Tuesday, November 29, 2011

Appreciating the Heavens

Since acquiring a dog...  about four years ago this week, as a matter of fact...  Norene and I have been paying more attention to what's above us.  That's because Riqui's (officially 'Suncatcher's Periquita') last walk of the day happens between 10:30pm and 11:30pm.  We have started to pay more attention to things like 'summer constellations' and 'winter constellations' and phases of the moon (because we can walk the golf course's cart paths from about half-moon through full-moon and for a few days after).

The moon rises about 50 minutes later every day.  Because the moon's cycle is about 28 days (more or less), it rises 1/28th of a day later each day.  There are 1,440 minutes in a day, and 1/28th of that is 51 minutes and 20-some-odd seconds.  Seven days' worth of that is 358+ minutes — pretty close to 6 hours.  At 'new moon', the moon rises just around dawn.  Half-moon (first quarter) is seven days later and has the moon rising around noon.  At full-moon, the moon rises near sunset — the sun and moon are on opposite sides of the Earth.  That's what makes the moon 'full'.  From full moon on, the moon rises closer to sunrise than to sunset.  Last quarter has the moon rising around midnight.

The stars are a different matter.  The stars make a complete circuit (360 degrees) over the course of a year — 365 days — close enough for government work.  The stars rise 1/360th of a day earlier each day.  That comes out to about four minutes (plus or minus).  Thirty days times four minutes is 120 minutes, two hours, 1/12 of a day, and one sign of the zodiac.

Over the course of a year, someone who looks up at the sky about the same time every night will watch the sky gradually change as the moon and the constellations creep across the firmament.

I recommend it highly.

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