A student claims, “An astronaut’s mass decreases when she travels from Earth to the Moon because she feels lighter there.” Which of the following statements best explains why the student’s claim is incorrect?
(a) Because the Moon’s surface gravity is about one-sixth that of Earth, the astronaut’s inertia is one-sixth as great, so her mass is one-sixth smaller.
(b) The astronaut’s mass decreases because the gravitational force is proportional to mg, and g is smaller on the Moon, so m must also be smaller to keep the product the same.
(c) Mass is the amount of matter in the astronaut and does not change with location; only her weight changes because the Moon’s gravitational field is weaker.
(d) Mass decreases whenever the local gravitational field strength decreases, so the astronaut really does lose mass on the Moon.