ASTR 1010 1st EditionLecture 15Outline of Last Lecture I. The Earth’s AtmosphereA. LayersB. Magnetic FieldC. Electric FieldII. The MoonOutline of Current LectureI. Lunar PhasesA. PhasesB. DiagramCurrent LectureI. Lunar MotionsA. Phases: the shape of the illuminated (sunlit) portion of the Moon as seen by an observer, usually on Earth. The lunar phases change cyclically as the Moon orbits the Earth, according to the changing relative positions of the Earth, Moon, and Sun.- New Moon: the phase of the moon when it is in conjunction with the sun and invisible from earth, or shortly thereafter when it appears as a slender crescent.- Waxing Crescent: The word crescent refers to the phases where the moon is less than half illuminated. Paired with the word waxing, it means the amount of illuminated surface as seen from Earth is increasing- First Quarter: the instant, approximately one week after a new moon, when one half of the moon's disk is illuminated by the sun.- Waxing Gibbous: the sunlit portion of the moon is more than half and is still increasing- Full: the surface of the moon seen from Earth is fully illuminated.- Waning Gibbous: more than half of the moon is illuminated but the illuminated portion is decreasing,- Third Quarter: half of the moon facing the Earth is illuminated.- Waning Crescent: less than half of the moon is illuminated and is decreasing.B.
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