Law of Gravitation and New ‘Fifth Force’ Theory

“You reported in an editorial (Jan. 15), “The Wonder of It All,” about a proposal to explain some small irregularities in an old (1909) experiment (by Roland von Eotvos) as being due to a new “fifth force.” You correctly said I didn’t believe it--but brevity didn’t give you a chance to tell why. Lest your readers get to think that science is decided simply by opinion of authorities, let me expand here.

If the effects seen in the old Eotvos experiment were due to the “fifth force” proposed by Prof. Ephraim Fischbach of Purdue University and his colleagues, with a range of 600 feet it would have to be so strong that it would have had effects in other experiments already done. For example, measurements of gravity force in deep mines agree with expectations to about 1% (whether this remaining deviation indicates a need for a modification of Newton’s law of gravitation is a tantalizing question). But the “fifth force” proposed in the new paper would mean we should have found a deviation of at least 15%. This calculation is made in their paper by the authors themselves (a more careful analysis gives 30%).

Although the authors are aware of this (as confirmed by a telephone conservation) they call this “surprisingly good agreement,” while it, in fact, shows they cannot be right.

Such new ideas are always fascinating, because physicists wish to find out how Nature works. Any experiment that deviates from expectations according to known laws commands immediate attention because we may find something new.

But is is unfortunate that a paper containing within itself its own disproof should have gotten so much publicity. Probably it is a result of the author’s “over-enthusiasm.”

RICHARD P. FEYNMAN

Professor of Physics

Caltech