Chapter 3 with a little help from Chapter 2

(The History of) the Science of Astronomy

# Cycle of the Moon

29 1/2 days to go through the cycle

some calendars based on the lunar cycle

# Cycle of the Sun, as experienced from the Earth

some ancient architecture was set up for the Sun's cycle

Ocmulgee Earth Lodge ner Macon:
door to Earth Lodge
top view of Earth Lodge -- door at ~116 degrees from north, i.e., winter solstice sunrise

Chaco Chanyon Sun Dagger:
winter Solstice (noon) from Navaho website www.lapahie.com
summer Solstice (noon)

knowing time of year was useful for scheduling crop plantings

# Dividing Day or Night into smaller pieces

can determine the time of day from the position of Sun in sky (figure repeat)

constellations drift across sky during night 8pm midnight

Ancient people used the cycles of the Sun, Moon, and constellations
in order to create calendars and determine the time of day or night

# Astronomical Models of the Ancient Greeks

first known use of conceptual astronomical models without divine intervention

Anaximander (610 - 546 BC): Geocentric Universe and Celestial Sphere

Aristotle (384-320 BC): lunar eclipses show that the Earth is round

Eratosthenes (276 - 194 BC): estimates size of Earth

Plato (428 - 348 BC) asserted Sun, Moon, stars move in perfect circles

Eudoxus (400 - 347 BC) solution: simplified diagram b simplified diagram c

refinements:

Apollonius (240 - 190 BC)

Hipparchus (190 - 120 BC)

Ptolemy (100 - 179 AD) worked out the math, predicted positions of
planets in future, published predictions ==> called Ptolemaic model

recording the Greek ideas

# The Copernican Revolution

The Sun-centered (heliocentric) model of Aristarchus (310 - 230 BC) hadn't caught on

Ptolemy's geocentric model and later calculations were used through the middle ages

Nicholas Copernicus (1473 - 1543 AD) again proposed Sun-centered model

did not see angles between stars change

thought that the planets orbited the Sun which orbited the Earth

observed a "new star" in 1572

Kepler's laws of planetary motion: #1, #2, #3

Galileo Galilei (1564 - 1642 AD) argued for a heliocentric model

Objects in motion remain in motion unless affected by a force

Parallax might be too small to see

Observed all phases of Venus, which is possible in heliocentric system
but not in geocentric system

Winning point: Kepler's model predicted planetary motion more accurately

# The Nature of Science

Science makes progress by:

new observations -- Galileo saw Jupiter's moons through telescope

intuition

(idealized) Scientific Method

signs of pseudo-science

scientific theories

# Astrology is not a science

rarely makes specific predictions

predictions don't match observations any more often that random chance predicts

no physical correlation between human events and planets and stars

gravitational effects are miniscule

constellations are accidental alignments of stars at various distances