Across
- 1. 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
- 4. 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
- 6. 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
- 7. a circle on the surface of a sphere that is the curve of intersection of the sphere with a plane passing through its center
- 9. a great circle on the terrestrial or celestial sphere that passes through the poles
- 11. the time interval in which the phases repeat—say, from full to full phase
- 12. time as measured by the position of the Sun in the sky (the time that would be indicated by a sundial)
- 14. the period of the Moon’s revolution about Earth measured with respect to the stars
- 15. 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
Down
- 2. an arbitrary line on the surface of Earth near longitude 180° across which the date changes by one day
- 3. 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
- 5. the angular distance north or south of the celestial equator
- 6. when a body (for example, the Moon) rotates at the same rate that it revolves around another body
- 8. 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
- 10. time based on the rotation of Earth; mean solar time passes at a constant rate, unlike apparent solar time
- 13. 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