By newton's third law , we know that every action has an equal and opposite reaction .We move left when we push slightly on the right and move forward as we push backward. But how do rockets, satellites etc change their direction in the space as they have nothing to push on?
Crudely, just consider the burned rocket fuel that is ejected out of the back of the rocket due to chemical reactions. The rocket exerts a strong backward force on the burned rocket fuel. According to Newton's third law, required reaction is that the burned rocket fuel exerts an equal forward force on the rocket. This force accelerates the rocket forward.
Keep in mind that Newton's third law says nothing about pushing against something, the rocket does not need to push against "a medium" to accelerate forward.
Rockets fire matter backwards, which, together with conservation of momentum (i.e. Newton's third law), leads to them being propelled forward.
It works like in the video below, where soda is matter and the bottle is the rocket :)
As the net external force acting on the rocket-fuel system is 0 N, the system's linear momentum is constant, the same before and after the burning and ejection of some fuel. Note that linear momentum is a vector quantity with a magnitude equal to mass x speed. A change in one direction of part of the system results in a change of equal magnitude in the opposite direction
If part of the system's mass increases speed in one direction, another part will gain speed in the opposite direction. Fuel accelerated to a given speed in one direction results in the rocket and its remaining fuel gaining speed in the other direction.
Nothing external to the rocket-fuel system is required. In short, the rocket and the non-ejected fuel require nothing to push off from.