Astronomy Unit 1

Gravity

The force that places objects in order, for our universe

Why the Geocentric model did not work

*Geocentric model has the earth as the center of out solar system

*Geocentric module shows diffculty in explaining motion of our planets in the night sky

*We needed another model

How did Kepler save the day

*Kepler saw the simplicity of the situation

*Planets moved around the sun in elliptical orbits,sweeping out trianglur areas that are equal in equal time intervals

*A planet does not move at a constant speed aound its orbit to accomplish Pythagorans Theoreom

When were Keplers laws made?

Kepler’s first 2 laws in 1609 and 3rd law in 1919

Kepler’s 1st law

Planets move in elliptical orbits with the Sun at one focus

Kepler’s 2nd law

A Planet sweeps out an equal area in equal amount of time

Kepler’s 3rd law

A Planet’s orbital period squared is equal to the semi-major axis cubed

Newton’s Law of Gravity

explains the Mechanisms for Kepler’s laws of Planetary Motion

Newton’s Law of Gravitional Attraction

A force that only attracts objects with mass

Centripetal Force

A force keeping an object from crashing into a larger object with a large gravitational force

Ex:the moon going around the large earth

Why do Astronauts in the international space station feel weightless in their spacecraft

They are in constant free fall around the Earth (as in their Spacecraft)

Einstein Explanation of Gravity

*Einstein looked at space & time as a fabric (Like a net in space)

A mass placed on the net would bend the space-time fabric (net)
*Objects would fall toward the massive object, thus, like the attraction force of gravity

*A forward motion would prevent the objects from falling into the more massive objects

*Einstein proved Newton’s Law of Gravity and Planetary motion in a different way