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Earth in SpaceEarth in Space
Chapter 19 Section 1
Pages 659-664
Chapter 19 Section 1
Pages 659-664
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• The Study of the moon, stars and other objects in space.– Ancient Egyptians were among the first to
study the stars.– Ancient Astronomers studied the movements
of the sun and moon as they appeared to travel across the sky.
Astronomy
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• Earth’s rotation (spinning) on its axis.– Axis- Imaginary line that passes through
Earth’s Center and the North and South Poles.
– Rotates at 1,600km/h– Causes Day and Night– Takes 24 hours for one rotation.
Rotation
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• The movement of an object around another object.
• One complete revolution around the sun is called a year. (365.25 days)
• Earth revolves around the sun in an orbit.
Revolution
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• Ancient Egyptians- one of the first calendars. Had 12 months of 30 days, with an extra 5 days not apart of any month.
• Early people used moon cycles as a calendar.– 29.5 days– Called “Moonths” month.
Calendars
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• 365.25 creates the need for a leap year.
• The Romans adopted this calendar.– 11 months of 30 or 31 days.– February having 28 or 29 days.
Calendars
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• Sunlight hits the Equator directly.
• Closer to the poles, sunlight hits the surface at an angle.– The energy is
spread out.
How Sunlight hits Earth
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• Earth has seasons because its axis is tilted as it revolves around the sun.• Tilted 23.5˚
• Earth’s seasons are not affected by changes in Earth’s distance from the sun.– Furthest on July 4th
– Closest on January 4th
Earth’s Tilted Axis
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Reasons for Seasons
Reasons for Seasons
Chapter 19 Section 1
Pages 659-664
Chapter 19 Section 1
Pages 659-664
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• The sun’s most direct rays reach the hemisphere that is tilted more towards the sun. This day is known as the summer solstice.
• The most direct rays – are directly over 23.5˚N (Tropic of Cancer) for
the Northern hemisphere on June 20 or 21 – 23.5˚S (Tropic of Capricorn) for the Southern
hemisphere on December 20 or 21.
Summer Solstice
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• The hours of sunlight are the greatest
• The Sun is highest in the sky at noon. – At this time, the northern hemisphere is
pointing toward the Sun. (Position A). – The Southern hemisphere is pointed towards
the Sun. (Position C)
Summer Solstice
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• The northern or southern hemisphere is pointed away from the sun’s most direct rays. Known as the winter solstice.
• The hemisphere pointed away from the sun receives less direct rays.
• These rays are directly over– 23.5˚S (Tropic of Cancer) for the Southern
hemisphere on June 20 or 21 – 23.5˚N (Tropic of Capricorn) for the Northern
hemisphere on December 20 or 21
Winter Solstice
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• The hours of daylight get shorter and the Sun is lower in the sky at noon. – At this time, the northern hemisphere is
pointing away the Sun. (Position C) – The Southern hemisphere is pointed toward
the Sun. (Position A)
Winter Solstice
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• The Sun’s most direct rays are directly over the Earth’s equator.
• There is an equal amount of day and night (12 hours of day, 12 hours of night) every where on Earth. – Equinox means equal night.
Equinoxes
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• There are two equinoxes a year, – Autumnal Equinox (fall) - September 22 or
23 (Position B) – Vernal Equinox (spring) March 22 or 23
(Position D)
Equinoxes