Earth
Your own sky, worked out for your own town. Sunrise and sunset, tonight's moon and how full it is, and when the tide turns — for more than a thousand cities, on whatever date you pick. Every figure is computed from the real motions rather than looked up in a table.
What is the Tropic of Cancer? It is the circle at 23.4° north. The Sun is straight overhead there once a year, on the June solstice, and never north of it. That number is Earth’s tilt, not a climate zone someone drew.
Why do we have seasons? Not because Earth gets closer to the Sun. When it is summer in the United States it is winter in Australia, on the same planet, at the same distance. Seasons happen because the axis is tilted 23.4° and keeps pointing the same way all year.
Why does the Moon change shape? The Moon makes no light of its own. One half is always lit by the Sun. Phases are your changing view of that lit half as the Moon goes around Earth — about 29.5 days from full moon to full moon.
What causes tides? The Moon’s gravity pulls harder on the water nearer to it than on the Earth’s centre, and harder on the centre than on the far-side water. The ocean stretches into two bulges. Earth then turns under those bulges, so most coasts see two high tides a day.
Sunrise & Sunset
The cities below run north to south. The farther from the equator, the more day length swings with the season — long summer days, short winter ones.
Where the sun and moon are from your town, at any moment.
Start with a question — why don't the planets fall into the sun, and six more. Or jump across: Home · Time · Space · Classroom.