Course GoalsCourse Goals

What is Science?What is Science?

What is modern What is modern astronomy?astronomy?

What do we know about What do we know about the Universe?the Universe?

How do we know what How do we know what we know?we know?

Why Study Science?Why Study Science?

Scientific Method:Scientific Method:RigorousRigorous investigation involving investigation involving careful careful observationobservation, the formulation , the formulation of of hypotheseshypotheses, and , and experimentationexperimentation to test those to test those hypotheses. hypotheses.

Science:Science: The application of the The application of the Scientific MethodScientific Method to the to the natural world.natural world.

ScienceScience

Astronomy:Astronomy: The scientific investigation of The scientific investigation of astronomical phenomena.astronomical phenomena.

The Scientific MethodThe Scientific Method

The critical element is The critical element is

Experimental ProofExperimental Proof

Scientific TheoryScientific Theory

It’s It’s justjust a a theory!theory!

Scientific theory is not Scientific theory is not mere conjecture.mere conjecture.

Missing KeysMissing Keys

Sundials to tell the time of Sundials to tell the time of dayday

Telling TimeTelling Time

Predicting the SeasonsPredicting the Seasons

The Power of the GodsThe Power of the Gods

Ancient GreeceAncient Greece

First to create First to create theoretical theoretical models of models of naturenature

A HypothesisA HypothesisThe heavens are The heavens are perfect and perfect and unchanging.unchanging.

~Aristotle~Aristotle

Except…Except…The crystal spheres can’t explain The crystal spheres can’t explain

Retrograde MotionRetrograde Motion

The Ptolemaic ModelThe Ptolemaic Model

Ptolemy is now noticeably Ptolemy is now noticeably inaccurateinaccurate

An Alternative ModelAn Alternative Model

Sun centered model, Sun centered model, 15431543

•Simple retrograde Simple retrograde solutionsolution

•Simple orbital Simple orbital period calculationperiod calculation

•Position Position predictions predictions stillstill inaccurate.inaccurate.

Nicholas CopernicusNicholas Copernicus

New ObservationsNew Observations

Tycho Tycho BraheBrahe

Took 2 decades worth Took 2 decades worth of naked eye planet of naked eye planet observationsobservations

Accuracy to within 1 Accuracy to within 1 minute of arcminute of arc

ABCDABCDWhat was different about Ptolemy’s model versus Aristotle’s?What was different about Ptolemy’s model versus Aristotle’s?

A.A. The spheres were glass, not crystal The spheres were glass, not crystal

B.B. The Sun is at the center, not the Earth. The Sun is at the center, not the Earth.

C.C. He included EPICYCLES He included EPICYCLES

D.D. Some of the crystal spheres went backwards. Some of the crystal spheres went backwards.

Why wasn’t Copericus’s model immediately accepted as truth?Why wasn’t Copericus’s model immediately accepted as truth?

A.A. Don’t be silly, it was a SMASH hit! Don’t be silly, it was a SMASH hit!

B. B. It’sIt’s predictionspredictions were only as accurate as Ptolemy’s but were only as accurate as Ptolemy’s but

no better.no better.

C.C. Copernicus was just not well liked. Copernicus was just not well liked.

D.D. It’s It’s predictionspredictions were MUCH worse than Ptolemy’s. were MUCH worse than Ptolemy’s.

Johannes Johannes KeplerKepler

TheoryTheory

•A student of TychoA student of Tycho

•Studied Tycho’s dataStudied Tycho’s data

•Discovered three Discovered three empirical empirical relationshipsrelationships

•Believed CopernicusBelieved Copernicus

•Suggested that the Suggested that the Sun exerts a force on Sun exerts a force on the planets.the planets.

Kepler’s 1Kepler’s 1sstt Law Law

Orbits are ellipsesOrbits are ellipses

Kepler’s Second LawKepler’s Second Law

Planets move:Planets move:

•Fast at Fast at perihelionperihelion

•Slow at Slow at aphelionaphelion

Perihelion:Perihelion: Point in an orbit closest to the Point in an orbit closest to the Sun.Sun.Aphelion:Aphelion: Point in an orbit furthest from the Point in an orbit furthest from the Sun.Sun.

Equal areas in Equal areas in Equal timesEqual times

Kepler’s Third LawKepler’s Third Law

Orbital Period:Orbital Period:The time required to complete one orbitThe time required to complete one orbit

The harmonic law:The harmonic law: A precise mathematical relationship A precise mathematical relationship between the between the orbitalorbital periodperiod and the semi and the semi major axis.major axis.

PP2 2 = = aa33

The End of Geocentrism The End of Geocentrism … ?… ?

Mountains and SunspotsMountains and Sunspots

Moons of JupiterMoons of Jupiter

Phases of VenusPhases of Venus

The Rise of Modern The Rise of Modern PhysicsPhysics

Isaac NewtonIsaac Newton• Three laws of Three laws of

motionmotion• Universal Universal

GravitationGravitation• The CalculusThe CalculusSimple central principals Simple central principals from which all motion, from which all motion, either on Earth or in the either on Earth or in the heavens, can be derived.heavens, can be derived.