1. FORMATION OF THE SOLAR SYSTEM What Do We Know So Far?

2. COMING UP WITH A THEORY Any theory on the formation of the solar system must provide a reasonable scientific explanation for the similarities and differences in the physical and orbital properties of the planets.

3. ORBITAL PROPERTIES - SIMILARITIES Planets are all spheres Planets all spin counterclockwise (EXCEPT Venus – tilted by impact) Planets all orbit the sun counterclockwise Planets all orbit the sun in nearly the same plane of orbit (disk-shape) Planets all orbit the sun in nearly circular orbits

4. ORBITAL PROPERTIES - DIFFERENCES Axial tilts are random

5. PHYSICAL PROPERTIES Inner planets are small, rocky bodies, with very little to no hydrogen or helium gas. Outer planets are all mostly made of hydrogen and helium gas, and probably have small, rocky cores.

6. PHASES OF THE MOON Moon phases are NOT caused by Earth’s shadow on the moon (that would be an eclipse); Only one-half of the Moon is sunlit (like Earth); Moon orbits Earth every 29.5 days; As the Moon orbits, we see varying portions of the sunlit surface of the moon. https://www.youtube.com/watch?v=Jip3B bZBpsM (Phases of the Moon, Veritasium) https://www.youtube.com/watch?v=Jip3B bZBpsM