Thursday, June 25, 2009

Chasing the New Moon

For about six months now, I've been trying to catch the first day that you can see the crescent moon in the first quarter of its cycle. I never seem able to get closer than the second day. Have caught the second day before the New Moon, maybe even the last day, but not right afterward.

Monday was the New Moon and I tried to catch it yesterday. But despite a half-clear sky, what clouds there were seemed to congregate over the setting sun (I suspect there's an actual metereological reason for this involving the concentration of solar heat in the west at that time of day, but haven't worked out what just yet). So, I didn't see it until tonight, when it was a bit more than a sliver.

Due to the usage of the lunar cycles in many religious calendars, astronomical observation is actually a critical matter of good religious observance. Yes, for all of the denigration of religion in some quarters as antiscience, religious calendars are in fact heavily based on science, especially astronomy.

For example, there was considerable dispute over when to start Ramadan among Muslims until easy and quick reporting from Mecca became available. It doesn't seem like much to non-Muslims, but for Muslims, Ramadan is a holy month. If you start and end it too early, you're doing the wrong thing. If you don't start it once the moon reappears in the sky, you're doing the wrong thing. Think of it as if Christmas were based on the lunar calendar: you would want to know the exact date, but the date would be partially dependent on good astronomical observation--and weather.

Passover and Easter are also regulated by a lunar calendar--or, they were originally. Because they are so strongly connected to the spring (i.e. a solar/seasonal calendar), the lunar part of their calculation is restricted to a period in spring of about two months. This is why both float around the spring months of the calendar each year. And because the Christian aspect of Easter was originally a Passover festival, the two festivals not-infrequently fall on the same date.

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