There is almost nothing that could make the Moon fall towards the Earth that wouldn’t disrupt the orbit of the Earth around the Sun as well as the other planets. However, there is no apparent violation of the laws of physics in this trailer. As surprising as that may sound physics allows for things far stranger than the Moon colliding with the Earth. The real question is what could put the Moon on a collision course with the Earth in such a short time frame that we would not see it coming for millions or billions of years in advance? Aliens of course. Which may violate the laws of biology if they are human looking which while not impossible is not probable.
The Moon’s Origins.
The first thing to know is that planet sized bodies have collided in the past and will collide again if the solar system last long enough. There is a non-zero chance that given another five billion years Earth will collide with Venus, or Mercury or Mars. What could cause or accelerate this? Gravitational interactions with passing stars, or other massive objects such as Black holes. These would not need to get anywhere near the solar system to have an effect.
Even at 1-2 light years such an object could perturb the planets on to a collision course that might take a billion or more years to play out. This would only speed up perturbations of our orbit due to interactions between the planets themselves.
That these things are happening so quickly that we’d be surprised by it is the most unrealistic aspect of the movie. Like, we could go from a normal Tuesday to a Wednesday where the Moon is orbiting 200 miles above us and ripping the Earth’s crust apart.
That is not likely.
That said, in the deep past planetary collisions were much more likely because the number of planet sized bodies was greater. According to many lines of evidence, geology, geophysics, and geochemistry of rocks on Earth and on the Moon, it has been concluded that the Earth and Moon were created when the proto-Earth was hit by a Mars sized body called Theia. Of course, we give this hypothetical body that name now, but when this collision occurred about 4.4 billion years ago, 0.1 billion years after the formation of proto-Earth, and .5 billion years after the formation of the solar system, nothing was around to name it.
What About Aliens?
Aliens here are a plot device and possibly also a way for the creators of this movie to depict a slightly more realistic yet mass marketable version of an alien invasion. If aliens were going to come and invade the Earth, they’d not sent fighters and soldiers. They could just hurly moderately sized asteroids at the Earth from a safe distance and we’d not be able to do anything to stop them right now.
Since the average person has no real solid idea about the asteroids, and that would take some explanation, but everyone EVERYONE has seen the Moon, they just have the aliens use the Moon.
What MIGHT violate physics is the source of energy the Aliens would use to redirect the orbit of the Moon on a short time scale, a matter of a day or a week. It would take something on the order of a small Black Hole to do that. Changing the energy of the Moons orbit so that it would orbit the Earth More closely would require a VAST amount of energy. So lets see if they give the aliens an impressive energy source. If these aliens are capable of faster than light travel via something like Warp Drive or Wormholes then who knows what else the can do.
Scott Manley a really good YouTube creator made a video about this.
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