Is it theoretically possible for a comet, in an eighty-year elliptical orbit around the earth, to change trajectory due to a friction-like mechanism, resulting in orbital decay that will impact the earth within the length of one orbit, i.e., about sixty years?

  • $\begingroup$ This might be a better fit for Worldbuilding. $\endgroup$ Aug 13, 2022 at 18:45
  • 1
    $\begingroup$ Why would a comet orbit the Earth? Comets orbit the Sun, they don't orbit planets. $\endgroup$
    – PM 2Ring
    Aug 13, 2022 at 20:13

1 Answer 1


There's no way to have an eighty year orbit around the earth. Such an orbit would be so large that the sun's gravity would dominate. There might be some solar orbits that line up by chance with the earth.

Any orbit that large that is in the planetary plane could easily interact with the outer planets to cause major changes. It's possible that a pass near Saturn or Jupiter is sufficient to modify the orbit that it intersects with the earth and the two collide.

  • $\begingroup$ There is. Halley's Comet has an orbital period of about 75 years and yet, it did not collide with the Sun nor with Jupiter $\endgroup$ Aug 13, 2022 at 19:36
  • $\begingroup$ @QuantumYitian No. Halley's Comet is orbiting the Sun, like all comets in the Solar system do. $\endgroup$
    – PM 2Ring
    Aug 13, 2022 at 20:12
  • $\begingroup$ @QuantumYitian, Halley's comet orbits the sun, not the earth. It is also not stable over long periods of time. It is expected to pass fairly close to Jupiter 3000 years from now. The orbit cannot be well calculated past that point. $\endgroup$
    – BowlOfRed
    Aug 13, 2022 at 22:18
  • $\begingroup$ @BowlOfRed I'm so sorry! I didn't read the question properly, I thought it was the Sun $\endgroup$ Aug 14, 2022 at 8:05
  • $\begingroup$ Thanks, everyone. I have changed my approach. Now my comet is merely on a collision course with earth (deleting my whole premise of orbiting the earth.) $\endgroup$
    – An-Ima
    Aug 19, 2022 at 17:57

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.