What is the difference between mass and gravity?
This is like asking: What is the difference between electricity and weight? Mass is the amount of physical material in an object, and gravity is a force. You may be asking about the fact that the mass of an object (under ordinary non-relativistic conditions) remains the same even if the object is floating freely in space. On the other hand, the weight of an object is a measure of the amount of gravitational force exerted on an object. On the surface of the earth, an object may weigh many tons, and have an associated mass measured in grams. That same object is weightless in space but has the same number of grams of mass no matter where it is. This is why you might see answers indicating that the earth or some other planet is weightless. This seems absurd, but it is true. The planets are very massive, but unless you can put them on a scale in a gravitational field, they don’t weigh a thing.
