An astronaut who visits the moon will therefore experience a change in weight the force applied to an object by gravity (measured in Newtons) , but their mass how much matter an object contains (measured in g/kg) will still be the same. The moon is a lot smaller than the Earth, so its gravity force which draws objects towards the centre of a planet, or other body is a lot weaker. Astronauts use safety tethers to stop them from floating away into space.