A 70-kg astronaut stands on a weighing scale inside a satellite orbiting Earth. What does the scale read? What would it read on Earth's surface? Step 1: A scale measures the normal reaction N, not gravity itself. Step 2: In orbit, satellite and astronaut fall together with acceleration g toward Earth. Relative to the satellite, the astronaut has zero acceleration, so no floor pushes on him: N = 0. Step 3: On Earth's surface the floor pushes up with N = mg = 70 × 9.8 = 686 N. Answer: The scale reads 0 in orbit (complete weightlessness) versus 686 N on the ground. Gravity at 400 km is still ~8.7 m/s² — the zero reading is because everything falls together, not because gravity vanished.