History of AstronomyMotions of the sky

caused by and controlled by gods.

Big Horn Medicine Wheel

Temple at Caracol

Greek Astronomy - 600 BC

Science - “to learn”

Thales - the world is logical/understandable.

Stars are “balls of fire.”

Predicted solar eclipse.

Pythagoreans

Math is the language of music; language of science

Perfect triangle - divine number.

Pythagorean Theorem

Round earth & moon

Classical Greece - 450-300 BC

Socrates (470-399 BC)

Plato (430-350 BC)

Aristotle (384-322 BC)

Alexander the Great

DemocritusAristotle

Helenistic Era:350 BC - 400 AD

Alexandria - intellectual hub of the world.

Aristarchus (310-230 BC) -

earth orbits the sun

Erastosthenes

Circumference of Earth

(276-200 BC)

Ptolemy - Geocentric Universe

127-145 AD

Deferents & Epicycles

Retrograde Motion

Almagest - “Greatest of All Books”

Geocentric Universe

Earth at center Spheres for each planet

(Mercury, Venus, Mars, Jupiter & Saturn); Moon, Sun, Zodiac constellations, stars.

Retrograde Motion

Hipparchus (190-120 BC)

Catalog stars

Calculate lunar month

Precession of equinoxes

Europe - The Dark Ages

• Calendars didn’t work!• Mercury and Venus were different.• Occam’s Razor

The Copernican Revolution

Nicolas Copernicus 1473 - 1543; Poland Canon in church; Calendar reform Heliocentric model “On Revolutions”

Explanations of Retrograde Motion

Ptolemaic CopernicanEpicycles & Deferents Inner Planets move

faster

Tycho Brahe (1546 - 1601) Great naked-eye observer Supernova of 1572 Comet - outside of atmosphere Uraniborg observatory Prague & Kepler

My Tycho

Johannes Kepler (1571 - 1630) Tycho’s assistant - 1600

Determine the orbit of Mars

Astrology

Three Laws of Planetary Motion

1st Law of Planetary Motion

The orbits of planets are ellipses with the sun at one focus.

1. Semi-major axis - Astronomical Unit2. Eccentricity; e = c/a

2nd Law of Planetary Motion

Planets travel faster at perihelion, slower at aphelion; but sweep out equal areas of space in equal amounts of time.

3rd Law of Planetary Motion

The square of a planet’s orbital period is proportional to its semi-major axis cubed.

k = P2/R3

Period is in Earth years Radius is in AU k = 1

P2 = R3

Galileo Galilei (1564 - 1642)

1609 - Telescope1. Venus2. Sun3. Moon4. Jupiter5. Saturn

1610 - Published 1632 “Dialogue

Concerning the Two Chief World Systems”

House Arrest

Telescope; diagrams of planets

Sunspots; Jupiter’s Moons

Isaac Newton (1642 - 1727)

Born Christmas Day Cambridge; closed for

plague Age 23-24; 18 mos.

invented calculus Optics Laws of Motion, Law of

Universal Gravitation Explained Kepler’s Laws “Principia”

Newton’s Laws of MotionFirst Law: Every body continues in a state of rest or in a state of motion in a straight line unless it is compelled to change that state by a force acting on it.

Second Law: When a force F acts on a body of mass m, it produces and acceleration a equal to the force divided by the mass.Thus, a=F/m, or F=ma.

Third Law; To every action there is an equal and opposite reaction.

GravitationEvery particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of the masses of the particles and inversely proportional to the square of the distance between them.