Chapter 23Chapter 23

Sun-Earth-Moon Sun-Earth-Moon SystemSystem

Key TermsKey TermsRotationRotation – the spinning of – the spinning of

Earth on its axis (takes 24 Earth on its axis (takes 24 hours )hours )

RevolutionRevolution – Earth’s – Earth’s yearly orbit around the yearly orbit around the sun.sun.

Key TermsKey TermsEllipseEllipse – an elongated, – an elongated,

closed curve (Earth orbits closed curve (Earth orbits the Sun this way)the Sun this way)

SolsticesSolsticesSolsticeSolstice – the day when – the day when

the Sun is farthest north the Sun is farthest north or south of the equator.or south of the equator.

Occurs twice yearly - Occurs twice yearly - summer & winter (June summer & winter (June 21/22 & Dec. 21/22)21/22 & Dec. 21/22)

Moon Rotation/RevolutionMoon Rotation/Revolution

The Moon’s rotation takes The Moon’s rotation takes 27.3 days – the same 27.3 days – the same amount of time it takes to amount of time it takes to revolve once around Earth.revolve once around Earth.

Thus, we Thus, we alwaysalways see the see the same side of the Moon!same side of the Moon!

Phases of the MoonPhases of the MoonThe phases of the Moon The phases of the Moon

depend on the positions depend on the positions of the Moon, Earth, and of the Moon, Earth, and the Sun.the Sun.

There are 8 phases.There are 8 phases.

New MoonNew MoonOccurs when the Moon is Occurs when the Moon is

between Earth and the Sun.between Earth and the Sun.The lighted ½ faces the Sun, The lighted ½ faces the Sun,

the dark ½ faces Earth.the dark ½ faces Earth.It’s in the sky but can’t be It’s in the sky but can’t be

seen.seen.

Waxing PhasesWaxing PhasesOccur after a new Moon, and Occur after a new Moon, and

more of the lighted half of the more of the lighted half of the moon can be seen each night.moon can be seen each night.

Waxing CrescentWaxing Crescent – can be – can be seen about 24 h after a new seen about 24 h after a new moon as a thin slice.moon as a thin slice.

Waxing Waxing CrescentCrescent

11stst Quarter Phase Quarter PhaseCan be seen about 1 week Can be seen about 1 week

after a new moon.after a new moon.Appears to about ½ of the Appears to about ½ of the

lighted side of the Moon.lighted side of the Moon.

Waxing GibbousWaxing GibbousOccurs when more than ¼ Occurs when more than ¼

of the Moon is visible.of the Moon is visible.

Full MoonFull MoonOccurs when all of the Occurs when all of the

Moon’s surface facing Earth Moon’s surface facing Earth reflects light.reflects light.

Remember, Earth is Remember, Earth is between the Sun and Moon.between the Sun and Moon.

Waning PhasesWaning PhasesWaning occurs Waning occurs afterafter a full a full

moon, and you see less of moon, and you see less of its lighted half each night.its lighted half each night.

The lighted parts will be on The lighted parts will be on the left side of the Moon!the left side of the Moon!

Waning GibbousWaning GibbousBegins just after a full Begins just after a full

moon.moon.To me, you can see about To me, you can see about

¾ of the lighted Moon.¾ of the lighted Moon.

Third-Quarter PhaseThird-Quarter PhaseOccurs when you can see Occurs when you can see

only ½ the lighted side.only ½ the lighted side.

Waning CrescentWaning CrescentOccurs when you can see a Occurs when you can see a

small lighted slice on the small lighted slice on the left side.left side.

Will occur just before Will occur just before another new moon.another new moon.

Once you can located the New and Full Once you can located the New and Full moon on a diagram always move counter moon on a diagram always move counter clockwise from the NEW to the FULL clockwise from the NEW to the FULL phase. If you go counter clockwise the phase. If you go counter clockwise the first set of phases are the WAXING first set of phases are the WAXING phases then after you reach the FULL phases then after you reach the FULL moon the set of phases are the waning moon the set of phases are the waning phases,phases,