Earth-Moon-Sun System

Rotation vs. Revolution

Rotation The amount of time it takes for Earth to

spin around once. ONE DAY

Revolution The amount of time it takes for Earth to

go around the Sun once. ONE YEAR

Movements in Orbit

Perigee At its closest point in orbit▪ Object appears large

Apogee At its farthest point in orbit▪ Object appears small

What do they all do?

Sun Provides light,

warmth Source of most of

energy that fuels our society

Moon Raises tides in

ocean Illuminates sky with

monthly cycle of phases

Daily Motions

Sun, moon, planets, and stars rise in east and set in west Caused by Earth’s

rotation

Rotation & Length of Day

Length of day is a little longer than the time it takes Earth to rotate once on its axis. As Earth rotates, it also moves in its

orbit▪ It has to turn a little farther

Solar Day The time period from one sunrise or

sunset to the next▪ Our timekeeping system is based on the solar

day

Annual Motions

Length of day and temps may range depending on latitude What is latitude?

Annual changes are due to Earth’s orbital motion around the Sun Earth’s orbit is in an ecliptic plane▪ Oval-shaped

The Moon

Does not emit visible light Reflection of the Sun’s light

Phases of the Moon The changes of position in the sky is a result of

the movement of the moon around the Earth Lunar Phases▪ The sequential changes in appearance of the moon

Waxing Increase in portion of sunlight side of the moon

Waning Decrease in amount of sunlit side of the Moon

Phases of the Moon

New Moon Moon is between Earth and Sun Dark side of the moon faces Earth

Waxing Crescent Less than half the lit portion during

increaseFirst Quarter

Half the sunlit side during increase

New Moon, Waxing Crescent, First Quarter

Phases of the Moon (cont’d)

Waxing Gibbous More than half of the lit portion during

increaseFull Moon

Earth is between Moon and Sun Can see entire sunlit side of moon

Waning Gibbous More than half the lit portion during

decrease

Waxing Gibbous, Full Moon, Waning Gibbous

Phases of the Moon (cont’d)

Third Quarter Half the sunlit side during decrease

Waning Crescent Less than half the lit portion during

decreaseNew Moon

Beginning of cycle again

Third Quarter, Waning Crescent, New Moon

Third

Moon Rotation

As the moon orbits, the same side always faces Earth at all times It spins exactly once each time it orbits

EarthLunar Month

The length of time it takes for 1 complete cycle of phases▪ About 29.5 days

Tides

The moon’s gravity pulls on Earth Creates bulges of ocean water on near

and far sides of Earth

Eclipses

Solar Eclipse When the Moon passes directly between

the Sun and Earth▪ Moon blocks out view of Sun

Lunar Eclipse When the Moon passes through Earth’s

shadow▪ Only occurs with there is a full moon