January 15, 1986
Purdue Physicists Help Rewrite A Classic
West Lafayette, Ind.--When Aaron Szafer first saw the results, he couldn't believe his eyes.
"We were absolutely stunned. We were surprised to find such direct evidence of a new force from a classical experiment that was believed to rule out such a possibility," says Szafer, a Purdue University doctoral student.
Szafer was part of the team that conducted a series of studies that has lead to evidence of a fifth force of physics. The new force, dubbed hypercharge, challenges Galileo's 400-year-old findings on the force of gravity.
Under the direction of Purdue Physics Professor Ephraim Fischbach, Szafer and his co-workers, Daniel Sudarsky and Carrick Talmadge of Purdue and S. H. Aronson of the Brookhaven National Laboratory in New York, reanalyzed results from a 1922 experiment conducted by the Hungarian scientist Roland von Eotvos. The results of their study were published in the Jan. 6 issue of "Physical Review Letters."
"Eotvos' study was considered one of the classical verifications for Galileo's theory of gravitation," says Szafer.
Galileo had predicted that, in a vacuum, gravity would work equally on all objects, causing them to fall to earth at the same rate of speed. Eotvos tested this theory, using objects of different composition and weights, and believed he found results in agreement with Galileo's theory.
"Actually, his results did not agree with Galileo's theory. And we attribute this discrepancy to a fifth force of nature," says Szafer.
Early this fall, Fischbach's group decided to re-evaluate the experiment after careful analysis of several other studies indicated that some force other than gravity could also come into play.
"I had noticed some discrepancies between the results we were obtaining and earlier results measuring the same quantities," Fischbach said in a telephone interview from the University of Washington in Seattle, where he is on sabbatical leave until August. "Later, I talked to Australian researcher Frank Stacey, who had also found some unexpected results in his experiments in mines."
Fischbach, who has studied the possibility for the existence of new forces for eight years, speculated that the same force could be causing the effects seen in both experiments. The analysis of these findings led the group to reanalyze Eotvos' work.
"At that point, we had enough evidence from our studies to theorize a little about this new force. At the same time, we realized that if such a force actually existed, it would have shown up in Eotvos' experiments," said Fischbach.
The group carefully examined the details of the original study and found that Eotvos and his co-workers had inadvertently overlooked evidence that a force other than gravity was also at work in the experiment.
"We were very surprised," said Fischbach. "Nobody would have anticipated that this ancient experiment could have shown such clear-cut evidence for this new force."
"In contrast to gravity, which is attractive, the new force is repulsive, pushing objects away from it upwards). But because the new force is much weaker than gravity, objects still fall to earth, as we know from everyday experience," says Szafer.
Another feature that distinguishes the new force from gravity is that its strength depends on the chemical composition of the object, he adds.
"For example, let us consider an experiment in which a coin and a feather are released together in a place where there is no air. If gravity were the only force acting on the objects, they would reach the floor together. The presence of the new force, however, would make the feather reach the ground before the coin does," Szafer explains.
"Also, gravity acts between objects even if they are very far apart. This new force, however, is of importance only when the objects are separated by 600 feet or less," he says.
If further experiments confirm the existence of this new force, it would be the fifth, and weakest, basic force of the universe. The others are gravity; electromagnetism; the strong force, which holds the nucleus of the atom together; and the weak force, which is responsible for some forms of radioactivity.
The new force could also play a key role in finding the long sought-after theoretical framework that would give a unified view of all the forces of nature, says Szafer. "It's like finding new pieces to a puzzle. They could help put together the complete picture."
The new force might also have technological applications, though it is hard to speculate what they might be, says Fischbach. "The new force can be manipulated and controlled, so we think we will be able to do something with it."
Though this discovery offers some exciting possibilities for physics research, it will probably not have an immediate impact on the field, says Fischbach.
"I don't think we need to rewrite the books, yet. Our understanding of this new force indicates that the laws of physics, as we know them today, still stand," he says.
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