The Earth as a Rotating Planet

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The Earth as a Rotating Planet

• Chapter 1

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The Shape of the Earth

• Earth or Sun moving?
• Early sailors view
• Is the Earth a perfect sphere?
• (Quasi-sphere)Rotation causes it to bulge at
  the Equator and flatten at the Poles Oblate
  Spheroid

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Earth Rotation

• What is rotation?
• What direction does the Earth rotate?
• How long does it take to rotate?
• 3 main effects of rotation
• Why is rotation important?
• Axis serves as reference for geographic grid
  (latitude and longitude)
• Measure for time (time zones)
• Affects physical and life processes

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Earth Rotation
Figure 1.2 (P. 26)
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The Geographic Grid

• What is a geographic grid?
• A system for locating or determining the location
  of places on the Earths surface
• Demarcations for hemispheres
• Latitude-Distance N or S of the Equator (0
  degrees latitude) Parallels
• Tucson is approximately 30 degrees North
• Longitude-Distance E or W of the Prime Meridian
  (0 degrees longitude)

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A few more points about the latitude and
longitude...

• Location of a point is given as
• latitude (in degrees N or S), longitude (in
  degrees E or W)
• There are two techniques for indicating a more
  detailed location
• Decimal degrees 32.13
• Degrees, minutes, seconds 32 07 48

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Determining a location with latitude and longitude
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Parallels and Meridians
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Examples

• What city is located at 37S and 144E?
• Melbourne, Australia
• What city is located at 40N and 105W?
• Denver, CO
• What city is located at 51N and 0W?
• London, England
• Distances Given the fact that the circumference
  of the Earth is 24,860 miles and there are 360
  in a circleHow many miles are there in 1 of
  longitude at the Equator?

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Calculating Distances between Lines of Latitude

• Latitude(69 miles) x (difference in degrees
  latitude)
• Example 1 Calculate the number of miles between
  Atlanta (33N, 84W) and New York City (40N,
  74W).
• Latitude(69) x (7)483 miles
• Example 2 Calculate the number of miles between
  Prague (50N, 14E) and Tripoli, Libya (32N,
  13E).
• Latitude(69) x (18)1,242 miles

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Calculating Distances between Lines of Longitude
(Difficult)

• Longitude(69 miles) x (COS of parallel traveled)
  x (difference in degrees long.)
• Example 1 Calculate the number of miles between
  Cairo, Egypt (30N, 31E) and New Delhi, India
  (28N, 77E). Assume travel along the 29N
  parallel.
• Longitude(69) x (COS 29) x (46)2,777 miles

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Map Projections

• A map is just an abstraction or representation of
  the real world. The art and science of
  map-making is called cartography.
• When you are trying to represent a curved surface
  on flat paper, you get distortion. Why?
• Map units

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From Earth to a map

• Start with ellipsoid
• Difficult, if not impossible, to take a curved
  surface and place it on a flat surface
• Result is distortion
• All maps have some type of distortion

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Five Types of Distortion 1 more

• Type Example
• Shape Circle becomes oval
• Scale Map scale changes
• Area Land mass gets bigger
• Distance Space between cities increases
• Direction Line varies N to NW

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Polar Projection

• Characteristics a circular map centered on North
  or South Poles and usually showing one hemisphere
  at most meridians are straight lines parallels
  are circles
• Advantage Preserves shapes
• Disadvantages scale and area distortion

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Mercator Projection

• A type of conformal projection
• Characteristics rectangular meridians and
  parallels are both straight lines
• Advantage straight line drawn on map represents
  a constant compass direction
• Disadvantages scale, area, and distance
  distortion

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Goode Projection

• A type of equal-area projection
• Characteristics odd shape meridians both
  straight and curved lines parallels are straight
  lines
• Advantage Preserves area
• Disadvantage shape distortion

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Global Time

• How many world time zones? US?
• Not exactwhy?
• Solar noon period when Sun appears to be highest
  in the sky
• Lines of longitude used for time zones
• 15 of longitude 1 hr of time (360 in one
  rotation 24 hrs 15 per hour)
• Example 1 If it is 1 a.m. in Washington D.C.,
  what time is it in Honolulu, Hawaii?
• 8 p.m
• Example 2 If it is Noon in Charlotte, NC, what
  time is it in Madrid, Spain?
• 6 p.m.

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U.S. time zones
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Time zones
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Global Time (contd)

• International Date Line
• Located approximately along 180
• Why? 180 15 per hr 12 hr. So if its 1pm
  on the Prime Meridian, the IDL is 1am (next day).
• West adds a day
• East subtract a day
• Daylight Savings Time
• Midnight Meridianthe meridian that is
  experiencing midnight (the midnight meridian is
  NOT stationary)

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Time Examples

• If it is 10 a.m. in Santiago, Chile on Tuesday,
  May 25, what is the time and date in Taipei,
  Taiwan?
• 10 p.m. the same day
• If it is 1 p.m. in Juneau, Alaska on Saturday,
  June 12, what is the time and date in Tokyo,
  Japan?
• 7 a.m. the next day (June 13)

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Longitudnal Time Problems

• Example 1 If you depart Washington D.C. (33N,
  77W) at Noon, at what speed would you have to
  travel to arrive in Denver, CO (39N, 105W) at
  Noon? Assume travel along the 35N parallel.
• Miles(69) x (COS 35) x (28)1,582 miles
• 1,582 miles / 2 791 mph
• Example 2 If you depart Philadelphia, PA (40N,
  75W) at 1 p.m., at what speed would you have to
  travel to arrive in Seattle, WA (48N, 122W) at
  2 p.m.? Assume travel along the 45N parallel.
• Miles(69) x (COS 45) x (47)2,293 miles
• 2,293 miles / 4 573 mph

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Earths Revolution

• Movement of the Earth around the Sun
• Counterclockwise if viewed from above
• One revolution 365.242 days 1 yr
• Responsible for
• Seasons
• Amount of daylight (along with Earths tilt)

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Earths Revolution (contd)

• When viewed from above, notice that path of Earth
  is not a perfect circle, but an ellipse or oval.
• Perihelion
• When Earth is closest to the Sun
• Occurs in January (Northern Hemisphere winter)
• Aphelion
• When Earth is farthest from the Sun
• Occurs in July (Northern Hemisphere summer)

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Earths Revolution
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Earths Revolution (contd)

• Along with perihelion and aphelion, other times
  in revolution also have specific names equinoxes
  and solstices.

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Equinoxes

• March (vernal) and September (autumnal)
• Suns rays hit equator at 90 (subsolar pt.)
• All latitudes receive 12 hrs of daylight
• Circle of illumination from North Pole to South
  Pole

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Solstices

• Occur in June (summer) and December (winter)
• Subsolar point in June Tropic of Cancer
  (23.5N) in Dec Tropic of Capricorn (23.5S)
• June solstice areas from 66.5N to North Pole
  receive 24 hrs of daylight (movie Insomnia)
• Winter solstice areas from 66.5S to South Pole
  receive 24 hrs of daylight