Chapter 23: The Sun-Earth-Moon System Aim: What are Earth’s physical properties?

Physical Properties of Earth Spherical shape Rotates on an axis Rotation of Earth: causes day and night 1rotation= 1 day Magnetic field North and south pole Protects you from harmful solar radiation by trapping charged particles from the Sun

Magnetic axis is different from its rotational axis Magnetic axis-the line joining the north and south poles When you follow a compass you are following the magnetic axis not rotational axis

Aim: What causes the seasons to change?

Orbiting the Sun 1revolution=1year Earth’s orbit is an ellipse Distance from the Earth to the sun changes Earth is closest to the sun in January Earth is farthest from the Sun in July

Earth’s tilted axis causes seasons 2. A Titled Axis Earth’s tilted axis causes seasons The number of daylight hours is greater for the hemisphere that is tilted towards the Sun Winter-hemisphere titled away from the Sun Less sunlight each day Summer-hemisphere titled towards the sun Longer periods of sunlight each day

the Sun’s radiation strikes at a higher angle causing it to be hot Earth’s tilt also causes the Sun’s radiation to hit the Earth at different angles Summer the Sun’s radiation strikes at a higher angle causing it to be hot Winter the hemisphere that is not tilted toward the sun, experiences less radiation

Solstices The day when the Sun reaches its greatest distance north or south of the equator Northern Hemisphere Summer Solstice occurs on June 21 or 22 Longest day of the year hours of sunlight begin to decrease Winter Solstice occurs on December 21 or 22 Shortest day of the year hours of sunlight begin to increase

Southern Hemisphere Winter Solstice is in June Summer Solstice is in December

Equinoxes Occurs when the Sun is directly above the equator Causes fall and spring #of daylight and night time hours are equal Neither the Northern or Southern Hemisphere is tilted toward the Sun

Northern Hemisphere Southern Hemisphere Spring Equinox-March 20 or 21 Fall Equinox-September 22 or 23 Southern Hemisphere Spring Equinox-September Fall Equinox- March

Aim: How does the Moon move around the Earth?

The Moon Rotates on an axis Revolves around the Earth Moons rotation and revolution both take 27.3 days Because of this the same side of the moon always faces Earth Moon’s surface reflects sunlight Half of the moon is lighted, while the other half is dark

The moon’s appearance changes as the Moon revolves around the Earth and you see different portions of its lighted side

Aim: What are the phases of the Moon?

Phases of the Moon Different forms that the moon takes in appearance from Earth Phase depends on position of the moon, Earth and sun New moon Occurs when the moon is between the Earth and the sun Lighted half of the moon is facing the Sun and dark side is facing the Earth can not be seen Rises and sets with the sun

Waxing Phases Begins after a new moon Waxing-more of the illuminated half of the moon can be seen each night Waxing crescent 24 hrs after a new moon you see a thin slice of the moon First quarter phase See ¼ of the moon’s surface Waxing gibbous More than ¼ of the moon is seen Full moon Occurs when all of the moon’s surface faces Earth

Waning Phases Happens after a full moon You see less of the moon’s surface Waning gibbous begins just after a full moon Third-quarter phase See only half of the lighted side of the moon Waning crescent Occurs just before a new moon

Takes about 29.5 days for the moon to complete its cycle of phases Discrepancy between cycle of phases and the moons revolution is due to Earth’s revolution

Aim: Why do lunar and solar eclipses occur? Video

Causes of Eclipses Caused by the revolution of the moon Occur when the Earth or moon block out the sun Can only occur when the sun, Earth and moon are lined up perfectly Solar eclipse happens during a new moon Lunar eclipse happens during a full moon

Solar Eclipses Occurs when the moon moves directly between the sun and the Earth It casts a shadow over part of the Earth Umbra-darkest part of the Moon’s shadow Experience a total solar eclipse-can only see a pearly white glow around the edge Penumbra-lighter shadow that surrounds the umbra Experience a partial solar eclipse Never look directly at the Sun, it can cause permanent eye damage

Lunar Eclipse Earth’s shadow falls on the Moon Begins when the moon moves into the Earth’s penumbra Curved shadow from Earth forms on the Moon Total lunar eclipse-Moon completely in Earth’s umbra Partial lunar eclipse-portion of the Moon moves into Earth’s umbra Sunlight bent through Earth’s atmosphere-eclipse moon is red

Aim: How can features of the moon give us information about Earth?

Moon’s Surface craters-caused by meteorites, asteroids and comets Dark, flat regions are called maria Formed from lava Igneous rock is 3-4 billion years old Moon must have once been geologically active as Earth is today

Inside the Moon Use seismograph to study moonquakes Has helped them draw models of moons interior Figure 11 Pg 671

Origin of the Moon Apollo mission supported a new theory about Moon: The Moon formed billions of years ago when Earth collided with a Mars-sized object A ring of gas and debris formed around earth Particles joined together to form the moon

Studying the moon has helped scientists draw conclusions about: Earth’s shape Movement of Earth and Moon around the Sun Presence of surfaced features on bodies other than Earth

Aim: How have scientists studied the moon? Students independently read Pgs 676-677. They worked in pairs and threes to identify the Luna, Lunar Orbitors, Apollo and Clementine Mission. Who launched it? When it was launched? Goal/objective of mission Was it successful?