# Revolution/Rotation Day/Night Phases of the Moon Seasons.

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Revolution/Rotation Day/Night Phases of the Moon Seasons

Astronomy = the study of the moon, stars, and other objects in space Astronomers were interested in the movements of the sun and moon as they seem to move across the sky.

 Axis = the imaginary line that passes through Earth’s center and the North and South poles  Earth is tilted on its axis at an angle of 23.5 degrees.  Rotation= the Earth’s spinning on its axis CFU: What is the degree of Earth’s tilt?

 Earth’s rotation on its axis causes day and night. It takes Earth about 24 hours to rotate once on its axis.  It is day on the side of Earth facing the sun.  It is night on the side of Earth facing away from the sun. CFU: Part of the Earth is always in daytime and part of the Earth is always in night time. (True or False)

 Earth also travels around the Sun. Its path around the sun is called its orbit. The shape of its orbit is a slightly flattened, oval shape.  The movement of one object around another is called revolution.  One complete revolution around the sun is called a year. CFU: What is the movement of one object around another in space called?

What is one complete rotation of the Earth called? What is one complete revolution of the Earth called?

 The moon revolves around the Earth just as the Earth revolves around the sun.  The relative positions of the moon, Earth and the sun are always changing and cause the phases of the moon, eclipses and tides. CFU: What causes phases of the Moon?

 It takes the moon about 27.3 days to revolve around the Earth.  The moon does not produce the light you see, it reflects light from the sun.  The different shapes you see from Earth are called phases. CFU: Does the moon produce it’s own light? Why does it look bright in the sky?

 Since the moon revolves around the Earth you see the moon from different angles.  One side of the moon is almost always in sunlight.  The phase of the moon you see depends on how much of the sunlit side of the moon faces Earth. CFU: How much of the moon is always in sunlight?

 New Moon  Waxing Crescent  First Quarter  Waxing Gibbous  Full Moon  Waning Gibbous  Third Quarter  Waning Crescent

 The sun lights the side of the moon facing away from Earth. The side of the moon that faces Earth is dark.

 You see more and more of the lighted side of the moon.

 You see half of the lighted side of the moon.

 The moon continues to wax. The moon is called Gibbous.

 You see the whole lighted side of the moon.

 The fraction of the lighted side of the moon that you see gets smaller each day.

 You can see half of the moon’s lighted side.

 You see a crescent again.

 On rare occasions, the moon completely blocks the sun.  When the moon’s shadow hits Earth or the Earth’s shadow hits the moon, an eclipse occurs.  An eclipse occurs when an object in space comes between the sun and a third object. CFU: What is an eclipse?

 Solar eclipse  Lunar eclipse

 Occurs when the moon passes between Earth and the sun, blocking the sunlight from reaching Earth.  Happens only during new moon phase.

 Occurs only at full moon when Earth is directly between the moon and the sun.  Earth blocks sunlight from reaching the moon and the moon looks dark. CFU: What is the difference between a solar and lunar eclipse?

 Its ok to look at the sun during a partial solar eclipse but not during a total solar eclipse.

 False Its not ok to look during a partial lunar eclipse.

 The force of gravity pulls the moon and Earth toward each other.  Tides occur because of differences in how much the moon pulls on different parts of the Earth.  There are 2 high tides and 2 low tides on Earth at any given time.

 Most places have four distinct seasons: winter, spring, summer, and autumn.  If Earth’s axis were straight up and down relative to the sun, temperatures in any given place would remain the same year round.  Earth has seasons because its axis is tilted and moves around the sun.

 As Earth revolves around the sun, its axis is tilted away from the sun for part of the year and toward the sun for part of the year.  When the North End of Earth’s axis is tilted toward the sun, the Northern Hemisphere has summer.  At the same time, the South End is tilted away from the sun and the Southern Hemisphere is experiencing winter.

 Summer and Winter are not affected by changes in Earth’s distance from the sun.

How is Earth’s axis tilted when the Northern Hemisphere has summer?

 Occurs when the noon sun is overhead at either 23.5 degrees north (summer) at the Tropic of Cancer and 23.5 degrees south (winter) at the Tropic of Capricorn.  Summer solstice is around June 21 st and is the longest day of the year.  Winter solstice is around December 21 st and is the shortest day of the year.  Northern and Southern Hemispheres experience Winter and Summer Solstices at opposite times of year.

 The southern and northern hemispheres experience the summer solstice on the same exact day.

 Halfway between the solstices, neither hemisphere is tilted toward or away from the sun.  This occurs only 2 days a year and is known as an equinox. (September 21 st and March 21 st )  Equinox means “equal night” and during an equinox, the lengths of nighttime and daytime are about the same. CFU: What is the difference between a solstice and an equinox?

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