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Message: <blockquote data-quote="FrogReaver" data-source="post: 7993851" data-attributes="member: 6795602">Actually Astronauts do weigh something in space while orbiting the earth.We can determine the force of the gravitational force acting upon them at that altitude.  We can determine their mass.  After that it's just force times mass equals weight.  Keep in mind weight is specifically derived from the gravitational force acting upon a massThere's some terribly shoddy physics in here.On Weightlessness:What weightlessness means is not that astronauts are no longer affected by any gravity - as that would be impossible.  It means there is another force acting upon them in an equal and opposite direction - centripetal force.  Because gravity still effects them they still have weight in that situation.Instead what we typically mean by weightless is that you are in state such that you are behaving as if you were weightless.  Another force counteracting gravity may cause this - in the case of orbiting the earth.  Or being far away from any massive object could also cause this as the magnitude of the gravitational force becomes very small.To be actually weightless you need to be infinitely far away from all other matter - or at least in a position such that the gravitational forces of all matter in the universe netted out to 0 on you.</blockquote>