Phases, Eclipses, and TidesChapter 9 Section 2

The Moon’s OrbitThe moon revolves

around Earth and rotates on its own axis

The moon revolves around Earth once every 27.3 days in an oval orbit

The moon rotates on its axis once every 27.3 days (1 moon day = 1 moon year)

The same side of the moon always faces Earth; called the “near side”

Cyclical Phases of the Moon

What Causes Phases?

The Cycle of the Phases

Phases- the different shapes of the moon you see from Earth

Phases are caused by changes in the relative positions of the moon, Earth, and the sun

New moon Waxing Crescent First quarter Waxing Gibbous Full Moon Waning Gibbous Third Quarter Waning Crescent

EclipsesThe moon’s orbit around Earth is

slightly tilted with respect to Earth’s orbit around the sun

When the moon’s shadow hits Earth or Earth’s shadow hits the moon, and eclipse occurs

Eclipse- occurs when an object in space comes between the sun and a third object, and casts a shadow on that object

Solar Eclipse

Total Solar Eclipses Partial Solar Eclipses

Solar eclipse occurs when the moon passes between Earth and the sun, blocking the sunlight from reaching Earth

Umbra- cone-shaped darkest part of the moon’s shadow

Only the Earth within the umbra experience a total solar eclipse

Penumbra- largest part of the moons shadow where part of the sun is visible from Earth

Eclipse visible in the penumbra is a partial eclipse

Lunar Eclipses

Total Lunar Eclipses Partial Lunar Eclipses

Lunar eclipse occurs at a full moon when Earth is directly between the moon and the sun

When the moon is in Earth’s umbra, you see a total lunar eclipse

A lunar eclipse when Earth, the moon, and the sun are not quite in line cause a partial lunar eclipse

A partial lunar eclipse occurs when the moon passes partly into the umbra of Earth’s shadow

Tides

What Causes Tides? High Tides

Tides- the rise and fall of water Gravity pulls the moon and

Earth (including the water on Earth’s surface) toward each other

Tides occur mainly because of differences in how much the moon pulls on different parts of Earth

Moon’s gravity pulls water toward the point on Earth’s surface closest to the moon

The moon pulls on water at Earth’s surface more strongly than on Earth as a whole

Water facing the moon is pulled toward the moon creating high tide

The farthest point from the moon pulls less strongly on the water at Earth’s surface than on Earth as a whole; Earth is pulled toward the moon, leaving the water behind, creating another high tide

The Tide Cycle Spring and Neap Tides

Low tides occur on the sides of the Earth perpendicular to the high tides

Tides cycle every 25 hours

Spring tide- tide with the greatest difference between low and high tide caused by the pull of gravity of both the sun and moon in the same direction

Neap tide- tide with the least difference between low and high tide caused when the sun’s pull is at right angles to the moon’s on the Earth

Local Tide EffectsShapes of bodies of water and depths of

the ocean floor affect the flow of waterOcean tides can sometimes extend far

up rivers and can flow upstream as the tide comes in and downstream as the tide goes back out

Intertidal zone- strip of land that under water at high tide but becomes dry land at low tide

Animals living in intertidal zone must be adapted to changing conditions

ReviewWhy does the moon change its phases as the

month progresses?

Describe the relative positions of Earth, the sun, and the moon during a solar eclipse and during a lunar eclipse

Explain why there are two high tides and two low tides each day.

Why are a “day” and a “year” on the moon the same length?