STUDENT

1. The Earth Rotation

2. Equatorial Diameter 12756km
Polar Diameter
12714km
Mass 6×1024
kg
Mean distance from Sun 150 M km
Rotation Period 23h
56min
Solar orbit period 1 year
Surface gravity 9.8 m/s2
Surface Temperature 15o
C

3.  What is rotation?
 The Earth's axis runs from the North Pole to the South Pole. It
takes the Earth 24 hours, or one day, to make 1
complete rotation around this invisible line. As the
Earth rotates, each area of its surface gets a turn to face and be
warmed by the sun
 A rotation is a circular movement of an object around a center
of rotation. A three-dimensional object can always be rotated
around an infinite number of imaginary lines called rotation
axes.
 Why is rotation important?
• Axis serves as reference for geographic grid (latitude and
longitude)
• Measure for time (time zones)
• Affects physical and life processes

5.  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 Earth’s tilt)

6.  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)

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

9.  March (vernal) and September (autumnal)
 Sun’s rays hit equator at 90° (subsolar pt.)
 All latitudes receive ~12 hrs of daylight
 Circle of illumination from North Pole to
South Pole

10.  Occur in June (summer) and December (winter)
 Subsolar point in June: Tropic of Cancer (90°N); in Dec:
Tropic of Capricorn (90°S)
 June solstice: areas from 66.5°N to North Pole receive 24
hrs of daylight
 Winter solstice: areas from 66.5°S to South Pole receive 24
hrs of daylight