Angular momentum

Angular Momentum = <math>mvr</math>

where m is mass, v is velocity, r is the radius of the circle.

Of Planet Earth

Mass = 5.9736×1024 kg

Average orbital Velocity = 29.78 km/s

Radius = distance from sun = Aphelion + Perihelion / 2 = 149,598,261 km

Angular Momentum = 5.9736×10^24 kg * 29.78 km/s * 149,598,261 km = 177.90x10^24(kg*km/s) * 149,598,261 km = 2.66x10^34(kg*km^2/s)

Conservation of

Assuming no external torque changes, angular momentum of an object is constant. Using the example of an ice skater, the friction of skates on ice is very small (assume zero for this.) The ice skater's mass is constant. With her arms extended, angular momentum could be represented as M = mass * velocity * Rextended. Changing the radius by bringer her arms in, the momentum could be represented as M = m * v * Rin. Since Re is greater than Ri, and all other parts of the equation are fixed, something must change to compensate. The velocity is the only thing that can change, so her angular velocity increases to maintain constant angular momentum.

The same principle applies to clouds of gas. It is assumed that most if not all gas clouds have some rotation, if minute. As gravity pulls them in, density increases, and the radius of the cloud decreases. As with the skater, if the radius decreases, something must compensate for this, and once again it is velocity. Thus, the velocity at the center of the cloud increases. This causes more friction, which leads to heat, pressure, gravitation increases, etc, and a star is formed.