Important terms:

axis - an imaginary line that passes through a planet’s center and its north and south poles, about which the planet rotates

rotation - the spinning motion of a planet on its axis

revolution - the movement of an object around another object

orbit - the path of an object as it revolves around another object in space

gravity - the attractive force between objects; the force that moves objects downhill

mass - a measure of how much matter is in an object

inertia - the tendency of an object to resist a change in motion

eclipse - the partial or total blocking of one object in space by another

umbra - the darkest part of a shadow

penumbra - the part of a shadow surrounding the darkest part

tides - the periodic rise and fall of the level of water in the ocean

the earth’s tilt on its axis - the reasons earth has seasons

solstice - When the sun appears farthest North of the equator once each year and farthest south once each year

Northern Hemisphere summer solstice (the sun is farthest North) - June 21

North Hemisphere winter solstice (the sun is farthest South) - December 21

equinox - when neither hemisphere is tilted towards the sun; means “equal night”

March 21 and September 22 - equinox dates

how the moon phases start - new moon

left - the way the moon shines in a waning phase

right - the way the moon shines in a waxing phase

a month - how long it takes to go through all moon phases

Solar eclipse - occurs when the moon passes directly between Earth and the sun

lunar eclipse - occurs when the earth is between the sun and moon

what causes a spring tide - a new moon and full moon

how high tides are in a spring tide - higher than usual

how low tides are in a spring tide - lower than usual

spring tide - tides with the biggest difference between consecutive low and high tides

what causes a neap tide - first quarter and third quarter moon

how high tides are in a neap tide - lower than usual

how low tides are in a neap tide - higher than usual

neap tide - tides with the least difference between consecutive low and high tides