Stand at the coast and raise your eye height (scroll the view, or click an emoji preset, from a person up to low orbit) to watch the sea-horizon drop and curve below the dashed eye-level line — the app’s one honestly to-scale effect. Look around by dragging or with the arrow keys: there are things at every bearing, and overhead a live sky of Sun, Moon, planets, stars, and satellites on an idealised model. Hover anything for a telescope (with the planets’ phases, Saturn’s rings and Jupiter’s moons). Then switch to a free-flying cosmic view, or open the top-down God’s-eye orrery below.
Drag to look · arrow keys look around · scroll wheel changes height · hover an object for the telescope.
The horizon dip below eye level, the distance to the
horizon, and how much of a distant object the curve hides come from exact geometry (a 6371 km
sphere and your eye height) and are rendered to scale — the surface occludes the far side via the depth buffer. Everything
in the sky — Sun, Moon (and its phase), planets, stars, the satellites — moves on an idealised
model from orrery.js (circular orbits, constant rates, 23.44° tilt; observer at 40°N): the angles, phases and
elongations are right, but it is not an ephemeris. In the telescope, body and Moon sizes are exaggerated
for visibility (as are the God’s-eye planet sizes and the Moon’s orbit); a giant’s shadow is dropped onto
the globe rather than projected exactly. Object placement on one coast is stylised. Runs entirely in your browser — no
network, no data leaves the page.