The heavens were literally composed of 55 crystalline spheres to which the celestial objects were attached
Each sphere __________________ at a constant velocity (although some spheres rotated faster than others)
Motions of the “Wanderers”
The ancient Greeks tracked __________ objects that seemed to move against the background of fixed stars in the sky: the Sun, the Moon, Venus, Jupiter, _____________, Mercury, and Mars
They named them “planets” (the Greek word for wanderers), and Aristotle’s model could not explain the motion of these wanderers who sometimes even appeared to move backwards from one night to the next.
Ptolemaic Model of the Universe
Ptolemy created a model that more accurately explained the motions of the sky, including the retrograde (backwards) motion of the planets
Ptolemy’s model became the standard used by scholars for 1,500 years because:
It worked! It could predict the __________________ of a planet to within 2°.
It accounted for the observed planetary motions, including retrograde motion and variations in brightness.
It placed the _____________ in its “natural place” at the center of things
Invented __________________ as a necessary tool to solve mathematical problems related to motion
Discovered the three laws of _______________
Discovered the universal law of mutual _____________________
Newton’s Laws of Motion
Newton’s 1st Law of Motion - A body at rest continues to rest, and a body in motion will continue in uniform motion in a straight line unless it is acted upon by some net force. (AKA- ____________________)
Newton’s 2nd Law of Motion - Acceleration (a) of a body is inversely proportional to its mass (m), directly proportional to the net force (F), and in the same direction as the net force. (F = m a)
Newton’s 3rd Law of Motion- to every action there is an equal and opposite ______________________
Newton’s Universal Law of Gravity
More Mass = ____________ gravitational force
More Distance = _____________ gravitational force
Mass vs. Weight
Your weight is a measure of the force of gravity acting on your body