What causes objects such as stars and black holes to spin?

Answer 1

Inertia. If the mass that collects is spinning to begin with with a very large diameter, and then contracts by immense gravitational forces, the rate of spin must increase. So if a star was spinning maybe once per day, then contracted into itself and the diameter shrunk to 1 millionth of the original, the rotational inertia must be preserved. So the period of rotation decreases astronomically, far greater than 1 million times. So you get rotation many times per second.

Answer 2

All mass has inertia...a resitance to change in mass or velocity over time. So to set a mass into spinning, there has to have been a net force acting on that mass at some time in its evolutionary history.

This follows from the fact that spinning is a change in velocity by definition of what velocity means...a change in position over time. By spinning, the angular position of the spinning object is changing over time and so the spinning object has angular velocity. And tangential velocity is nothing more than angular velocity times the radius of the spinning object.

What forces might there be to get things spinning (including black holes consisting of highly compressed mass)? Well, the big bang, if you beleive this theory, is a really big source of energy. And E = Fd; where F is force acting over a distance d...this is the so-called work function. So all that energy from the big bang as the universe expands gives us plenty of available force F = E/d.

Apply some of that force off center to a clump of matter and you get a spin. As the availabe forces are HUGE, the mass that it starts into spinning can also be huge...super galactic in size for example. Or, perhaps, super massive black holes. And, the little stuff, like planets and moons, are a piece of cake.

In the beginning, the first matter after the big bang was rather gas like...spread out over wide volume of space. Even so, it had angular momentum (spin momentum) from the massive energy/force of the big bang. As the universe cooled and gravity pulled the cloud like matter together into clumps, that angular momentum was conserved...in fact, we call it the conservation of angular momentum law. So the clumps contiinued to have angular momentum and spun.

Once that clump of matter gets spinning, it keeps on ticking like the Timex watch. Why? Because there is nothing, no force, to stop the spin. And Newton's first law, the one about momentum, says it takes a force to change velocity, mass, or both over time. And when the mass isn't changing, this gives us F = ma; we need a force to decelerate that spin.

In fact, there are forces at work to stop spinning, but they are comparatively weak. Earth, for example, is slowing down its spin. This is due to gravity effects that cause tides; and the frictional losses of the tides result in the forces that slow the spin. But not to worry, the slow down is very slow, a matter of a few seconds each year; so it'll be a long time before Earth stops.

Answer 3

ALL objects in the universe spin. This is a result of the way the Big Bang occurred. Even the smallest imbalance in space will cause an object to spin. And imbalance is the key to HOW the original singularity came to be.

Answer 4

Because the velocities of the gasses that formed them never exactly balance out, once the gasses collect to form a star or other body, conservation of momentum (both linear and rotational) is conserved.

Answer 5

Not true. Its the force that everything with mass has. Its called inertia and is defined as the resistance of a mass to accelerate or change direction (acceleration is defined as a change in speed which includes going slower and faster). When gravity attracts a previously moving object wit with mass its inertia will stop it form changing direction so it starts an orbit and moves in a circular motion. You should research Newton's Second Law of Motion which deals with inertia.

Answer 6

Gravity and momentum.