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| time as measured by the position of the Sun in the sky (the time that would be indicated by a sundial) |
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| the angular distance north or south of the celestial equator |
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| a circle on the surface of a sphere that is the curve of intersection of the sphere with a plane passing through its center |
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| an arbitrary line on the surface of Earth near longitude 180° across which the date changes by one day |
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| an eclipse of the Moon, in which the Moon moves into the shadow of Earth; lunar eclipses can occur only at the time of full moon |
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| time based on the rotation of Earth; mean solar time passes at a constant rate, unlike apparent solar time |
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| the different appearance of light and dark on the Moon as seen from Earth during its monthly cycle, from new moon to full moon and back to new moon |
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| the coordinate for measuring the east-west positions of celestial bodies; the angle measured eastward along the celestial equator from the vernal equinox to the hour circle passing through a body |
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| Earth’s rotation period as defined by the positions of the stars in the sky; the time between successive passages of the same star through the meridian |
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| the period of the Moon’s revolution about Earth measured with respect to the stars |
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| Earth’s rotation period as defined by the position of the Sun in the sky; the time between successive passages of the Sun through the meridian |
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| an eclipse of the Sun by the Moon, caused by the passage of the Moon in front of the Sun; solar eclipses can occur only at the time of the new moon |
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| the time interval in which the phases repeat—say, from full to full phase |
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| when a body (for example, the Moon) rotates at the same rate that it revolves around another body |
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| alternate rising and falling of sea level caused by the difference in the strength of the Moon’s gravitational pull on different parts of Earth |
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