Chapter 1 The Copernican Revolution Lecture Outline Chapter 1 The Copernican Revolution

quiz Show SEM map and view from earth for following phases Full moon Waning gibbous 3rd quarter ½ moon Lunar eclipse Show SEM system with proper distances in proportion

In the news http://www.space.com/27016-galaxy-supercluster-laniakea-milky-way-home.html

9 sept: Chapter 1 The Copernican Revolution

Units of Chapter 1 Preview the chapter…. The Motions of the Planets The Birth of Modern Astronomy The Laws of Planetary Motion Newton’s Laws Summary of Chapter 1

Who is Aristarchus of Samos? 250 BC, the time of the first critical, non-mystical thinkers in Greece Could see the sun was big by the earth’s shadow on the moon Reasoned that the Earth should orbit around the bigger sun This idea was lost for 1600 years as Asia and Europe slipped into mystical thinking

1.1 The Motions of the Planets The Sun, Moon, and stars all have simple movements in the sky, consistent with an Earth-centered system. But the Planets: (Show on Stellarium) Move with respect to fixed stars Change in brightness Change speed Have retrograde motion Are difficult to describe in earth-centered system

1.1 The Motions of the Planets A basic geocentric model, showing an epicycle (used to explain planetary motions)

1.1 The Motions of the Planets Lots of epicycles were needed to accurately track planetary motions, especially retrograde motions. This is Ptolemy's model.

1.1 The Motions of the Planets A heliocentric (Sun-centered) model of the solar system easily describes the observed motions of the planets, without excess complication. So, what is the primary advantage of the heliocentric model?..

*13 sept; 1.2 The Birth of Modern Astronomy Observations of Galileo: The Moon has mountains, valleys, and craters. The Sun has imperfections, and it rotates. Jupiter has moons. Venus has phases. All these were in contradiction to the general belief that the heavens were constant, perfect, and immutable.

1.2 The Birth of Modern Astronomy The phases of Venus are impossible to explain in the Earth-centered model of the solar system.

The birth of modern astronomy https://www.youtube.com/watch?v=zHUWP9zu4W8 Watch until 10:45, modern physics

From this video, know Aristotle Ptolomy Renaissance Copernicus Tycho brahe Kepler Galileo Newton

1.3 The Laws of Planetary Motion Kepler’s laws: 1. Planetary orbits are ellipses, Sun at one focus.

**1.3 The Laws of Planetary Motion Kepler’s laws: 2. Imaginary line connecting Sun and planet sweeps out equal areas in equal times. When an orbiting planet or comet is near the sun, it goes fast, and when it’s far away, it goes slowly.

1.3 The Laws of Planetary Motion Kepler’s laws: 3. Square of period of planet’s orbital motion is proportional to cube of semimajor axis. Compare this to Kepler’s second law. The period of a planet goes up as the radius of the planet increases

Who was Kepler? The greatest astronomer. Born 1571. Worked for Tycho Brahe (“teesho”) Analyzed motion of the planets, worked out laws of planetary motion An interesting 20 min video of this history http://www.youtube.com/watch?v=IBvMhpx8Q0Q plus http://www.youtube.com/watch?v=ShQXRBDBfaA Video is a little dense

1.3 The Laws of Planetary Motion The Dimensions of the solar system The distance from Earth to the Sun is called an astronomical unit. Its actual length may be measured by bouncing a radar signal off Venus and measuring the transit time.

1.4 Newton’s Laws Newton’s laws of motion explain how objects interact with the world and with each other. Newton’s first law: An object at rest will remain at rest, and an object moving in a straight line at constant speed will not change its motion, unless an external force acts on it.

1.4 Newton’s Laws a = F/m Newton’s second law: When a force is exerted on an object, its acceleration is inversely proportional to its mass: a = F/m Newton’s third law: know this one!!!! When object A exerts a force on object B, object B exerts an equal and opposite force on object A.

1.4 Newton’s Laws Gravity On Earth’s surface, the acceleration due to gravity is approximately constant, and directed toward the center of Earth.

1.4 Newton’s Laws Gravity For two objects, the gravitational force is proportional to the product of their masses divided by the square of the distance between them. The closer they are, or the bigger (more massive) they are, the harder they pull on each other.

1.4 Newton’s Laws Gravity The gravitational pull of the Sun keeps the planets moving in their orbits. Compare to a spinning ball on string….

1.4 Newton’s Laws Two or more Massive objects orbit around each other. look at http://phet.colorado.edu/sims/my-solar-system/my-solar-system_en.html and see binary star or double double to see various types of orbit. Set to show double star wobble of sun Speed of orbit depending on elliptical position

1.4 Newton’s Laws Kepler’s laws are a consequence of Newton’s laws.

21 sept. Quiz on chapter 1 The shape of every orbit is Circle b. square c. parabola d. ellipse Which was NOTan observation of Galileo? The Moon has mountains, valleys, and craters. B. The Sun has imperfections, and it rotates. C. Jupiter has moons. D. Venus has moons Which of these people was NOT part of the Copernican revolution Copernicus b. Aristotle c. Kepler d. Newton What is the force that holds all planets, moons, comets, asteroids, galaxies, and stars in their orbits? a. Gravity b. Magnetism c. Jedi d. Mass

Look at variation with time Why change size Moon on sept 27, 9:40pm 18 Sept 2015 Quiz on Stelarium Find your object Any moons? Their period Magnitude, phases Look at variation with time Why change size Moon on sept 27, 9:40pm Turn on equatorial grid Find your zodiac constellation Where was the moon when you were born?

Summary of Chapter 1 First models of solar system were geocentric, but couldn't easily explain retrograde motion. Heliocentric model does. Galileo's observations supported heliocentric model. Kepler found three empirical laws of planetary motion from observations.

The varieties of orbital motion http://phet.colorado.edu/sims/my-solar-system/my-solar-system_en.html Look at the range of possibilities Check: why are only stable orbits present in our solar system & galaxy? Are all orbits stable? Examples….

Summary of Chapter 1, cont. Laws of Newtonian mechanics explained Kepler’s observations. Gravitational force between two masses is proportional to the product of the masses, divided by the square of the distance between them.

Update on New Horizons http://pluto.jhuapl.edu/

Show this tool in google earth

NY Times yesterday

Practice for exam 1 1) In an annular eclipse, A) the Moon is totally blocked by the Earth. B) the Sun is partially blocked by the Earth. C) the Moon appears as a thin, bright ring. D) the Sun appears as a thin, bright ring. E) the Sun is totally blocked by the Moon. 2) The interval from new Moon to first quarter is about a(n) A) month. B) day. C) hour. D) year. E) week. 3) Put these important scientists in proper order of when they lived and worked a. Galileo, b. Copernicus, c. Newton, d. Ptolomy, e. Kepler