why is the moon big tonight

The Moon looks big tonight because it is a supermoon, specifically the Harvest Supermoon of October 2025. A supermoon happens when the full Moon is at its closest point to Earth in its elliptical orbit, known as perigee, making it appear up to 14% larger and 30% brighter than usual. Additionally, when the Moon is near the horizon, a well-known optical effect called the Moon illusion makes it seem even bigger to observers on the ground. This illusion happens because the brain compares the Moon with objects on the horizon, like trees or buildings, making the Moon appear larger than when it is higher in the sky. The October 2025 full Moon is also called the Harvest Moon, which historically helped farmers work late in the season due to its bright light.