Astronomy / Earth

Moon phases and the terminator

Move through a lunar month. Compare the illuminated fraction seen from Earth with the Sun–Earth–Moon geometry.

Actual application image

The model and its limits

Circular orbit; sizes and distances are independently enlarged. The large Moon is an Earth-facing diagram; surface appearance uses LRO maps with exaggerated bump shading.

Equations used in the module

Equations
f = (1 - cos(2πp))/2; age = 29.53059 p days

Related experiments

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Astronomy

The Moon’s hidden edges

Increase orbital eccentricity and follow the difference between uniform rotation and nonuniform orbital motion. Surface markers reveal the rocking.

Astronomy / Earth

A year written by the Sun

Trace the Sun at the same mean solar time throughout a year. Remove tilt or eccentricity to discover the two sources of the figure eight.

Astronomy

Worlds in the habitable zone

Move a planet through the stellar radiation field. Compare absorbed and emitted energy as stellar luminosity and cloud reflectivity change.