Dead end for a fifth force.Dead end for a fifth force Precise measurements of the gravitational grav·i·ta·tion n. 1. Physics a. The natural phenomenon of attraction between physical objects with mass or energy. b. The act or process of moving under the influence of this attraction. 2. force at various heights on a 300-meter tower in Erie, Colo., furnish the best evidence yet that Newton's law of gravity accurately predicts the magnitude of the attractive force between two objects. In effect, the new findings rule out the existence of a "fifth force" of nature strong enough to make itself felt in such an experiment. If a fifth force exists at all, it would have to be much weaker than theorists had imagined. Newton's law gravity specifies that increasing the distance between two objects should reduce the gravitational force between them in a well-defined way. Several years ago, however, a number of measurements of the gravitational force at different heights on a tower and depths in a borehole bore·hole n. A hole that is drilled into the earth, as in exploratory well drilling or in building construction. hinted that the measured attractive force may be somewhat less than expected, suggesting the influence of a small, additional force acting on a scale of 10 meters to 10 kilometers (SN: 7-26/86, p.55). Those disturbing fragments of data prompted an intensive, four-year quest for evidence of a new force of nature to join the four types already known: gravity, electromagnetism electromagnetism Branch of physics that deals with the relationship between electricity and magnetism. Their merger into one concept is tied to three historical events. Hans C. , and the strong and weak nuclear interactions Weak nuclear interactions Fundamental interactions of nature that play a significant role in elementary particle and nuclear physics, and are distinguished from other such interactions by special properties such as participation of all the fundamental fermions . Data from the latest tower experiment closely mirror the Newtonian predictions, leaving little room for the existence of anything but an extremely weak fifth force. "Agreement of the measured values with the Newtonian predictions is clearly excellent and the validity of [Newton's law of gravity] under the conditions of the experiment is confirmed," report James E. Faller Dr. James E. Faller is an American Physicist who specializes in the field of Gravity. He conceived the Lunar Laser Ranging Program, that shoots laser beams at special retroreflectors placed on the Moon by Apollo program Astronauts. of the Joint Institute for Laboratory Astrophysics in Boulder, Colo., and his colleagues in the Oct. 15 PHYSICAL REVIEW LETTERS Physical Review Letters is one of the most prestigious journals in physics.[1] Since 1958, it has been published by the American Physical Society as an outgrowth of The Physical Review. . Various other experiments have produced similar null results (SNd 9/22/90, p.183). |
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