Astronauts and cosmonauts in orbit around the Earth (say, on the space shuttle or on Space Station Alpha) feel weightless. Explain why this is.

1. They are essentially in freefall, with the gravitational force providing the centripetal acceleration required to orbit.
2. They are above the Earth's atmosphere, so the Earth's gravity does not affect them.
3. They are so far from the Earth that the Earth's gravity does not affect them.
4. None of the above.