The phenomenon of a supermoon occurs when the moon is at or near its closest point to the Earth during a full moon.

When the moon is at its closest point during a full moon, it's called a super full moon, while being at its closest point during a new moon is termed a super new moon.

Due to the elliptical orbit of the moon around the Earth, the distance between the moon and Earth varies, resulting in the appearance of a larger full moon when it occurs closer to Earth. However, during a new moon, the moon's dark side faces Earth and aligns with the sun, making it difficult to see with the eye, let alone notice a super new moon compared to a regular new moon.

Therefore, discussions of supermoons often refer to the super full moon, as it is more noticeable when rising in the east or setting in the west, appearing particularly large and displaying a golden hue.

Many mainstream astronomers prefer the term "perigee full moon" over "supermoon" due to its scientific accuracy. The term "supermoon" commonly refers to the perigee full moon in media reports, excluding the perigee new moon, which is scarcely visible and lacks the visibility necessary for moon gazing.

The concept of a supermoon was initially proposed by American astrologer Richard Nolle in 1979. Astronomers note that while the moon appears larger and brighter during a perigee full moon compared to an apogee full moon (its farthest point from Earth), these differences in size and brightness are not easily noticeable to the eye.

Why are there so many occurrences of "supermoons"?

There were four occurrences just last year.

Having two supermoons in a month is rare, but supermoons themselves are quite common. In a typical year, there are usually 12 or 13 full moons.

Following the definition of a supermoon mentioned earlier, there would be at least 3-4 occurrences of perigee full moons within a year.

Astronomical experts explain that the period between the moon reaching its perigee occurs every 27.55 days, while the period between two full moons occurs within a synodic month, lasting between 29.27 and 29.83 days. Due to these slightly differing cycles, the occurrences of "supermoons" in a year do not exceed four.

What constitutes a rare "supermoon"?

The full moon is when the Earth-Moon distance is at its minimum.

The distance between the Earth and the moon varies cyclically when the moon is at its perigee, usually ranging between 356,400 kilometers and 370,400 kilometers.

A truly rare "super-supermoon" occurs when the moon's perigee distance is at 356,400 kilometers and coincides with a perigee full moon, presenting the largest and roundest moon visible from Earth. This can be dubbed the "super-supermoon."

How rare is this "super-supermoon"? In the 21st century, the closest Earth-Moon distance (356,400 kilometers) will occur on December 6, 2052. Following this event, the next closest occurrences of the "super-supermoon" will be on November 25, 2034, and November 14, 2016.

During a supermoon, the oceans experience additional gravitational forces. Normally, a full moon (and new moon) in conjunction with the sun results in larger-than-usual tides known as spring tides. However, during a supermoon, tides are even higher and stronger than usual. For those near coastlines, beware of the possibility of high tides in the days surrounding a supermoon!

Does the supermoon affect human bodies? The answer is no.

Although all objects on Earth experience the gravitational pull of the moon, the impact is negligible. For instance, during the supermoon of March 19, 2011, the effect on an adult might have been equivalent to the weight of one or two strands of hair.