Chapter 2 Kepler's Laws & Heliocentric Model

Heliocentric Model

Sun-centered solar system model proposed by Copernicus

Kepler's Third Law

Relates a planet's orbital period to its distance from the Sun

Pluto's Orbit

Takes longer due to Kepler's Third Law

Kepler's Second Law

States equal areas are swept out in equal times

Earth's Orbit

Most similar to option A

Phases of Venus

Contradicted geocentric model observations by Galileo

Speeding Up Orbit

Occurs only during one portion of the planet's orbit

Planetary Orbits

Follow Kepler's laws; A is least like Earth's orbit

Epicycles

Used to explain planet brightness and retrograde motion in geocentric model

Ancient Astronomy

Observed skies, built structures, tracked celestial events

Geocentric Model

Earth-centered system with Ptolemy's epicycles

Telescope Invention

Around 1600; Galileo used it to support the heliocentric model

Kepler's Laws

Derived from Tycho Brahe's observations; include ellipses, equal areas, orbital periods

Aphelion

Farthest point from the Sun (A)

Perihelion

Closest point to the Sun (C)

Period

Time for a planet to orbit the Sun once

Semi-Major Axis

Measure of an ellipse's size

Astronomical Unit

Earth's orbit size around the Sun; unit of length

Eccentricity

Measure of how flattened an ellipse is

Kepler’s third law applies to

A planet around a star other than the Sun, a planet around the sun, a satellite around a planet, a comet around the sun

Pluto takes longer to orbit the sun than earth. This is due to which of Kepler's Laws?

third

Why are the phases of Venus that Galileo observed at odds with this geocentric model?

Venus would not appear ¨Full¨as the Moon does

Which of the following people used epicycles to explain the retrograde motion of the planets while maintaining a geocentric model of the solar system?

Ptolemy

Epicycles are needed in the geocentric model to explain why?

Planets seem to vary in brightness and exhibit retrograde motion.

what is retrograde motion

Motion in the eastward sense is usually referred to as direct, or prograde, motion; the backward (westward) loops are known as retrograde motion

Copernicus revolution

1) Earth is not the center of everything, 2) Center of Earth is the center of the Moon’s orbit. 3) All planets revolve around the Sun. 4) The stars are much farther away than the Sun. 5) The apparent movement of the stars around the Earth is due to the Earth’s rotation. 6) The apparent movement of the Sun around the Earth is due to the Earth’s rotation. 7) Retrograde motion of the planets is due to the Earth’s motion around the Sun

Who built their own telescope and did observations

Galileo

What was Galileo’s observations

1) Moon has mountains and valleys, 2) Sun has sunspots and rotates. 3) Jupiter has moons 4) Venus has phases.