On 2011-09-22, David Woolley <[email protected]> wrote: > unruh wrote: >> On 2011-09-21, David Woolley <[email protected]> wrote: >>> unruh wrote: >>>> On 2011-09-21, David Woolley <[email protected]> wrote: >>>>> Richard B. Gilbert wrote: >>>>> >>>>>> It's unfortunate that the earth DOES NOT rotate exactly 360 degrees in >>>>>> exactly 24.000000000000 hours. This bit of poor design causes all sorts >>>>> It's nothing like it. It out by approximately 1 degree a day! >>>> well, not if you define the rotation with respect to the "mean sun" >>>> rather than the stars. Then it is only out by a few PPB. >>>> >>> It makes a big difference for GPS, though. I believe their orbital >>> period is half a sidereal day, not 12 hours or even 43200 TAI seconds. >> >> The orbit is far faster than that. You mean the period of the orbit (not >> in the orbit) as seen from earth. >> > > I don't understand. > > The orbit plane is fixed relative to the fixed stars, so, for the orbit > to cover the same ground each time, it has to have a period that exactly > divides the sidereal day. The period is between successive maximum > North points.
It is the sattelite you see, not the orbital plane. The sattelite goes around its orbit in a much shorter time period than one siderial day. _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
