TIME AND SEASONS by mikesanye

VIEWS: 1 PAGES: 15

									TIME AND SEASONS
       TIME AND SEASONS
A. Earth Movements Measure Time
   1. Earth spins and makes one complete
   turn in about 24 hours.
   2. This spinning causes the Sun to appear
   to move across the sky from east to
   west.
   TIME AND SEASONS
3. If Earth spins approximately 360° in
24 hours, then it spins through 15° in
one hour.

4. A time zone is an area 15° wide in
which time is the same.

5. For convenience, time zones are
modified to fit around city, state, and
country borders, and other key sites.
TIME AND SEASONS
     TIME AND SEASONS
B. The Date Line
  1. A day is added to the time at the
  International Date Line.

 2. This line is drawn down through the
 Pacific Ocean directly opposite the
 Prime Meridian, the starting point for
 this worldwide system of measuring
 time.
     TIME AND SEASONS
C. Rotation Measures Days
  1. Rotation is the spinning of Earth on
  its axis, an imaginary line drawn through
  Earth from its rotational north pole to
  its rotational south pole.
  2. The apparent movement of the Sun
  from noon one day until noon the next
  day is called a solar day.
TIME AND SEASONS
     TIME AND SEASONS
D. Revolution Measures Years
 1. Revolution is the motion of Earth in
 its orbit around the Sun
     TIME AND SEASONS
E. Why do Seasons Change?
  1. Seasonal changes are caused by
  Earth’s rotation, its revolution, and the
  tilt of its axis.
  2. This means that the number of hours
  of daylight each day varies and the
  angle at which the sunlight strikes
  Earth’s surface varies at different
  times of the year.
     TIME AND SEASONS
F. Changing Angle of Sunlight
  1. The hemisphere tilted toward the Sun
  receives sunlight at higher angles than
  the hemisphere tilted away from the
  Sun.
       TIME AND SEASONS
G. More Hours of Daylight in the Summer
  1. As the year progresses, the number of hours of
  daylight each day becomes fewer. In the northern
  hemisphere, it reaches a minimum on Dec. 21 and a
  maximum on June 21.

  2. The hemisphere of Earth that is tilted toward
  the Sun receives more hours of daylight each day
  than the hemisphere tilted away from the Sun.
  This longer period of daylight is why summer is
  warmer than winter.
TIME AND SEASONS
     TIME AND SEASONS
H. Equinoxes and Solstices
  1. The Sun reaches an equinox when it is
  directly above Earth’s equator, and the
  number of daylight hours equals the
  number of nighttime hours all over the
  world. At this time, neither the northern
  nor the southern hemisphere is tilted
  toward the Sun. In the northern
  hemisphere, the spring equinox is on March
  21 and the Fall Equinox is on September
  21.
     TIME AND SEASONS
H. Equinoxes and Solstices
 2. The solstice is the point at which the
 Sun reaches its greatest distance north
 or south of the equator. In the summer
 solstice (June 21), there are more hours
 of daylight than during any other day of
 the year. In the winter solstice (Dec.
 21), there are less hours of daylight
 than during any other day of the year.
TIME AND SEASONS

								
To top