The problem with previous theories is that they could explain some aspects of the moon's properties quite well, such as its mass and its orbit, but they had very important gaps that they failed to explain, for example, a pending mystery has been why the composition of the moon is so similar to that of the Earth.
We know this because scientists can study the composition of a rock, dust, or any other material based on its isotopic signature, which is a chemical clue to how and where the material formed.
To explain what these isotopes are in a simple way, we know that there are elements such as iron, carbon, oxygen, and others; elements that are made up of atoms, atoms are made up of a nucleus with neutrons, protons and around them we have electrons, but and here is the important thing, not all atoms of the same element are the same, they can have the same number of protons but different number of neutrons, with a different number of neutrons we have different isotopes and this is very interesting to study the mysteries of the Cosmos.
For example, there are three stable oxygen isotopes and eight unstable ones and each one has different properties and origin, which can give us a lot of information about the formation and where the elements come from. Let's imagine that we find a meteorite and that in it we see that it has a specific isotope of iron, another of silicon and another of carbon, that specific combination of isotopes can coincide with the analysis of a sample from Mars, with which we could conclude that its origin is the planet red, since the meteorite and the Mars samples share the same isotopic signature.
Each object in the Cosmos has a characteristic isotopic signature, the rocks of Mars have one signature, those of Mercury have another, those of Venus have theirs, and each asteroid also has its own signature, although many share the same signature, so we could deduce that they are the remains of a larger body, curiously the analyzed samples of the moon have isotopic signatures very similar to those of the earth and that is quite rare, for this reason scientists deduce that much of the material that forms the moon is very possible that it comes from the primitive land.
The simulation of the new theory presented, we see how a large amount of earth materials are ejected into space due to the impact with tehia, particularly large amounts of the outer layers of the earth pulsating, which can help explain the mystery of the similar composition of the lunar rocks with respect to the rocks of the earth.