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    Earth in Space

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    Defensor Pison Gringgo
    The discussion on the planet earth, the things that compose it and the pther aspects of the blue planet

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    Attribution Non-Commercial (BY-NC)
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    Earth in Space

    Uploaded by

    Defensor Pison Gringgo
    17 views16 pages
    The discussion on the planet earth, the things that compose it and the pther aspects of the blue planet

    Copyright

    © Attribution Non-Commercial (BY-NC)

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    PPT, PDF, TXT or read online from Scribd

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    The discussion on the planet earth, the things that compose it and the pther aspects of the blue planet

    Copyright:

    Attribution Non-Commercial (BY-NC)
    Download as PPT, PDF, TXT or read online from Scribd
    Download as ppt, pdf, or txt
    17 views16 pages

    Earth in Space

    Uploaded by

    Defensor Pison Gringgo
    The discussion on the planet earth, the things that compose it and the pther aspects of the blue planet

    Copyright:

    Attribution Non-Commercial (BY-NC)
    Download as PPT, PDF, TXT or read online from Scribd
    Download as ppt, pdf, or txt
    of 16

    EARTH IN SPACE

    Key Concepts How does Earth move in space? What causes the cycle of seasons on Earth?

    Key Terms
    Astronomy Axis Rotation Revolution Orbit Calendar Solstice Equinox

    How Earth Moves


    Astronomy the study of the moon, stars and other objects in space Earth moves through space in two major ways: rotation and revolution Rotation- the spinning of Earth on its axis
    Axis imaginary line through Earths center and North and South poles Rotation causes day and night Takes 24 hours for one rotation

    Revolution- movement of one object around

    another One complete revolution of Earth around the sun is a year Earth follows a slightly elliptical orbit around sun

    Rotation vs Revolution

    Checkup
    How many rotations of Earth take

    place in one revolution around the sun?

    Calendars
    A Calendar is system of organizing the

    time that defines the beginning, length and divisions of a year People of many cultures have added to our idea of a calendar Egyptians determined that there are 365 days in a year Many people followed moon cycles there are about 29 days in a moon cycle or month Problem = 12 moon cycles of 30 days only adds up to 354 days.

    Calendar
    Romans borrowed Egyptian calendar of 365 days Problem: It actually takes the Earth 365 days to complete one revolution. The Romans added 1 day every 4 years. The 4th year is known as a leap year Problem: Roman calendar still off by 11 min. Over the centuries the minutes added up and by 1500s the beginning of spring was coming 10 days early Pope Gregory XIII dropped 10 days from the Calendar to correct. He also made other minor changes. This is the calendar we use today

    Check up
    What is a leap year?

    Explain why it was difficult for ancient

    peoples to develop workable calendars

    The Seasons on Earth


    Temperate places on Earth have 4 seasons:
    Winter, spring, summer, fall How sunlight hits the Earth affects how warm

    an area is. Sunlight hits more directly and a smaller area at the equator so it is warmer Sunlight hits at an angle and over a greater area at the poles so it is colder

    Earths Tilted Axis


    Earth has seasons because its axis

    is tilted as it revolves around the sun. (23.5 from vertical) As Earth revolved around the sun, the north end is tilted towards the sun for half of the year and tilted away the other half Summer and winter are caused by the Earths tilt not by changes in Earths distance from the sun Earth is actually farthest from the sun during the northern hemispheres summer

    Earth in June
    North end of Earths axis

    is tilted toward the sun


    Sun is higher in the sky and there are more hours of

    sunlight Suns rays are more direct It is summer in Northern Hemisphere

    South end of Earths axis is tilted away Sun is low in the sky, days are shorter than nights Suns rays are more slanted It is winter in southern hemisphere

    Earth in December
    Southern Hemisphere receives most direct

    sunlight summer Northern Hemisphere receives slanted rays winter

    Solstices
    Solstice when sun is farthest north or south of

    the equator Day when the sun is farthest north of the equator = about June 21 = Summer Solstice in the Northern Hemisphere and Winter Solstice in Southern Hemisphere Day when the sun is farthest south of the equator = about December 21= Winter Solstice in Northern Hemisphere and Summer Solstice in Southern Hemisphere

    Equinoxes
    Halfway between the solstices, neither hemisphere is tilted toward or away from sun
    Noon is directly overhead at the equator

    Day and night are equal lengths - about 12 hours each


    Occurs twice a year around March 21(Vernal

    or spring equinox) and September 21 (autumnal equinox)

    Solstices and Equinoxes

    Check up
    If Earths axis were not tilted, what would happen to the length

    of days over the course of a year?

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