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> we need to have an agreed starting point, and by historical accident we've all adopted an estimated (likely slightly incorrect) birth year for the founder of

> we need to have an agreed starting point, and by historical accident we've all adopted an estimated (likely slightly incorrect) birth year for the founder of one of the world's major religions. It is hard to pick a culturally-neutral starting point There are some astronomical cycles that could be used as a neutral reference. For example, due to the precession of the Earth's axis, the star which is the North Star changes over a 41000 year period. So we could pick the time when the axis was pointing most closely at the star Vega, 11000 years ago, as the epoch.

skissane 5y ago
> For example, due to the precession of the Earth's axis, the star which is the North Star changes over a 41000 year period. That's a great idea you have there. I like it. I am going to quibble with some of the finer details though: 41,000? I thought the best estimate for the Platonic year, the time for the precession of the equinoxes to complete one revoution, was 25,772 years? The Gregorian calendar has a 400 cycle. If we are sticking with the Gregorian calendar, any new epoch needs to be aligned with the 400 year Gregorian cycle, or else leap year calculations will suddenly get more complicated. So that suggests using something like -23600 CE (23601 BCE) as the starting point. That's 64 Gregorian cycles before 2000 CE, which is the closest possible whole number of Gregorian cycles to 1 Platonic year prior to 2000 CE (a Platonic year is 64.43 Gregorian cycles). The Gregorian cycle is of course based on the AD/CE chronology, modulo 400, so it is still an indirect link to Christianity. But I think it is as practically close to culturally neutral as we could get, without also changing the calendar. (Which isn't really Christian in origin anyway – it was developed in pagan ancient Rome, and the 7 day week is pre-Christian in origin as well, through Judaism, and possibly some ancient Babylonian influence as well – the only Christian to touch it was Pope Gregory XIII, and his aim was only to make its leap year rule more astronomically accurate, albeit he ended up linking it more tightly to the AD/CE year numbering in the process.)
- wcoenen 5y ago
  > 41,000? I thought the best estimate for the Platonic year, the time for the precession of the equinoxes to complete one revoution, was 25,772 years? Yes, I mixed up the precession cycle with the obliquity cycle.

skissane 5y ago

> For example, due to the precession of the Earth's axis, the star which is the North Star changes over a 41000 year period. That's a great idea you have there. I like it. I am going to quibble with some of the finer details though: 41,000? I thought the best estimate for the Platonic year, the time for the precession of the equinoxes to complete one revoution, was 25,772 years? The Gregorian calendar has a 400 cycle. If we are sticking with the Gregorian calendar, any new epoch needs to be aligned with the 400 year Gregorian cycle, or else leap year calculations will suddenly get more complicated. So that suggests using something like -23600 CE (23601 BCE) as the starting point. That's 64 Gregorian cycles before 2000 CE, which is the closest possible whole number of Gregorian cycles to 1 Platonic year prior to 2000 CE (a Platonic year is 64.43 Gregorian cycles). The Gregorian cycle is of course based on the AD/CE chronology, modulo 400, so it is still an indirect link to Christianity. But I think it is as practically close to culturally neutral as we could get, without also changing the calendar. (Which isn't really Christian in origin anyway – it was developed in pagan ancient Rome, and the 7 day week is pre-Christian in origin as well, through Judaism, and possibly some ancient Babylonian influence as well – the only Christian to touch it was Pope Gregory XIII, and his aim was only to make its leap year rule more astronomically accurate, albeit he ended up linking it more tightly to the AD/CE year numbering in the process.)

wcoenen 5y ago
> 41,000? I thought the best estimate for the Platonic year, the time for the precession of the equinoxes to complete one revoution, was 25,772 years? Yes, I mixed up the precession cycle with the obliquity cycle.