The rotating mirror rested on a diamond pivot and was driven-typically at 200–250 rotations per second-by a pair of air turbines, one above and the other below, which acted in concert to minimize twisting of the mirror. The rotation of the mirror during the light’s travel to and from the remote reflector was divided by its angular velocity to obtain the light’s roundtrip travel time. The angle between the transmit and receive paths, which were offset vertically to avoid glare in the eyepiece, was set so that the return image of the slit could be centered on cross hairs by finely adjusting the angular velocity of the rotating mirror. The light reflected from a four-sided rotating mirror (inset), traveled to and from a remote mirror, and was then reflected to an observer’s eyepiece. In Simon Newcomb’s experiment, a heliostat reflected sunlight onto an adjustable slit in the focal plane of a lens, which produced a bright collimated beam of light. Years later, in response to an inquiry from Newcomb’s eldest daughter Anita Newcomb McGee, Einstein wrote that Newcomb’s life work was “of monumental importance to astronomy” and that he was “the last of the great masters who … calculated with painstaking care the motions in the solar system.” 9 Velocity-of-light experimentsįigure 4. Einstein was, of course, pleased by the close agreement between Newcomb’s findings and his theory of general relativity. The distortion of space-time caused by the Sun’s gravitational field changed the expected precession of Mercury’s orbit to almost exactly that found by Newcomb. The problem was settled in 1915 when Albert Einstein announced his theory of general relativity. But Newcomb continued to consider the anomalous precession of Mercury’s orbit an unsolved problem for future astronomers to deal with. A small increase in the exponent would explain the observations. ![]() He was even willing to consider the possibility that gravitational attraction did not decrease with exactly the square of the distance between bodies. Struggling to explain his findings, Newcomb suggested that there might be a disk of fine matter in the inner regions of the solar system with sufficient mass to disturb the orbit of Mercury. Using the best observations he could obtain, in 1882 Newcomb found the discrepancy in the precession to be 43 seconds per century, even larger than the 38 seconds per century found by Le Verrier. Until, that is, he revisited the issue of the anomalous precession of Mercury’s orbit, discovered by the French astronomer Urbain Le Verrier in 1855. Simon Newcomb never doubted the fundamental correctness of Newtonian physics and assumed that any apparent anomalies in the observed motions of the planets and moons in the solar system could be explained by imperfect accounting of gravitational interactions among them.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |