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Aristotle (c. 349 BC)
Natural State of motion: rest.
Force causes motion.
Heavy objects fall faster.
•Natural State of motion:
Circular
•Earth is the Center of the
Universe
TERRESTRIAL CELESTIAL
Nicholas Copernicus (1543)
Natural State of motion: rest.
Force causes motion.
Heavy objects fall faster.
•Natural State of motion : Circular
•The Sun is the Center
TERRESTRIAL CELESTIAL
Johannes Kepler (c. 1610)
Earth Motion:
Same as Aristotle
•Planets have elliptical orbits
•The Sun is the Center
TERRESTRIAL CELESTIAL
Kepler’s Laws of Planetary Motion
Law #1: The paths of the planets’ orbits
around the sun are ellipses With the sun at one focus of the
ellipse
Kepler’s Laws of Planetary MotionNo. 2
A line from sun to planet sweeps out equal areas in equal time intervals
Planets move faster when closer to sun
Planets move slower when farther from sun
Kepler’s Laws of Planetary MotionNo. 3:
TA2 = rA
3
TB2 rB
3
WhereTA = period of planet ATB = period of planet BrA = avg. distance of planet A from sunrB = avg. distance of planet B from sun
Example Prob. Kepler’s Law Galileo discovered the moons of Jupiter.
He could measure their orbital sizes only by using the diameter of Jupiter as a unit of measure. He found that Io, which had a period of 1.8 days, was 4.2 units from the center of Jupiter. Callisto, Jupiter’s 4th moon, had a period of 16.7 days. Using the same units that Galileo used, predict Callisto’s distance from Jupiter.
Galileo (1564-1642)
Law of Inertia: Uniform Motion
Force causes change in motion
All objects fall with the same acceleration
Celestial Realm is imperfect
Solar System is not unique
TERRESTRIAL CELESTIAL
Sir Isaac Newton (1642- )
Quantified Galileo’s ideas
Formulated Newton’s 3 Laws of Motion
Gave mathematical expression to gravity with the Law of Universal Gravitation
Gravity whichkeeps the Moon in orbitaround the Earth is thesame force that attractsall objectsto Earth.
Sir Isaac Newton (1642- )
Major Philosophical Shift!
TERRESTRIAL CELESTIAL
Terrestrial and Celestial MotionObey the same physical laws!!
You mean: The same laws of Physics work everywhere!!?
They are UNIVERSAL
Newton’s Law of Universal Gravitation
The gravitational force between two bodies is
Directly proportional to the product of their masses
Inversely proportional to the inverse square of the distance between them
F ~ mA mB / d2
Albert Einstein (1916)
General Theory of Relativity:
Explained the cause of gravity through the concept of curved “space-time”
Albert Einstein (1916)
..and also stated that: A uniform gravitational field is equivalent to a uniform acceleration. Therefore….
The lady in the elevatorCan’t tell if she is on earthAt rest or in deep space And accelerating at 9.8 m/s2 !