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Unit 5
The Earth-Moon-Sun System
Term | Definition |
---|---|
Rotation | the spinning of a body, such as a planet, on its axis |
Day | the time it takes a planet to complete one full rotation on its axis |
Axis | an imaginary straight line that runs from the North Pole to the South Pole |
Revolution | the motion of a body that travels around another body in space |
Year | the time it takes for Earth to complete a full revolution around the sun (365¼ days) |
Season | a pattern of temperature and other weather trends typical for an area during a particular time of year |
Equinox | occurs when the Earth’s position in relation to the sun causes the sun’s light to shine equally on the Northern and Southern hemispheres |
Solstice | occurs when the Earth’s position in relation to the sun causes the sun’s light to shine at its maximum in one hemisphere and at its minimum in the other |
Northern Hemisphere | the half of Earth between the equator and the North Pole |
Southern Hemisphere | the half of Earth between the equator and the South Pole |
Satellite | a small body that is held in orbit around a larger body by that body’s gravity |
Gravity | the force of attraction that an object with mass exerts on another object with mass |
Lunar phases | the changing appearance of the moon due to changes in the portion of the moon that reflects sunlight back to Earth |
Waxing | occurs when the portion of the moon that is visible is increasing |
Waning | occurs when the portion of the moon that is visible is decreasing |
New moon | the part of the lunar cycle when the near side of the moon receives no sunlight and the moon is not visible from Earth |
Waxing crescent | the part of the lunar cycle when the portion of the moon that is visible is a crescent shape and increasing |
First quarter | the part of the lunar cycle when the portion of the moon that is visible has increased from a thin crescent to one half of the moon being visible |
Waxing gibbous | the part of the lunar cycle when the portion of the moon that is visible is more than half and continuing to increase |
Full moon | the point in the lunar cycle when the whole near side of the moon is in sunlight and visible from Earth |
Waning gibbous | the part of the lunar cycle when the portion of the moon that is visible is more than half but is decreasing |
Third quarter | the part of the lunar cycle when the portion of the moon that is visible has decreased from a full moon to one half of the moon being visible |
Waning crescent | the part of the lunar cycle when the portion of the moon that is visible is a crescent shape but is decreasing |
Eclipse | an event during which one object in space casts a shadow onto another |
Lunar eclipse | event when the Earth’s position blocks the moon from receiving any sunlight; the moon is in the Earth’s shadow |
Solar eclipse | event when the moon’s position blocks the Earth from receiving sunlight; the Earth is in the moon’s shadow |
Umbra | the complete shadow that an object casts; the darkest part of the shadow |
Penumbra | a spreading cone of lighter shadow around the darkest part of the shadow |
Tide | daily changes in the level of ocean water caused by differences in gravitational forces of the sun and moon across Earth |
Tidal force | gravitational forces exerted on the Earth by the sun and the moon which contribute to the tides |
High tide | water level that is higher than the average sea level |
Low tide | water level that is lower than the average sea level |
Tidal range | the difference between the levels of ocean water at high tide and low tide |
Spring tide | tides that have the largest daily tidal range |
Neap tide | tides that have the smallest daily tidal range |