A | B |
rotation | to turn on an axis; one rotation = 24 hrs. |
axis | imaginary line from pole to pole |
time zones | occur approx. every 15 degrees longitude(24 in all) |
inclination | tilt--earth's is 23.5 degrees-causes seasons |
orbit | path taken during revolution |
revolution | movement of one heavenly body around another |
summer solstice | most hrs. daylight; about June 22 |
winter solstice | least daylight, most hrs. darkness; about Dec. 22 |
vernal equixox | hours of day and night equal; sun directly over equator |
tropic of cancer | direct rays of sun strike here at summer solstice |
tropic of capricorn | dierct rays of sun strike here at winter solstice |
autumnal equinox | length of day and dark equal; about Sept. 22 |
phases of moon | changes in appearance of moon as revolves around earth, due to light reflected from Sun; one complete cycle takes approx. 28 da. |
new moon | disk of moon not visible |
waxing | growing larger |
first quarter moon | right 1/2 of moon is illuminated |
full moon | full disk of moon illuminated; occurs approx 7 da. after first qtr. |
last (third) quarter moon | left 1/2 of moon is illuminated, occurs approx 7 da. after full |
gibbous | rounded on both sides |
waning | growing smaller |
lunar eclipse | earth's shadow obscures the moon |
unbra | zone of complete shadow |
penunbra | zone of partial shadaw |
solar eclipse | moon's shadow falls on earth |
synchronous rotation | accounts for why we see only one side of the moon |