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The Earth in Space. Physical properties of Earth. diameter (equator)- 12,756 km diameter (poles)- 12,714 km circumference (equator)- 40,075 km average distance from sun- 149,600,000 km. In The Past. people thought the sun, moon, and stars orbited around the Earth
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Physical properties of Earth • diameter (equator)- 12,756 km • diameter (poles)- 12,714 km • circumference (equator)- 40,075 km • average distance from sun- 149,600,000 km
In The Past • people thought the sun, moon, and stars orbited around the Earth • thought the Earth was flat
Earth’s Motion and Seasons • Earth’s tilt has fluctuated throughout geologic time from 21.5o- 24.5o. • above the Arctic Circle receive 24 hrs. of daylight • below the Antarctic Circle 24 hrs. of darkness • Earth’s axis wobbles in a large circle that that takes >26,000 years to complete.
Earth’s Motion • Solstice- sun reaches its greatest distance from the equator. • Equinox- days and nights are equal length. • When the northern hemisphere points towards the sun we experience summer.
Solstices • northern hemisphere- June 21st • southern hemisphere- December 21st
Equinoxes • northern hemisphere- March 21st • southern hemisphere- September 21st
Earth’s Moon • probably formed when a large object collided with Earth shortly after it formed • moon rocks range from 3.2-4.6 billion years • crust, mantle, and solid iron core • craters- form when meteorites strike the moon
Lunar Motion The same side of the moon always faces the Earth. • distance from earth- 384,000 km • complete orbit takes 27.3 days
Solar Eclipse • occurs when the Earth moves into the moon’s shadow
Lunar Eclipse • occurs when the sun, Earth, and moon line up. • the full moon moves into Earth’s shadow.
The Moon’s Formation • co-formation hypothesis • capture hypothesis • collision hypothesis
Our Solar System • composed of sun, planets, asteroids, and comets • >99% of all the solar system’s matter is contained in the sun
Planets Inner Planets Outer Planets Jupiter Saturn Uranus Neptune Pluto Mercury Venus Earth Mars
Asteroids and Comets • asteroids are small, rocky bodies that lie mostly in a belt between Mars an Jupiter. • comets are made mostly of rock and ice
Origin of the Solar System The sun and planets probably condensed from a nebula (large cloud of gas, ice, and dust) about 5 billion years ago.