orbit
the path of an object as it revolves around another object in space
orbital period
the time required for a body to complete a single orbit
Earth's orbit
nearly circular; range of distance from the sun: 147-152 million km; Earth is closest to the sun in January
revolution
the movement of an object around another object
rotation
the spinning of an object on its axis in space
Earth's rotation
24 hours
seasons
caused by the tilt (23.5 degrees) of Earth on its axis as it revolves around the Sun
solstice
the day when Earth's rotational axis is the most toward or away from the Sun; June 20 or 21 & December 21 or 22
equinox
the day when Earth's axis is not learning toward or away from the Sun; March 20 or 21 & September 22 or 23
Sun's apparent motion
seems to move across sky from east to west
Moon's rotation
27.3 Earth days on its axis = 1 lunar day.
sidereal month
time for moon to complete one full revolution around Earth; 27.3 Earth Days
synodic month
time for moon to complete a phase cycle (new moon to new moon); also called a lunation; 29.5 Earth days
27.3 days and is the same time as the rotation
Moons Revoloution
tidal locking
the synchronization between orbital period and period of rotation of one body (such as the Moon) orbiting another body (such as the Earth)
Moon's formation
mars sized planet hits Earth (Theia)
Early Locking Hypothesis
explains difference in appearance and crustal thickness of the near and far side of moon; soon after the Moon's formation
maria
dark-colored, relatively flat regions of the Moon formed when ancient lava flowed up through the Moon's crust and solidified
phase
lit part of the Moon or a planet that can be seen from Earth;
waxing phase
occurs when more of the Moon's near side is lit each night
waning phase
occurs when less of the Moon's near side is lit each night
new moon
phase that occurs when the Moon is between Earth and the Sun
quarter moon
the phase where half of the Moon's near side is illuminated by the Sun
gibbous moon
the phase where greater than half (but not a full moon) of the Moon's near side is illuminated by the Sun
Moon's apparent motion
seems to move across sky from east to west
Moon's orbital tilt
5 degrees; this is why eclipses do not occur every month
Moon's orbit
counter-clockwise
lunar eclipse
occurs at a full moon when Earth is directly between the moon and the Sun
solar eclipse
occurs when the Moon passes directly between the Sun and Earth and casts a shadow over part of Earth
syzygy
the straight line configuration of 3 celestial bodies (as the sun and earth and moon) in a gravitational system
umbra
the darkest part of the moon's shadow
penumbra
the lighter part of a shadow where light is partially blocked
tide
the periodic rise and fall of the sea level under the gravitational pull of the moon
spring tides
a tide just after a new or full moon
neap tides
a tide just after the first or third quarters of the moon when there is the least difference between high and low water
view of moon
we view the same side of the moon
EMS System
Earth-Moon-Sun system
orrery
a mechanical model of the EMS or solar system used to represent relative positions and motions