Top 10 Fascinating Facts About the Moon You Might Not Have Known

The Moon follows an elliptical orbit around Earth, not a circular one, meaning the distance between the centers of Earth and the Moon constantly changes. At perigee (when the Moon is closest to Earth), the distance is 363,300 km (225,740 miles), while at apogee (the farthest point), it's 405,500 km (251,970 miles). As a result, when the full Moon occurs at apogee, it appears 14% larger and 30% brighter than a typical full Moon.

The Moon's phases and its orbit are mysteries to many. For example, we always see the same side of the Moon. This happens because it takes 27.3 days for the Moon to rotate on its axis and orbit Earth. The phases—full moon, waning moon, or new moon—occur as the Moon reflects sunlight, and how much of it we see depends on the relative positions of the Moon, Earth, and Sun.

By studying the craters on the Moon, scientists have determined that the Moon (and Earth) underwent a period known as the Late Heavy Bombardment about 4 billion years ago. Recent theories suggest that life could have existed there if organisms found a stable environment. Moreover, the craters on the Moon's surface tell the story of its violent history, as the Moon lacks atmosphere and has minimal internal activity. These craters are remnants of impacts that occurred billions of years ago.

The Moon has no real soil, as it contains no life-sustaining material. Instead, its surface is covered by a substance called regolith—a fine powder consisting of rock fragments and volcanic glass particles mixed with larger rocks. When astronauts studied the Moon rocks they brought back, geologists discovered the following characteristics: The maria rocks are mostly basalt, an igneous rock formed from cooled lava.

The highland regions are primarily made up of a type of magma rock called anorthosite and breccia. When comparing the relative ages of these rocks, the highlands are much older than the maria (4 to 4.3 billion years old compared to 3.1 to 3.8 billion years old). Moon rocks contain very little water and volatile compounds (indicating they were heated), and resemble rocks found in Earth's crust. The oxygen isotopes in the Moon and Earth rocks are similar, suggesting both formed at the same distance from the Sun.

According to NASA's Lunar Reconnaissance Orbiter website, the Moon is not a perfect sphere but rather an oblong shape, resembling an egg. The Moon's mass is not centered in the middle of its orbit but is offset by about 2 kilometers (1.2 miles) from its geometric center. Similarly, Earth also bulges at its equator. When we look up at the Moon, the smaller end of this 'egg' shape is what faces us.

The shape of the Moon is influenced by its rotation, with the larger end of the egg pointing toward Earth. Many people mistakenly believe the Moon is spherical because of its round appearance when full. However, when we observe the Moon, we're only seeing a small illuminated portion. The appearance of the Moon depends on its position relative to the Sun, which creates the different lunar phases visible from Earth.

According to studies by the Apollo astronauts, they used seismometers during their missions to the Moon and discovered that the gray sphere is not entirely lifeless, geologically speaking. These 'moonquakes' originate several miles (kilometers) below the surface, caused by the gravitational pull of Earth. Occasionally, small cracks appear on the surface, allowing gases to escape. As a result, scientists speculate that the Moon may have a partially molten core, similar to Earth's core.

Seismographs at the four Apollo landing sites on the Moon recorded 28 shallow moonquakes from 1969 to 1977, ranging from 1.5 to 5 on the Richter scale. Theoretically, some of these shallow quakes could be the result of activity along lunar fault lines, though the exact locations and depths of the sources are uncertain. However, data from NASA's Lunar Prospector spacecraft in 1999 indicated that the Moon's core is small, possibly only 2% to 4% of its total mass. This size is tiny compared to Earth's, where the iron core makes up about 30% of the planet's mass.

Ever wondered why tides occur on Earth? The answer lies in the Moon. Tides are primarily caused by the gravitational pull of the Moon. When the Sun, Moon, and Earth align, such as during a new moon or full moon, higher tides, called spring tides, are created compared to normal tides.

Tides occur due to the gravitational forces of the Sun and Moon on Earth. Without the Sun, the Earth's oceans facing the Moon would bulge in response to the Moon's gravity, creating high tides. The difference in gravitational pull on the near and far sides of Earth means that there are also high tides on the far side of Earth at the same time. Since the oceans are fluid, between two high tides there are two low tides. As Earth rotates, these tidal bulges move around the globe every 24 hours, meaning each coastal location experiences two high tides and two low tides each day.

When the Sun, Moon, and Earth are aligned, their combined gravitational forces create spring tides (though confusingly, they do not occur in the spring). During these tides, the high tides are slightly higher and the low tides are slightly lower than usual. Conversely, when the Sun and Moon are at a right angle to each other, the Sun’s gravitational pull partially cancels out the Moon’s, resulting in neap tides. These tides are characterized by slightly lower high tides and slightly higher low tides compared to the average.

