Why Do Stars and Galaxies Keep Spinning?

[samsara15]

It takes a continuous input of energy to spin, otherwise things would fly apart or stop spinning. So why do large macro objects spin, and continue to spin?

 

[Crazy Tosser]

Ever heard of angular momentum?

 

[samsara15]

Consider the following situation. A spinning globe of pure ice, say a small meteor, a meter in diameter, spinning around its own axis, approaching the sun, so that as it approaches the sun, it melts. Are you saying that the globe of ice will continue to remain a globe of water, still a meter in diameter, even after it melts?

 

[mgb_phys]

Yes and it will still spin with the same angular momentum

 

[Vanadium 50]

It takes a continuous input of energy to spin

There's your problem right there. It doesn't. Unless an external torque is applied, once an object starts spinning, it stays spinning.