I understand how mathematically is possible to have one object with elliptical or circular orbit around another object in space.

so can I think of it as a limit cycle? If yes, then is it stable or unstable? and why?

The intuition behind my question is to know if due to friction we will have a Moon-Earth collision or not.

  • $\begingroup$ What do you mean by saying due to friction ? $\endgroup$ – Rijul Gupta Oct 27 '13 at 10:55
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    $\begingroup$ Related: physics.stackexchange.com/q/9290/2451 $\endgroup$ – Qmechanic Oct 27 '13 at 10:58
  • $\begingroup$ well I thought that space had friction, even though very very small. consider a small asteroid colliding with the moon head on! Can I substitute that for friction? $\endgroup$ – gota Oct 27 '13 at 11:08

Moon laser ranging suggests that distance from Earth to Moon increases by 3.8cm per year, so we are not going to collide.

Friction in space is significant only on low orbits (<500km). For moon much more important things like liquid core and tides on the Earth.

Source: http://en.wikipedia.org/wiki/Lunar_Laser_Ranging_experiment#Results

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