Cosmogony: model of our place in the

Universe

Celestial Mechanics

Celestial MechanicsDefinition:

is the branch of astronomy

that deals with the motions of

celestial objects.

Most of the reading you will be receiving will come from this website.

http://csep10.phys.utk.edu/astr161/lect/index.html

Ancient to Modern Astronomy

Wandering Stars

Website with Wandering Stars and Retrograde motion animation:• http://www.keplersdiscovery.com/Intro.html

1. Imaginary sphere around the Earth in which stars in space appear – It is not physical as the ancients believed!

2. Represents only the stars we can see with our eyes. And the are fixed (So no, planets, exoplanets, pulsars, other stars we can’t see, etc…)

3. Earth centered

Celestial Sphere – A model

• Earth centered• 55 concentric crystalline

spheres• Buffering spheres in between• Attached to one main sphere -

Controlled by the Prime Mover• Each sphere rotated at a

different rate• Orbits were in

Uniform circular motion

Aristotle’s Universe

Beliefs of Aristotle and Ptolemy

1. All motion in the heavens is uniform circular motion.

2. The objects in the heavens are made from perfect material, and cannot change their intrinsic properties (e.g., their brightness).

3. The Earth is at the center of the Universe.

Apparent Motion of Planets on the Celestial Sphere

Reading and Applet:• http://

csep10.phys.utk.edu/astr161/lect/retrograde/retrograde.html

Observation Issues

Starry Night Pro Simulationhttp://www.youtube.com/watch?v=cSU5VwIQTNI&feature=related

1. Retrograde Motion2. Varying brightness of the planets

Retrograde Motion

http://www.mhhe.com/physsci/astronomy/applets/Retro/frame.html

Handout: Retrograde motion (this handout is not available as digital copy. Please see Mrs. Carter for this handout)

Another good retrograde motion simulator: http://astro.unl.edu/classaction/loader.html?filename=animations/renaissance/retrograde.swf&movieid=retrograde&width=700&height=600&version=6.0.0

Geocentric Models: Aristotle and Ptolemy

Aristotle: Epicycle Ptolemy: Epicycle upon Epicycles

http://csep10.phys.utk.edu/astr161/lect/retrograde/aristotle.html

http://www.polaris.iastate.edu/EveningStar/Unit2/unit2_sub1.htm

Ptolemy’s model of the orbit of Mars

http://astro.unl.edu/classaction/loader.html?filename=animations/renaissance/marsorbit.swf&movieid=marsorbit&width=825&height=550&version=6.0.0

Motions of Mercury and VenusObservations• Mercury and Venus were

always close to the SunConclusions• The Spheres of Mercury,

Venus and the Sun must be connected.

SUNRISE

Development of Modern Astronomy

Copernicus Kepler Brahe Galileo Newton Einstein

Ancient Astronomy

From Ancient to Modern (Up to Newton)http://www.youtube.com/watch?v=fMepqsms-bk Another video The Universe: Aristotle and Ptolemy Videohttp://www.youtube.com/watch?v=wGZdaOsuodQ&feature=relmfu

The Copernican model: A Sun-Centered Universe (1543)

Copernican Heliocentric Universe

http://www.history.com/shows/the-universe/videos/playlists/beyond-the-big-bang#beyond-the-big-bang-copernicus

New views of the heavens• Sun Centered• Stars do NOT revolve around the Earth• Earth rotates in 24 hours

But…Planets still have perfectly circular orbits and EPICYCLES ARE STILL NEEDED

Retrograde motion and the varying brightness of planets in the Heliocentric Model:http://csep10.phys.utk.edu/astr161/lect/retrograde/copernican.html

Copernicus determines Mars is beyond our orbit

What time is it in this picture?Link to me:• Sun rise – 6:20 am• Sun set – 5:55 pmLength of Day ~ 11.5 hoursWhen is the middle of the night?

Aristotle's Common Sense

Let’s see how much common sense you have:1. Why don’t objects fly off the Earth as the Earth

spins?2. Why don’t we leave behind the birds, airplanes

and satellites that are in the air as we orbit around the sun?

3. Why don’t we notice an apparent shift in position of the stars as we move around the sun?

TRY THIS1. Close one eye2. Line your index finger up with this

rectangle3. Now switch eyes4. Is your finger still lined up with the

rectangle.5. Switch back and forth between eyes.6. Observe the apparent change in position

of your finger.How does changing the distance your finger is from your eye affect the apparent shift in your

fingers position?

Basic Concept Comparison of Large and Small Angles

Stellar Parallax simulation:http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::800::600::/sites/dl/free/007299181x/78778/Parallax_Nav.swf::Stellar%20Parallax%20Interactive

Parallax

Observed Parallax

Aristarchus of Samos (310BC - 230BC)

Link to the image to learn more about Aristarchus of Samos

and his theory behind why the moon orbited the earth and the earth orbited the Sun.

