Earth's shadow. Sequence of images showing the rise of the Earth's shadow, known as the 'Belt of Venus', as the Sun's light fades after sunset. In clear conditions before dawn and after dusk, Earth's horizon can be seen projected onto the sky. Below the line is dark, but the Sun's light still reaches above it and so the sky there appears lighter. At dusk this line gradually rises higher (top to bottom) as the Sun drops further below the horizon; whereas before dawn the line will drop, until the Sun appears on the opposite horizon.