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- From: brody@eos.arc.nasa.gov (Adam R. Brody )
- Newsgroups: sci.space
- Subject: Re: Calendar and Zodiac
- Message-ID: <1992Jul28.232811.3646@eos.arc.nasa.gov>
- Date: 28 Jul 92 23:28:11 GMT
- References: <9207281206.AA27240@cmr.ncsl.nist.gov> <1992Jul28.201048.21009@pony.Ingres.COM>
- Distribution: usa
- Organization: NASA Ames Research Center
- Lines: 22
-
- gmcquary@Ingres.COM (George F. McQuary) writes:
-
- >The main question is will the seasons occur in other months of the year than
- >currently. The answer is no. The Gregorian year is defined as starting
- >exactly ten days after the winter solstice. The current system of leap days is
- >a forecast of how to maintain the constant of Dec 21, but would change if
- >necessary. (If a large enough metor hit the earth to change the current
- >forecasts, however, there would probably be larger problems to deal with than
- >resetting the calendar...) As long as the calendar is kept in sync with the
- >sun, the rhythm of the seasons will continue to occur at the same time in the
- >calendar.
-
- >George F. McQuary
- >"He is mad, bad and dangerous to know." -Lady Caroline Lamb
-
- The point is that while the period of revolution around the sun (year) is
- roughly constant, the seasons shift backwards roughly one month every
- 2000 years due to precession. You can think of it as the Earth's axis
- getting tangent to its orbit (equinox) before a complete revolution (year).
- Over 2000 years, the equinox will be at Feb 21 rather than March 21.
- Accepting the fact that Pope Gregory corrected for the past 2000 years,
- how are we currently accounting for precession in the calendar?
-