19.3 Phases, Eclipses, and 19.3 Phases, Eclipses, and TidesTides

p. 670-677p. 670-677

The moonThe moon

We only see one side of the moon. The dark We only see one side of the moon. The dark side of the moon never faces Earth and has side of the moon never faces Earth and has only been seen by astronauts and in pictures. only been seen by astronauts and in pictures. This is because of how the moon moves in This is because of how the moon moves in space.space.

The moon rotates on its axis every 27.3 days The moon rotates on its axis every 27.3 days and revolves around the Earth in the same time and revolves around the Earth in the same time 27.3 days. Since its rotation and revolution are 27.3 days. Since its rotation and revolution are equal, the same side always faces Earth.equal, the same side always faces Earth.

Phases of the moonPhases of the moon

The changing positions of the Earth, moon and The changing positions of the Earth, moon and sun cause the phases of the moons, eclipses, sun cause the phases of the moons, eclipses, and tides to occur.and tides to occur.

Every revolution around the Earth the moon Every revolution around the Earth the moon goes through a set of phases. Because sunlight goes through a set of phases. Because sunlight lights up the moon where the moon sun and lights up the moon where the moon sun and Earth are in relation to one another determines Earth are in relation to one another determines whether we see a full, quarter or crescent moon.whether we see a full, quarter or crescent moon.

Phases of the MoonPhases of the Moon

The phase of the moon you see depends The phase of the moon you see depends on how much of the sunlit side of the on how much of the sunlit side of the moon faces EARTH.moon faces EARTH.

1. New Moon1. New Moon

Dark side faces Earth, Dark side faces Earth, lighted side faces Sunlighted side faces Sun

Looks like the moon Looks like the moon has disappearedhas disappeared

This is the first phase This is the first phase in 8 to take placein 8 to take place

2. Waxing Crescent2. Waxing Crescent

Thin slice of the moon Thin slice of the moon is lit up by the Sun is lit up by the Sun and is shown on and is shown on EarthEarth

Occurs about 24 Occurs about 24 hours after a new hours after a new moonmoon

3. First Quarter3. First Quarter

Occurs about a week Occurs about a week after a new moonafter a new moon

You can see half of You can see half of the lighted side from the lighted side from EarthEarth

Half of the lighted Half of the lighted side is also called, side is also called, one quarterone quarter

4. Waxing Gibbous4. Waxing Gibbous

More than one-More than one-quarter of the moon is quarter of the moon is visible from the earthvisible from the earth

5. Full Moon5. Full Moon

The whole surface of The whole surface of the moon facing Earth the moon facing Earth is lit upis lit up

Exact opposite of a Exact opposite of a new moonnew moon

6. Waning Gibbous6. Waning Gibbous

Occurs right after a Occurs right after a full moonfull moon

The amount of the The amount of the moons lighted side moons lighted side becomes smallerbecomes smaller

7. Third Quarter7. Third Quarter

You can only see half You can only see half of the lighted side of the lighted side from Earthfrom Earth

Just like first quarter, Just like first quarter, but backwardsbut backwards

8. Waning Crescent8. Waning Crescent

Occurs just before a new Occurs just before a new moonmoon

The amount of the moon The amount of the moon seen on Earth becomes seen on Earth becomes smallersmaller

Only a small slice of the Only a small slice of the moon is shownmoon is shown

Cycle begins again at Cycle begins again at new moon.new moon.

The entire phases take The entire phases take 27.3 days.27.3 days.

Solar EclipsesSolar Eclipses

Solar EclipseSolar Eclipse

Solar EclipseSolar Eclipse- occurs - occurs when the moon when the moon moves directly moves directly between the sun and between the sun and earth and casts a earth and casts a shadow on part of shadow on part of earth.earth.

Parts of a Solar EclipseParts of a Solar Eclipse

UmbraUmbra- darkest part of the moon’s - darkest part of the moon’s shadow.shadow.Only a person standing in the umbra can see Only a person standing in the umbra can see

a total solar eclipse.a total solar eclipse.PenumbraPenumbra- lighter shadow on the earth’s - lighter shadow on the earth’s

surface surrounding the umbra.surface surrounding the umbra.A person standing in the penumbra can see a A person standing in the penumbra can see a

partial solar eclipse.partial solar eclipse.

Parts (cont.)Parts (cont.)

The only part of the The only part of the sun that is visible sun that is visible during a solar eclipse during a solar eclipse is part of its is part of its atmosphere, which atmosphere, which appears as a pearly appears as a pearly white glow around the white glow around the edge of the eclipsing edge of the eclipsing moon.moon.

Caution!!Caution!!

Regardless where Regardless where you are, you should you are, you should nevernever look into a look into a solar eclipse. The solar eclipse. The light will permanently light will permanently damage your eyes. damage your eyes. Scientists wear Scientists wear special glasses!special glasses!

Lunar EclipseLunar Eclipse

Can only occur at Full MoonCan only occur at Full MoonMoon passes through some portion of Moon passes through some portion of

Earth’s shadowEarth’s shadowPenumbra-Earth blocks part of the sun’s Penumbra-Earth blocks part of the sun’s

rays from the Moonrays from the MoonUmbra-Earth blocks all direct sunlight from Umbra-Earth blocks all direct sunlight from

the Moonthe Moon

Penumbral Lunar EclipsePenumbral Lunar Eclipse

The Moon passes through Earth’s The Moon passes through Earth’s penumbral shadowpenumbral shadow

Subtle and quite difficult to observeSubtle and quite difficult to observe35% of eclipses are penumbral35% of eclipses are penumbral

Partial Lunar EclipsePartial Lunar Eclipse

A portion of the Moon passes through A portion of the Moon passes through Earth’s umbral shadowEarth’s umbral shadow

Easy to seeEasy to see30% of eclipses are partial 30% of eclipses are partial

Penumbral Lunar EclipsePenumbral Lunar Eclipse

The Moon passes through Earth’s The Moon passes through Earth’s penumbral shadowpenumbral shadow

Subtle and quite difficult to observeSubtle and quite difficult to observe35% of eclipses are penumbral35% of eclipses are penumbral

Total Lunar EclipseTotal Lunar Eclipse

The entire Moon passes through Earth‘s The entire Moon passes through Earth‘s umbral shadowumbral shadow

Quite striking, vibrant colorsQuite striking, vibrant colors35% of eclipses are total35% of eclipses are total

Total Lunar EclipseTotal Lunar Eclipse

The entire Moon passes through Earth‘s The entire Moon passes through Earth‘s umbral shadowumbral shadow

Quite striking, vibrant colorsQuite striking, vibrant colors35% of eclipses are total35% of eclipses are total

TidesTides

Caused by the moonCaused by the moonOccur every 6 hours Occur every 6 hours 2 high tides and 2 low tides every day2 high tides and 2 low tides every daySpring tides: tides are higher than normalSpring tides: tides are higher than normalNeap tides: are less effective than normalNeap tides: are less effective than normal