Download Earth is an

Earth In Space
Chapter 3
Shape of the Earth

Ancient Greeks

Earth casts a circular shadow on the moon during a lunar eclipse
Shape of the Earth

Ancient Greeks

Ships were observed to “disappear” below the horizon as they sailed
away from the viewer
____________
(276-195 B.C.)

Astronomer

used geometry to ___________ the ___________ of the _________
Eratosthenes
(276-195 B.C.)

Sunlight shone straight down a well at Syene, Egypt

June 21

Alexandria is 800 km from Syene
Eratosthenes
(276-195 B.C.)

Measured shadow cast by tall obelisk in Alexandria

Calculated angle


7° 12’
exactly 1/50 of a circle
Eratosthenes
(276-195 B.C.)


If the angle is 1/50 of a circle
Then the distance between Alexandria and Syene must be
1/50th the circumference of the Earth
Eratosthenes
(276-195 B.C.)

50 x 800 km = 40,000 km

Actual distance

40,075 km
Earth is an _______ ___________
Earth in Motion

Rotation


~1000 mph
Revolution

Moon around Earth
 2300

mph
Earth around Sun
 66,000
mph
Earth in Motion

Revolution

Solar system around Milky Way
 230,000
mph
Three Main Movements of the Earth

____________

____________

______ on Axis
Revolution
1 trip takes ____________ days
 Earth moves ______ at _________, _________ at
__________.

Rotation

The Earth’s axis maintains an average incline, or ______, on
its axis. (______°)

Axis points _______ the _______ for _________, then turns
________ for ____________.

3 effects: length of day/night, changing seasons, changing
climates with latitude (know this)
Earth’s Tilt (KNOW)


Full daylight at NP
Full darkness at SP
Full daylight at SP
Full darkness at NP
Solstices

________ Solstice

the sun is at its ________ point
 _______
has 24 hour light
overhead ______________ of _______________
____________
 directly
Solstices

__________ Solstice

the sun is at its __________ point
 ________
has 24 hour light
overhead _____________ of ______________
______________
 directly
Equinoxes

___________ __________


_________ ______
sun’s rays strike the equator almost directly and Earth is illuminated
from pole to pole
Equinoxes

___________ ___________


__________ ___
___________
sun’s rays strike the equator almost directly and Earth is illuminated
from pole to pole
What causes the seasons?

Caused by Earth’s _________


length of time sunlight falls on a particular location
angle at which sunlight hits a region determines amount of
solar energy
Seasons in Northern Hemisphere
Wobble on Axis

_________ is ______ ____________ at 23.5 degrees
Wobbles back and forth from 22.1 degrees to 24.5 degrees
and back to 22.1 degrees.
 Caused by ___________ _________ of Sun and Moon on
______________ _________.

Evidence of Rotation

Observation of other planets rotating

Rotating planets are oblate spheroids just like earth
Jean Bernard Foucault (1851)

________ ____________

Slowly turns clockwise

demonstrates counter-clockwise __________ of the __________ under
the swing of the pendulum
Pantheon in Paris
Pendulum Swing Changes with Latitude

North Pole


Complete turn every 24 hours
Equator

No turn at all
Rotational Velocity

Different latitudes have different speeds

_________ rotational ________ at __________

A point at the equator has to go farther than a point in Alabama, so it must go
faster
Coriolis Effect

An __________ _________ of the path of an object that moves
within a ___________ coordinate system
Coriolis Effect

Objects moving __________ from the equator will be moving
east _______ than the ground

Appear to be forced ________ east
Coriolis Effect

Objects moving __________ the __________ will be moving
__________ than the east-moving ground

Appear to be forced farther ________
Coriolis Effect

Northern Hemisphere

Objects moving north or south will appear to turn to the right (KNOW)
Coriolis Effect

Southern Hemisphere

Objects moving north or south will appear to turn to the left (KNOW)
Identifying Your Location on Earth
Parallels

East and west running circles parallel to the equator
Latitude (parallels running east and
west)--know

