This question already has an answer here:

Would a large enough ship generate enough gravity to affect earths course?


marked as duplicate by Organic Marble, uhoh, called2voyage Sep 26 '18 at 16:11

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • $\begingroup$ I think you need a definition of how much you want it affected as all matter gravitationally affect each other. Also might be a better fit for worldbuilding SE $\endgroup$ – lijat Sep 26 '18 at 14:36
  • 1
    $\begingroup$ I'm voting to close this question as off-topic because imaginary giant alien spaceships are not related to space exploration. $\endgroup$ – Organic Marble Sep 26 '18 at 15:50
  • $\begingroup$ This could also be a duplicate to Does launching a device into orbit change earth's orbit? and answers there do a nice job of answering this question. $\endgroup$ – uhoh Sep 26 '18 at 16:00

Any spaceship (or other mass) anywhere in the universe will affect Earth's orbit. Just not very much! For instance, a 1 million ton stealth spaceship magically hovering just above the surface of the Earth would accelerate the Earth at about $10^{-15} m s^{-2}$ towards it. This would give a displacement of about 0.5 meters over a year.

  • $\begingroup$ Except for the fact that it would have to exercise a force on earth that is exactly as strong as the gravitational force but in the oposite direction in order to not fall down. Momentum of the earth / ship system has to remain constant (as far as we know) therefore hovering doesn't work for moving earth. Maybe you could hover by shooting neutrions through earth? That might result in some net acceleration. $\endgroup$ – Christoph Sep 26 '18 at 14:58
  • $\begingroup$ @christoph point taken. I've added "magically" $\endgroup$ – Steve Linton Sep 26 '18 at 15:00

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