Talk:Solar time
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i think this definition lacks the idea that the origin of these times is noon, ie it is 0h solar time when the mean/true sun crosses the meridian. Anyone to confirm this? If so needs editing this page and maybe the related as explanations are often done through comparisons.
- Well, for one thing, mean solar time explicitly does not follow that rule. But it could be worked into that first section, as long as it's made clear that it's only the case for apparent solar time. -- John Owens 19:50 May 13, 2003 (UTC)
- Do you have explicit references of that "exception"? Relying on some books here i have Meus say that the meridian crossing is the reference for mean time as well as true solar time. I agree that this is only a convention matter, but those details just screw half a day... It is precised though that civil time's origin is midnight.
- I think it would be much better just to say that solar time is based on the apparent position of the sun in the sky. -Smack
- Well, yes, centuries ago astronomers counted time from noon, so in registers of astronomical observations the date and time "January 1, 00:00" would mean January 1 at noon, and January 1, 12:00 astronomical would be midnight in the night from January 1 civil to January 2 civil. Currently astronomers use TU and some other timescales in all of which Greenwich noons fall near 12:00. The only exception is the "Julian day" day-count, in which a date like 24356789.0 means a noon and 24356789.5 means a midnight. "Greenwich mean time" used to be a valid timescale for astronomers in which 00:00 meant noon, but this name is no longer used by astronomers (some people use these words to mean Universal Time, but the IAU disallows this practice).
Suggestions re: Mean Sun, etc.
I was linked to this page when I searched 'mean sun', but that term is not defined on this page. I realise that the sidereal measure is used in contructing the path of the mean sun, but an explicit explanation of how this is done would, though complicayed, be nice. Also, when the rate of one metrical process is compared to another in the form 'n units of this process = m units of that process +/- x time units' (e.g., '1 apparent solar day may differ from a mean solar day...by -22 seconds to 29 seconds'), it would be clearer if the standard process for the time units (e.g., "seconds") was given explicitly (e.g., 'atomic seconds' or 'sidereal seconds').
Thanks, Hemlock