The phenomenon of a larger-looking full moon is often referred to as a "supermoon." A supermoon occurs when the moon is at its closest point to Earth in its elliptical orbit, known as the perigee, while also coinciding with a full moon phase. During this time, the moon can appear slightly larger and brighter than usual, although the difference is often subtle and may not be noticeable to everyone.
The apparent size of the moon can be influenced by a combination of factors. The most significant factor is the moon's elliptical orbit around Earth, which means its distance from our planet varies throughout its orbit. When the moon is at its perigee, it is about 30,000 kilometers closer to Earth compared to when it is at its apogee (the farthest point in its orbit). This difference in distance can make the moon appear slightly larger in the sky.
Other factors, such as the moon's position on the horizon and atmospheric conditions, can also contribute to the moon appearing larger. When the moon is low on the horizon, it can create an optical illusion known as the "moon illusion," where it appears larger compared to when it is high in the sky. This effect is still a subject of scientific debate and not yet fully understood.
It's worth noting that while a supermoon may appear larger, the actual size of the moon remains the same. The term "supermoon" is more of a popular designation used to describe the visual effect of a slightly larger and brighter full moon.