burn up the universe.

Reines (pronounced rines) is conducting the experiment at the bottom of the Ohio salt mine because the 1979 winners of the Nobel Prize predicted that the proton had a finite lifetime, not an infinite one as physicists have believed for the last 100 years.

The Nobel Prize winners (Sheldon Glashow and Steven Weinberg of Harvard University) won their prize in part for a theory that suggests that the electromagnetic and the weak and stron nuclear forces of nature are all manifestations of the same force. This means the proton and electron are linked, which tells physicists that the heavier proton can emit a flash of light and decay to an electron.

"This says the universe as we see it is only in a transitory phase," said Dr. Rolf Sinclair of the National Science Foundation. "This means that all matter could ultimately decay to electrons."

The experiment conceived by Reines involves filling a hole at the bottom of a salt mine with purified water, which is composed mostly of protons that make up the hydrogen atom in the water molecule of hydrogen and oxygen.

The salt mine was chosen because the rock and salt will block out any cosmic rays from outer space that could strike the Earth and confuse the photoelectric cells surrounding the water into thinking they had seen the decay of a proton.

Reines said the hole will be filled with 10,000 tons of water to supply what in effect will be almost a limitless number of protons for the experiment. wHe said there are 10 to the 29th power protons (10 with 29 zeros) in each ton of pure water.

In the theory that won them the Nobel Prize, Glashow and Weinberg said that the "average" proton would last between 10 to the 30th (10 and 30 zeros added) and 10 to the 34th (10 with 34 zeros added) years. Reines said if their theory is right, one proton in the water bath at the bottom of the salt mine would decay and emit a flash of light in each year the water bath sits there.

Reines said his experiment will be ready in a year. If he detects a flash of light at any time in the year after that, no one should panic. That would still mean the world has a long way to go. The universe is estimated to be 20 billion years old, which is 20 plus nine zeros. That still leaves between 21 and 24 zeros for time to go on.