Are there better estimates of the ET second nowadays (relative to the SI second)? It would be interesting to know what the cesium frequency "should have been" if much better estimates of the ephemeris-time second were available at the time. One would think that with all the solar-system data JPL and others have had at their disposal since the 1970s, a very good ET-second number could be cooked up; better than 1950s Moon cameras at any rate.
For that matter, what are the inherent long-term limits on ET as a timescale? I gather the observation noise is very high on short timescales, but what is the situation for, say, tau>1year? It's not as if the Earth's orbit is randomly perturbed very much, I'm guessing, and any deterministic perturbations or relativistic corrections would be compensated for; it's the noiselike processes that would be interesting. (Solar wind?) Cheers, Peter _______________________________________________ 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.
