Chapter 3: The Science of Astronomy

• natural part of human behaviour
• we draw conclusions based on our experiences
• progress is made through "trial and error"

• completed in 1550 BC
• famous structure in England, used as an observatory
• Aubrey holes are believed to be an analogue eclipse computer 
• if you stand in the middle : the directions of sunrise and sunset on the solstices is marked, as are the directions of extreme moon rise and set

• 400 - 1200 AD
• lived in central America
• accurately predicted eclipses
• Venus was very important
• marked zenial passages
• Mayan mathematics was a base 20 system
• they invented the concept of "zero"

• 1000 AD
• lived in "four corners" area of SW USA
• built structures to mark solstices and equinoxes

• star maps and sighting circles were drawn on the ground to mark...
• solstice rising points of sun
• helical rising points of stars

• all natural motion is circular
• reason > observation

• physics
• elements: earth, water, air, fire

• measured the circumference of Earth
• the sun is at zenith in the city of Syene at noon on the summer solstice
• at the same time in Alexandria, it is 7° from the zenith

• inferred that Alexandria was 7° of latitude north of Syene.
• the distance b/w the 2 cities is 7/360 times the earth's circumference
• his result of 42 000 km is very close to the right number: 40 000 km

• Almagest: star catalogue, instruments, motions and model of planets/sun/moon
• geocentric model, earth is at the center. sun orbits earth. planets orbit through epicycles. 

his model fit the data, made accurate predictions, but was horribly contrived

• the apparent motion of a planet in the opposite direction to that of other bodies within its system
• ex. over a period of 10 weeks, Mars appears to stop, back up, then go forward again

• Copernican Revolution: shift from geocentric model to heliocentric model
• Heliocentric model, sun is at the center. earth orbits like any other planets. inferior planets are smaller. 
• retrograde motion occurs when we "lap" Mars and the other superior planets

• greatest observer of his day
• charted accurate positions of planets
• observed a nova in 1572

• 1) Each planet's orbit around the Sun is a ellipse, with the Sun at one focus.
• 2) As a planet moves around its orbit, it sweeps out equal areas in equal times.
• 3) The square of a planet's orbital period is proportional to the cube of its average distance from the sun (semi-major axis). p² = a³ 

Greatest theorist of his day. A mystic. There were no heavenly spheres. Forces made the planets move.

• first man to point a telescope at the sky
• wanted to connect physics on earth with the heavens
• saw chadows cast by the mountains on the moon
• observed craters
• the moon had a landscape; it was a place, not a perfect heavenly body
• discovered Jupiter has 4 moons and is the center of its own systems

his observation of the phases of Venus was the final nail in the coffin of the geocentric model. Dialogue Concerning the Two Chief World Systems got him in trouble with the Church

• Copernicus created the heliocentric model
• Brahe provided the data needed to improve this model
• Kepler found a model that fit Brahe's data

• 1. Question
• 2. Hypothesis (a tentative explanation)
• 3. Prediction
• 4. Test
• 5. Result (confirm, reject or modify)

Hypothesis and Result should be the same no matter who conducts the test

• science seeks explanations for observed phenomena that rely solely on natural causes
• science progresses through the creation and testing of models of nature that explain the observations as simply as possible
• Occam's Razor- a scientific model must make testable predictions that could force us to revise or abandon the model

a model which survives repeated testing

masquerades as science, but doesn't follow the scientific rules of evidence

establishes "truths" through belief