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

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

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

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.

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.

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

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

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

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

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

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

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