Asri-unix.541 net.space utcsrgv!utzoo!decvax!ucbvax!menlo70!sri-unix!ES@MIT-MC Sat Jan 16 14:55:54 1982 Absolute velocity of the Earth From: Gene Salamin The tenets of special relativity, that absolute velocity is physically meaningless and that there is no lumeniferous ether, are generally considered as established because of the agreement between the predictions of the theory and experimental results. Although there is no ether with respect to which we can measure the velocity of the Earth, the vacuum of space is actually filled with black body radiation at a temperature of 3 K, and it is possible to define one's velocity with respect to this radiation. An observer is at rest when the radiation is isotropic (independent of direction). An observer in motion with respect to the black body radiation will measure a higher temperature in the direction toward which he is moving, and a lower temperature in the direction opposite, as a consequence of Doppler shift. The optical absorption length for this radiation is larger than the radius of the known universe, so the reference frame defined by the radiation is of a cosmological scale (although not necessarily of the entire universe). Using balloon carried microwave sensors, the "absolute" velocity of the Earth has been measured. It is something like 300 km/sec. ----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen of http://communication.ucsd.edu/A-News/ This Usenet Oldnews Archive article may be copied and distributed freely, provided: 1. There is no money collected for the text(s) of the articles. 2. The following notice remains appended to each copy: The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.