# If initial oblique velocity is the reason why moon has not crashed into Earth, what caused this initial veloci

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The angular momentum of the solar system is the same as it was when the solar system was still a cloud of gas.

This cloud of gas (the remains of exploded stars) had some small initial rotation. As the cloud shrunk, the rate of rotation increased, in accordance with conservation of angular momentum:

L = I*omega

where I = moment of inertia and omega = rate of rotation.

During the formation of the solar system, many rocks were all crashing into each other. It is merely by chance that the Moon did not collide with the Earth, or miss it completely and go flying off into space. Instead, it settled into a stable orbit.

• ZikZak
Lv 6

Nothing causes velocities. Uniform motion is the natural state of a body. A body in motion remains in motion, until acted upon by an outside force.

In the case of the Moon, however, we know that the Moon is made of the Earth's mantle material which was blasted into orbit by a collision with a planetoid about 4 million years ago. So in this particular case, the material that made the moon was given kinetic energy by the collision that created it.

The Moon is the only body to have formed in this way, however. All other bodies in the solar system formed out of a spinning cloud of gas, most of which ended up in the Sun. Some small amounts of material that had large angular momenta continued in their orbits instead of drifting into the Sun, and thus we have the planets and moons, except for the Moon.

That initial spinning was imparted to the solar system simply as a consequence of the conservation of angular momentum. Whatever minuscule amount of spin the original nebula had just at random was imparted to the solar system when it collapsed. Like an ice skater drawing in her arms, the nebula spun faster and faster as it contracted by many orders of magnitude.

• Anonymous