Chapter 18 Studying Space Chap 18, Sect 1 (Astronomy: The Original Science) Objectives: Describe two early ideas of the structure of the universe. Describe the contributions of Brahe, Kepler, Galileo, Newton, and Hubble to modern astronomy.

The guys with their eyes on the skies History of Astronomy The guys with their eyes on the skies

Claudius Ptolemy AD 140 like the Greeks (Aristotle) he thought Earth was at the center of the system of planets Geocentric Model accepted for over 1,500 years (“what the church says, goes!”)

Geocentric versus Heliocentric Ptolemy's Geocentric Universe Copernicus's Heliocentric Universe Geocentric versus Heliocentric

Nicolaus Copernicus 1500's (died in 1543) Put Sun in the center of our universe Heliocentric Model Insisted Earth rotated...stars chasing across sky was an illusion caused by rotation Afraid of Church revenge he published his theory on his death bed

Tycho Brahe late 1500's Favored geocentric theory (sun & moon revolve around earth) BUT thought other planets revolve around sun His team observed and recorded data, data, data for more than 20 years His data was the basis for later discoveries

Johannes Kepler 1600's One of Brahe’s assistants proved that orbits were NOT perfect circles: they are ellipses

Galileo Galilei Early 1600's Changed lenses in telescope to mirrors Using the telescope he proved the heliocentric model with the following discoveries: 4 moons revolving around Jupiter phases of Venus craters on the Moon Sunspots on Sun Proved these were not wandering stars but physical bodies like Earth

Summary of the Universe in Galileo’s Eyes

Heliocentric Theory Prevails Since Galileo’s theory clashed with the religious views of the time, he underwent many trials and tribulations, eventually being sentenced to house arrest for his remaining years. But his view has withstood the test of time. Today we talk about our solar system, not our Earth system

Sir Isaac Newton 1665 explained why the planets stay moving around the sun: inertia and gravity 1st law: inertia -a body will continue in a straight line unless acted on by a force. Gravity keeps the moving planets in orbit around Sun

Newton Brainpop