What was one obstacle Newton encountered in developing his theory of universal gravitation from his observation of heavenly bodies?
a. He had to prove that Earth was nearly spherical.
b. He had to figure out why the Moon doesn't fall down.
c. He had to spend many years observing the movement of the planets.
d. He had to prove that the mass of the Earth acts as if it was concentrated at the planet's center.
e. He had to prove the inverse-square law.
Question 2
What changed Newton's original work on the movement of the Moon around the Earth into the law of universal gravitation?
a. His conclusion that the same laws applied to all heavenly bodies, not just the Earth and the Moon.
b. His conclusion that the same laws applied to all objects, no matter how small.
c. His conclusion that planets move in elliptical orbits around the Sun.
d. His connection of gravitation to his first law.
e. His connection of gravitation to Kepler's observations of planetary movement.