"Moonfall" Revelation: Will the Moon deviate from its orbit and crash into the Earth?

For billions of years, the moon has been the Earth's "close companion". Under the bondage of Earth's gravity, it has become Earth's closest friend. However, is this normal state eternal?

In the 2022 sci-fi film Moonfall, a mysterious force throws the moon out of its orbit, setting it on a collision course with the Earth, foreshadowing a doomsday catastrophe that could completely shatter our blue planet in just a few weeks.

Faced with such a thrilling and unimaginable disaster threat, the warriors in the film stepped forward and launched a race against time to save the earth. In the process, they were surprised to find that the true face of the moon is much more complicated than we imagined.

In this suspenseful and intelligent science fiction film, the moon is conceived as a magnificent building carefully built by intelligent aliens billions of years ago. Although this setting only exists in the fantasy world of the movie, it is deeply rooted in the field of science fiction. So, in the real space, is there some mysterious force that can really push the moon away from its orbit?

The Moon is a rocky body covered with a thin layer of gas - the exosphere. It was created almost at the same time as the Earth, about 4.5 billion years ago.

One popular theory about the Moon's origin is that it formed from debris from a collision between the young Earth and a smaller protoplanet called Theia. Another hypothesis holds that both the Moon and Earth were the product of a collision between two bodies five times the size of Mars.

Currently, the average distance between the moon and the earth is about 385,000 kilometers. Its mass exceeds 735 billion tons, which is roughly equivalent to 1.2% of the mass of the earth, and its diameter is about one-quarter of the earth.

This conceptual illustration shows a body about the size of our Moon colliding with an object about the size of Mercury.

From the images of the moon, we can see that its surface is covered with craters of various sizes, which are traces left by historical collisions.

However, most of these fragments were formed billions of years ago, when the solar system was full of debris. According to Paul Chodas, director of the Center for Near-Earth Object Studies (CNEOS) at NASA's Jet Propulsion Laboratory, as planets formed, the rocky debris that once filled the solar system has been greatly reduced, so the frequency of celestial body collisions in the modern solar system has significantly decreased, and there are fewer asteroids that can collide with the Earth or the Moon.

CNEOS has been identifying and tracking near-Earth objects, such as asteroids and comets, that could pose a threat to Earth, the Moon or other cosmic neighbors. So far, they have tracked and discovered about 28,000 near-Earth objects that approach the Earth no closer than 1.3 astronomical units (about 194.5 million kilometers).

"We have studied collisions between planets and asteroids in great detail, as well as impacts on the Moon," Chodas explained. "Typically, asteroids are less likely to hit the Moon than Earth because our planet is more massive and has a stronger gravity. If a wayward space rock were to enter the Earth-Moon orbit region, it would be more likely to be pulled by Earth's gravity than by the Moon's."

The booster rocket of the Apollo 16 lunar landing mission hit the moon in April 1972, and the picture shows the impact mark left behind.

He further pointed out that when considering the threat of an asteroid to the Earth, its size is also an important factor. According to NASA, to classify a near-Earth object as a threat, its diameter must be at least 140 meters. To push the moon out of its orbit and cause damage, the impacting asteroid must be at least the same size as the moon.

Given the huge size of the Moon itself, such an asteroid would have to be massive and hit it at a very high speed. Fortunately, however, all known asteroids in the solar system are smaller than the Moon.

The largest asteroid known to date has a mass of about one-seventieth of the Moon's. Its orbit is located in the main asteroid belt between Mars and Jupiter, about 180 million kilometers away from Earth.

Therefore, when we look up at the moon in the night sky, we can rest assured that it will not disappear anytime soon, nor will a devastating disaster between the Earth and the Moon be caused by an impact event.

Reference Information:

https://www.livescience.com/moonfall-moon-knocked-from-orbit

Compiled by: Youyou

Planning: Zhang Chao, Li Peiyuan, Yang Liu

Reviewer: Liu Yong, Researcher at the National Space Science Center of the Chinese Academy of Sciences, Ambassador of China's Space Science Popularization