Earth-Sun-Moon System

1-1: Movement in Space The Night Sky Stars, Planets, and the Moon What can we see in the night sky with our naked eye? Stars, Planets, and the Moon Stars - are seen as dots of light, but are really giant balls of gas Planets – orbit around the Sun (star) Moon – Earth’s natural satellite

1-1: Movement in Space - Meteors and Comets Meteors are flashes of light when a meteoroid (small rock) burns up in atmosphere Comets are chunks of dust and ice that orbit a star, they form tails when close to the Sun

1-1: Movement in Space Constellations -Patterns seen in a group of stars -People imagined they saw figures, animals, or objects -Sky is divided up into 88 constellations - Some constellations are named for Greek myths

1-1: Movement in Space Movement in the Sky Movement of objects in the sky depend on the movements of Earth Seasonal Changes Constellations and star patterns change from season to season Ex. Orion visible in winter, not in summer

1-1: Movement in Space Movement in the Sky Planets Appear to move against the background of stars Appear to move through a narrow band in the sky called the zodiac

Models of the Solar System 1-1: Movement in Space Models of the Solar System Geocentric Model Aristotle based model on observations Earth at the center of the universe All planets and stars circle Earth Ptolemy added to model, planets made small circles as they moved in their orbit paths

1-1: Movement in Space Models of the Solar System Heliocentric Model Copernicus proposed that Earth’s rotation and revolution around the Sun explained the movements of stars and planets Brahe and Kepler Used Brahe’s observations to determine the orbit of each planet is an ellipse, not a perfect circle Galileo Discovered moons around Jupiter, showed that not everything travels around Earth

1-2: Earth’s Movement in Space How Earth Moves Rotation Earth spins on its axis Earth rotates from west to east Stars, the moon, the Sun appear to move from east to west in the sky Earth takes 24hr, or a day, to complete 1 rotation

1-2: Earth’s Movement in Space How Earth Moves Revolution Movement of Earth around the Sun Earth follows a path, or orbit Earth’s orbit is an ellipse, but very close to being a circular path Earth takes 365.25 days, or one year, to complete 1 revolution

1-2: Earth’s Movement in Space The Seasons Sunlight hits in different amounts due to Earth’s shape Locations near the equator get direct sunlight, locations near the poles get angled sunlight. This why it is warmer near the equator and colder at the poles

1-2: Earth’s Movement in Space The Seasons cont’d Seasons depend on the tilt of the Earth’s axis Earth’s axis is tilted 23.50 Earth’s tilt creates changes in temperature due to amount of sunlight Earth has seasons because its axis is tilted as it revolves around the Sun.

1-2: Earth’s Movement in Space The Seasons cont’d Day Length Part of Earth tilted toward the sun get more hours of daylight than the part of Earth tilted away from the sun Summer = Longer daylight hours Winter = Shorter daylight hours

1-2: Earth’s Movement in Space The Seasons cont’d Solstices and Equinoxes Solstices When Northern or Southern Hemisphere is tilted toward or away from the Sun December Solstice, June Solstice Equinoxes When hemisphere is tilted toward or away from the Sun

Solstices

Equinoxes

1-2: Earth’s Movement in Space Gravity and Orbits Gravity Force that keeps the Earth in orbit around the Sun Newton’s Law of Universal Gravitation Every object in the universe attracts every other object Strength of force of gravity between 2 objects depends on – Masses of objects Distance between objects

1-2: Earth’s Movement in Space Gravity and Orbits Inertia Inertia keeps the Earth from being pulled into the Sun The tendency of an object to resist a change in motion Newton’s 1st Law = Inertia An object at rest will stay at rest and an object in motion will stay in motion unless acted upon by a force

1-2: Earth’s Movement in Space Gravity and Orbits Orbital Motion Inertia and Force of gravity keep objects in their orbital motion Earth’s gravity pulls the moon toward it The Moon’s inertia keep it in its orbital path Without Earth’s gravity, the Moon would fly off into space in a straight line

The Appearance of the Moon 1-3: Phases and Ellipses The Appearance of the Moon The Two Sides of the Moon Near side – faces Earth Darker areas – maria Lighter areas – highlands Craters Far side – faces away from Earth

1-3: Phases and Ellipses The Appearance of the Moon Motions of the Moon The Moon rotates and revolves The Moon’s rotation period and revolution period are both about 1 month The same side of the moon always faces the Earth From space, half of the moon is always lit from the Sun From Earth, the lit part of the moon visible from Earth changes

1-3: Phases and Ellipses The Appearance of the Moon Phases of the Moon Different shapes of the lit side of the moon visible from Earth New moon Waxing cresent First quarter Waxing gibbous Full moon Waning gibbous Third quarter Waning cresent

1-3: Phases and Ellipses The Appearance of the Moon Eclipses When an object in space comes in between the Sun and a third object it casts a shadow Shadow has 2 parts Umbra – darkest shadow, total eclipse Penumbra – lighter shadow, partial eclipse 2 types of Eclipses Solar Eclipse – moon between Earth and Sun Lunar Eclipse – Earth between Moon and Sun

1-3: Phases and Ellipses The Appearance of the Moon Tides Rise and fall of ocean water that occur about every 12.5 hr The Moon and the Sun Moon’s gravity pulls on the side of Earth facing the moon Pull causes a tidal bulge on one side of the Earth Another tidal bulge forms on the opposite side of the Earth As Earth rotates, the tidal bulge will move creating high and low tides

1-3: Phases and Ellipses Tides cont’d The Moon and the Sun The Sun’s gravity can influence tides as well, just not as much as the Moon The changing positions of the Sun and Moon affect the changing levels of the tides Spring and Neap Tides Spring Tide – most significant difference in low and high tides Neap Tide – least significant difference in low and high tides