History of Astronomy

1. History of Astronomy • Astronomy is the study of everything in the universe. • astron= “star”; nomos= “law” or “arrangement of” • Oldest Science • Navigation, the North Star doesn’t “move” • Predict seasons, Big Dipper – plant crops • Timekeeping • Keeping track of Time • All of our time-keeping conventions are astronomically based: • The Year is based on the time it takes Earth to orbit the Sun. • The Month is based on the cycle of the Lunar Phases • The Day is based on the time it takes the Earth to rotate once on its axis relative to the Sun. • Astrology, “predict” human behavior

2. Greeks • Pythagoras (570 BC – 495 BC) Believed that Earth was a perfect sphere centered in a celestial sphere, also a spherical shell

3. Greeks • Aristotle – (384 BC – 322 BC) planets move different from stars • Geocentric model - Planets and stars revolve around Earth on spherical “shells”; Earth is the center of universe (Ptolemaic system) • geo = Earth; centric = “center”

4. Geocentric Model

5. Dark Ages/Middle ages500 AD – 1400 AD • Intellectual darkness: the period seems "dark" because of the scarcity of artistic and cultural output,including historical records when compared with both earlier and later times in history.

6. Renaissance1400 - 1700 • Revival of art, literature, and learning • Nicolaus Copernicus (1473 – 1543) Mathematician and astronomer • Identified the concept of the Heliocentric solar system. A system in which the Sun rather than the Earth is the center. Still had fundamental problems with concept though. • helio = “sun”; centric = “center” • Scientific Method of Investigation

7. Heliocentric model

8. Renaissance • Tycho Brahe – (1546 – 1601) known for his accurate and comprehensive astronomical and planetary observations. • Recorded enough data on the motion of stars & planets to within 1 arc minute • Johannes Kepler – (1571 – 1630) Tycho’s assistant • Orbit of planets are ellipses • Unification of astronomy and physics

9. ellipse

10. Renaissance • Galileo Galilei (1564 – 1642) Italian Scientist considered Godfather of modern astronomy. • Turned toy into telescope • Observed/discovered sunspots • Stars not fixed to celestial sphere. • Venus goes through phases similar to Moon showing that both Earth & Venus orbit the Sun. • 4 moons of Jupiter proved that not everything in the sky revolves around the Earth. • His ideas were considered controversial; he was tried and sentenced to house arrest for the rest of his life.

12. 4 moons of Jupiter

13. Basilica di Santa Croce Florence, Italy

14. History of Astronomy response • Draw and explain the Geocentric model. • Draw and explain the Heliocentric model. • Draw and explain an ellipse. • Draw and explain Galileo Galilei’s contributions to astronomy