So, how big would an asteroid or planet have to be...

[dave_the_nerd]

Answered pretty well here: https://www.reddit.com/r/askscience/comments/3jv4ah/what_is_the_largest_space_object_from_which_a/

 

[Paratus]

Answered pretty well here: https://www.reddit.com/r/askscience/comments/3jv4ah/what_is_the_largest_space_object_from_which_a/

Small celestial bodies are weird like that. They are massive compared to our everyday things but are so low in gravity you can run and or jump off some of them.

One of the theoretical methods to deflect a small to medium size asteroid is to simply put as big a satellite as you can in orbit around it. The satellite will slowly drag the asteroid off course through their mutual attraction. This is called a gravitational tractor.

 

[dave_the_nerd]

Small celestial bodies are weird like that. They are massive compared to our everyday things but are so low in gravity you can run and or jump off some of them.

One of the theoretical methods to deflect a small to medium size asteroid is to simply put as big a satellite as you can in orbit around it. The satellite will slowly drag the asteroid off course through their mutual attraction. This is called a gravitational tractor.

Yeah - gravity is a really weak force, relatively speaking.

But it works over long distances, and even with the 1/r^2 dropoff, there's a LOT of mass involved.