New Data Backs Theory of Another Force in Nature

Precise measurements of gravity in a hole extending a mile below the Arctic icecap in Greenland have provided new support for the controversial proposal that there exist more than four fundamental forces of nature, researchers reported Monday.

Like another experiment reported last December, the new study suggests that as many as six fundamental forces could exist. While the existence of more than four forces would have few practical effects on everyday life, it could have ramifications for astronomy and theoretical physics.

The work was performed by an international team headed by Mark Zumberge of the Scripps Institution of Oceanography in San Diego and Mark Ander of the Los Alamos National Laboratory in New Mexico.

Until 2 1/2 years ago, it was widely believed that only four fundamental forces--gravity, electromagnetism, and the strong and weak forces that hold the atom together--were necessary to explain all things in nature.

But in January, 1986, physicist Ephraim Fischbach of Purdue University claimed to have seen evidence of a fifth force that acts in opposition to gravity over distances of less than about 600 feet. Such a force would mean that in a vacuum at certain distances, a feather would fall faster than a lead weight.

While trying to confirm the existence of this so-called fifth force, a team of U.S. Air Force researchers measuring gravity along the side of a massive television tower in North Carolina found evidence of a sixth force as well. They reported last December that this sixth force enhanced the normal effect of gravity, acted over somewhat longer distances than the fifth force, and was slightly stronger.

The new results show no evidence of the fifth force, but they do support the existence of this proposed sixth force. Ander reported at a colloquium in Los Alamos on Monday that the new force is from 1.5% to 4% as strong as gravity and that it enhances the effect of gravity over distances from 1,600 to 5,500 feet.

Their work is considered the most definitive yet and provides strong evidence that theoreticians do not yet have a firm grip on the fundamental nature of gravity.

“This field continues to grow more interesting,” said physicist Paul Boynton of the University of Washington. Boynton noted that physicists are gathering in Perth, Australia, next week for a meeting that will cover the fifth force, among other physics topics. “It looks like we will have a lot to talk about,” he said.

Implications for Missiles

The discovery of a fifth and a sixth force could have many scientific ramifications. The Air Force researchers, for example, were studying the effect because of small inaccuracies in the ability of inertially guided missiles to hit distant targets.

Confirmation of the new forces could also necessitate recalculating the masses of planets and stars, as well as the mass and estimated age of the universe, according to a spokesman for the National Science Foundation, which supported the research. And most important, it could provide clues to the development of what has long been the Holy Grail of physicists--a unified “theory of everything” (called a unified field theory) that would combine all the forces of nature into one mathematical formulation.

Two-Month Experiment

The new results are based on an experiment performed over a two-month period last summer at the U.S. Air Force’s DYE-3 radar station about 60 miles south of the Arctic Circle. In the early 1980s, a team of U.S. geophysicists drilled a four-inch-wide, mile-deep hole to obtain ice specimens containing air from the distant past.

The principal advantage of the site for studying the effects of gravity, Ander said, is that the ice and soil around the hole are uniform with only a few large boulders or other rock formations that might affect the gravitational measurements.

The researchers carefully lowered a 300-pound, quarter-million-dollar instrument down the hole and measured the pull of gravity on the instrument at various distances from the surface. They found that the measured pull of gravity was slightly larger than what they calculated it should be.

Surprised by Results

The team did not expect the results they obtained. “We were totally surprised,” Ander said in a telephone interview. “We tried like hell to make it go away, but it just wouldn’t.”

Not everyone agrees that the new results mean that a fifth or sixth force exists. Physicist Michael Nieto of Los Alamos, for example, argues instead that gravity is simply more complex than had previously been believed and that there may be a form of super-gravity that is only now being discovered.

Even if that is the case, however, the new results may still lead to the development of a unified field theory, Ander said.

Meanwhile, about 35 groups around the world are studying the existence of the fifth force. Most have yet to be heard from.