ANCIENT ASTRONOMY

ASTRONOMY Astronomy is the oldest science. It is about 70, ,000 years old. The origin of the oldest artifacts is Africa. Archeoastronomy is a science that studies artifacts relating to astronomy (Page 2- Vocab). Scientists must infer what ancient man knew about astronomy by studying ancient artifacts and structures left behind Difficult to exactly know how much ancient man knew about astronomy because no written records were left behind. Worldwide there are man examples of ancient astronomy Page 8

Why Did Ancient Man Study The Sky? Survival Time of Day Time of Year (Seasons) Direction (celestial compass) Recreation Page 8

Stonehenge Alignments with locations of sunset, sunrise, moonset and moonrise at summer and winter solstices Probably used as calendar. Summer solstice Heelstone Constructed: 3000 – 1800 B.C.

Other Examples All Over the World Big Horn Medicine Wheel (Wyoming)

Other Examples All Over the World (2) Caracol (Maya culture, approx. A.D. 1000)

Some believe that notches carved on antler bone by the Cro-Magnon people of Europe some 25,000 years ago depict the changes in the phases of the Moon - a rudimentary lunar calendar. A 77,000 year old piece of hematite from South Africa inscribed with geometrical designs - the earliest known astronomy artifact - precedes that. Page 9

The Aztecs were highly developed and used their art to create a calendar that was very accurate to the actual one we have today. Instead of numbers, however, they used special symbols and glyphs. The Aztec Calendar Page 9

Built their buildings and roads to align with certain stars as where they would rise and set each night

Chinese Considered one of the best sources of ancient astronomical data. The Chinese recorded detailed astronomical observations since 3000 B.C. Page 9

Ancient Greeks Used mathematical models to learn and understand the Universe Go to student powerpoint Thales of Miletus ( BC) Measured apparent diameter of Sun accurately. Page 9

Examples of Greek Mathematical Models Pythagoras ( BC) Earth is Sphere: Ships over horizon, positions of stars and poles change in relation to Earth if move N or S Aristarchus of Samos ( BC) Worked in Alexandria. Info that does survive is his On the Sizes and Distances of the Sun and the Moon. When the Moon is at dichotomy (half-phase), the angle Earth-Moon- Sun is 90°. The angle Moon-Earth-Sun will give the shape of the triangle formed by the three bodies

Eratosthenes (~ 200 B.C.): Calculation of the Earth’s radius Angular distance between Syene and Alexandria: ~ 7 0 Linear distance between Syene and Alexandria: ~ 5,000 stadia  Earth Radius ~ 40,000 stadia (probably ~ 14 % too large) – better than any previous radius estimate. Page 9

Eratosthenes’s Experiment (SLIDESHOW MODE ONLY)

Library of Alexandria Page 9

Library of Alexandria Built in 300 B.C. Major focal point for gaining knowledge Stands for 700 years then was burned to the ground by religious extremists Hypathia, woman librarian was thought to be teaching black magic there Library was burned down and Hypathia was tortured and killed by angry mob One of the greatest losses of human history

Islamic Influence Created the “House of Wisdom”, a library in Baghdad, like that in Alexandra where all faiths could study. The early Greek used the names of many stars and constellations according to their Arabic names Page 9

Nazca Lines Located in the Atacama Desert in Chile- Has not received rain in 400 years

Transition From Ancient To Modern Astronomy Ancient man used the sky to help him survive. He studied and interpreted the motions and positions of various celestial objects(Information). In 600 B.C. Greek philosophers and mathematicians wanted to answer questions. Such as why does the sun rise in the East? Etc……………………………………….. Page 10

Transition From Ancient To Modern Astronomy Men like Plato, Hipparchus, Eratosthenes, and Aristotle began to develop conceptual and mathematical models to explained the motions and apparent motions of celestial objects. Physical models were built later to better understand the structure of the universe and motions of celestial objects. Page 10

Ancient Greek Astronomers (1) Unfortunately, there are no written documents about the significance of stone and bronze age monuments. First preserved written documents about ancient astronomy are from ancient Greek philosophy. Greeks tried to understand the motions of the sky and describe them Page 10

Aristotle BC Father of the Geocentric model of the universe Geocentric model = Earth Centered Explained structure of the “heavens” and motions of celestial objects

Ancient Greek Astronomers (2) Models were generally wrong because they were based on wrong “first principles”, believed to be “obvious” and not questioned: 1.Geocentric Universe: Earth at the Center of the Universe. 2.“Perfect Heavens”: Motions of all celestial bodies described by motions involving objects of “perfect” shape, i.e., spheres or circles.

Ancient Greek Astronomers (3) Eudoxus (409 – 356 B.C.): Model of 27 nested spheres Aristotle (384 – 322 B.C.), major authority of philosophy until the late middle ages: Universe can be divided in 2 parts: 1. Imperfect, changeable Earth, He expanded Eudoxus’ Model to use 55 spheres. 2. Perfect Heavens (described by spheres)

Geocentric Model According to the Greeks

Geocentric Model What motions can the Geocentric model accurately explain? Sun…YES Stars…YES Moon…YES Planets…NO!!!!!!

Retrograde Motion The apparent backward movement of a planet. NOT real motion, only observed motion What accounts for retrograde motion? Why did they see backward movements of planets? Why to you think planet Mars was studied the most?

Retrograde Motion What accounts for retrograde motion? Why did they see backward movements of planets? THE PLANETS ARE REVOLVING AROUND THE SUN AT DIFFERENT VELOCITIES FURTHER PLANETS MOVE SLOWER RETROGRADE EXPLANATION

Geocentric Model (600 BC AD) Why did the Geocentric model last for so long even though it was wrong? The Church Comfortable Lack of Technology to disprove Geocentric model No other good theories being developed. Why? Bubonic plague