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Index of Subjects Quoting David & Alison Webster <dwebster@glinx.com>: > I just dug out my 1st yr Physics (Weber, White & Manning, 1952) and > they consistently refer to 'speed of light' as opposed to 'velocity > of light'. Four other sources (1941, 1948, ~1965 &1962) have velocity. * indeed, it would be ineffective to purge society, or even literature, of all who misuse speed/velocity or weight/mass. Or, to bring it closer to natural history, all who refer to nonhemipterans as "bugs." fred. =============================================== > ----- Original Message ----- From: "David & Alison Webster" > <dwebster@glinx.com> > To: <NatureNS@chebucto.ns.ca> > Sent: Friday, September 21, 2012 7:44 PM > Subject: Velocity of light > > >> Dear All, Sept 21, 2012 >> The recent discussion about transmission of electricity, reading >> of HEAT and reading some of Energy... brings to the forefront a >> question that has nagged me for decades. Perhaps someone can clarify. >> >> In the typical elementary physics text we are told that velocity >> is a vector quantity, and to quote one text "velocity... may be >> defined as the rate of change of position in a given direction". >> But "In cases where the direction of motion does not require to be >> considered , the term speed is employed to express the rate of >> travelling." >> >> Based on the above I would think that the rate of movement of >> light should be called speed, i.e. speed of light but I think it is >> always called velocity. >> For example, if light from the sun is reflected from two 45o >> mirrors then a beam of light could be directed from the earth back >> to the sun and, the velocity would then be minus 3 x 10^10 cm/sec. >> Or if variously scattered or reflected then the velocity, relative >> to the initial sun to earth direction, would always be less than 3 >> X 10^10 and after several reflections might be zero. >> >> Is there some good reason why the speed of light is termed >> velocity of light ? Or is it called velocity because the textbook >> authors forget what they said in chapter one by the time they write >> chaper eleven ? (And they all copy from each other) >> Yt, Dave Webster, Kentville > > ------------------------------------------------------------ Frederick W. Schueler & Aleta Karstad Bishops Mills Natural History Centre - http://pinicola.ca/bmnhc.htm Mudpuppy Night in Oxford Mills - http://pinicola.ca/mudpup1.htm Daily Paintings - http://karstaddailypaintings.blogspot.com/ South Nation Basin Art & Science Book http://pinicola.ca/books/SNR_book.htm RR#2 Bishops Mills, Ontario, Canada K0G 1T0 presently in Cochrane - 49.06274N 81.02415W - on the great Ontario Claybelt (613)299-3107 <bckcdb at istar.ca> http://pinicola.ca/ ------------------------------------------------------------
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