3 ms·

We don’t know exactly how far away the stars are, so when we convert earth time to star local time, we are being less accurate. Better to keep times stored loca

We don’t know exactly how far away the stars are, so when we convert earth time to star local time, we are being less accurate. Better to keep times stored local to earth, and let distances get more accurate as we learn more.

raattgift 9y ago
Sure, that's one of the points I made. There isn't really any more precise timekeeping equipment available to us than atomic clocks here on (and near) Earth, so using those are expedient. In principle we could measure the spectra of the relic fields, but with current technology we can't do that for the cosmic neutrino background, and while the cosmic microwave background (CMB) is an attractive option (we have lots of instruments measuring it in excruciatingly fine detail) its utility as a quasi-universal clock is based on picking out an ideal observer who sees no non-cosmological redshift (i.e., no contributions from proper motion or local gravitation), and such an observer isn't really physical. Converting local measurements of the CMB to an ideal observer's in a way which achieves precision approaching that of our terrestrial atomic timescales depends on understanding our own local (~ Mpc scale) environment better than we do today. (Probably we will get there by using CMB observations to steer local oscillators, much as we do in atomic clocks, H2 masers, and so forth, and use those steered oscillators to predict CMB spectrum on the (well-supported) assumption that it is that of an ideal blackbody with a certain temperature). However, we'll still record actual observations at local CMB temperature (perhaps recording what the "universal" CMB temperature would be if we were a "universal" observer). We are still stuck with the problem of position of the observed object, since we cannot directly observe the CMB temperature at an event like this flare. In other words, the coordination (or if you like, localization) problem here isn't solved by switching to a different set of coordinates. Indeed, a different set of coordinates might make things worse (which was the thrust of what you replied to, and essentially what you write yourself).

raattgift 9y ago

Sure, that's one of the points I made. There isn't really any more precise timekeeping equipment available to us than atomic clocks here on (and near) Earth, so using those are expedient. In principle we could measure the spectra of the relic fields, but with current technology we can't do that for the cosmic neutrino background, and while the cosmic microwave background (CMB) is an attractive option (we have lots of instruments measuring it in excruciatingly fine detail) its utility as a quasi-universal clock is based on picking out an ideal observer who sees no non-cosmological redshift (i.e., no contributions from proper motion or local gravitation), and such an observer isn't really physical. Converting local measurements of the CMB to an ideal observer's in a way which achieves precision approaching that of our terrestrial atomic timescales depends on understanding our own local (~ Mpc scale) environment better than we do today. (Probably we will get there by using CMB observations to steer local oscillators, much as we do in atomic clocks, H2 masers, and so forth, and use those steered oscillators to predict CMB spectrum on the (well-supported) assumption that it is that of an ideal blackbody with a certain temperature). However, we'll still record actual observations at local CMB temperature (perhaps recording what the "universal" CMB temperature would be if we were a "universal" observer). We are still stuck with the problem of position of the observed object, since we cannot directly observe the CMB temperature at an event like this flare. In other words, the coordination (or if you like, localization) problem here isn't solved by switching to a different set of coordinates. Indeed, a different set of coordinates might make things worse (which was the thrust of what you replied to, and essentially what you write yourself).