Why do seasons, moon phases, eclipses and tides happen?

Almost everything you can see in the sky from one spot is a consequence of the same few facts: Earth’s axis is tilted 23.4°, the Moon orbits Earth every 27.3 days, and the Sun lights whatever faces it. This route takes the four big effects in the order that each one uses the last.

Start with the seasons, because the tilt explains why the Sun climbs and falls through the year. Phases then show what changes when the Moon, not the Earth, is the thing turning. Eclipses need both ideas at once, and tides put the Moon’s pull on a scale you can measure.