Wednesday, 24 December 2008

Lunar cycle - a bit like the penny farthing but bigger

I realised I've mentioned gibbouses and crescents and waxing and waning without telling you what they mean. So let me run through the moons, their shapes, their sizes and their names. Let me present the lunar cycle.

Imagine a round drain cover surrounded by marbles...no, imagine a lion's mane decorated in baubles at each quartered segment...no, imagine a-- imagine a clock-face with-- without a-- in a--

Ah, forget it, and please look at this:



1. New moon - when the moon sits between the sun and Earth; she's lit from behind and thus is invisible to the human eye

2. Waxing crescent - a crescent moon (ie less than half full) on the wax (ie growing)
3. First quarter - she's a quarter through her cycle but looks half full (ie half lit by the sun) to Earthlings
4. Waxing gibbous - do do do the funky gibbous; a gibbous moon is more than half full and getting bigger

5. FULL MOON - my moon

6. Waning gibbous - a gibbous (ie still more than half) but on the wane
7. Third quarter - she's three quarters in - so that's half full - but ever-decreasing now
8. Waning crescent - a fingernail of her former self and preparing for the next new-moon

Of course there's far more to it than this but here's a start. Next time we'll battle angles, acuteness, axes (more than one axis rather than more than one axe), Earth shine, moonshine and more.

But we've got plenty of time for that lunar fun.

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