What are the main 'arguments' for the theory that the Moon is an 'artificial celestial body' or 'spaceship' brought to Earth?

Hey friend! That question you asked is incredibly fascinating—it's like something straight out of a sci-fi novel coming to life. The theories about the Moon being an "artificial celestial body" or a "spaceship" are quite widespread in certain circles and sound pretty convincing with a sci-fi twist. Below, I'll break down the main "arguments" most commonly cited by supporters of these theories.

Let's treat this like listening to an exciting sci-fi story and explore these wildly imaginative ideas!

Key Arguments for the "Moon Spaceship" Theory

The core idea of this theory is that the Moon is not a naturally formed object, but a hollow structure created by some super-advanced civilization. It was supposedly placed precisely in Earth's orbit, possibly to monitor Earth, serve as an interstellar travel base, or fulfill other purposes beyond our imagination.

Supporters typically look for "evidence" in the following areas:

Argument 1: The Perfect Coincidence – Behind the "Heavenly Dog Eats the Sun" (Solar Eclipse)

This is the most widespread argument.

Phenomenon: From Earth, the Moon and the Sun appear almost exactly the same size. This allows the Moon to perfectly cover the Sun during a total solar eclipse.
"Suspicious Point": The Sun's diameter is about 400 times that of the Moon, and the Sun is also about 400 times farther from Earth than the Moon is. Supporters argue that among so many celestial bodies in the universe, how could such a "precise" and "coincidental" ratio exist? It seems almost deliberately designed so that people on Earth can witness the astronomical spectacle of a total solar eclipse. They believe such a perfect mathematical coincidence is unlikely to occur naturally.

Argument 2: Is the Moon a "Hollow Ball"? – The "Moonquake" Experiment

This is a very core piece of "evidence".

Source: During the US Apollo program in the last century, after completing their missions, astronauts would jettison parts of the lunar module, letting them crash into the Moon's surface. Seismometers on the ground detected the "moonquakes" caused by these impacts.
"Suspicious Point": It's claimed that after impact, the Moon "rang like a great bell," with vibrations lasting a very long time (some reports say over an hour). Supporters infer that if the Moon were a solid rocky sphere, the seismic waves would decay and disappear quickly. Only if it were hollow, with a hard metallic shell, could it produce such a prolonged, bell-like resonance. This leads them to believe the Moon has a hard metallic shell and is hollow inside.

Argument 3: Density Too Low, Defying Logic

Data: The Moon's average density is about 3.34 grams per cubic centimeter, while Earth's average density is 5.5 grams per cubic centimeter.
"Suspicious Point": For a rocky body, the Moon's density seems abnormally low. Supporters argue that if the Moon were solid, its density should be higher. This low density, they claim, supports the "hollow Moon" hypothesis. A giant hollow metal sphere would naturally have a lower average density.

Argument 4: "Artificial Metals" in Moon Rocks

Source: Lunar rock samples brought back by the Apollo missions.
"Suspicious Point": Rumors suggest scientists found extremely pure metals in moon rocks, such as pure iron and pure titanium. In nature, metals usually exist as compounds (ores), rarely forming high-purity elemental forms. Additionally, it's said alloys not found on Earth and even unexplained artificial fibers were discovered. This is considered direct evidence the Moon is "artificial," with these metals possibly being materials for the spacecraft's hull.

Argument 5: The Bizarre Orbit and the Forever Hidden "Dark Side"

Phenomenon:
1. The Moon's orbit is very close to a perfect circle (though actually elliptical, it's much rounder than many other moons).
2. The Moon is "tidally locked" to Earth, meaning only one side ever faces us. We never see its far side (the so-called "dark side," though it is illuminated by the Sun).
"Suspicious Point": Supporters argue that a natural satellite "captured" by Earth's gravity would typically have a more elliptical orbit. The Moon's near-perfectly circular orbit seems "deliberate." Furthermore, only showing us one face is seen as a telltale sign ("protesting too much") – perhaps hiding a secret base or spaceship entrance on the far side?

Argument 6: A "Moon" That's Too Big

Comparison: In our solar system, there's usually a huge size difference between a planet and its moons. For example, Jupiter is much larger than its biggest moon.
"Suspicious Point": The Moon's diameter is about 27% of Earth's. This ratio is extremely rare in the solar system, making the Moon seem disproportionately large for Earth. Supporters feel a rocky planet like Earth, not exceptionally large itself, would struggle to capture such a large "little brother" through gravity alone. It seems more like it was "escorted" here.

So, What Does the Scientific Community Think? (Time for a Reality Check)

While the arguments above might sound coherent and persuasive, mainstream science views most of these "suspicious points" as based on misunderstandings, exaggerations, or even outright myths.

The Eclipse Coincidence: It is a beautiful coincidence, but not "perfect." The Moon's orbit is elliptical, so its distance from Earth changes, making its apparent size vary. This is why we have total, annular, and partial solar eclipses. In a universe so vast, some mathematical coincidences are not surprising.
The "Hollow Bell Ringing": The prolonged lunar vibrations ("ringing") are real, but the cause isn't hollowness. The Moon's interior is extremely dry, lacking water and air, with very intact and rigid rock structures. Seismic waves propagate through such material with very slow energy dissipation, causing vibrations to last a long time. This is similar to striking a large, dry, intact block of granite and has nothing to do with being hollow.
The Density: The currently most widely accepted "Giant Impact Hypothesis" explains the Moon's low density well. It proposes that early in Earth's formation, a Mars-sized body collided with the proto-Earth. The debris ejected primarily consisted of lighter mantle and crust material from Earth, which eventually coalesced to form the Moon. Naturally, the Moon lacks Earth's heavy iron core, resulting in lower density.
The "Artificial Metals": This is a complete myth. Moon rocks do contain metals like titanium, but they exist as oxides (like ilmenite), which is entirely normal. No "pure iron," "brass," or unexplained artificial materials have ever been found in lunar samples.
The Orbit and the Far Side: "Tidal locking" is a very common gravitational phenomenon between planets and their close-orbiting moons; many moons in the solar system are tidally locked. The Moon's orbit is also not perfectly circular but elliptical with a distinct perigee (closest point) and apogee (farthest point).

To Summarize

In conclusion, the "Moon Spaceship" hypothesis is a captivating story. It weaves together astronomical phenomena and early exploration data in an imaginative way, satisfying human curiosity about the unknown universe and alien civilizations.

However, based on all current scientific evidence, these "arguments" don't hold water. The formation and evolution of the Moon are explained more reasonably and comprehensively by natural theories like the Giant Impact Hypothesis.

So, you can view this hypothesis as a very cool sci-fi concept—it makes for a great conversation starter with friends. But for now, it remains just that: an imaginative "brainstorm" or speculation, not scientific fact.

Hope this explanation was both interesting and helpful for understanding!