Moon Phases: Light, Not Shadow
View from Above (North Pole)
Drag the Moon around Earth's orbit
As Seen from Earth
Waxing
Schematic (not to scale).
Phase
Full Moon
Angle
0deg
Illuminated
100%
Days since new
14.8d
Illumination model
$f = (1 + \cos\alpha)/2 =$ 1.000
- Observable: the lit fraction grows or shrinks as the Moon moves.
- Model: illumination depends on the Sun-Earth-Moon phase angle $\alpha$.
- Inference: phases are geometry, not Earth's shadow.
- Schematic geometry (not to scale, no orbital tilt).
- Illumination uses $f = \frac{1 + \cos\alpha}{2}$ with $\alpha$ in degrees.
- Earth's shadow appears only when toggled and only for eclipse insight.