1. The Early Astronomers

2. Astronomy Astronomy: the study of the universe
Earth = 1 of 8 planets & many smaller bodies orbiting the sun
Sun = 1 of billions of stars in our galaxy - Milky Way Galaxy
Milky Way = 1 of billions of galaxies making up the Universe

3. Claudius Ptolemy Geocentric Model- (Geo= Earth, Centic=Center)
Earth is at the center of the universe
The sun and planets revolved around Earth
Evidence: All objects seem to fall towards the center of Earth.
Observation of the sun and planets from Earth

4. Geocentric Model
Eventually Proven Incorrect

5. Review Questions
1. List two types of evidence that Ptolemy used to create the geocentric model.
2. What is the main difference between the geocentric and heliocentric models?
3. Kepler discovered that the planets orbit in an ________ around the sun.

6. Nicolas Copernicus Heliocentric Model- (Helio: Sun, Centric: center)
All the spheres revolve about the sun as their mid-point, and therefore the sun is the center of the universe.
Earth is a planet

7. Johannes Kepler
Born
Started working on lenses for magnification
3 Laws of Planetary Motion (we only need the 1st one)
1. every planet orbits in an ellipse around the sun

8. I. The orbits of the planets are ellipses, with the Sun at one focus of the ellipse.

9. Kepler's Third Law AU= 1 astronomical unit.
implies that the period for a planet to orbit the Sun increases rapidly with the radius of its orbit.
Thus, we find that Mercury, the innermost planet, takes only 88 days to orbit the Sun but the outermost planet (Pluto) requires 248 years to do the same.
AU= 1 astronomical unit.
1AU= 150,000,000km from sun to earth.

10. Galileo Galilei
"father of modern observational astronomy",
Galileo di Vincenzo Bonaiuti de' Galilei

11. Discoveries
Invented and used the Telescope. Used the lens that Tycho had invented.
Discovered that planets are round balls.
Galileo Sun-Centered System PBS LearningMedia.mp4

12. Early Telescope like Galilei’s

13. Phases of Venus

14. Galileo Galilei Discovered Moon’s surface is not smooth, He saw
Mountains,
Craters
Plains

15. Galileo Galilei Discovered the sun has “sun Spots” that change
Discovered that the sun rotates also.

16. Sir Isaac Newton
Newton was the first to formulate and test the law of universal gravitation.
He believed that everybody in the universe attracts every other body with a force between their centers of mass.

17. Gravity…
Newton proved that without the influence of gravity, planets would move in a straight line out into space.
..\Gravity at Earth's Center Science Classroom Resources PBS Learning Media.mp4