Tycho Brahe (1546 - 1601)

Danish AstronomerInstruments

These instruments were able to measure parallax

Observations of Tycho Brahe

Reading:http://csep10.phys.utk.edu/astr161/lect/history/brahe.html

Precise observations of Mars’s position

NO OBSERVED PARALLAX – MUST NOT BE CLOSE BY!

(This was something that changed!)

Could not measure parallax for the stars!

Supernova 1572

Tychonic Geo-Heliocentric Model

Characteristics• The Moon and Sun

orbited the Earth

• The other planets orbited the Sun

Link to animationhttp://www.keplersdiscovery.com/Hypotheses.html

Drama Time

It’s been said that maybe Kepler killed Brahe. Use the internet to research Johannes Kepler and Tycho Brahe to see what you can find about this rumor. Why hasn’t Hollywood made this movie yet!! Total Drama.

All orbits are slightly eccentric

All Planet Orbits

The Earth is not always the same distance from the Sun

Kepler’s 3 Laws of Planetary Motion

LAW 1: ALL PLANETS ORBITS

ARE ELLIPSES

Reading: http://csep10.phys.utk.edu/astr161/lect/history/kepler.htmlApplethttp://solarsystem.colorado.edu/home/highRes.html

Ellipses

One focus is the sunAphelion – furthest point from the sunPerihelion – nearest point to the sunMajor axis – long axisMinor axis – short axis

http://www.keplersdiscovery.com/Elipse.html

Eccentricities

Eccentricities: Bound & Unbound Orbits

Describe how e changes as the focal distances axis increases.

Describe how e changes as the focal distance decreases.

Calculate the eccentricity of a• Line• Circle

Planet Eccentricities

Equal Areas in equal Times

Kepler’s Second Law of Planetary motion

Kepler's Laws Animations

Link with excellent animations:http://

www.keplersdiscovery.com/AreaTime.html Handout: Kepler's 2nd and 3rd Laws

Review:http://schools.wikia.com/wiki/Newton's_Law_of_Universal_Gravitation#Kepler.27s_First_Law:_on_Orbits

Kepler’s 3rd Law of Planetary Motion

Distances in the Solar System

The Astronomical Unit

Read this article about the AU• http://www.iau.org/public/measuring/

The IAU and astronomical units

Using the AU

Calculating distances to the planets in Astronomical Units

Galileo and the telescopeReading

http://csep10.phys.utk.edu/astr161/lect/history/galileo.htmlhttp://csep10.phys.utk.edu/astr161/lect/history/aristotle_dynamics.html

Web link to Galileo Videos 1. http://

www.history.com/shows/the-universe/videos/playlists/beyond-the-big-bang#beyond-the-big-bang-galileo-galilei

Galileo’s idea of Inertia

1. Inertia: tendency of an object to resist changes in its velocity

2. Velocity is the change in an objects motion (either speed or direction)

Galileo’s idea on Falling Objects

Galileo’s Experiment Reenactment• replace

Galileo’s Experiment on the Moonhttp://www.youtube.com/watch?v=L55jImEhNZ0

Galileo's Observations

Galileo used a telescope to make observations of objects that were too far or dim to see with the unaided eye.

One of the Greatest Religious Debates in History

Galileo and the Church1. http://

www.youtube.com/watch?v=NAra0BVjJp4&feature=related 2. http://

www.youtube.com/watch?v=P3X_OZq7f70&feature=relmfu3. http://

www.youtube.com/watch?v=RsqHCnLMz_A&feature=relmfu 4. http://

www.youtube.com/watch?v=ebZxMjvAu8Y&feature=relmfu

These observations include:http://www.bbc.co.uk/science/space/solarsystem/scientists/galileo_galilei

An imperfect Moon

Moon through a Telescope like Galileo’s

http://www.youtube.com/watch?v=8bPUvsgCEnU

Moon Dance Videohttp://www.astro.washington.edu/IYA/lunar_librations.html

Galileo's ObservationsPhases of Venus

Phases of Venus

According to the Geocentric Modelhttp://astro.unl.edu/classaction/loader.html?filename=animations/renaissance/ptolemaic.swf&movieid=ptolemaic&width=900&height=660&version=6.0.0

According to the Heliocentric modelhttp://astro.unl.edu/classaction/loader.html?filename=animations/renaissance/venusphases.swf&movieid=venusphases&width=870&height=600&version=6.0.0

Galileo's Observations

Moons around Jupiterhttp://www.youtube.com/watch?v=SsWMaAF0kmU

Galileo’s Observations

Ears on Saturn(it’s rings)

http://www.redorbit.com/news/video/space_2/2585749/are_saturns_rings_disappearing/

Galileo’s Observations

Stars in the Milky Way

FUN FRIDAY

Carl Sagan on the history of Astronomyhttp://www.youtube.com/watch?v=IEhDkKfkWoI&feature=fvsr

Carl Sagan: COSMOS