I have seen a few posts regarding the physics in space and I think there could be a simple misunderstanding. I had to have it explained to me a number of years ago aswell.
Although there is no gravity in space, objects in space still have mass. The confusion arises when we think of weight as the same thing as mass. They are different. In fact, weight is a product of mass and gravity. And because there is no gravity in space, you get an equation times zero, thus zero weight. But the mass remains constant (unless you eat lots of jelly donuts...then your mass increases...mmmm, jelly donuts).
Anyway, mass still has an effect on objects moving through space. Newtonian science says that "an object in motion tends to stay in motion". The crux of this law is that once an object of any given mass is traveling in a straight line, in a frictionless environment, that object will have a tendency, ie, will WANT to continue to travel in that line. Thus, it becomes more difficult to change the trajectory or velocity of that object. And the more mass that object has, the more difficult it becomes to alter that object's range of motion. Thus, a MASSive frieghter requires more forces acting upon it (thrust, turning arc, etc) in order to change it's direction.
Anyway, the point is mass does not equal weight. Weight is irrelevant in space, since there is no gravity. Mass, however, is very relevant.
Ok, physics lesson over. Now this message is likely to be corrected, amended, disputed, or altered by the numerous scientists, engineers and physicists who very likely know more about this stuff than I do.
Now...time for those jelly donuts...
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