Researchers Question Own Evidence of 5th, 6th Forces in Nature
SAN FRANCISCO (AP) _ Experiments suggesting the universe is ruled by more than four fundamental forces of nature may be fatally flawed, say researchers who now question their own evidence for fifth and sixth forces that slightly counteract and boost gravity.
The scientists backtracked on statements they made last July when they reported strong evidence suggesting Sir Isaac Newton’s 301-year-old law of gravity was wrong. Now they say the evidence is inconclusive.
That’s because their measurements of gravity inside a drill hole in Greenland’s ice sheet could have been flawed by variations in the density of rock beneath the ice, said the researchers from Los Alamos National Laboratory in New Mexico, Scripps Institution of Oceanography in La Jolla, Calif., and AT&T Bell Laboratories in New Jersey.
A new analysis of the Greenland study shows ″our results do not need new forces of nature,″ and can be explained by the existing law of gravity, Robert Parker, a team member from Scripps, said Wednesday during the American Geophysical Union’s fall meeting.
One critic took a stronger stance.
″There are only four forces in nature. Read my lips. No new forces,″ said Los Alamos physicist Richard Hughes.
Scientists believed for decades that there were only four fundamental forces that govern the behavior of all matter in the universe. They are gravity; electromagnetism, which creates light, electricity, radio waves and microwaves; the strong force, which holds the center of atoms together; and the weak force, which lets some atoms decay radioactively.
But in 1986, an analysis by Purdue University physicist Ephraim Fishbach suggested the existence of a very weak ″fifth force″ that slightly counteracts gravity over distances of roughly 10 to 1,000 yards. The theory gained support from gravity measurements made at varying depths inside a mine shaft by Frank Stacey of the University of Queensland, Australia.
Subsequent gravity measurements made on a North Carolina television tower and in the Greenland ice hole also suggested there was a ″sixth force″ that was different than gravity but gave a 1.5 percent to 4 percent boost to gravity’s attraction between objects that were 1,600 to 5,500 feet apart.
The mine, tower and ice studies all found slight deviations from Newton’s law, which says the gravitational attraction between two objects decreases with the square of the distance between them. For example, when two objects that were one foot apart are moved two feet apart, the gravity they exert on each other should become only one-fourth as strong.
The three studies’ failure to consider variations in rock densities means that ″as yet there’s no convincing evidence″ for a fifth or sixth force of nature, Parker said.
Oceanographer Alan Chave, of AT&T Bell Labs, said planned gravity measurements at varying levels within the ocean should avoid that problem and settle the debate over whether the new forces are real.
If the fifth and sixth forces exist, ″the masses of the planets and stars, as well as the universe’s mass and age, would have to be recalculated,″ the Geophysical Union said in a news release.
Such forces also would change scientists’ understanding of ″the evolution of the universe in its earliest stages″ after it formed in the gargantuan explosion called the ″big bang,″ said Los Alamos physicist Mike Nieto.
Physicists believe that before the big bang, the four known forces existed as a single, ″unified″ force, but that in the explosion, they instantaneously diverged into separate forces and matter came into being.
The ultimate goal of modern physics is to find an elegant ″theory of everything″ that explains all the forces and all the matter that make up the universe, and how they evolved from the unified force.
The discovery of distinct fifth and sixth forces could contribute to finding such a theory by helping physicists explain how gravity is a manifestation of the original unified force.