Earths rotation and revolution

1
Earths rotation and revolution

• Rotation and revolution

2
The earths rotation and time

• The earth undergoes one complete rotation along
  its axis in 24 hours.
• For one complete rotation, the earth passes
  through 360 degrees of longitude.  
• For every one-hour time, a point on the earth
  moves through 15 degrees of longitude (360/24
  hours 15o).
• For every 4 minutes, a point on the earth passes
  through 1 degree of longitude

3
Earths rotation and time

• The earth rotates in an anti-clockwise direction
  (From West to East).
• Places on the East side of a given point on the
  earth are ahead of time while those to the West
  side of the same point always lag behind in time.
  
• The most important result of the earth's rotation
  is the daily pattern of DAYS and NIGHTS

4
Longitude and Time
5
Coordinated Universal Time
6
Standard Time in North America

• In 1878, Canadian Sir Sanford Fleming suggested a
  system of worldwide time zones.
• Fleming proposed that the globe be divided into
  24 time zones, each 15 degrees of longitude in
  width.
• Railroad companies in Canada and the United
  States began using Fleming's time zones in 1883.
• In 1884, an International Prime Meridian
  Conference in Washington D.C. accepted it.

7
Time Zones in North America

• Mainland US is divided into 4 Time Zones
• Eastern Time Zone New York, Boston
• Central Time Zone - Chicago
• Mountain Time Zone Denver
• Pacific Time Zone Los Angeles

8
International date line

• Each new calendar day begins at midnight on the
  International Date Line (Longitude 180o).
• Crossing the date line causes adjustments to
  clocks dates.
• Traveling from West toward East (Hawaii to Japan)
  one jumps into a new day on crossing the Date
  line.
• From East towards West (Japan to Hawaii), one
  looses a day after crossing the line

9
Environmental Effects of Rotation

• The Imposition of Day/Night rhythm
• The redirection of the flow paths of both air and
  water that flows over the earths surface.
• Flows in the Northern Hemisphere Right
• Flows in the Southern Hemisphere - Left
• Rise and fall in Tidal Waves over the oceans.

10
Earths revolution round the Sun

• The earth revolves around the Sun on its own
  ORBIT (oval-shaped path).
• Perihelion A point on the orbit where the earth
  is closest to the sun - January 3rd
• Aphelion A point where the sun is farthest away
  from the SUN - July 4th.
• On its orbit round the sun, the earth moves
  through a plane called the PLANE OF THE ECLIPTIC.

11
Earths inclination and the Seasons
12
Earths revolution

• The earth's axis is inclined to the orbit at an
  angle of 23.50
• Inclination of the earths axis during the
  movement round the Sun results in the following
• 1. different positions of the noon Sun
• 2. different positions of Sun rise and sun set
• 3. different length of days nights in a year
• 4. different shadow lengths during the seasons

13
Results of the resolution Equinoxes

• March 21 is Spring Equinox and
• September 21 is Autumnal Equinox.
• On these days, the noon Sun is points directly on
  the equator so
• ALL PLACES on the earths surface receive
  approximately 12 hours of daylight and 12 hours
  of darkness.

14
Images of the four seasons
1. Summer
2. Fall (Autumn)
3. Spring
4. Winter
15
Results of the revolutionSummer solstice

• June 21st (Summer Solstice)
• Places in the Arctic circle points directly
  toward the sun so the Northern Hemisphere receive
  more sunlight (hence longer days and shorter
  nights)
• On this day, places in the Southern Hemisphere
  receive less sunlight (so shorter days and longer
  nights).

16
Northern Hemisphere during the Summer Solstice

• In summer the earths axis lean toward the sun so
  the energy we receive from the sun is more direct
• The sun also remains in the sky for longer
  periods and as such the earths surface absorbs
  more solar energy
• The high temperatures produce summer conditions.

17
Winter solstice

• December 21st (Winter Solstice)
• On this day, the Sun moves into the Southern
  Hemisphere and places there receive more sunlight
  and experience longer days and shorter nights.
• The Northern hemisphere receive less sunlight (so
  shorter days and longer nights).

18
Northern Hemisphere during the Winter Solstice

• Because the earths axis point to the same
  direction toward the North Star, the Northern
  hemisphere leans back on the Sun during winter
• The Sun is lower in the sky and its energy is
  more widely distributed
• The Sun is also visible for a much shorter time
  giving off little energy so temperature goes down
  producing winter conditions

19
Summer and Winter Seasons
NORTHERN SUMMER
NORTHERN WINTER