The motion, about equal to the pressure of a sheet of paper on the palm of your hand, is so gentle it would be useless on Earth.
But in space, where there is no counteracting gravitational force, momentum builds up over time.
A: no counteracting gravitational force: an old misconception that in space there is “no gravity” as opposed to “everything is in free fall so whoops there goes my pen”, but!
B: is so gentle it would be useless on Earth. Useless? Then why aren’t all the bits of paper on your desk drifting up to the ceiling, Mr Smarty-Pants Journalist?