CUPOLA / EARTH SCIENCE
The line between day and night.
Watch the constantly shifting daylight boundary from orbit, and understand why solar geometry and visual brightness are different kinds of information.
A geometric boundary, not a cloud image
The solar terminator is the curve separating the illuminated and unilluminated halves of Earth. CUPOLA calculates its location from astronomical positions.
Why days differ by latitude
Earth's axial tilt changes the day-night distribution over a year. The polar regions can experience continuous daylight or darkness near solstices.
Local sunlight versus what the camera shows
A shaded location on the globe is not proof that a satellite has photographed its exact darkness. Cloud, terrain and artistic exposure affect the rendered appearance.
From calculation back to the globe
CUPOLA uses the same Sun-Earth geometry in the live 3D scene. The view changes as Earth rotates under the calculated solar direction.