Astronomical evidence concerning non-gravitational forces in the Earth-Moon system
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The most conspicuous effects of non-gravitational forces in the Earth-Moon system are the accelerations of the Earth's spin and of the Moon's mean angular velocity. Evidence indicates that the present acceleration of the Moon is between −20 and −52 s of arc per century per century and that the present average acceleration of the Earth is between −5 and −23 parts in 109 per century. Over the past 2000 yr, the average for the Moon has been about −42 s per century per century and for the Earth has been about −28 parts in 109 per century; these values are probably correct within 10%. Evidence that does not involve any assumptions about the present values shows strongly that there was a ‘square wave’ in the accelerations that lasted from about 700–1300, and that the accelerations were different by a factor of perhaps 5 during the time of this wave from what they were at neighboring times.
An effect that seems to be changing the obliquity of the ecliptic has been reported in recent literature, on the basis of data obtained within the past century. The effect amounts to about 1/4 s of arc per century if it is real. Older data are not accurate enough to give information about an effect this small.
There are no satisfactory explanations of the accelerations. Existing theories of tidal friction are quite inadequate.
KeywordsAngular Velocity Recent Literature Past Century Satisfactory Explanation Average Acceleration
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- Al-Biruni, Abu al-Raihan Muhammad bin Ahmad: 1967,The Determination of the Coordinates of Positions for the Correction of Distances between Cities, 1025. The quotations are from the translation into English by Jamil Ali, published by The American University of Beirut, Beirut, Lebanon.Google Scholar
- Aoki, S.: 1969,Astron. J. 74, 284–91.Google Scholar
- Dicke, R. H.: 1966, in B. G. Marsden and A. G. W. Cameron (eds.),The Earth-Moon System, Plenum Press, New York, pp. 98–164.Google Scholar
- Duncombe, R. L. and Clemence, G. M.: 1958,Astron. J. 63, 456–9.Google Scholar
- Explanatory Supplement to the Astronomical Ephemeris and the American Ephemeris and Nautical Almanac, Her Majesty's Stationery Office, London, 1961.Google Scholar
- Fotheringham, J. K.: 1920,Monthly Notices Roy. Astron. Soc. 81, 104–26.Google Scholar
- Holmberg, E. R. R.: 1952,Monthly Notices Roy. Astron. Soc., Geophysical Suppl. 6, 325–30.Google Scholar
- Jeffreys, Sir Harold: 1968,Geophys. J. Roy. Astron. Soc. 16, 253–7.Google Scholar
- Jeffreys, Sir Harold: 1970,The Earth, Fifth Edition, Cambridge University Press, Cambridge.Google Scholar
- Kakuta, C. and Aoki, S.: 1971, in P. Melchior and S. Yumi (eds.), ‘Rotation of the Earth’,IAU Symp. 48, 192.Google Scholar
- Kozai, Y.: 1967,Trans. Roy. Soc. A262, 135–6.Google Scholar
- Markowitz, W.: 1970, in L. Mansinha, D. E. Smylie, and A. E. Beck (eds.),Earthquake Fields and the Rotation of the Earth, D. Reidel Publ. Co., Dordrecht, Holland, pp. 69–81.Google Scholar
- Martin, C. F.: 1969, ‘A Study of the Rate of Rotation of the Earth from Occultations of Stars by the Moon, 1627–1860’, a dissertation presented to Yale University. Expected to be published in theAstronomical Papers Prepared for the Use of the American Ephemeris and Nautical Almanac.Google Scholar
- Melchior, P. and Georis, B.: 1968,Phys. Earth Planetary Interiors 1, 267–87.Google Scholar
- Miller, G. R.: 1966,J. Geophys. Res. 71, 2485–9.Google Scholar
- Munk, W. H. and MacDonald, G. J. F.: 1960,The Rotation of the Earth, Cambridge University Press, Cambridge.Google Scholar
- Needham, J.: 1959,Science and Civilisation in China, v. 3 (Mathematics and the Sciences of the Heavens and the Earth), with the collaboration of Wang Ling, Cambridge University Press, Cambridge, England, pp. 287–91.Google Scholar
- Neugebauer, P. V.: 1929,Astronomische Chronologie, W. de Gruyter and Co., Berlin.Google Scholar
- Newton, R. R.: 1968,Geophys. J. Roy. Astron. Soc. 14, 505–39.Google Scholar
- Newton, R. R.: 1970,Ancient Astronomical Observations and the Accelerations of the Earth and Moon, The Johns Hopkins Press, Baltimore.Google Scholar
- Newton, R. R.: 1972,Medieval Chronicles and the Rotation of the Earth, Johns Hopkins Press, Baltimore, in press.Google Scholar
- Plutarch,De Facie Quae in Orbe Lunae Apparet, ca. 90. There is a translation by Harold Cherniss inPlutarch's Moralia (ed. by H. Cherniss and W. C. Helmbold),v. 12, Harvard Press, Cambridge, Mass., 1957.Google Scholar
- Ptolemy, C.: ‘E Mathematike Syntaxis, ca. 152. There is an edition by J. L. Heiberg inC. Ptolemael Opera Quae Exstant Omnia, B. G. Teubner, Leipzig 1898. There is a translation into German by K. Manitius, Leipzig 1913. The chapter numbering used here is that of Heiberg and Manitius, and differs from that of some older editions and translations.Google Scholar
- Spencer Jones, H.: 1939,Monthly Notices Roy. Astron. Soc. 99, 541–58.Google Scholar
- van Flandern, T. C.: 1970,Astron. J. 75, 657–8.Google Scholar