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Earth & Moon Notes

Chapter 19

Earth’s Movement

The Earth moves in 2 waysoRotation

oRevolution

The effects of the

movements

oDays/Nights

oSeasons

Rotation• Rotation is spinning of

the earth on its axis

–Axis- imaginary line that passes through the center of the earth and the North and South poles

The Axis

•The axis is tilted at an angle–23.5o

•The axis is responsible for the difference in the length of sun light hours

–Sun light hours are NOT constant (the same)

Rotation

• Responsible for day and night

–It takes 24 hours to rotate once

•There are 24 hours in one day

Revolution

• Revolution the movement of one object around another

–The earth revolves around the sun

•One complete revolution is a year

Revolution

–Orbit: the Earth’s path around the sun.

•Orbit’s Shape = Elliptical

The Seasons

• Due to the tiltof the earth’s axis

–NOT due to the distancefrom the sun.

Direct/Indirect Rays

• Sun has direct and indirect rays

–Direct rays strike area around equator

•Warmer near equator

Direct/Indirect Rays

–Indirect rays (slanted rays) strike the north and southpoles

•Cooler near poles

Direct Rays

Indirect Rays

Solstice

• Solstice: the sun reaches its greatest distance North or South of the equator

–Summer in N. Hemisphere = Winter in S. Hemisphere

Summer Solstice

When are the solstices?

–Summer Solstice: June 21

•Longest day of the year (Northern Hemisphere)

–Winter Solstice: December 21

•Shortest Day of the year

Winter Solstice

Equinox

• Equinox: equal night (12 hour day, 12 hour night)

–The sun is directly over the Equator

•Day = Night

Equinox

When are the equinoxes?

–Vernal Equinox: March 21 (First day of Spring)

–Autumnal Equinox: September 21 (First day of Fall)

Gravity

• Gravity: force that attracts all objects to each other

–Force: push or pull

• Law of Universal Gravity

–Its everywhere

Strength of Gravity

• Strength depends on 2 factors

–Mass: amount of matter in an object• The bigger it is the stronger the gravity is

• The smaller it is the weaker the gravity is

–Distance: decrease gravity with increase distance• The closer it is the stronger the gravity is

• The farther it is the weaker the gravity is

The effects of Gravity

–Tides

–Weight

Inertia

• Inertia: The tendency of an object to resist a change in motion

• Newton’s First Law of Motion: an object at rest will stay at rest, and an object in motion will stayin motion until another force acts on it.

Orbital Motion

• Inertia and Gravity combine to keep the Earth in orbit around Sun

• Inertia and Gravity combine to keep the Moon in orbit around Earth.

The Moon

• The moon rotates once on its axis in the same amount of time it takes to revolve around the earth.–Moon day = Moon Year

–The same side of the moon always faces the earth•A “day” or “year” on the moon = 29 days

Is the Moon Close or Far?

• Perigee: point of the moon’sorbit closest to the earth

• Apogee: point of the moon’s orbit farthest from the earth

Phases of the Moon

• Phases: the shapes of the moon as seen from the earth

–Depends on how much of the moon that is reflecting sun light faces the earth

Waxing Crescent First Quarter Waxing Gibbous

Waning Gibbous Waning CrescentThird QuarterFull Moon

New Moon

Eclipses

• Eclipse: partial or total blocking of an object in space

• Two types of eclipses

–Solar- Sun

–Lunar- Moon

Solar Eclipse

–Moon directly between Earth & sun, blocking sunlight •occurs with at New Moon

–Types of Solar Eclipses•Total Solar Eclipse•Partial Solar Eclipse

Lunar Eclipse

–Occurs when the earth is between the sun and the moon•Occurs with a full moon

–Types of Lunar Eclipses•Total Lunar Eclipse•Partial Lunar Eclipse

Lunar Eclipse

Moon Phase Video

Tides

• Tides: the rise and fall of the oceans

–Due to the moon’s gravity

• There are 2 high tides and 2 lowtides at any one time on earth.

Spring Tides

–Occur at the New Moon and Full Moon

–When the sun and moon both pull in the same direction

•Very high tide

–Spring Tide = Straight Line

Neap Tides

–Occurs at the 1st quarter and 3rd quarter moon

–When sun, earth and moon form a 90o Angle

•The high tide is not very high

Moon’s Surface

• Galileo is the first scientist who looked at the moon with a telescope

Features of the Moon

• Maria: dark, flat surface

–Thought they were “seas” (oceans)

–Really hardened rock

• Craters: large pits on the surface of the moon

• Highlands: mountains on the moon

–light colored

Characteristics of the Moon

• Size & Density

–¼ of the earth’s diameter

–Density is about the same as the earths outer layers

Characteristics of the Moon

• Temperature & Atmosphere

–light side: 130oC = 266oF

–Dark Side: -180oC = -292oF

• There is no atmosphere so the temperature always changes

Characteristics of the Moon

• Water

–No Liquid Water

• Gravity

–Gravity on the moon is about 1/6th as strong as on the earth