Angular distance from equator to parallel

measured in degrees
Meridians

North and south running arcs that intersect at both poles
Longitude (arcs running north and
south) - know

Angular distance from prime meridian east or west

measured in degrees
_________ Observatory, ________

_______ __________ of the world

Longitude _______

Every place on Earth is measured east or west from here
Finding a Location

New Orleans


30° N, 90° W
Subdivisions of angular distance


1° = 60 minutes (60’)
one minute = 60 seconds (60”)
Other Points of Reference

Tropic of ____________

__________

_________ border of the ____________


Northern Solstice
Tropic of __________

_________

___________ border of the ____________

Southern Solstice
Other Points of Reference

_________ Circle

___________


__________ limit of area where sun does _______ ________ on __________
solstice
__________ Circle

____________

________ limit of area where sun does______ ______ on _________ solstice
Measuring Time
Sun Time and Clock Time
What is “noon”?

When the sun crosses the _________ ________, _______ has
occurred
_______ ______ Noon
Whenever noon occurs at a given location (longitude)
 A.M. = _______ _________



morning hours before sun crosses meridian
P.M. = _______ ________

afternoon hours after sun crosses meridian
________

_______ _______ _______ time

time from the position of the Sun in the sky

the shadow of the gnomon on the sundial
Caesar Augustus’ Sundial
Rome, Italy
Apparent Local Solar Time Changes

Nonuniform and fluctuating

Reasons
 Earth
moves sometimes faster and sometimes slower in its
elliptical orbit around sun
 Tilt
of Earth
Apparent Solar Day vs. Sidereal Day

_________ _______ Day

interval between _______ ____________ ____________ of the
celestial meridian by the Sun

_______ ____________
Apparent Solar Day vs. Sidereal Day

_________ Day




interval between ________ _________ _________ of the celestial
meridian by a particular ______
time for Earth to rotate on axis (KNOW)
sidereal means “_______”
______ hrs ______ min ______ sec
Why is the Apparent Solar Day ______?

Earth must rotate a little farther to compensate for orbit

______ extra minutes
Apparent Solar Day vs Sidereal Day



At time 1, the sun and a certain distant star are both overhead.
At time 2, the planet has rotated 360° and the distant star is overhead
again (1→2 = one sidereal day).
But it is not until a little later, at time 3, that the sun is overhead again
(1→3 = one solar day).
Apparent Solar Day vs Sidereal Day
Apparent Solar Day vs Sidereal Day
Standard Time Zones

Each longitudinal line has a different “measure” of
time

360°  24 longitudinal lines = 15° each
Moving _____ = ______ 1 hour
 Moving ______ = ______ 1 hour


International Date Line (______ °)

Moving __________– __________ day
Moving __________ – __________ day

What is a Year?

__________ Year

Interval between two consecutive ___________ equinoxes

365 days, 5 hours, 48 minutes, and 46 seconds
 365.24220
mean solar days
What is a Year?

________ year
time required for the Earth to move around its orbit so the
Sun is again in the same position relative to the stars
 _______ than tropical year by ____ minutes

Fixing the Calendar

________ Calendar

Julius Caesar (46 B.C.)
 _____
days per year
day year every fourth year (______ year)
 Year started at Spring Equinox
 July (after Julius) & August (after Augustus)
 366th
Fixing the Calendar

_________ Calendar (_______ ________)

Pope Gregory XIII (1582)
 Revised

Julian calendar
off by 11 minutes 14 seconds per year
only century years divisible by 400 are leap years
the year 2000 is leap year
the year 2100 is not a leap year
The Moon
The Moon

384,000 km from Earth (238,000 miles)

Diameter



~3500 km
~2200 miles
Revolution


3680 km/hr
~2300 mi/hr
The Moon

_______ _________


_______-colored
__________

gravel or boulders compacted together

Density (2.9 g/cm )

meteorite impacts
3
The Moon

________ (“______”)


Smooth _____-colored
________

lava rock

Density (3.3 g/cm )
3
The Moon


No atmosphere
Temperature



-300 degrees F (night)
417 deg F (day)
205 deg F (at poles)
The Moon
 _________
is covered with fine, glassy
_______
 ____________
The Moon

Moon’s period of rotation is ________ to one revolution
around the Earth


always see same side of moon from Earth (KNOW)
_______ days
Earth-Moon System

Moon is about 1/81 the mass of the Earth


Large enough to move center of mass away from center of Earth
Slightly wavy path around Sun

Act as a system
Earth-Moon System
Moon is > ¼ Earth’s diameter
larger in comparison to its planet than any other moon
provides just enough
light
large enough to keep
spherical shape
Phases of the Moon

Results from Sun, Earth, & Moon positions




_______ _______
_______ _______
_______ _______
_______ _______
The Rest of the Story
Moon Phases
________ _________

The Moon’s __________ side is facing the ___________.

Not visible except during solar eclipse
__________ ________

The Moon is _____________ than __________ illuminated by
direct sunlight

__________ of the Moon’s disk that is illuminated is _______________
_________ Quarter

____________ the moon is _________ by direct sunlight

____________ of moon’s disk that is illuminated is ____________
____________

__________ than __________, but not fully, ______________

____________ of moon illuminated is _______________
__________ Moon

______________ _____________ on side ____________ Earth
___________ ___________

_________ than ______________, but not fully, ___________

____________ of moon illuminated is ________________
_________ Quarter

___________ of moon is ____________

____________ of moon illuminated is _______________
__________ __________

Moon is _________than _________ illuminated

___________ of moon illuminated is __________
Eclipses

Earth’s or Moon’s shadow falling on the other body (know
this)


Uncommon because of 5° incline of Moon to Earth
Sun, Moon, and Earth have to be in line
Eclipses

Any shadow of any body consists of two parts


___________ – region of _________ ___________
________________ – outer _________ of ___________ _________
Lunar Eclipse
Occurs when the Moon passes through some portion
of Earth’s shadow. (KNOW)
 CAN ONLY OCCUR AT ______ ______

Lunar Eclipse Types

________________


________________
________________
Penumbral Lunar Eclipse


Full moon enters earth’s penumbral shadow
Moon dims a little
Partial Lunar Eclipse


Part of the moon is within Earth’s umbra
Moon is partially shadowed
________ ________ Eclipse

Moon is completely shadowed by earth



________________ ________________ ________________
No direct light from sun reaches the moon
Varies in color




Near black
Red
Copper
orange
Lunar Eclipse
Why does the moon turn
RED???
Lunar Eclipse
_________ Moon
Light
from sun is __________(bent)
by Earth’s atmosphere and
___________
Lunar Eclipse animation
Solar Eclipse

Occurs when the Moon passes between the Earth and
Sun (KNOW)

CAN ONLY HAPPEN AT _______ ______

Next solar eclipse visible from US: August 21,
_________
Annular Solar Eclipse

Moon covers center of sun, but not its edges

Moon is too far away from Earth
Tides

________ _______ and _______ of sea level
Greatest range = _____ and ______ moon
 Least range = ________ moons


____ high tides and _____ low tides daily in a coastal
location
Tides

___________ __________ attracts water and land

nearness of moon to Earth makes its gravity twice as effective as
Sun’s
Tides

Side ________ moon


________ tide
________ side

Earth is pulled away from from the ocean



______ tide
tidal trough
Other sides 90 degrees away

______ tide
Tides

_________ tidal range at ______moon and _______ moon

____________ Tides


Gravity of Sun and Moon act on Earth
All in line
Tides

___________ tidal range at quarter moons

__________ Tides


Sun and moon are at right angles
______________ ____________ of Moon
Tides

Greatest Spring Tides

Moon is closest to Earth

Perigee


28,000 miles closer than Apogee
Moon is Full or New
Tides

Size of Tides also determined by size, shape, and depth of
water basin

Coastal Regions

3-10 feet

Gulf of Mexico

Lakes and ponds

Bay of Fundy



1 foot
too small
50 feet