Astronomy and the Renaissance

Lesson Overview  Copernicus and the Sun-Centered Model  Kepler’s Laws of Planetary Motion Chapter 1, Lesson 2

Copernicus and the Sun-Centered Model © Image Select/Art Resource

Why Copernicus Searched for a Better Model  Ptolemy’s predictions were off by 2%  More accurate data for the Roman Catholic Church calendar  Theory of epicycles didn’t adequately explain changes in Mars’ brightness Chapter 1, Lesson 2

Key points Copernicus’ Heliocentric System  Earth, one of several planets revolving around the Sun  heliocentric or Sun-centered model  Plane of Earth’s equator tilted – causes earth seasons

Key Copernicus’ Heliocentric System  Moon revolves around Earth  Included relative distances of planets from Sun  Earth’s atmosphere simply follows Earth as it rotates Chapter 1, Lesson 2

Comparing the Copernican Model With the Ptolemaic PtolemyCopernicus Accuracy of Data Predictive Power Simplicity Chapter 1, Lesson 2

Tycho Brahe’s Observations of Planetary Motion Tycho Brahe’s Observations  Tycho’s observations didn’t confirm the more recent Copernican model, however  If the Earth orbited the Sun, then the nearby stars would show parallax © Photos.com

 Tycho’s model put Earth at the center of Sun’s orbit  Other planets orbiting Sun  Wrong conclusion for a good reason © Detlev van Ravenswaay/Photo Researchers, Inc. Tycho Brahe’s Observations of Planetary Motion

Kepler’s First Law: Each planet’s path around the Sun is an ellipse  Kepler took over most of Tycho’s records after he died.  Kepler kept trying to devise a system of circles and epicycles that would accurately predict the positions of Mars.  But the shape that finally fit the data, Kepler found, was the ellipse.  Ellipse – a geometrical shape of which every point is same total distance from two fixed points  Each planet’s path around the Sun is an ellipse

Kepler’s Second Law: The Planets’ Changing Speeds  A planet speeds up when it is closer to the Sun, and slows down when it is farther away  sweeps over equal areas in equal intervals of time

How Kepler’s Third Law Harmonic Law  Kepler hypothesized that a force held the planets near the Sun— today we recognize it is gravity  Harmonic Law: direct relationship between the time a planet takes to orbit the Sun and its distance from the Sun Courtesy of National Library of Medicine

Activity 1: Your Own Ancient Observatory  Your worksheet lists some of the tools you would probably find in an observatory today  At the time of the Renaissance, these tools had not been invented yet  What tools would you use instead, since these were not available? Chapter 1, Lesson 2

Review  Copernicus’s Heliocentric system put Earth as just one of several planets revolving around the Sun  Tycho’s observations didn’t confirm the more recent Copernican model, however  Kepler’s First Law of Planetary Motion holds that each planet’s path around the Sun is an ellipse  Kepler’s second law tells us about a planet’s speed as it moves around the Sun  Kepler’s third law implied the force of gravity Chapter 1, Lesson 2

Summary  Copernicus and the Sun-Centered Model  Kepler’s Laws of Planetary Motion Chapter 1, Lesson 2

Next… Done – Astronomy and the Renaissance Next – The Enlightenment and Modern Astronomy Chapter 1, Lesson 2 Courtesy of NASA