On Tue, 29 May 2007 22:27:42 +1200, Dr Bruce Griffiths wrote: >Bill >Bill Beam wrote: >> On Tue, 29 May 2007 16:31:40 +1200, Dr Bruce Griffiths wrote: >> >> >>> Ulrich, Didier >>> >>> Talking about forces, gravitational fields etc makes no physical sense >>> if the observer's reference frame isn't specified. >>> For an observer in/on a satellite orbiting about the Earth with their >>> reference frame fixed with respect to the satellite. >>> There is no gravitational field, whatever methods chosen to measure a >>> gravitational field (within the satellite) will always produce a null >>> result. >>> >> >> Not true. >> Very simple experiments will show occupants of the satellite that they >> are in a non-inertial reference frame. (Release a few test masses >> about the cabin and you will observe that they move/accelerate for no >> apparent reason, unless the satellite is in free fall which you'll know soon >> enough,) The experimenter must conclude that the satellite is undergoing >> acceleration due to the influence of an attractive (gravitational) field. >> >> Just because NASA calls it 'microgravity' doesn't make it true. It means >> NASA is wrong. Weightlessness is not the same as zero-g. >> >> >Only, if you insist on sticking to Newtonian physics with all its >attendant problems.
This discussion began as a classical problem. The relativistic effects are many orders of magnitude smaller than Newtonian (v/c=2.6e-5). For example: A test mass released on the Earth side of the satellite cabin will advance in its own orbit a few mm/sec faster than one released on the far side due to purely classical differences in orbits. Easily observable without even using a timepiece. Once your feet leave the ground, not even Newtonian mechanics is intuitive. Who would have thought that 'putting on the brakes' to leave orbit would cause a satellite to speed up.... > >>> Pendulum clocks fail to work, given an initial push they will just >>> rotate around the pivot, provided the pivot suitably constrains the >>> motion of the pendulum (ie a shaft running in a set of ball or roller >>> bearings or similar and not a knife edge pivot). Run the numbers - depends on how hard the push. Consider sheeparding of material in Saturn rings by small moons. >>> >>> If, however the satellite acts as a rigid body and has a large enough >>> diameter then it would be possible for an observer on the satellite to >>> detect a gravitational field gradient. >>> >> >> Therefore, you must conclude that somewhere inside the satellite g is not >> zero. >> >> >A finite gradient doesn't imply that the field itself is nonzero, except >of course towards the extremeities of the satellite. Of course it does. If g=0 everywhere in the neighborhood of a point then the gradient is zero. Else, what is the meaning of gradient? Grad not zero implies field not uniform implies not(field zero everywhere). >> >> Regards, >> Bill Beam (PhD, physics 1966, past tenured Associate Professor of Physics) >> >> >> Bill Beam >> NL7F >> >> >> >Bruce > > >_______________________________________________ >time-nuts mailing list >time-nuts@febo.com >https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts Bill Beam NL7F -- No virus found in this outgoing message. Checked by AVG. Version: 7.5.467 / Virus Database: 269.8.0/818 - Release Date: 5/25/2007 12:32 PM _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts