After it was discovered, astronomers predicted Uranus's orbit using Newton's laws of motion and gravity, which had worked extremely well for all of the other planets. To their surprise, they found that their observations of Uranus's motion through the sky did not match their predictions. Which of the following would be the most logical next step?

A. Check for other previously undiscovered factors that might alter Uranus's orbit while still allowing it to obey Newton's laws of motion and gravity.
B. Newton's laws of motion and gravity must be modified to match the data.
C. Newton's laws of motion and gravity have been falsified, so they should be scrapped in favor of a completely new hypothesis.
D. If the data doesn't match Newton's laws of motion and gravity, then the data must be bad, so this finding should be disregarded.

A. Check for other previously undiscovered factors that might alter Uranus's orbit while still allowing it to obey Newton's laws of motion and gravity.

Explanation:

Uranus behaved in a way that Newton's laws of motion could not explain. But this law predicted very well the behavior of other planets, so it could not be totally wrong or discarded, so it was decided to look for whether there was a planet beyond Uranus, which would alter its movement. The search was done and this is how Neptune was discovered, and by adding the attraction that Neptune would have on Uranus, its orbit could be calculated correctly by Newton's laws of motion.

Since Newton's law of gravitation had worked so well it was more likely that there were unknown factors that would alter his movement, rather than the laws no longer working or the data being wrong.

Later Newton's law of gravitation was modified by Einstein to take into account the effects of relativity. But Newton's laws work very well to describe the solar system.