No one has commented on my graph. I would have thought that change would easily be detected.
Jim On Sunday, March 20, 2011, cook michael <[email protected]> wrote: > Le 20/03/2011 05:59, Bruce Griffiths a écrit : > > > jimlux wrote: > > > > > A 10-12m diameter dish is probably close to the minimum feasible aperture. > A 4m dish can be made to work in conjunction with a mauch larger dish > (eg 30m). > > > > The original speculation was for measuring the small change in earth rotation > rate, for which some sort of interferometric measurement of a stellar source > could be used. > > > I sincerely doubt that it will be possible to get undisputed verification of > this speed up as the magnitude is swamped by the irregular diurnal and > sub-diurnal rotation rates induced by tidal effects that are at lease a > magnitude greater and for which the error bars are of the same order or > grater than the predicted shift. > > There was a similarly predicted rotation shift predicted for the Chile quake > of 28 February 2010 (1,26us). There was IIRC no verification of that AFAIK. > Check the tidal effects at > > http://bowie.gsfc.nasa.gov/ggfc/tides/intro.html for the tidal effect > and > http://hpiers.obspm.fr/ for rotational measured speed changes > http://hpiers.obspm.fr/eop-pc/index.php?index=news for the statement of > detectability. > > > > > > > > The source has to be bright (so you can detect it with a practical antenna.. > not everyone has a 30m dish in their back yard) > The source has to be small angle (or at least something that you could > accurately determine the centroid of) > The source has to be "not moving" (which I think leaves out using something > like jupiter) > The frequency of measurement has to be somewhere that the atmosphere won't > dominate the uncertainty (leaving out optical, I think) > > > SO what's the brightest small angular radio source out there? > > > 3C273 > > RA 12:29.1 DEC 02:03.1 > > > > > As someone else has pointed out, measuring the earth surface position > relative to spacecraft orbits, e.g. GPS, would be another technique. In > fact, a high resolution measurement of the position of a geosync sat might > do.. If the earth's rotation rate changes you'd have to adjust the height of > the satellites in Clarke orbit to keep them stationary. > > Unfortunately, for earth orbiters, there's enough other perturbations that > you probably can't see it. They already have to move satellites around to > compensate for things like solar wind, air drag (for LEO), etc. > > But maybe for a spacecraft in deep space, between planets, which is on a well > understood trajectory? > > > > Bruce > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
