This question says that, at relativistic speeds, an object's increased mass will result in increased weight or gravitational force. But if we have increased mass and corresponding gravitational effects, does that mean that the object actually contains more matter? Does the increase in velocity result in an increase in the number of atoms in the object?
- If so, where does the additional matter come from? How is it distributed? E.g. if I drive my car at 0.9c, is there some law that decides whether the added matter goes to my engine block or to my headlights?
- If not:
- How does mass increase if there is no increase in matter? The SI system defines mass in terms of a physical artifact (or a number of atoms, according to one proposal), but Wikipedia has seven different definitions of mass, so I'm not sure which one(s) applies here.
- Does it make sense to ask how the added mass is distributed throughout the object?