Transcript Models and Dimensions of Earth

Earth’s Shape and
Coordinate Systems
Shape of Earth
► Oblate
Spheroid – flattened sphere
 Flatter at the poles
 Bulges at the equator
► Diagram
of an oblate spheroid
 Equatorial Circumference –
24,900 mi
 Polar Circumference –
24,860 mi
Causes of Earth’s Shape
► Gravity
– an inward pulling force; causes
Earth to be spherical
► Centrifugal Force – an apparent
outward pulling force; caused
by spinning/rotating
 Causes Earth to bulge at equator
 As Speed
, there is greater centrifugal force
Centrifugal Force
► How
long does it take each location to rotate
360o?
► Which location travels the greatest distance during
a complete rotation?
X
► Which
Y
location has a greater speed?
► Which location has a greater centrifugal force?
Evidence of Earth’s Shape
► Photographs:
► Ships
almost a perfect sphere.
over the horizon: evidence that the
Earth is curved.
Evidence of Earth’s Shape
► Eclipse
of the Moon:
 As viewed form space:
2
From Earth:
Earth’s
Shadow
1
Position 2
Earth’s
Shadow
Full
Moon
Position 1
 As the moon orbits Earth it passes through
earth’s shadow; showing a spherical shadow.
Evidence of Earth’s Shape
► Gravity:
 Newton’s Law: gravity is greater when objects
are closer to each other.
 Where are you closer to
the center?
Equator
Force of
 Where would you weigh
gravity
more?
 What would make me
weigh the same everywhere on Earth?
Evidence of Earth’s Shape
► Polaris;
the North Star
 The altitude of Polaris changes as an observer
moves north or south (N. Hemisphere.)
Altitude: height measured in degrees that a
heavenly body is above the horizon to the observer.
►
 This is due to Earth’s spherical shape and
curved surface.
Altitude of Polaris
Location 1 = 90o N. Lat.
Location 3 = 35o N. Lat
Location 2 = 60o N. Lat.
Location 4 = 0o Lat
 The altitude of Polaris is equal to the latitude of
the observer.
 Measure angel from equator and from horizon.
► Locating
the North Star
Science and Math
(bro’s from way back)
► Math
was Science and Science was Math.
 How philosophers, intellectuals and students
connected with each other and tried to explain
their observations of the Earth.
►Galileo,
Newton, Einstein, Hawking
► Eratosthenes:
Greek Mathematician
 Determined the circumference of the Earth by
observing shadows and established a set of
ratios.
Eratosthenes
(273 – 192 BC)
•Draw a solid line
connecting each
location point to the
center of the Earth
•Measure angles with
your protractor.
Eratosthenes’ Methods
► Method
for determining Earth’s
circumference:
 Part
Whole
► Earth’s
Angle = Distance
xo/360o = d/c (circumference)
other measurements:
 Diameter: C =
d
 Radius: r = 1/2d
 Volume: (of a sphere) V = 4/3r3
 Area: A = 4r2
Latitude
► Angular
distance North and South of the
equator.
 Equator: 0o Latitude; starting place for North
and South latitudes
 North/South Poles: 90o Latitude; maximum
latitude on Earth.
 Parallels: lines used to
measure N & S latitude
run: “east to west”
►Parallel to the equator
►
Latitude: Parallels
► Draw
and label all parallels; using exact
measurements
to 90oNorth
► Color code labels
► 0o
End Product
Longitude
► Angular
distance east or west of the Prime
Meridian.
 Prime Meridian: 0o Longitude; starting point for
East and West longitude. Greenwich, England
 International Date Line: 180o Longitude;
maximum measurement for longitude.
► Meridians:
lines used to measure longitude;
run north to south.
 Lines converge at the poles.
Longitude: Meridians
► Mark
dot.
and draw a line every 15o to center
 Show direction (N.S.E.W.)
Earth’s Time Zones
► Half
of the Earth Faces the sun at all times
 ½ – Daylight
½ - Darkness
► When
the sun is directly above any meridian
(long) it is noon at or around that meridian.
► How
fast is Earth’s rotational speed?
► How many time zones are on Earth?
International Date Line
► If
it is Wednesday;
traveling West across
the IND; what day
will it become?
► Tuesday; traveling
East across IND; what
day will it become?
Use the map below to determine the latitude and longitude of
these numbered and lettered locations.
Name the Continents and Oceans indicated by the letters.
Practice
► How
many time zones?
► Earlier is CA or
NY?
► 8 EST = ? PST
► 6MST = ? EST
Reading a Map
► Complete
the
statements on pg 19
using the map
provided.