What, if any, evidence did Galileo have for the law of inertia?
A) A smooth ball slows down when rolling uphill, and speeds up when rolling downhill, so it should maintain an unchanging speed on a level surface.
B) Noting that the length of the year does not change, he concluded that Earth must maintain an unchanging speed when moving around the sun.
C) Using a telescope, he observed meteors and comets moving at unchanging velocity through outer space.
D) All of the above.
E) He didn't have direct evidence, but proposed the law of inertia only because of the known failures of Aristotelian physics.

Question

Quizplus · Accepted Answer

Galileo observed that a ball rolling down an incline speeds up, and a ball rolling up an incline slows down. He reasoned that on a perfectly level surface, without friction, the ball would maintain a constant speed, leading to his formulation of the law of inertia.

What, If Any, Evidence Did Galileo Have for the Law