Welcome to brain Stuff from house stuff Works dot com where smart Happens. I am Marshall Brain with today's question, where did the Moon come from? This question became famous because of Bill O'Reilly, but it's a classic house stuff Works kind of question, so let's take a look at it. It's a basic tenet of science that everything in nature has some kind of explanation. So therefore, the moon has to have some kind of explanation. It had to come
from somewhere or something. And scientists have been thinking about this and pondering this for a long time. They've come up with a number of theories that didn't really work
when they looked at them deeper. So one example would be that the Earth and the Moon formed together when the Solar System was forming, there was an accretion process that allowed dust to accumulate into planets, and perhaps the Moon formed in the same way the Earth formed, and they formed next to each other and became this kind of orbiting system. There's a couple of reasons why we can say that isn't the case, but one really good reason is the fact that the Moon and the Earth
have different compositions. The amount of iron in the cores of these two planets is remarkably different. If they had formed together, you'd expect them to be the same, So that,
along with other things, kind of rules that out. Another theory that scientists came up with was the centrifugal force idea, the idea that the Earth formed with the Solar System, and it was much bigger than it is today, and it was spinning extremely quickly, and a chunk of it in the molten state just kind of flung off as a blob, and that became the Moon. So scientists looked at that and they thought about it, and they modeled
it with computers. And there's a couple of problems with that theory, the main one being that the Earth would have to be spinning way too fast for it to fling a chunk of itself off, and it if it had been spinning that fast when the Moon was formed, then it would be spinning much faster than it is today. A day wouldn't be twenty four hours long, it would be much much shorter. Another theory is some kind of
asteroid capture event. So an asteroid comes by and it somehow gets caught in Earth's gravitational field and it becomes our moon. The problem with this theory is that there would have to be something that would break the asteroid or slow it down once it approached Earth, and the atmosphere is one thing that could have done that. But because of the size of the Moon and the thickness of Earth's atmosphere and a couple other things, that theory
doesn't really work very well either. But it probably is what happened with the little moons that are surrounding Mars right now. A fourth theory is the one that most scientists are currently pretty comfortable with, and the basic idea
here is pretty easily stated. A planet like object with a size roughly equal to Mars hit planet or shortly after these two bodies formed, you know, maybe fifty million years after these two bodies formed, and the Moon was formed by matter that was ejected into orbit by that collision.
So it would have been a massive collision with a lot of energy, and these objects would have formed into another molten ball in a chunk just was blasted out into orbit, and it would have been blasted out into orbit. Probably is is bits and pieces that would have formed or aggregated together to create the Moon that we have today. Science is based on evidence. So what evidence do we have to support this view of the Moon's origin. One piece of evidence came back from the Apollo Moon missions.
The moon rocks collected by the Apollo astronauts support this theory. Another thing that support is the size of the core of the Moon. Is mentioned earlier. The core of the Moon, being of iron, is much smaller than the core of the Earth, and that fact is easily explained by some kind of collision event. In that event, mostly mantle would have been ejected into the uh into orbit around Earth rather than the iron core, it's thought, and so the Moon would therefore have less iron in its core as
a result. Another piece of evidence is the canting of the Earth's rotational axis. You know, the fact that the axis is tilted, and this is what gives us our seasons and the length of the Earth day. And another is the distance of the Moon from the Earth and the increase in that distance over time. So you take pieces of evidence like this and they work together with each other to support the theory that the Moon was
created by a collision event. There's a great deal of cheerill available through Google if you'd like to increase your scientific understanding of the Moon's origin. It really is an interesting question. If you think about it and you know in theory, you could come up with another idea for where the moon came from, and if you have the evidence, you could bring it forward and create another scientific discovery. That's How Science Works. Be sure to check out our
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