DULL Holofernes and Nathaniel in Love's Labour's Lost resemble slightly the three quasiadolescent senior citizens of Last of the Summer Wine. Dull is something of a know all: "Can you tell me by your wit," he asks his cronies, "what was a month old at Cain's birth, and that's not five weeks old as yet?" Nathaniel, the constable, is stumped, but Holofernes, schoolmaster that he is, has the answer for him in a flash: "The moon was a month old when Adam was no more, and raught not to five weeks when he came to fivescore." Our distant ancestors, indeed, believed that each time a crescent moon appeared, it was literally a new moon - and so we call it to this very day.
The moon shines only by reflected sunlight. When it is on the same side of the Earth as the sun it is invisible, because we are looking at its unilluminated hemisphere. The four "phases" which follows occupy 29 1/2 days, the length of time it takes the satellite to orbit the Earth and return to its original spot with reference to the sun.
The very slender crescent seen in the western sky at sunset just after the "new" phase gradually thickens with each successive evening after a week of waxing, or growing, it has assumed a semi circular appearance and lies due south when the sun sets; rather confusingly for a half moon, it is then said to have moved to "first quarter". In yet another week the moon is on the opposite side of the earth from the sun, and we see the fully illuminated hemisphere as a bright disc dominating the sky; the full moon rises at around sunset in the eastern region of the sky.
During the succeeding 14 days or so, shade encroaches from the side of the moon where the crescent first appeared, and as the moon begins to wane, the lighted area gradually diminishes. At the end of the fourth week the moon ends up just west of the sun and appears in the sky just before dawn as a crescent curving in the opposite direction to that which it had formed at first. And finally, it moves past the sun, to show up as a crescent just after sunset, and whole rigmarole begins again.
The boundary between the dark and bright lunar hemispheres that appears to travel across the moon, and then return, in the four weeks or so of a lunation is the terminator. Lunar mountains and craters can be seen most clearly near the terminator, because at this position the sun is either rising or setting on that part of the moon, and shadows, therefore, are at their longest.