At 9:29 AM 3/20/5, Grimer wrote: >At 06:06 am 20-03-05 -0900, Horace wrote: > >> Actually it would be turning in sidereal time, maintaining fixed >> relationship with the stars. > > >Quite so. But why let an inconvenient mismatch get in the way of a >good story. 8^) > > >> A gyroscope very well gimballed in all axes and oriented in the equatorial >> plane should work (though not as a pendulum). A nifty thing about that in >> the old days is it could have replaced an accurate clock as the means of >> determining longitude. A good gyro, combined with an accurate lunar >> ephemieris... > > >A case of two eyes being better than one, eh. <G>
Yes, it's handy to be able to have even one bad eye open when the other is obscured. > > >> ...to be used for periodic gyro calibration, could have been used >> to achieve fairly accurate navigation and mapping. The technological >> problems then "merely" consist of achieving frictionless bearings and a >> nearly perfect vacuum. > > >That would have really taxed Harrison's workmanship; Yes indeed! I have a copy of *Longitude*, by Dava Sobel, the saga of John Harrison and his clock, and it is a real comfort at times when the inevitable depression comes from continually attempting and failing at diffcult or impossible things. >and talking of lunar >thingees, it is interesting that the moon is now acting as a slow >pendulum with respect to the earth. I am not aware of this pendulum phenomenon. The moon does have librations, but these are not really pendulum effects, but rather periodic perspective changes that occur due to ordinary orbital motions. Do you have specifics or a reference? >Is this because its centre of mass >and its centre of gravity with respect to the earth are different and >so the compound pendulum has an effective length less than infinity - >or is it because the moon is lopsided in some way or other. There may be alternative explanations, but it would be best to know exactly what and how big the "pendulum" effects are to which you refer. Very minor perterbations in the moon's orbit could occur due to magma shifts in the earth, which are probably now occuring because a pole shift is in progress. If multiple fast spinning and precessing black holes were in the vicinity, then the gravimagnetic theory predicts the gravimagnetic field of such could cause oscillating changes in the precession of the moon's (and earth's) axis, but that is an unlikely thing to occur, and it would show up in the measurments of the earth's polar orientation, which are made regularly. Also, the effects of the gravitational field itself would probably be observed long before the gravimagnetic effects, though I suppose we might be getting slow gravimagnetic waves from some great black hole event somewhere in the galaxy. Just some idle speculation. Regards, Horace Heffner
