Results 1 to 3 of 3

Thread: Rotating system

  1. #1 Rotating system 
    Forum Freshman almirza's Avatar
    Join Date
    Nov 2005
    Why every thing in the space is rotating round a fixed point ???
    I understand that the sun is holding the Earth family planets and prevent them from wandering into the space.

    Reply With Quote  


  3. #2  
    Forum Radioactive Isotope mitchellmckain's Avatar
    Join Date
    Oct 2005
    Salt Lake City, UTAH, USA
    Your question needs a bit of context, but since this is in a Astronomy and Cosmology forum I will assume that you mean in the context of current cosmological theory. And the answer is ultimately asymmetry in the universe. This asymmetry means that gravitational collapse will not be perfectly radial. Gravitational collapse itself is due to asymmetry. But when matter is collapsing into some gravitational center, if any of that matter is moving in any direction other than exactly directly towards that gravitational center, then this contributes angular momentum to the system. Matter moving non-radially only to a very small degree at large distances contributes a large angular momentum which becomes a very high degree of rotation when that matter has collapsed to a short distance.

    So in the context of cosmology, the reason why the planets rotate is exactly the same reason as why they orbit the sun, which is the same reason why the sun orbits the center of the galaxy.

    This issue of angular momentum is a big deal. It is why black holes don't swallow up everything in the universe. Because of angular momentum, black holes swallow very little at all. They may rip things up a bit, but mostly the matter just ends up circling the black hole in its accretion disk. Spiral galaxies are really like super big accretion disks around super-massive black holes, so this angular momentum is a big deal indeed.

    See my physics of spaceflight simulator at

    I now have a blog too:
    Reply With Quote  

  4. #3  
    Forum Freshman John L's Avatar
    Join Date
    Oct 2004
    Cary, NC
    You forgot to mention the fact that the very principle you are describing results in the presence of a "super massive" black hole at the center of the galaxy, just as there exists a star at the center of each solar system.
    We must all hang together or assuredly we will all hang seperately. -Benjamin Franklin
    Reply With Quote  

Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts