Originally Posted By: preearth
When two planets collide they stick together (unless the speeds are astronomically fast).


Quote:
Assume both objects have the same mass. Then the force, pulling the objects together, is proportional to the mass squared.


When extraterrestrial objects strike Earth, they do so at astronomical speed. These objects are very much smaller than Earth, so the force pulling them together is less than in your planetary example. Why should objects of similar mass come together more slowly?

There never was nothing.