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Lesson 1-4 History of Astronomy Renaissance Astronomy (1400 A.D. to 1640 A.D.)

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Presentation on theme: "Lesson 1-4 History of Astronomy Renaissance Astronomy (1400 A.D. to 1640 A.D.)"— Presentation transcript:

1 Lesson 1-4 History of Astronomy Renaissance Astronomy (1400 A.D. to 1640 A.D.)

2 Lesson overview  Copernicus (heliocentric theory)  Brahe (observations via instruments)  Kepler (3 laws of motion)  Galileo (telescopes to observe the solar system)

3 Introduction  Renaissance period—four people established the way we see our solar system:  Nicolaus Copernicus—challenged earlier theories  Tycho Brahe—made amazing observations  Johannes Kepler—built on Brahe’s observations; created three basic laws  Galileo Galilei—used a telescope to observe the Moon, Sun, and three planets  His observations and Keplar’s math destroyed the earlier geocentric theories

4 Nicolaus Copernicus ( )  Polish physician and lawyer, renaissance humanist and Catholic cleric  Had trouble with Ptolemy’s geocentric (earth-centered) model  Believed in Aristarchus’ heliocentric (sun-centered) model  Asserted Earth rotates on its axis once per day


6 Heliocentric and retrograde motion?  Ptolemy used epicycles to explain retrograde motion (but got very complicated)  Heliocentric models explain retrograde motion as a natural result of two planets passing each other as they revolve counterclockwise around the Sun

7 More Copernicus  Wrote “On Revolutions of Celestial Spheres”  Calculated with accuracy the relative distances of the planets to the sun using geometry  Could not explain lack of “stellar parallax” when viewing stars  Copernicus surmised the distances were too great to have any parallax effects  People at the time couldn’t imagine such vast distances  Theory rejected as a model of reality but embraced as useful for calculations

8 Tycho Brahe (1546  1601) Brahe’s Quadrant Build island observatory -- “Uraniborg” Invented “modern” instruments to observe planets Accurately measured the locations of the planets Gathered other data – Mars in particular

9 Azimuthal Semicircle For measuring altitude or angular distances

10 Armillary Sphere

11  Observed things that suggested heavens were changeable and complex  Observed comet traveling through the orbits of several planets  Shattered Aristotle’s crystalline-sphere theory  Proposed different, but still incorrect, geocentric model  Geo-heliocentric model  The Sun and the Moon revolved around the Earth  Everything else revolved around the Sun  Lacked mathematical know-how to explain the motion of the planets  Hired Johannes Kepler Tycho Brahe (1546  1601)


13 Johannes Kepler ( )  Challenged by Brahe to explain mathematically Mars’ orbit around the sun  Used Brahe’s data on Mars to show the orbit was elliptical  Put the sun at one focus resulting in 3 laws of motion

14 Kepler’s First Law  The orbits of the planets are ellipses with the sun at one focus of the ellipse.

15 Kepler’s Second Law  The line joining the planet to the sun sweeps out equal area in equal times.  What does this mean? When a planet in its orbit is closer to the sun, it must speed up to sweep out an equal area…

16 Kepler’s Third Law  The square of the orbital period (time it takes to complete one orbit) is directly proportional to the cube of the mean (average) distance from the sun to the planet  What does this mean? A larger orbit requires more time to make one complete revolution.  Kepler predicted EXACTLY how much time each planet’s orbit would take.

17  Brought new emphasis on finding and quantifying causes of motion  United geometric or kinematic description of orbits with their physical, dynamic force that causes it  Authored fictional account of a space journey, the Somnium  Described trip to the Moon  Inspired other fiction writers, including Jules Verne and H. G. Wells Johannes Kepler ( )

18 Galileo Galilei ( )  Refined telescope design to a state-of-the-art 20X  Observed several things about the physics of motion  Ushered in new era of space exploration

19 Galileo’s Discoveries  Saw imperfections in “perfect bodies” of Aristotle’s model of the universe  Mountains and valleys of the Moon  Sun spots (noticed the sun rotated like the Earth)  Discovered four moons orbiting Jupiter  Disproved Aristotle’s assessment that everything revolved about the Earth  Noticed the phases of Venus indicating it too revolved around the sun  Observed the Milky Way and noted its vast size  Telescope’s inability to magnify stars confirmed Copernicus’s guess about their vast distances

20 Galileo and Gravitation  Measured time for spheres to reach bottom of an incline  Dropped stones from the Leaning Tower of Pisa  Weight didn’t affect time to reach the bottom –both balls had the same acceleration  Previously, people thought heavier objects fall faster  Theory proven during Apollo 15 using a hammer and feather

21 Galileo vs the Pope  His “theories” were at odds with Church “law”  In 1610, published “Starry Messenger”  Non-technical style—readable for common class  Presented as dialogue of the Copernican system between a wise teacher (him) and an unbeliever he named Simplicio (the Pope)  In 1632, published “Dialogue Concerning the Two Chief World Systems” with the approval of the Inquisition  Supposed to be neutral, but wasn’t  In 1633, placed under house arrest for the rest of his life (church admitted its mistake in 1992)

22 Lesson review  What idea did Copernicus develop and promote?  Used planetary parallax to argue for heliocentric (Sun-centered) solar system  Measured relative distances of planets from the Sun  Surmised the vast distances to stars

23 Lesson review (cont’d)  How did Tycho Brahe contribute to our understanding of space?  Invented new instruments  Observed and accurately recorded the locations of the planets over time  Had a wacky theory of a geo-heliocentric solar system

24 Lesson review (cont’d)  What are Kepler’s three laws? 1.Planets move in elliptical orbits around the sun 2.The closer to the Sun, the faster they move 3.The larger orbit requires longer time to complete  What did Galileo do?  Telescope observations led to the downfall of Aristotle’s geocentric model  Confirmed vast distances to stars  One of the first to study gravity

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