Tukuk-OSEvery phase you see is one half of the Moon being lit by the Sun and your view slicing that lit half at a different angle. A crescent is not “Earth’s shadow on the Moon” — Earth’s shadow on the Moon is an eclipse, and it can only happen at full Moon. The slow-changing “Earthshine” on the dark part of a crescent is sunlight bounced off our own planet onto the Moon and back — the classic test of whether the telescope age had begun to see clearly.
The Moon recedes from Earth by about 3.8 centimetres a year — measured by bouncing lasers off mirrors left by the Apollo missions. That small change lengthens our day by roughly a millisecond or two per century. Tides are the friction behind it: the Moon’s gravity pulls harder on the near side of Earth than the far side, and the oceans stretch into two bulges — one facing the Moon, one opposite. As Earth turns under those bulges, most coasts get two high tides about 12 hours and 25 minutes apart, not 12.
When Sun and Moon align — full or new Moon — the bulges stack: spring tides, the biggest. At quarter phases they partially cancel: neap tides, the smallest. “Spring” here has nothing to do with the season; it means the sea springing up.