TimeAndSpace.Science
Gravity, motion, time and space. A day is Earth turning. A year is it going round. Seasons are that turn being tilted. Built for classrooms and for anyone else who is curious.
Earth
Where is the Sun right now?
Half the Earth is in daylight right now — this map is live, repainted from the real motions every minute. Everything on this site works like that.
The sun is overhead at 10.2° N, 131.1° W — the yellow marker on the map (press Now to put it on this minute). This time of year the sun is moving from summer toward fall, and days in the northern half of the world are getting shorter because Earth is tilting away from the sun in Earth’s orbit.
What is the subsolar point? It is the one place on Earth where the Sun is straight overhead right now — where a flagpole casts no shadow. It is the yellow dot on the day/night map, and it is where the Sun-centre to Earth-centre line hits the surface.
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.
What is the terminator? The terminator is the line between day and night — the circle on Earth where the Sun sits on the horizon. Sunrise is where you cross it going into the light; sunset is where you cross it going out.
Earth
The Moon around the Earth
The Sun holds still on the left. Earth and the Moon sit to the right so there is more sky between them. The Moon is about a quarter the width of Earth — that size is true. Distances are not: the simulator says by how much.
27.3-day orbit. This picture is the phases. A month passes in about 24 seconds.
Open the Sun, Earth & Moon simulator →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 is a synodic month? A synodic month is the time from one full moon to the next, about 29.5 days. It is longer than the Moon’s trip around Earth relative to the stars, because Earth has moved and the Moon must catch up to the same angle with the Sun.
What is tidal locking? The Moon keeps the same face toward Earth because it turns once in the same time it goes around us. That match is tidal locking — not a dark side that never sees the Sun.
Space
The solar system, flat-on
The inner planets on their real orbits. Mercury laps everybody — that difference in speed is the whole story of orbits. Distances are compressed so they fit.
A year every 24 seconds. Positions are real. Planet dots are not — they would be smaller than a pixel.
Open the solar system simulator →Why don’t planets fall into the Sun? They are falling. They are also moving sideways. By the time a planet has fallen, the Sun is no longer where it was falling toward. Falling and missing, without end, is an orbit. There is no outward force holding them up.
How does an orbit work? At every instant a planet has a velocity — where it is already going — and gravity adds a small pull straight toward the Sun. Bend a path by the same small amount at every step and it closes. That closed path is the orbit.
The rest of the site
A hint, not a catalogue. Each tab is its own page.
Time
Clocks, and what they are counting — a world clock, a countdown to the day you are waiting for.
Earth
Your own sky: day and night, sunrise, the Moon, and why the tropics sit where they do.
Space
Where everything actually is — planets, orbits, gravity, and the questions that open the door.
Classroom
Projector mode, questions written for ten-year-olds first, and a way to send the lesson you already run.
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