Genesis: In the beginning God created the Genesis: In the beginning God created the heavens and the earth. And the earth was waste heavens and the earth. And the earth was waste and void; and darkness was upon the face of the and void; and darkness was upon the face of the deep: …deep: …

Hesiod: In the beginning there was only Hesiod: In the beginning there was only “chaos” [the infinite emptiness]. Then out of “chaos” [the infinite emptiness]. Then out of the void appeared Earth (Gaia) and Eros (god of the void appeared Earth (Gaia) and Eros (god of love or desire). Out of the Void or Chaos came love or desire). Out of the Void or Chaos came Darkness (Erebus) and Night (Nyx). Then Darkness (Erebus) and Night (Nyx). Then Erebus slept with Night, who gave birth to Erebus slept with Night, who gave birth to Ether, the heavenly light. Earth produced the Ether, the heavenly light. Earth produced the Sky (Uranus [Uranos]) to cover herself., ...Sky (Uranus [Uranos]) to cover herself., ...

Edda: In the beginning there was no earth or Edda: In the beginning there was no earth or heaven, no sand nor sea nor cooling waves. heaven, no sand nor sea nor cooling waves. There was only Ginnungagap, a great void. In There was only Ginnungagap, a great void. In the north there was Nilfheim, and from Nilfheim’s the north there was Nilfheim, and from Nilfheim’s spring flowed eleven rivers, known as Elivagar. spring flowed eleven rivers, known as Elivagar. As the rivers flowed south, they cooled and As the rivers flowed south, they cooled and hardened into ice. ...hardened into ice. ...

The world at first was endless space in which existed The world at first was endless space in which existed only the Creator, Taiowa. This world had no time, no only the Creator, Taiowa. This world had no time, no shape, and no life, except in the mind of the Creator. shape, and no life, except in the mind of the Creator. Eventually the infinite creator created the finite in Eventually the infinite creator created the finite in Sotuknang, whom he called his nephew and whom he Sotuknang, whom he called his nephew and whom he created as his agent to establish nine universes. …created as his agent to establish nine universes. …

In the beginning there was an egg and nothing else. The egg In the beginning there was an egg and nothing else. The egg was the universe but there were no heavens and no earth, just was the universe but there were no heavens and no earth, just darkness. From the darkness, the first creature was born. His darkness. From the darkness, the first creature was born. His name was Pangu and he slept in the darkness for many name was Pangu and he slept in the darkness for many thousands of years. thousands of years.

Over these year he grew and grew until eventually he was a Over these year he grew and grew until eventually he was a giant and was so big that he awoke and broke the egg. All of giant and was so big that he awoke and broke the egg. All of the light parts flew up and became the sky and all of the heavy the light parts flew up and became the sky and all of the heavy parts sank and became the earth. Pangu was frightened that parts sank and became the earth. Pangu was frightened that they would connect so he pushed them apart ... they would connect so he pushed them apart ...

• AnthropomorphismAnthropomorphism• Action of a supreme craftsmanAction of a supreme craftsman• Generation from a seedling/eggGeneration from a seedling/egg• Imposition of order over “chaos”Imposition of order over “chaos”• Life cycle dominates over Life cycle dominates over

eternal/unchanging: there is a eternal/unchanging: there is a beginningbeginning

• Hybrid schemes: act of creation, but Hybrid schemes: act of creation, but supreme being/chaos existed foreversupreme being/chaos existed forever

• AnthropocentrismAnthropocentrism

Earliest Known:Earliest Known:• 27,000 year old Ukraine artifact

StonehengeStonehenge, on the Salisbury Plain in , on the Salisbury Plain in southern England, was built in stages from southern England, was built in stages from about 2800 BC to about 1075 BC to about 2800 BC to about 1075 BC to observe the sun and the moon, and thus observe the sun and the moon, and thus bring regularity to the builder's calendar.bring regularity to the builder's calendar.

Big Horn Medicine Wheel, Big Horn Medicine Wheel, an arrangement of rocks an arrangement of rocks resembling a 28-spoke wheel in the Big Horn Mountains resembling a 28-spoke wheel in the Big Horn Mountains of Wyoming, was used as a calendar by the Plains of Wyoming, was used as a calendar by the Plains Indians from about 1500-1700 A.D. for planting cropsIndians from about 1500-1700 A.D. for planting crops

The The Caracol Temple Caracol Temple on the Yucatan on the Yucatan peninsula is a 1000-year-old peninsula is a 1000-year-old astronomical observatoryastronomical observatory.

•Worship of Venus: “Quetzalcoatl”•Upper 2/3 destroyed

Anaxagoras – Around the 5th century BCE– gave the correct explanation

for the phases of the moon, – explained solar and lunar

eclipses, – and realized that the moon

was illuminated by the sun.

Plato (478-347 BC) argued that the reality we see is only a distorted shadow of the perfect ideal form. Further, he taught that the most perfect form was the circle.

Aristotle (384-322 BC) suggested two reasons to believe the Earth was round. First, when a ship came over the horizon, the mast was initially visible, then the deck, and then the entire ship. Second, he observed that the Earth's shadow on the moon during a solar eclipse was curved. Only an Earth which was curved could produce this. He also proposed a geocentric (Earth-centered) solar system.

Eudoxus

~ 400 BCE– Student of Plato– tried to account for

the motion of the stars and planets

– realized that there were 7 'wanderers' (5 planets, the sun and moon) that moved relative to the stars

Eudoxus

– believed that Earth was motionless, at the center of the universe, and surrounded by transparent, concentric, crystalline spheres. All the fixed stars were on the outermost shell, and the planets occupied the inner spheres.

