& the Advent of the Scientific Method

ASTRONOMY

ASTRO DAY 1

ASTRONOMY – SCIENTIFIC* STUDY OF SPACE

Observations and explanations of celestial bodies, universe geography, movement, formation, energy…

Includes cosmology, the study of the origin of and the behavior of the universe.

* Not to be confused with Astrology a pseudoscience that uses celestial positions to predict events on Earth

Ancient Peoples Studied the Skies

Built physical calendars - need to know the time of the year for planting & harvesting

Community cultural centers - pagan celebrations of the solstices

South America

Europe Asia

North America

They Observed, and Inferred

Scientific observatory (Incan) Mythical explanation (Mayan)

Observation 1=Sun, Moon, Stars in Motion

http://vimeo.com/42576356

ASTRONOMY & WESTERN THOUGHT

Observed: stars/moon/sun in motion but no

evident Earth motion

Inferred: geocentric universe-all object revolve in perfect circles around Earth

Why circles?-the perfect geometric shape

No experimentation; Aristotle's reasoned explanation was enough

Aristotle 384-322 BC

‘Wandering’Stars Pose a Challenge

Mars in Gemini December

Mars in Leo July

Planets Move Independent of ConstellationsPlanet= wanderer in Latin

‘Wanderers’ Change Course

Retrograde motion

http://www.davidcolarusso.com/astro/http://www.lasalle.edu/~smithsc/Astronomy/retrograd.html

Planets Appear to move backwards (Retro) and then forward again

What might cause this?

New Observations Dictate a New Hypothesis

Ptolomy creates epicycles- orbits on orbits - to explain retrograde motion

Many tries but can’t make epicycles work (80+!) Still, a lasting hypothesis

http://astro.unl.edu/naap/ssm/animations/ptolemaic.swf

Ptolomy 140 AD

ASTRO DAY2

Need a New Hypothesis

Unable to make epicycles work also

Instead: Proposes the universe is heliocentric (sun centered); orbits are still perfect circles

Waited until old age to publish, and then in Italian, not Latin why?

Copernicus 1473-1543 AD

http://science.larouchepac.com/kepler/newastronomy/part1/copernicus.html

Copernicus -no evidence it just made sense

Its an optical illusion -

• the planets simply move at different speeds

• like passing a slower car on the freeway: it appears to go backwards

Possible Explanation to Retrograde

The Advent Of Empiricism

Used a telescope to generate evidence in support of heliocentric model

1. Discovered Jupiter had moons

2. Phases of Venus make clear Venus orbits the sun

Gailileo Galilei 1564-1642

Venus phases diagram and animation

Data Makes The Difference

Tycho Brahe 1546-1601

Johannes Kepler 1571-1630

Inferred the movement of the planetary orbits & made 3 laws

Couldn‘t make sense of it

35 yrs of detailed data on planet positions

Inherited and analyzed the data

Video summary

Kepler’s 1st Law of Planetary Motion:

‘ovalness’ = eccentricity

http://www.physics.sjsu.edu/tomley/Kepler12.html

The planets orbits are ellipses with the sun at one of two foci

Kepler’s 2nd Law of Planetary Motion

Planet must go faster when closer to sun and slower when farther from sun

Almost worked out gravity!

http://www.physics.sjsu.edu/tomley/Kepler12.htmlhttp://highered.mcgraw-hill.com/sites/0072482621/student_view0/interactives.html#

The planets sweep out equal areas in equal time

Kepler’s 3rd Law of Planetary Motion

p2=d3

p = period in years

d = distance in astronomical units (AU)

1AU = distance between sun and Earth

(150,000,000km)

boojum.as.arizona.edu