Riddle of the Lily Pads

There is great truth in the oft-quoted riddle of the lily pads. A pond (a lake, an ocean, all apply) starts with a single lily pad. Each pad doubles per day; the pond will be full in thirty days. When is the pond only half full? On the twenty-ninth day. After the next day, the thirtieth, further growth is so fast it will, if somehow continued, overwhelm the pond and everything in it in a matter of hours.

 The Moon is Binary in Nature

Having heard the poem, Monkey went up to him and said, "Master, you only know about the moon's beauty, and you're homesick too. You don't know what the moon's really about. It's like the carpenter's line and compasses−−it keeps the heavenly bodies in order. On the thirtieth of every month the metal element of its male soul has all gone, and the water element of its female soul fills the whole disk. That is why it goes black and has no light. That's what is called the end of the old moon. ...