Earth's Shadow & Belt of Venus

The Earth's shadow, in the context of atmospheric optics, refers to the shadow cast by the Earth onto its atmosphere, most visibly seen during twilight (dawn or dusk). When the sun is near or below the horizon, its light passes through the atmosphere, and the Earth's shadow projects onto this atmospheric layer, creating observable phenomena.

Best seen shortly after sunset or before sunrise in clear skies.
Look toward the eastern horizon at dusk or the western horizon at dawn.
The shadow is more distinct when the horizon is flat (e.g., over an ocean or plain) and when the atmosphere is clear.

The Belt of Venus, also known as the anti-twilight arch, is an atmospheric optical phenomenon visible during twilight, just after sunset or before sunrise. It appears as a pinkish or reddish glow above the horizon opposite the sun, often accompanied by a darker bluish-gray band below it, which is the Earth's shadow.

Key Details:

Appearance:

A pink to reddish arc or band in the sky, typically 10–20° above the horizon. Below it lies the Earth's shadow, a darker blue-gray region where direct sunlight is blocked.

The pinkish hue contrasts with the darker shadow, making it visually striking.

Cause:
The Belt of Venus forms due to backscattering of sunlight by the atmosphere. Reddish light from the setting or rising sun, which is rich in longer wavelengths (reds and oranges due to atmospheric scattering), is scattered back toward the observer from the upper atmosphere.
The upper atmosphere is still illuminated by sunlight, while the lower part is in the Earth's shadow, creating the contrast.

Observation:
Best seen in clear skies, looking east at dusk or west at dawn.
Most prominent when the sun is 2–6° below the horizon.
Visible over flat horizons (e.g., oceans or plains) but can be seen in varied landscapes with clear conditions.

Relation to Earth's Shadow:
The Belt of Venus sits just above the Earth's shadow in the atmosphere. The shadow blocks direct sunlight, creating the darker band, while the pink glow occurs in the still-illuminated upper atmosphere.

Taken with Reolink Security Camcorder from Mid April to Mid May 2025.