Accelerating Motion in Space: Virtual Particles?

[Joanna Dark]

I'm curious as to how a vehicle might change velocity or direction in space? Do virtual particles act as a medium by which an engine can achieve this? Or does an engine not need a medium and why?

 

[malawi_glenn]

conseravaton of momentum.

If a space man is moving away from his space ship, he can throw a thing in the direction he is moving and he will then move back towards the spaceship due to conseravation of linear momenta.