lecture 1 history of astronomy tmw

8/10/2019 Lecture 1 History of Astronomy Tmw

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How did the ancients describe

the place of the Earth?

How did Copernicus change theplace of the Earth?

Why was Galileo condemned by

the Inquisition?How did Copernican astronomers

solve the puzzle of planetarymotion?


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The study of the astronomical siteswhich have left us withno written recordsor names of the people who set up the

ruins that we study today.

It is understanding how these sites were used, and the

determination of what these ancients knew by studying the

geometry and alignments of the sites.

Archaeoastromy


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Stonehenge, Salisbury

Plain, England

Pyramids,

Gizeh near Cairo,

Egypt


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Nabta


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Stonehenge


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Nazca Lines in Peru


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Ancient Chinese Depiction of the

Celestial Sphere

Places near the

North Pole were

assigned to

nobility, with lesser

beings relegated to

lower latitudes.

This image dates

from the T'ang

Dynasty (600-800a.d.) (The Granger

Collection)


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Ancient Building in India

This is Konarak, a temple (c. 1240 a.d.) located on the Bay

of Bengal, south of Calcutta. It is dedicated to Surya, the

Hindu sun god, and is constructed with astronomicalalignments. (J. M. Malville).


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The Venus Tables in the Dresden

Codex (Maya)

These tables show

that the Mayans

attached particular

significance to the

planet Venus.

(Historical Pictures

Service)


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The Caracol Tower at Chiche

Itz

This is one of the most significant of the many astronomically

oriented structures in Mesoamerica. (J. A. Eddy)

P I di Sk M


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Pawnee Indian Sky Map

This chart, embossed on hide, appears to depict constellations

of the Northern Hemisphere skies. (From Von DelChamberlain 1982, When Stars Came Down to Earth:

Cosmology of the Skidi Pawnee Indians of North America

[Ballena Press: Los Altos, Calif.] Skidi Pawnee chart of the

heavens, Field Museum of Natural History, photograph byVon Del Chamberlain)


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North American Native

Petroglyphs

This Anasazi

drawing on a

ledge in Chaco

Canyon, NewMexico, is

thought to

depict the great

supernova of

1054 a.d. (J. A.

Eddy)


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Sun Dagger

On FajadaButte in Chaco

Canyon is this

spiral pattern,

which isbisected by a

sliver of light

at the time of

the summer

solstice.

(National Park

Service)


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The Bighorn Medicine Wheel

This prominent and well-studied North American Indian

medicine wheel is located in the Bighorn Mountains of

Wyoming. (U.S. Forest Service, provided by J. A. Eddy)


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Greek Philosophy - Rational Thought, Observation,Explanation, Hypothesis testing

Thales

The Universe is knowable, understandable

Pythagoras

Nature governed by geometry or mathematical

relations

Plato

Heavens perfect, perfect form (sphere), principleof uniform circular motion

AristotleHeavens perfect, Geocentric universe, earthsphere, immobile

Aristarchus

Earth rotated on its axis and revolved around the

sun

Historical Development


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By Ptolemys time

Earth at centre of the universe andheavens move in uniform circular motion

Observed motion does not fit theory e.g.retrograde motion of planets

Ptolemy followed a geocentric modeland developed the most sophisticatedmodel of small circles (epicycles) to

demonstrate star and planetarymotions


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The Copernican Revolution

Heliocentric universe, uniform circular

motion

Explains retrograde motion of the planets

Small variation of motion of sun, earth,

moon that he could not explain


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GalileoA new way of knowing

about the world

What Galileo saw

Moon not perfect

Milky way made up of lots of stars Moons circling around Jupiter

Sunspots on the sun and it moves

Venus goes thorough phases like moon


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Arguments from observation

Observation: Moon not perfect, it has mountains

and valleys.

Argument against Ptolemaic model

Heavens not perfect, it is imperfect like Earth

Observation: Sunspots on the sun and it moves

Argument against Ptolemaic model

The sun is not perfect, sun rotates on its axis


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Arguments from Observation

Observation: Moons moving around Jupiter

Argument for Ptolemaic model

Earth could not move, otherwise moon leftbehind.

Argument for Copernican model

Jupiter moved yet kept its moons, so Earth couldmove and keep its moon.

Jupiters moon revolve around Jupiter, so therecould be other centers of motion.


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Argument from observation

Observation: Venus goesthorough phases like the moon

Argument for Copernicanmodel

In the Ptolemaic model, Venus

moves around an epicyclecentered on a line betweenEarth and the Sun. Venuswould always be seen as acrescent.

Since Venus goes throughphases, then it must revolvearound the sun.


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Tycho Brahe

Could not measure parallax for the stars

earth had to be stationary

Geocentric universe

Lots of observational data


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Kepler

Heliocentric universe

Eliptical path

Threee laws of planetary motion


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Ptolemy

Greek Cosmos

Kepler


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Size of Earth

Eratosthenes Altitude of sun at noon on Jun21

At zenith in Syene

7 south in Alexandria

Distance between cities 5000 stadia

5000 stadia____ = 7

Circumference of Earth 360

Circumstance of Earth = 5000 x 360

7

= 250,000 stadia

(about 40 000 km)

lecture 1 history of astronomy tmw

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