Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Why do stars and galaxies spin?

  1. Dec 17, 2008 #1
    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?
  2. jcsd
  3. Dec 17, 2008 #2
    Ever heard of angular momentum?
  4. Dec 17, 2008 #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?
  5. Dec 17, 2008 #4


    User Avatar
    Science Advisor
    Homework Helper

    Yes and it will still spin with the same angular momentum
  6. Dec 17, 2008 #5

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2015 Award

    There's your problem right there. It doesn't. Unless an external torque is applied, once an object starts spinning, it stays spinning.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Why do stars and galaxies spin?
  1. Why do stars twinkle? (Replies: 8)

  2. Why do things spin? (Replies: 4)