What phenomenon causes the moon to appear darkened during a lunar eclipse?

During a lunar eclipse, the moon appears darkened primarily due to the Earth's shadow being cast upon it. When the Earth comes directly between the sun and the moon, it blocks sunlight that would normally illuminate the moon. This results in the moon being enveloped in the Earth's shadow, leading to a noticeable darkening.

The Earth's shadow consists of three parts: the penumbra, where a partial shadow occurs; the umbra, where a total shadow exists; and the antumbra. For a total lunar eclipse, the moon passes entirely into the Earth's umbra, causing it to appear darkened.

Other options, such as sunlight blockage or atmospheric reflection, do not directly explain the mechanism behind the phenomenon of a lunar eclipse. Sunlight blockage can refer to various situations but is not specific to the interaction of the Earth, moon, and sun in this context. Cloud cover would obscure the view but not cause the moon to darken in the way described during an eclipse. Atmospheric reflection involves light scattering and is unrelated to the shadowing effect experienced during a lunar eclipse.