– Created Nested Sphere Theory

– No parralax of stars

June

December

March

A perspective effect: If the Earth moved, constellations should

appear distorted at different times of the year.

Smaller separationEarth at Center

June

December

March

Smaller and shorter

Normal

Earth at Center

June

December If stars were at different distances, they should appear to change East-

West order

Order flipped

Crystal Spheres

Aristarchus (c. 200 BC) Aristarchus (c. 200 BC) proposed a theory that the proposed a theory that the Earth rotated on its axis and orbited about the sun.Earth rotated on its axis and orbited about the sun.

• Used the Used the Method of Lunar DichotomyMethod of Lunar Dichotomy to calculate to calculate the relative distance of the Earth to the Moon the relative distance of the Earth to the Moon compared to the relative distance from the Earth to compared to the relative distance from the Earth to the Sun (1:19)the Sun (1:19)

Eratosthenes (c. 200 BC) devised a method for determining the Earth's circumference to within 5 percent of the currently accepted value, based on different shadow lengths.

• Estimated the Radius of Earth by measuring shadow of vertical stick– Tropic of Cancer on

solstice (no shadow)– Alexandria on solstice

(7° shadow)

• Took distance a camel can go in 50 days, multiplied by (360°/7°)

• Right to 10%!!

(Tropic of Cancer)

North Pole

Hipparchus (c. 150 BC)– Observed that simple circular motion doesn’t work,

predictions fail– spheres centered not on earth, but “near” earth:

“eccentrics”– discovered precession and made the first catalog of

stellar magnitudes.

Planet

Earth

Center

“Equant”

Eccentric

Claudius Ptolemacus (Ptolemy) lived and worked in the Greek settlement of Alexandria (now Egypt).

Ptolemy found that simple spheres were not enough to account for the motions of the planets.

Planets sometimes move faster, sometimes slower, and occasionally appear to slow to a stop and move backward over a period of days or months. This is called retrograde motion.

He accounted for this motion by placing the planets on small circles (epicycles) that moved along larger circles (deferents).

Ptolemy said that planets appear to speed up and slow down because they do not revolve around the earth at a uniform rate.

Instead, he found a point, the equant, which was equal and opposite the earth from the center. If one were to stand at the equant, he would see the planet going around at a uniform rate.

Finally, to explain retrograde motion, Ptolemy decided that the planet traveled along an epicycle, or a sub-orbit. This epicycle travelled along the deferent.

His work was published in 140 AD in what is now known as the Almagest.

Retrograde motion• East-to-west (“backwards”) motion of

planets across the sky• Planets undergo temporary retrograde

motion roughly once per year• Planets get brighter as they regress• MUST be explained by any credible

model

• earliest models• inspired by teachings of Aristotle and Plato (~4th c. BC)• Earth is stationary and lies at the center of the solar system• employed the perfect form ○ THE CIRCLE

- Sun, moon, and all planets are perfect spheres- orbit Earth with uniform motion in perfect concentric circles

(simplest explanation)• could not account for retrograde motion or observed variations in planetary brightness

• employed by astronomers to provide a geometric explanation for retrograde motion

• extra circles

• center of epicycle orbits Earth in a prograde manner

• planet orbits center of epicycle in a prograde manner

• therefore, retrograde motion is not “apparent” – planets really are changing direction as they orbit Earth!

• planet’s distance from Earth also changes, explaining variable brightness

Earth

Moon

Mercury

Venus

Sun

Mars

Jupiter

Saturn

Moon

Earth

SunVenus

Mercury

Mars

Jupiter

Saturn

Equant

Deferents

Epicycles

• Model couldn’t fit observations– put the Earth off center– epicycles upon epicycles– total of more than 100 epicycles – Nevertheless errors in the predicted positions

of planets accumulated to several degrees by ~ 1400 A.D.

King Alfonso: “If the Lord Almighty had King Alfonso: “If the Lord Almighty had consulted me before embarking upon consulted me before embarking upon Creation, I should have recommended Creation, I should have recommended something simpler”something simpler”

Nicolas Copernicus (1473-1543) (Latinized form of Niclas Kopernik) lived and worked in what is now Poland.

Because of his long and abiding relationship with the Christian Church, he hesitated to publish his revolutionary ideas in astronomy, so he distributed an unsigned pamphlet in 1507, which outlined his hypothesis of a heliocentric (sun-centered) solar system.

• Venus makes incredibly complicated loops

• Mars makes complex retrograde motions

• Retrograde motion is only apparent – results from differences in orbital sizes and speeds

• Copernicus found that planets further from the Sun move slower

• In the Copernican System– Retrograde is the simple

(and general) result of viewing one orbiting body from another…

– No Epicycles necessary!

Mars retrograde

Sun

Mercury

Venus

Earth

Mars

Jupiter

Saturn

Moon

• influenced by Greek thinking

- circles

- small epicycles

What about retrograde motion?

Copernicus worked on his book, De Revolutionibus, over a period of many years. It was published in 1543, when he realized he was dying. The final printed copy was handed to him the very day he died.

The Copernican system explained retrograde motion without epicycles, and was elegant and simple compared to the Ptolemaic system.

Not accepted by everyone because the:

1. model gained little in accuracy over the geocentric ideas

2. heliocentricity contradicted all previous thinking and religious teachings

3. placed Earth in a non-central, undistinguished place in the solar system

4. work was published in Latin (which only the scholars could read)

Roman Catholic Church did not take the ideas seriously enough to ban!

- until 1616 (73 years after publication), when Copernicus’s writings were placed on the Index of Prohibited Books