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28 terms

Vocab of Chapter 21 The Sun-Earth-Moon System

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What shape is Earth?
Spherical
How would you describe this shape?
It bulges at the equator and flattens at the poles
Axis
Imaginary line around which Earth spins
How long does one complete Earth rotation take?
24 hours
What are the names of Earth's poles?
The north and south poles
Revolution
yearly orbit of the Earth around the Sun
Ellipse
elongated, closed curve; describes Earth's revolution path
The ________ between Earth and the Sun changes during Earth's yearlong orbit.
distance
Earth's axis is tilted ___ _______ from a line perpendicular to its orbit
23.5 degrees
What does this tilt cause?
The seasons
Equinox
When the Sun is directly above the equator
Spring Equinox
March 20th/21st
Fall Equinox
September 22nd/23rd
Solstice-the point at which the Sun reaches its greatest ________ north or south of the equator.
distance
Summer Solstice
June 21st/22nd
Winter Solstice
December 21st/22nd
What causes changes in the moon's appearance?
Revolution of the Moon
How often does the Moon rotate on its axis?
27.3 days
How long does it take the Moon to revolve once around Earth?
27.3 days
Moon phases
the changing appearances of the Moon as seen from Earth.
New Moon
Moon phase that occurs when the lighted half of the Moon faces the Sun and the dark side faces Earth.
Waxing
occurs shortly after New Moon, when more and more of the Moon's lighted side becomes visible.
Waxing Crescent
24 hours after the New Moon, you can see a thin slice of the side of the Moon that is lighted by the Sun.
First Quarter
When half the Moon is lighted by the Sun for the first time in the cycle after the New Moon.
Waxing Gibbous
More than one quarter of the Moon is visible before a Full Moon.
Full Moon
When all the side of the Moon facing the Earth is lit by the Sun.
Waning
Occurs after a Full Moon, when the amount of the Moon's lighted side that can be seen becomes smaller
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