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

How delicate is the Earth's Orbit?

  1. Jun 8, 2012 #1
    The Earth has at times been struck by very large asteroids but this has not knocked our planet out of it's orbit. Why not?

    Does the Earth have some method of 'self correction'? Or is it not a very 'fine tuned' system so that a few impacts really wont make any difference? Alternatively have we already been knocked from our orbit but just slightly so we won't notice it for millions of years?

    What about the increase in mass that our planet experiences? Wouldn't the planet have to orbit faster to maintain circular motion to compensate for this?

    Thanks very much. Any thoughts would be appreciated.
  2. jcsd
  3. Jun 8, 2012 #2


    User Avatar
    Science Advisor

    Planetary orbits are stable, meaning that if you give planet a small push, it will slightly alter ellipticity of the orbit, but the planet will still pass back through the point where it was pushed after completing a revolution.

    Say, you gave the planet just a bit of a push away from the Sun. The planet will start drifting away from its orbit, and so it will slow down. When it slows down, it starts falling towards the star, picking up the speed. It will overshoot its original orbit, now drifting towards the star. This will cause the planet to speed up and attempt to escape. Now it's again drifting away from the star, and the next time it intercepts its old orbit, it's traveling through exact same point and with exact same speed as the moment after you gave it a nudge. So that nudge altered the trajectory, but only slightly. The planet still ends up traveling along roughly the same path.
  4. Jun 8, 2012 #3


    User Avatar

    Staff: Mentor

    Another factor is that the Earth is large compared with most of the non-planetary junk floating around the solar system. For example, the Earth has maybe 2x10^9 times the mass of the Chicxulub meteor that is blamed for killing off the dinosaurs - as well try to knock a freight train off its tracks by throwing a pebble at it.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook