Earth and Its MoonChapter 3

3-1 The Earth in Space

Earth rotates on its axis Axis = imaginary line from North Pole

to South Pole 2 movements of the Earth affect the

seasons and both day & night1. Rotation2. Revolution

Day and Night Equator = imaginary line dividing

Earth into the Northern Hemisphere and Southern Hemisphere

Earth rotates abt 1600 km/hr 24 hours to rotate 1 time on its axis =

1 day Part of Earth faces the sun; other part

away from sun in darkness Day and night is caused by the rotation

of Earth on its axis

Looking down on Earth from North Pole see that rotates in a counterclockwise direction West to East Sun rises in East as Earth turns toward it Sun sets in West as Earth turns away from it

Earth’s day is not constant Changes b/c Earth’s axis is tilted at a 23½°

angle and is not straight up and down If axis were straight

daylight = 12 hrs and nighttime = 12 hrs, every day of every year

Tilted axis: when North Pole leans toward sun then South Pole leaning away from sun Daylight hours not constant Hemisphere that leans toward sun has long

days and short night Hemisphere leaning away from sun has short

days and long nights

A Year on Earth Earth takes 365.25 days to revolve 1

time around the sun = 1 year Extra ¼ day is left off calendar and

added every 4 years to the month of February

What is a year with an extra day called?

Seasons on Earth 4 seasons: Spring, Summer, Autumn,

Winter Mars, Saturn, Uranus, & Neptune all

have seasons while other 3 have little to no seasons

Why do some planets have seasons and other do not?

Planets have seasons because they are tilted on their axis

Different seasons on Earth caused by tilt of Earth’s axis

When hemisphere is tilting toward sun it’s summer and tilting away from sun it’s winter

Hemisphere tilting toward sun receives more direct rays from sun and have longer days Combination of these results in Earths

surface and atmosphere receiving more heat = summer

Summer in Northern Hemisphere begins June 20 & 21 Northern Hemisphere tilted full 23½°

toward sun Northern Hemisphere has longest day Southern Hemisphere has shortest day

Summer Solstice = longest day of year Solstice – Latin meaning sun and stop

Sun reaches its highest point in the sky on the summer solstice

After summer solstice sun begins to lower in the sky

December 21 & 22 = Winter Solstice Northern Hemisphere tilted full 23½°

away from sun Shortest day of year in Northern

Hemisphere Longest day of year in Southern

Hemisphere

Equinoxes- 2 times a year when poles are not tilted toward the sun (Spring & Autumn) Latin for equal night Day and night are of equal length all

over the world Vernal Equinox – in Northern

Hemisphere spring begins March 20 or 21

Autumnal Equinox – begins Sept. 22 or 23

A Magnet in Space Magnet Field – invisible lines of force

that connect the poles/ends of a magnet Earth similar to a magnet Earth has a magnetic field that forms

around it Comes from the movement of materials in the

Earth’s inner core Metals such as Iron and Nickel

Magnetic poles different from geographic poles

Geographic poles - opposite ends of tilted axis Magnetic poles – ends of lines of force that form

the Earth’s magnetic field

Magnetosphere – Earth’s magnetic field Begins at abt 1000km and extends to

abt. 64000km on the side facing the sun On side away from sun is a tail that

extends millions of km long caused by a stream of charged particles called the solar wind which continually reshapes the magnetosphere as Earth rotates

Van Allen radiation belts – 2 doughnut-shaped regions of charged particles formed as the magnetosphere traps particles in the solar wind Outer belt contains mostly negatively charged

electrons Inner belt contains mainly positively charged

protons Charged particles travel along magnetic lines of

force colliding with the Earth’s upper atmosphere Aurora – collisions of atmospheric particles that give off

visible light that appear as bands of shimmering colored lights

Aurora Borealis – a.k.a. “Northern Lights” near North Pole Aurora Australis – a.k.a. “Southern Lights” near South

Pole

3-2 The Earth’s Moon

Lunar – Latin word for moon Neil Armstrong & Buzz Aldrin first

men to walk on the moon

The Moon’s Characteristics

Moon – 3476km in diameter ¼ the diameter of Earth Gravity is 1/6 that on Earth (objects weigh

less) Avg. distance to moon = 384,403km

Measured using a mirror left on moon and bounced a beam of light back to Earth

Moonquakes measured using instruments left on the moon (approx. 3000 occur per year

Crust abt. 60km thick Inner layer abt 800km thick (denser rock) Core - melted iron

Apollo astronauts brought back moon rocks Oldest abt 4.6 billions yrs abt. same as

age of Earth Earth and moon appear to have formed

abt same time Moon rocks show no traces of water Scientist believe moon never has had

water Moon has no atmosphere, therefore no

weather Extreme temperature range 100°C to -

175°C The moon is dry, airless, and

barren.

