Somewhere just south of the Arctic Circle in Greenland, where pale-white ice is the only landscape for thousands of miles, a small team of scientists will scud out on snowmobiles this summer and lower a long, steel tube down a narrow hole in the ice.
The operation could be likened to the delicate threading of a giant needle: The hole in the ice is just four inches wide but nearly a mile deep. The steel tube will contain an instrument that is extraordinarily fragile and valued at a quarter of a million dollars.
The unorthodox experiment is designed to yield new insights into one of the most provocative questions in contemporary physics: Is there a fifth force in the universe?
So far, only four are known. They are gravity, electromagnetism and the strong and weak forces that govern the structure of the atom. Traditionally, the four forces have been thought to explain all things in nature.
But the classical tenets were questioned 18 months ago by Purdue University physicist Ephraim Fischbach. In a January, 1986, report, Fischbach claimed to have found evidence of a fifth force called hypercharge.
Fischbach said the force acts more strongly on chemical elements, such as iron and lead, than it does on heavier or lighter elements. He also concluded that this force influences objects over relatively short distances, for example, less than 600 feet.
Such a force, in effect, would act in such a way that a lead weight would fall at a slightly slower speed than a feather.
The aim of the Greenland experiment--and many others taking place around the world--is designed in part to explore the possible existence of a fifth force.
It seeks to measure the force of gravity as a specially designed gravity meter moves up and down the hole. The researchers will then compare those measurements to what would be predicted through Sir Isaac Newton's law of gravitation.
Any differences may suggest that the so-called gravitational constant changes with distance, contrary to traditional thought. If it does, some believe that it may point to the existence of the new force, working against gravity.
Some physicists believe that discovery of a fifth force could help tie together the other four forces in a single, long-awaited "unified theory." Difficulties fitting gravity into such a theory had prompted speculation in the past that there might be such a missing link.
Some contend that it could also affect astrophysics and cosmology because the fifth force could have a role in the birth of stars and planets.
"The implications are astounding," said Mark Ander, a geophysicist from Los Alamos National Laboratory in New Mexico who is heading the Greenland expedition. "This has implications for the age of the universe and the particular model (we use) of the Big Bang (theory)."
Already, about 35 research groups worldwide are exploring the fifth force theory in what to the layman might look like a bizarre series of stunts involving television transmission towers, mine shafts, cliffs, the ocean and 400 tons of lead submarine ballast.
- In a small town off U.S. 70, just south of Raleigh, N.C., two U.S. Air Force physicists intend to haul a gravity meter up the side of a 1,800-foot-tall TV transmission tower. From there, they plan to measure gravity at intervals of 150 feet.
- In the Pacific Ocean 250 miles north of Hawaii, a group from Scripps Institution of Oceanography in La Jolla plans to conduct similar tests next year. The group will make their measurements through water at intervals down to four to six kilometers.
- Other scientists are working with tools called torsion balances in a Nevada mine shaft, in a tunnel in the Cascade Mountains in northern Washington and at the Grand Canyon. One is using an instrument capable of measuring a force a billion times smaller than the weight of a postage stamp.
Fischbach, while searching for the evidence of a fifth force, had come across a classic paper published in 1922 by Hungarian physicist Roland von Eotvos.
Eotvos was trying to prove that gravity has the same effect on all materials. He also had used a torsion balance because he had no way of measuring the acceleration of falling objects. Testing various materials--including metals, asbestos and talc--Eotvos concluded that gravity exerted the same pull on all of them, within the limits of experimental error.
But when Fischbach looked at Eotvos' original data, he concluded that Eotvos' "experimental error" was in fact a manifestation of the fifth force.
But many scientists now attribute the discrepancies not to a fifth force but to factors such as air currents disturbing the torsion balance in Eotvos' laboratory. The doubters also believe that the gravity of nearby buildings had perhaps altered the results by causing the torsion balance to twist.