1. Chapter 22 Origin of Modern Astronomy
22.1 Early Astronomy
22.2 The Earth-Moon-Sun System
22.3 Earth’s Moon

2. 22.1 Early Astronomy
Astronomy is the science that studies the universe and deals with the properties of objects in space and the laws under which the universe operates.
Early Greeks believed in a Geocentric Model or the thought that the stars and other planets orbit around the Earth

3. 22.1 Early Astronomy
In 230 B.C. a new model was proposed that stated the Earth and Planets revolved around the sun called the Heliocentric Model
This model was established because planets and stars do not move in a way that indicates the Earth is still, This irregular movement is called Retrograde motion

4. 22.1 Early Astronomy
Nicolaus Copernicus- Concluded the Earth was a planet and that we are in a solar system with the sun at the center
Johannes Kepler- Concluded the planets rotate in an ellipse, and created the Astronomical Unit (AU) Distance from the sun to earth (150 million km)
Galileo Galilei- Used the telescope to observe celestial objects and made advancements in studying behaviors of moving objects
Sir Isaac Newton- The first to formulate and test the law of universal gravitation. He also determined that gravity and inertia are the forces keeping the planets in orbit.

5. 22.1 Early Astronomy
Universal Gravitation- Every body in the universe attracts every other body with a force that is directly proportional to their masses and inversely proportional to the square of the distance between their centers of mass.

6. CH 22.2 Earth-Moon-Sun System
Two main motions of Earth are Rotation and Revolution
Rotation is the turning, or spinning, of a body on its axis
Revolution is the motion of a body, such as a planet or moon, along a path around some point in space
Perihelion- Earth is closest from the sun
Aphelion- Earth is farthest from the sun
The change in tilt of earth is called Precession

7. CH 22.2 Earth-Moon-Sun System
The moon not only goes around the sun with us but it makes one revolution around the earth every month (29.5 days)
Since its revolution is elliptical it distance to earth changes
Perigee is when it’s the closest
Apogee is when it is the farthest

8. CH 22.2 Earth-Moon-Sun System
On a monthly basis, we observe the Phases of the moon as a change in the amount of the moon that appears lit

9. CH 22.2 Earth-Moon-Sun System
During a new-moon or full-moon phase, the moon’s orbit must cross the plane of the ecliptic (Sun’s light) for an eclipse to occur
When the moon moves in a line directly between Earth and the sun it casts a dark shadow on the Earth call a Solar Eclipse
The moon is eclipsed when it moves within Earth’s shadow, producing a Lunar Eclipse

10. 22.3 Earth’s Moon Moon Facts
¼ the diameter of Earth
1/6 Earths gravity
When Galileo first looked at the moon he saw 2 distinctively different types of landscapes
Dark and light areas
Most obvious areas on the moon are Craters, or round depressions
Most are created by the impact of rapidly moving debris
Young craters have Rays or splash marks

11. 22.3 Earth’s Moon
Light colored elevated areas on the moon are called Highlands
Maria (mare-singular), ancient beds of basaltic lava, originated when asteroids punctured the lunar surface, letting magma bleed out
The dust from bombardment from meteorites is call Lunar regolith

12. 22.3 Earths Moon
The most widely accepted model for the origin of the moon is that when the solar system was forming, a body the size of mars impacted earth
A piece of the liquid earth ejected and entered orbit around earth