Why Do Stars and Galaxies Keep Spinning?

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    Galaxies Spin Stars
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Discussion Overview

The discussion revolves around the reasons why large macro objects, such as stars and galaxies, continue to spin. Participants explore concepts related to angular momentum and the conditions under which spinning objects maintain their motion, touching on theoretical and conceptual aspects.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that continuous energy input is necessary for spinning objects to maintain their motion.
  • Another participant introduces the concept of angular momentum as a key factor in understanding why objects continue to spin.
  • A hypothetical scenario involving a spinning globe of ice melting as it approaches the sun is presented to question the effects of melting on the object's spinning behavior.
  • One participant asserts that the globe will retain its angular momentum and continue to spin even after melting into water.
  • Another participant challenges the idea that continuous energy input is required, stating that unless an external torque is applied, a spinning object will maintain its spin indefinitely.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of continuous energy input for spinning objects, with some supporting the idea of angular momentum as a sufficient explanation. The discussion remains unresolved with competing perspectives on the mechanics of spinning objects.

Contextual Notes

Some assumptions about the nature of energy input and the effects of external forces on spinning objects are not fully explored, leading to potential gaps in understanding the dynamics involved.

samsara15
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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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Ever heard of angular momentum?
 
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?
 
Yes and it will still spin with the same angular momentum
 
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.
 

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