History of Astronomy

Early Astronomy Astronomy Is science that the universe Greeks 600 B.C. – A.D. 150 Measured distances to the Sun and Moon

Eratosthenes  Successfully Measured the circumference of the Earth  1.7% Error 2400 Years Ago

Geocentric View  Pre 300 B.C.  Earth is the center of the Univerese  The orbs (Sun, Moon, Mercury, Venus, Mars and Jupiter) orbit the Earth each day  Surrounded by a Hollow Sphere

Heliocentric Aristarchus ( B.C.) Earth and the other planets orbit the sun Dominated Western Thought for over 2000 Years

Ptolemaic System Ptolemy (A.D. 141) Believed in Geocentric Model Observed Retrograde Motion – Planets Move to the East, but periodically they stop and reverse direction Social Bias in Science

Modern Astronomy Renaissance of Science Broke Away from Religious and Philosophical Views Used Natural Laws to explain the motions of the Heavens

Modern Astronomy Nicolas Copernicus Earth is a Planet Sun Centered Planets Orbited the Sun in Complete Circles

Modern Astronomy Tycho Brahe Spent 20 yrs. Measuring the Locations of the Heavenly Bodies Johannes Kepler Assistant to Brahe Discovered 3 Laws of Planetary Motion – Ellipse Determined the Distance from the Sun to Earth is 1AU = 150 Million km

Modern Astronomy Galileo Galilei 1564 – 1642 Major Contribution was the behavior of the Moving Objects Ground Lenses to make telescopes Made Discoveries that supported Heliocentric View Sir Isaac Newton Expanded on Galileo Force Formulated and tested the Law of Universal Gravitation at the age of 23 This is the force that makes planets revolve in a circle