EARLY ASTRONOMERS

Aristotle (~ BC) Define the five Elements: Water, Aether (the Heavens, and of course, Earth, Wind & Fire Geocentric Model – Earth is at the center of the solar system Order: Earth, moon, Venus, sun, Mars, Jupiter, Saturn Didn’t explain retrograde motion Change in a planet’s direction caused by the change in position we see the planet as Earth passes it

PTOLEMY

Ptolemy (~150 AD) Said planets move in small circles called epicycles Epicycles moved on a larger circle I.E. Frisbee’s spinning on the rim of a bicycle rim Theory survived until 1500’s

RENAISSANCE: COPERNICUS

COPERNICUS ( ) Polish lawyer Began the take down of geocentric model Heliocentric Model – Sun is at the center of the s.s. Model was proposed 2000 yrs earlier by Aristarchus – but it was rejected Explained how planets closer to sun have smaller orbits and farther planets have larger orbits Retrograde motion then is just the closer planets passing the further out planets.

TYCHO BRAHE

TYCHO BRAHE ( ) Danish Designed & built accurate instruments Measured planetary positions – very meticulous Data became crucial in supporting heliocentric theory and reveal true shape of planetary orbits Saw 1 st (known) supernova in 1572 Saw comet in 1577 & showed it was beyond the moon.

JOHANNES KEPLER

KEPLER ( ) Assistant to Brahe When Brahe died, took all his data With data, able to draw a detailed picture of the orbit of Mars Showed orbit is elliptical in shape Developed 3 laws of planetary motion (We’ll talk about these at a later time!)

GALILEO GALILEI

GALILEO ( ) First to use the telescope to look at the sky Invented by Johannes Lippershey a Dutch spectacle maker Studied the moon and sun Discovered Jupiter’s four largest moons Named the Galiean Satellites Found the phases of Venus Similar to the phases that our moon goes through Convicted of heresy in his 70”s and sentenced to house arrest for rest of life.

Psalm 93:1, Psalm 96:10, and 1 Chronicles 16:30 include text stating that "the world is firmly established, it cannot be moved."

MODERN: SIR ISAAC NEWTON

NEWTON ( ) Some consider to be greatest scientist of all time Worked/discoveries in mathematics, physics, and astronomy Pioneered modern study of motion, optics, and gravity Deduced the Law of Gravity Invented Calculus Developed 3 Laws of Motion Newton in part gave birth to Astrophysics Died of kidney infection, but more likely due to mercury poisoning.

OTHER NOTABLES: Sir William Herschel English 1781 discovered Uranus Islamic Civilization Named bright stars: Betelgeuse, Aldebaran Revolutionized math – Algebra Asian Civilization Recorded unusual celestial events: eclipses, comets, exploding stars Predicted eclipses