Features of the Moon Galileo first person to see the moon

through a telescope Highlands – mountain ranges soaring

thousands of meters into the black sky Maria - broad, smooth lowland plains;

appear as dark areas Latin word for seas

Craters are scattered across moon’s surface Range in size from microscopic to hundreds of

km Copernicus is one of the largest craters on the

moon (91km across) Most craters located in highlands, very few in

the maria

Craters formed from blasts of meteorites and some from volcanic activity

Maria filled with hardened rock from volcanic activity billions of years ago

Rilles – long valleys that crisscross much of the moon’s surface, Hadley Rille – 113 km long

Scientists unsure what made rilles, some possibilies: Evidence that there were active volcanoes Cut by rivers of flowing lava or Cracks in surface from moonquakes Moon’s hot surface cooling and shrinking

All is evidence that the moon was once hot and active

Movement of the Moon Earth revolves around sun and at same

time moon revolves around the Earth Perigee – point of the moon’s orbit

closest to the Earth (abt. 350,000 km) Apogee – point of the moon’s orbit

farthest from Earth (abt. 400,000 km) Moon moves west across the sky,

apparent movement caused by Earth’s rotation When viewed amongst the stars, movement of

moon eastward is observed

Earth rotates on axis 1 time every 24 hrs

Moon rotates 1 time on axis every 27.3 days

Moon revolves 1 time around Earth every 27.3 days Moon’s Period of Rotation = Period of

Revolution Same side of moon always faces the

Earth Apollo 8 astronauts were first humans

to view the dark side of the moon

Origin of the Moon Moon was “born” when a giant

asteroid the size of Mars struck the young Earth, tearing away a chunk of material The Pacific Ocean possibly could be the

hole what was left Evidence based from moon rocks and

explains why moon is so similar to Earth

Water would have vaporized as it was torn from the Earth

3-3 The Earth, the Moon, & the

Sun Relative motions of the Earth, the

moon, and the sun result in the changing appearance of the moon as seen from the Earth and the occasional blocking of the sun’s light

Phases of the Moon Moon revolves around the Earth Moon’s revolution causes moon to

appear to change shape in the sky Different shapes called Phases of the

Moon Goes through all phases in 29.5 days Moon reflects sunlight toward the

Earth, has no light of its own Phase depends on where moon is in

relation to sun and Earth

New Moon – moon has no visible light, btwn the sun and the Earth Sometimes faintly visible due to

earthshine (sunlight reflected off the Earth)

Waxing Crescent Phase – more of the lighted side of the moon is visible, a slim curved slice appears Moon is “waxing” when lighted area

appears to grow larger Moon is “waning” when lighted area

appears to grow smaller

First Quarter Moon – moon appears ½ lit 1 week after new moon , moon traveled ¼ the

way around the Earth Waxing Gibbous Phase – days after First

Quarter Phase and more of the lighted side of the Moon appears

Full Moon – 2 wks after New Moon Phase Entire lighted side of moon is visible Earth is btwn the Moon and Sun

2 weeks more and the Moon moves through the Waning-Gibbous, Last Quarter, & Waning-Crescent Phases & back the New Moon Phases

Eclipses Movement of the Earth, the Sun, and the

Moon lining up in the sky blocking out light or casting shadows

2 types of Eclipses Depends which body is blocked Sun or Moon

Solar Eclipse – new moon comes directly btwn moon’s shadow, sunlight blocked from reaching the Earth Shadow has 2 parts: Umbra and Penumbra Umbra – small, inner shadow Penumbra – larger, outer shadow

Only people directly in the path of the umbra can see a total solar eclipse (sun completely blocked) Never look directly into the sun during a total

solar eclipse

Why isn’t there a solar eclipse every time there is a new moon?

Lunar Eclipse – Earth comes directly btwn sun and the Full Moon Phase Moon passes through the Earth’s

shadow Total Lunar Eclipse – moon passes

through umbra Partial Lunar Eclipse – moon passes

through penumbra dims moon’s glow to a reddish color when

sunlight is reflected off moon and is bent as it passes through the atmosphere

Tides Gravitational attraction btwn Moon

and Earth due to closeness Gravitational pull of Earth on moon

results in a bulging of the Moon surface facing the Earth

Moon also exerts gravitational pull on Earth pulling results in the rise and fall of the oceans as the Moon moves around the Earth

Tides – rise and fall of oceans

2 places on Earth that bulge due to the Moon’s gravitational pull causing high tides: Side of Earth facing the Moon Side of Earth facing away from the

Moon Low Tides occur btwn the bulges 2 high tides and 2 low tides occur

every 24 hrs High and low tides occur abt 50 min.

later each day due to the moon’s risng 50 min. later

Spring Tides – higher than normal during full and new moon phases Due to sun and moon being in direct

line with the Earth and increased effect of sun’s gravity on Earth

Neap Tides – high tides that are lower that usual Occur during the first and last quarter

phases, gravitational pull on oceans is partially canceled by sun’s gravitational pull

Sun and moon at right angles of the Earth