The copernican revolution

geocentric

Earth centered

Ptolemaic model

used circles within circles to model the solar system

retrograde motion

a planet's apparent backward movement in the sky.

epicycles

small circles located on deferents

heliocentric

sun-centered

deferents

larger circles which contain epicycles

Copernican Revolution

describes the shift in thinking where the Earth is in space

Orbital period

the time it takes to orbit the sun once

gravity

universal force that holds planets in orbit

Flaw in Copernican model

Circular orbits

Aristarchus

Greek scientist who first stated that the Earth revolved around the Sun, and rotated on its axis.

Ptolmey

Egyptian Astronomer that adapted Aristotle's model account for retrograde motion

Copernicus

astronomer who developed the heliocentric theory

Tycho Brahe

Danish astronomer who collected data to prove that Copernicus was correct

Johannes Kepler

Assistant to Brahe; used Brahe's data to prove how the Earth moved

Galileo Galilei

Italian astronomer and mathematician who was the first to use a telescope to study the stars

Isaac Newton

Defined the laws of motion and gravity. Tried to explain the motion of the universe.

Stone Henge

stone alignments predicted celestial events

eccentricity

stretch of orbital path, how an orbit deviates from circular

Ellipse

A elongated circle, or oval shape, the shape of the planets orbit.

aphelion

point in a planet's orbit that is farthest from the sun

perihelon

orbital point nearest the sun

ecliptic

path of the Sun and planets across the sky

Astronomical Unit (AU)

the average distance between the Earth and the Sun

Kepler's First Law

The orbit of each planet around the Sun is an ellipse with the Sun at one focus.

Kepler's Second Law

As a planet moves around its orbit, it sweeps out equal areas in equal times

Kepler's Third Law

The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.

Newton's First Law

An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

Newton's Second Law

Force equals mass times acceleration

Newton's Third Law

For every action force there is an equal and opposite reaction force

Law of Gravitation

states that any two masses exert an attractive force on each other, the amount of which depends on the mass of the two objects and the distance between them

Major discoveries of Galileo

Jupiter's moons, sunspots, phases of Venus, craters on the Moon

As a planet moves further from the Sun, it orbits:

Slower

East to west

Direction the sky moves

Pre-Newton reason for gravity

Natural motion and violent motion