Space Cycles

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Space Cycles

• Review

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Cycle 1

• Day ? Night ? Day ? Night

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We have day and night because the Earth ROTATES

• On its axis
• Once every 24 ¼ hours
• ½ of the Earth is illuminated (lit up) at a time

http//www.gcse.com/eb/day2.gif
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Cycle 2The length of days

• Long ? Longer? Longest ? Longer ? Long? Short ?
  Shorter ? Shortest ? Short ? Shorter ? Shortest ?
  Long ? Longer ? Longest

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The length of day changes during the year

• The number of hours of daylight is different at
  different times of the year
• The number of hours of daylight is different at
  different latitudes

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Summary

• Days are longer (more hours of daylight) in
  summer, shorter in winter
• There are greater differences in day length
  further away from the Equator
• There is not much change in day length near the
  Equator

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Summary

• Days get LONGER (more minutes of daylight each
  day) from the Winter Solstice to the Summer
  Solstice
• Days get SHORTER (fewer minutes of daylight each
  day) from the Summer Solstice to the Winter
  Solstice
• Day length is about EQUAL everywhere in the world
  on the Autumnal Vernal Equinox

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Why does the length of day change?

• Because the Earth moves, or REVOLVES around the
  Sun
• This changes the way sunlight hits the Earth

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Cycle 3The Seasons

• Winter ? Spring ? Summer ? Fall ? Winter ?
  Spring ? Summer

http//www.getyourwebsitehere.com
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Seasons are caused by

• The tilt of the Earth
• The position of Earth in space
• The difference in direct and indirect light from
  the Sun

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Summary

• In winter
• Part of the Earth is tilted AWAY from the Sun
• Part of the Earth gets INDIRECT energy from the
  Sun

• In summer
• Part of the Earth is tilted TOWARD the Sun
• Part of the Earth gets DIRECT energy from the Sun

The position of the Earth in space determines
which part of the planet is tilted toward the Sun.
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Cycle 4Moon Phases

• New moon ? Waxing Crescent ? 1st Quarter ? Waxing
  Gibbous ? Full Moon ? Waning Gibbous ? 3rd
  Quarter ? Waning Crescent ? New Moon

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The Moon

• A moon phase cycle (LUNAR CYCLE) lasts 29 1/2
  days
• Moon phases are caused by the positions of the
  Moon, Sun, and Earth
• The moon also sees Earth phases

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What we see on Earth compared to the position of
the moon in space
http//www.astro.virginia.edu
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New Moon
DAY 1 The Moon's unilluminated (not lit by the
Sun) side is facing the Earth. The Moon is not
visible.
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WAXING CRESCENT
DAY 3 The Moon seems to be getting bigger more
of the lit side is showing.
Getting bigger WAXING The RIGHT ½ of the moon
is lit
Less than ½ the moon showing CRESCENT
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FIRST QUARTER
DAY 7 One-half of the Moon is illuminated by
direct sunlight.
One half of one half of the moon is visible.
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Waxing Gibbous
DAY 11 The Moon is more than one-half but not
fully illuminated by direct sunlight.
GIBBOUS more than half of the moon is visible.
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Full Moon
DAY 14 The Moon's illuminated side is facing the
Earth. The Moon is completely illuminated by
direct sunlight.
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Waning Gibbous
DAY 17 The Moon is more than one-half but not
fully illuminated by direct sunlight.
Waning getting smaller. Moon is lit on the LEFT
side
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Last Quarter
DAY 22 One-half of the Moon is illuminated by
direct sunlight.
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Waning Crescent
DAY 24 The Moon is less than one-half
illuminated by direct sunlight.
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http//www.facstaff.bucknell.edu
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Summary