Why Does the Moon Appear Larger Near the North Pole During Different View Angles?

The phenomenon where the Moon appears larger when viewed from the North Pole or any high latitude compared to when viewed from lower latitudes is primarily due to the Horizon Effect and perspective.

Horizon Effect

When the Moon is near the horizon, it can appear larger than when it is high in the sky. This is known as the Moon illusion. The effect is psychological rather than physical, as our brains perceive the Moon as larger when it is near objects on the horizon compared to when it is overhead.

Atmospheric Effects

At higher latitudes, the atmosphere can have a more pronounced effect on the appearance of celestial objects. When the Moon is closer to the horizon, it has to pass through more atmosphere, which can slightly distort its appearance and make it look larger. This phenomenon is related to the lens effect of the atmosphere, where light from the Moon is bent and focused by the curvature of the atmosphere.

Viewing Angle

From the North Pole, the path of the Moon across the sky can be different, especially during certain times of the year. Depending on the season, the Moon's trajectory can be more horizontal, which may contribute to a perception of increased size when it’s low on the horizon. Additionally, the Moon's apparent size can be influenced by the viewing angle, which can vary depending on geographical location and time of observation.

Lens Effect of the Atmosphere

The Moon, which is in orbit roughly above the equator of the Earth, enters the Earth's atmosphere at different angles. If you think of the Earth's atmosphere as a spherical lens, then the light from the Moon passes straight down to the equator but at the poles, that light is bent and focused by the curvature of the atmosphere, contributing to its perceived size.

Optical Illusions and Perception

The question of why the Moon seems much bigger at some times than at other times does not appear to have a satisfactory answer. It does not seem to be related to the actual size of the Moon, which varies only slightly during periods of the Super Moon. The optical illusion is complex and involves a combination of factors, including horizon perspective, atmospheric refraction, and viewing angle. No definitive explanation has yet been given for why the lunar illusion occurs, but ongoing research in the field of astronomy and human perception continues to explore this fascinating topic.

Keywords: Moon Illusion, Horizon Effect, Atmospheric Effects