The line between day and night, drawn where it actually is right now. Everything on the sunlit side is in daylight; everything beyond the far edge of the twilight bands is in full night.
Half of Earth is in sunlight at any moment. The dividing line — the terminator — is not a wall but a circle around the globe, and it sweeps west at about 1,670 km/h at the equator, which is simply the speed the planet turns. The map above draws it from the position of the Sun, so it bends through the seasons exactly as the real one does: near-vertical at the equinoxes, sharply tilted at the solstices, and sitting right across a pole in midsummer and midwinter.
There is exactly one place on Earth where the Sun sits at the zenith — straight up, casting no shadow at your feet. That is the subsolar point, marked in amber on the map. It races west with the terminator, and it drifts north and south across the year between the Tropic of Cancer (23.44°N) and the Tropic of Capricorn (23.44°S). That drift is what the tropics are. They are not a climate band someone drew; they are the furthest lines the overhead Sun ever reaches, and the reason the Sun is never overhead in London, New York or Tokyo.
On 18 July 2026 the Sun is overhead at about 20.9°N. The latitude shifts by well under half a degree a day, so it holds all day; the longitude, by contrast, moves 15° every hour — which is why the map computes it live rather than printing a number that would be wrong minutes after this page was built.
Night does not begin at sunset. The sky stays lit while the Sun is below the horizon but still illuminating the air above you, and that fades through three named stages. Each is simply how far the Sun has sunk:
Every one of those lines is the same shape as the terminator, just drawn a little wider around the subsolar point — which is why they nest so neatly on the globe.
The subsolar point here is computed from standard solar geometry and was checked against JPL Horizons (DE441) at 14 instants across a year, by asking that ephemeris for the Sun’s elevation at the exact coordinate this page produces. The worst disagreement was 0.01° — about 1 km on the ground. Checked 2026-07-17. The ephemeris is used to test this page, never to feed it: nothing here is fetched at runtime, so the map keeps working with no network and no key.