The Moon has been slowly moving away from Earth over the course of billions of years. It was once approximately 22,530 km (14,000 miles) from Earth, but now it is about 450,000 km (280,000 miles) away. Researchers suggest that when the Moon first formed about 4.6 billion years ago, it was much closer to Earth. The reason for its ongoing retreat is due to the Moon gradually stealing Earth's rotational energy, which causes it to push itself away by roughly 4 cm (1.6 inches) each year. This process has been ongoing for billions of years, and if it continues, Earth's day could extend to a month, or even 40 days.

Currently, the Moon is moving away from Earth at a rate of about 3.8 cm (1.5 inches) annually. Scientists refer to this phenomenon as the 'Moon's retreat.' The rate at which this occurs is not constant: at the start, it was 20.8 cm (8.2 inches) per year, and the rate has fluctuated between 0.13 cm (0.05 inches) and 27.8 cm (10.9 inches) per year. There have been three significant surges in the Moon's retreat rate in the past. The first occurred around 3.2 billion years ago, coinciding with early evidence of tidal activity, when the Moon was receding at 6.93 cm per year.

About 900 million years ago, the Moon's retreat increased dramatically to 7 cm per year, likely due to meteorite impacts. It continued at this rate when the supercontinent Rodinia broke apart. The third surge happened about 523 million years ago, during the Cambrian explosion, when life on Earth rapidly diversified and the Moon moved away at 6.48 cm per year.

The Blood Moon is a completely normal phenomenon, also known as a total lunar eclipse. It occurs when the moon moves into Earth's shadow, blocking the sunlight. Contrary to some apocalyptic beliefs, this is not a sign of the end times. A lunar eclipse can only happen during a full moon, when the sun completely illuminates the moon's surface. Usually, a full moon does not result in an eclipse because the moon orbits on a slightly different plane than Earth and the sun. However, sometimes the orbits align. Earth moves between the moon and the sun, cutting off sunlight and creating the lunar eclipse phenomenon.

If Earth blocks part of the sun, and the darkest part of its shadow falls on the moon's surface, it is known as a partial lunar eclipse. You'll see a dark spot slowly eating away at the moon. Occasionally, the moon passes through the lighter part of Earth's shadow, creating a penumbral lunar eclipse. Only experienced skywatchers can distinguish this, as the moon only darkens slightly.

During a total lunar eclipse, however, something fascinating happens. The moon is fully immersed in Earth's shadow. At the same time, a small amount of light from Earth's dawn and dusk (on the planetary disk) casts a red glow onto the moon's surface. Because the light waves are stretched out, they appear red. As this red light hits the moon, it turns the moon a deep red. This causes the Blood Moon phenomenon we often witness!

Many wonder why the Moon rises on one side of the sky and sets on the other. The reason lies in the same way the Sun and other stars behave in the universe: Earth's rotation on its axis towards the East pulls cosmic objects into view, and then they gradually fade from sight. Similarly, the Moon follows an orbit around Earth, completing a full cycle every 29.5 days. However, each day, the Moon rises about 50 minutes later than the previous day.

This explains why sometimes the Moon rises in the evening and climbs higher in the night sky, while at other times, it may rise briefly or mostly during the day. Each night, the Moon presents a different face to the sky. On some nights, we can see the entire Moon, other times just a part of it, and in some places, the Moon may not be visible at all. These phases are not random—they change regularly throughout the month and can be predicted. As the Moon travels through its 29-day orbit, its position shifts daily. Sometimes it lies between Earth and the Sun, and at other times, it is behind us. As a result, different parts of the Moon are illuminated by the Sun, creating different phases.

It is known that the Moon orbits Earth and rotates on its axis in the same amount of time, which is why we only ever see one side of it. Many people believe the Moon has a dark side, but in reality, the Moon has no dark side. There is simply a far side that is never visible from Earth. This is because, long ago, Earth's gravitational effects gradually caused the Moon to synchronize its rotation with its orbit. As a result, the Moon rotates slowly enough to match the length of its orbital cycle (the time it takes to orbit Earth), creating a stable effect.

As Earth rotates under the Moon’s gravitational pull, it creates regular high and low tides about every 12 hours. The Moon also helps stabilize Earth’s rotation. Without the Moon, Earth could tilt nearly 90 degrees from its axis, much like a spinning top gradually wobbling as it slows down.

Many people believe that the Moon has no gravitational pull. In reality, the Moon, like any other large object in the Universe, exerts a gravitational force on other massive objects. Even subatomic particles like protons and neutrons generate a gravitational pull on nearby objects, though it is so weak it is negligible. The Moon's size is only about 27% that of Earth, and it's not very large. Additionally, its gravity is only about 1/6th that of Earth's. For example, if we drop a stone on the Moon, it will fall more slowly than it would on Earth.

The term "surface gravity" refers to the "pull" objects experience when they rest or move on a larger body. The average surface gravity of Earth is around 9.8 m/s². For instance, when an object is thrown off the top of a building or cliff, it accelerates toward the ground at 9.8 m/s². The surface gravity of the Moon is roughly 1/6th of that, or about 1.6 m/s². This weaker gravity on the Moon is due to its much smaller size compared to Earth. Surface gravity is proportional to an object's mass but inversely proportional to the square of its radius.