1. Who’s Who in Early Astronomy Part 2
ELIZABETH MEGONIGAL

2. Galileo Galilei (about 1609) (Italian)
Used a telescope to observe celestial bodies. Discovered -4 moons orbiting Jupiter - craters and mountains on the moon, -sunspots on the sun and -phases of Venus Galileo's observations strengthened his belief in Copernicus' theory that Earth and all other planets revolve around the Sun.
SHOW THAT THE PLANETS WERE NOT JUST DOTS OF LIGHT– THEY ARE PHYSICAL BODIES LIKE EARTH!

3. Isaac Newton (1667)
Explained why the planets orbit the sun and why moons orbit planets. He said that the force that keeps all of these objects in their orbits is the same one that hold us on the Earth—GRAVITY! DEVELOPED 3 LAWS OF MOTION THAT DESCRIBE THE MOVEMENT OF OBJECTS IN TERMS OF FORCES

4. NEWTON’S FIRST LAW- LAW OF INTERIA

5. NEWTON’S 2ND LAW OF MOTION

6. NEWTON’S 3RD LAW https://youtu.be/EgqcGrB3re8
FOR EVERY ACTION, THERE IS AN EQUAL AND OPPOSITE REACTION.
FORCE A = - FORCE B

7. MODERN ASTRONOMY
1781- WILLIAM HERSCHEL- used a telescope to study the stars in our galaxy. He found small fuzzy patches in the sky. Herschel didn’t know what these patches were, but he did record their positions in a catalog EDWIN HUBBLE– used photography to discover that some of the patches Herschel had found are actually other galaxies beyond our own. (BEFORE THIS DISCOVERY, SCIENTISTS THOUGHT THAT THE MILKY WAY WAS THE ENTIRE UNIVERSE!) Hubble also discovered that the universe is expanding– distant objects in space are moving farther and farther away from each other.

8. Questions: Is Copernicus's theory completely correct? Why or why not?
What advantage did Galileo have over the astronomers that went before him and how did it help him?
Name two astronomers who favored an Earth-centered universe and two astronomers who favored a sun-centered universe.

9. Answers:
Copernicus proposed that the planets instead revolved around the sun. Although his model wasn't completely correct, it formed a strong foundation for future scientists to build on and improve mankind's understanding of the motion of heavenly bodies. The sun is not the center of the universe.
The telescope had been invented and he used it to study the skies.
Earth-centered: Ptolemy and Brahe
Sun-centered: Copernicus, Kepler, and Galileo