Imagine a one ton solid metal sphere hurtling through space at thousands of miles per second. Classic physics tells us that unless affected by external forces the total linear momentum of the sphere cannot change. Damn. We need to stop that sphere dead in its tracks but we have no way of physically interacting with it.
Well I guess we will just have to increase the velocity of all other matter in the universe to match the velocity of our sphere along its vecter effectively making its velocity zero in relationship to the rest of the universe.
Where did its momentum go?