The Beginnings of Cosmology

Earth and Space Science

Ancient People

• Sailors—used stars to navigate

• Farmers—used changes in seasons to plant and harvest

Mythology

• Constellations• Same Clusters, different pictures• Celestial Sphere• Ancient Chinese• Greeks• Middle Ages

– Chinese and Muslims still learned/Europe did not

Architecture

• Stonehenge

Temple and ancient calendar that shows positions of the sun and the moon at different times during the year.

Architecture• Chitzen Itza

People at Chichén Itzá can see “the snake,” an apparition made of shadows that descends the stairs at El Castillo during the solar equinoxes each spring and fall. At El Caracol, dubbed “the observatory,” narrow shaftlike windows frame important astronomical events. One such window marks an appearance of Venus at a particular point on the horizon that takes place—like clockwork—once every eight years.

Architecture

• Sun Dagger in Chaco Canyon, NM (calendar)

• At summer solstice, a vertical shaft of light pierces the main spiral exactly at its center. On the winter solstice, two shafts of light perfectly bracket the same spiral. Light shafts strike the center of a smaller spiral nearby on the spring and fall equinoxes.

Architecture• Big Horn Medicine

Wheel (28 Spokes)If you stand or sit at one cairn looking towards another, you will be pointed to certain places on the distant horizon. These points indicate where the Sun rises or sets on summer solstice and where certain important stars rise heliacally, that is, first rise at dawn after being behind the Sun. The dawn stars helped foretell when the Sun ceremonial days would be coming. The area is free of snow only for 2 months -- around the summer solstice.

Geocentric View

• Until 16th century

• Aristotle—4th century B.C.– Planets moved in circles around the earth

• Ptolemy—140 A.D.– 80 circles; very complex

• Aristarchus of Samos—3rd century A.D.– Proposed that planets orbit the sun

Heliocentric View

• Nicholas Copernicus—16th century– Earth spins on its axis and orbits the sun; only the moon

orbits the earth– Earth is round—studied lunar eclipses

• Galileo Galilei—16th century– Popularized Copernicus’s book. It was banned in 1611

by the Catholic Church until the end of the 18th century. He refused to stop teaching the heliocentric view and was placed under house arrest in 1633 for the rest of his life. (1642)

– Invented the modern telescope

Heliocentric View

• Johannes Kepler—1500s– Developed the laws of planetary motion– Worked for Tycho Brahe who compiled data

that led to Kepler’s conclusions.