Why do stars and galaxies spin?

In summary, the conversation discusses the concept of angular momentum and how it allows large macro objects to continue spinning without an external torque. A hypothetical situation is presented where a spinning globe of ice melts as it approaches the sun, but it will still maintain its shape and spin due to its angular momentum.
  • #1
samsara15
17
0
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?
 
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  • #2
Ever heard of angular momentum?
 
  • #3
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?
 
  • #4
Yes and it will still spin with the same angular momentum
 
  • #5
samsara15 said:
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.
 

Related to Why do stars and galaxies spin?

1. Why do stars and galaxies spin?

Stars and galaxies spin because of the conservation of angular momentum. This means that an object will continue to spin at a constant rate unless acted upon by an external force. When stars and galaxies were first formed, they had a slight rotation due to the spinning of the gas and dust clouds they were formed from. As they collapsed and became more compact, this rotation increased, causing them to spin faster.

2. What causes the rotation of stars and galaxies?

The rotation of stars and galaxies is caused by the initial angular momentum of the materials they were formed from, as well as the gravitational pull of neighboring objects. As the materials collapse and become more compact, their rotation increases due to the conservation of angular momentum.

3. Do all stars and galaxies spin in the same direction?

No, not all stars and galaxies spin in the same direction. Some stars and galaxies rotate in a clockwise direction, while others rotate counterclockwise. This is due to the random motions and collisions of materials in the early stages of formation.

4. How does the spinning of stars and galaxies affect their shape?

The spinning of stars and galaxies causes them to have a flattened, disk-like shape. This is because the centrifugal force caused by the rotation balances out the gravitational pull towards the center, resulting in a disk shape. This is known as the "disk-halo" structure.

5. Can the rotation of stars and galaxies change over time?

Yes, the rotation of stars and galaxies can change over time. This can happen due to interactions with other objects, such as collisions or gravitational interactions. Additionally, as stars age and burn through their fuel, their rotation may slow down due to the loss of mass.

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