How to we Observe Getting our Bearings The

How to we Observe? Getting our Bearings

The Moon

The moon is about 5° out of the plane of Earth’s orbit

Brief History of Astronomy And why you should care

What was Astronomy used for? • To tell time • To determine the seasons • Calendars • Navigation • Predict the future (eclipses & rainfall)

Greek Science • Did not rely on supernatural explanations • Used mathematics • Used logic and reasoning • Developed the idea of scientific models

Arabic Science • Much of the Greek knowledge was lost with the burning of the Library at Alexandria • Europe feel into Dark Ages, Baghdad became center • Influence from China, India, and Greece • Continued to develop math and astronomy • When Constantinople fell, scholars headed west, leading to European Renaissance.

Greeks and Planets Aristotelian Model • Geocentric • Concentric crystalline spheres

Retrograde Motion

Greeks and Planets Ptolemaic Model • Still geocentric • Explained Retrograde motion of planets • Used smaller circles called epicycles moving around bigger circles called the deferent • Very successful, used for 1500 years

Epicycle Equant Deferent

Copernican Revolution • Nicholas Copernicus born in Poland, 1473 • Adopted idea from Aristarchus • Heliocentrism – planets orbit the sun • Not really accepted quickly because It didn’t work

Tycho Brahe • Lived 1546 -1601 Tycho Brahe • Noticed Copernicus’s system didn’t work • Set out to collect better data • Once observed a supernova in 1572 • Lost his nose in a sword fight over who was the better mathematician • Had a tame pet elk Tycho Brahe

Johannes Kepler • Lived 1571 -1630 • Used Tycho’s data to find a model of planetary motion Three Laws: • Orbits are ellipses • Equal area in equal time • p 2=k a 3 Johannes Kepler

VS Tycho Brahe Johannes Kepler

Galileo Objections to Copernicus Galileo’s Responses • If Earth were moving, birds, clouds, etc. would fall off as Earth moved • Physics experiments leading to Newton’s first law • Heavens are perfect • Sunspots Imperfection circular orbits • If Earth orbits, should observe parallax • Observed parallax • Moons around Jupiter Not everything orbits Earth

Galileo • Lived 1564 -1642 • Did not invent the telescope, improved it • His championing of the Copernican model and his evidence to support it is why it became accepted