The Moon looks so big today mainly because it is a "supermoon," meaning it is at or near its closest point to Earth (perigee) in its elliptical orbit, making it appear up to 14% larger and 30% brighter than usual. Additionally, the Moon illusion, an optical trick where the Moon appears larger near the horizon due to brain perception comparing it with terrestrial objects, enhances this effect. This combination, especially around the time of the full Harvest Moon in early October 2025, creates a spectacularly large and bright Moon in the sky.
Reasons for the Big Moon Appearance Today
- Supermoon : The Moon is closest to Earth in its orbit, known as perigee, causing it to appear bigger and brighter than normal full Moons.
- Moon Illusion : When the Moon is near the horizon, our brains perceive it as larger by comparing its size to nearby objects like trees and buildings, though the actual size does not change.
- Harvest Moon Effect : This October's full Moon is the Harvest Moon, occurring near the autumn equinox, making the Moon rise closer to sunset and appear large for several nights in a row.
Additional Details
- The Moon's orbit is elliptical, hence it varies in distance from Earth, affecting its apparent size.
- The Moon may appear yellow-orange near the horizon due to atmospheric scattering of light.
- The supermoon event of October 6-7, 2025, is the first of three supermoons in late 2025 and is the biggest and brightest full Moon of the year so far.
Thus, the combination of being a supermoon near the horizon and the Moon illusion explains why the Moon looks especially large today.
