CHAPTER 24The Moon

Theory of The Origin of the Theory of The Origin of the MoonMoon

• Approx. 4.6 billion years ago Earth Approx. 4.6 billion years ago Earth collided with an object the size of Mars. It collided with an object the size of Mars. It is believed that Earth had a hard crust, is believed that Earth had a hard crust, but the inside was molten rock (still but the inside was molten rock (still liquid). This collision caused a large mass liquid). This collision caused a large mass of liquid rock to be thrown into space. It of liquid rock to be thrown into space. It cooled and hardened into what we know cooled and hardened into what we know as the moon. (THEORY BACKED UP BY as the moon. (THEORY BACKED UP BY EVIDENCE – BUT NOT A FACT)EVIDENCE – BUT NOT A FACT)

• Since the moon has no atmosphere to Since the moon has no atmosphere to protect it from debris floating in space, its protect it from debris floating in space, its surface is covered with impact craterssurface is covered with impact craters

50 miles

MOON MOTIONSMOON MOTIONS • revolves around Earth in an elliptical

orbit that it completes in 27⅓ days• Since the orbit is elliptical, the moon

is at times closest to Earth (perigee), and at other times farthest from Earth (apogee)

• The moon rises in the east and sets in the west, just like the sun (remember, this is caused by Earth’s rotation)

Perigee

356,410 km

Apogee

406,700 kmDisclaimer – this picture is NOT to scale!!!

Perigee Apogee

Link to 12 full moons animation

PHASES OF THE MOONPHASES OF THE MOON• beginning phase is called NEW MOON

– During this phase the moon’s surface is not visible

• The moon’s surface will then appear to become more visible each night until the FULL MOON phase – During this time when the surface becomes more

visible, the moon is said to be WAXING – Once the full moon is reached, the moon’s surface

will get less visible each night until the new moon phase is again reached

• During this time when the surface becomes less visible, the moon is said to be WANING

• (think like the Karate Kid…wax on, wane off)

……PHASESPHASES• *Important, the moon gets lighter from

right to left, and gets darker from right to left

• Go outside at night and practice determining if the moon is waxing or waning!

• The time it takes the moon to go from one new moon phase to the next new moon phase is called a lunar month. This takes 29½ days

Sun’s Rays

Phases of the Moon from New Moon back to New Moon – One Lunar Cycle

Blue Moon…

A blue moon is when there are 2 full moons in one calendar month. The moon isn’t actually blue though!

Question #1: Which month can NEVER have a “Blue Moon”?Question #2: What is the maximum number of Full Moons that

can occur in one year?

ECLIPSESECLIPSES

• Lunar eclipse – this occurs when the moon passes through Earth’s shadow cast into space. The moon is blocked from view.

• Luna is Eclipsed (blocked from our site)

• Solar eclipse – this occurs when the moon passes between the sun and Earth. The moon’s shadow is cast onto Earth’s surface. The sun is blocked from view.

• Sol is eclipsed (blocked from our site)

Total Lunar Eclipse – 3/03/07

TIDESTIDES

• The rising and falling of the levels of water caused by the pull of mostly the moon’s and, to some extent, the sun’s gravity on the water of the Earth.

• On average, many locations receive two high and two low tides each day (approx. six hours apart)

• Spring tides are when the high tides are especially high, and the low tides are especially low (it has nothing to do with the Season of Spring!!!)

• This occurs during the new moon and full moon phases, because the pull of the moon’s and sun’s gravity are working together

• They work together because they are in alignment with one another.

Sun, Moon and Earth in alignment. Moon’s and Sun’s gravity pulls working together…

Benedictine Abbey – Bay of Fundy (Nova Scotia, Canada) – founded in 708, highest tidal range in the world!

Same Abbey @ High Tide –

Man-made causeway added in 1992

• Neap tides are when the high tides are not very high, and the low tides are not very low (small tidal range)

• this happens twice a month during the waxing quarter and waning quarter, because the sun’s gravity is working against the moon’s gravity.

Sun, Moon and Earth NOT in alignment. Moon’s and Sun’s gravity pulls working against one another…