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If the original gas cloud that formed the solar system had not been rotating at all it would have indulged in a spherical gravitational collapse towards a point. However, in general any large gas cloud in space will have rotation. Thus it has angular momentum, a measure of the rotary motion of any object which is equal to the product of the mass times the circular velocity times the distance of the mass from the center of rotation. In the original solar system, the small amount of initial rotation is amplified during the process of collapse because the original gas cloud can collapse more easily down the axis of rotation, or the pole of the distribution, then along the equator where the motion resists the collapse. Thus, by the product of two forces, rotation and collapse, a large, slightly rotating gas cloud turns into a much denser gas cloud with a cylindrical or disk-like shape.

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