How does a lunar eclipse occur when Earth casts its shadow on the Moon?

A lunar eclipse occurs when the Moon moves into the shadow cast by Earth. This phenomenon happens only during a full moon when the Sun, Earth, and Moon align.12

The process involves two primary shadow regions:
* Penumbra: The outer, partial shadow where the Moon’s illumination dims only slightly.13
* Umbra: The darkest, central part of the shadow. When the Moon passes through the umbra, it experiences a total or partial eclipse.312

During a total eclipse, the Moon does not turn completely black. Instead, sunlight is refracted by Earth’s atmosphere into the shadow cone. Because the atmosphere scatters shorter wavelengths, the redder light reaches the Moon, often giving it a coppery or reddish-brown appearance. The exact brightness and color depend on atmospheric conditions, such as the presence of dust or particles.124