The question has two small problems:
#1). There's plenty of gravity in space.
#2). Gravity is not necessary for something to move.
Other than that, it's a fine question.
gravity
The warp drive engages.
Being in free fall is much like being underwater, in that you float freely. To move around in such an environment, you have to hold on to things, since you are not held in place by gravity.
No only when in earth's atmoshpere can the gravity be on.
These two are tied together. There is nowhere in the universe in which there are no gravity since the range of gravity is infinite. But Gravity gets weaker as get farther away, and therefore if you move far away enough, it would feel like there is no gravity. The reason why there is no air in space is that gravity attracts air, and without any gravity, all the atoms will either just slowly move around or just create their own gravity.
there is no gravity in space
gravity
The warp drive engages.
A force can cause an object to move if the amount of the force in the direction of movement is larger than the Frictional force of the object against the object on which it rests, and can overcome its Inertia.
the gravity moves the Earth in a circle
gravity keeps things in orbit
Being in free fall is much like being underwater, in that you float freely. To move around in such an environment, you have to hold on to things, since you are not held in place by gravity.
No only when in earth's atmoshpere can the gravity be on.
they are pulled by the Earths gravity
Gravity
it keeps you from going into space
That's what things do in gravitational fields. All objects that have mass have an associated gravity. Einstein's work suggests that gravity causes a bending of space, and objects move because of the bending of the space they occupy. Some current theories suggest that gravity (unlike the 3 other basic forces) is able to extend its effect across several dimensions (several more than the 3 common dimensions of our everyday experience of space).