What causes day and night What causes seasons REVOLUTION, ROTATION, and the TILT of our Earth and it

1

• What causes day and night?What causes seasons?
  REVOLUTION, ROTATION, and the TILTof our Earth
  and its
• YEARLY TRIP AROUND THE SUN

EARTH SUN RELATIONSHIP
2
Earths Yearly Trip

• Earth REVOLVES around the SUN each year, or every
  365 days, 5hrs, 48 min., 46 sec.
• (Solar Days 365.2422)
• Moves along w/ Milky Way Galaxy as Galaxy rotates
  moves through space.
• (it takes more than 200 mil yrs for the stars in
  MW to complete one rev. around Galaxys center)

REVOLUTION
3
Earths Yearly Trip

• As Earth revolves around sun, it ROTATES spins
  on AXIS (imaginary line that runs btwn N and S
  Poles)
• One complete rotation 1 Day 23 hrs. 56 min.
  4.1sec.
• Earths Axis of rotation is INCLINED (tilted)
  23.5 relative to its plane of revolution around
  Sun.
• WHAT IS THE IMPORTANCE OF THE TILT?

ROTATION
4
Earths Yearly Trip

• Creates Seasons
• Causes height of Sun in sky at noon to increase
  and decrease as seasons change
• The hemisphere that is tilted toward Sun has
  longer days, receives more Suns rays, and
  receives Suns rays more directly than hemisphere
  tilted away from Sun
• N. Hemisphere receives most energy from Sun
  when tilted toward Sun (SUMMER)
• S. Hemisphere WINTER and VICE VERSA
• Fall and Spring occur in btwn these orientations
• Tilt causes N. Pole to be tilted toward Sun for ½
  of year and S. Pole other half.

TILT
5

• N. Hemisphere receives most energy from Sun
  when tilted toward Sun (SUMMER)

SEASONS
6

• S. Hemisphere It would be winter

SEASONS
7
Earths Yearly Trip

• SEASONS one of four divisions of the year,
  defined by the position of Earth in its orbit
  around the Sun.
• winter, spring, summer, fall (autumn)
• Characterized by diff. in av. temp. and in amount
  of time that Sun is in sky each day.
• Occurs b/c axis on which Earth turns is tilted w/
  respect to the plane of Earths orbit around Sun.
• If Earths axis wasnt tilted each day/night
  everywhere would always be 12 hours long and
  there would be no seasons.

SEASONS
8
Earths Yearly Trip

• Seasons have unequal number of days b/c Earths
  orbit is slightly elliptical (oval shaped), and
  Sun is not exactly at center of orbit.
• Also Earth moves slightly faster when it is
  close to the Sun seasons occurring when Earth
  is close to Sun pass quicker
• When is Earth closest to Sun?
• January
• When is Earth furthest from Sun?
• July
• What does this mean?
• Summer is longer than Winter in the N. Hemisphere
  and Winter is longer than Summer in the S.
  Hemisphere.

SEASONS
9
SEPTEMBER MARCH

• Advancing 90 days, the Earth is at the fall
  equinox on or about September 21st. 
• As the Earth revolves around the Sun, it is
  positioned such that the Sun is directly over the
  equator.  
• Basically, the Sun's energy is balanced between
  the northern and southern hemispheres. 
• The same holds true on the spring equinox near
  March 21st, as the Sun is once again directly
  over the equator. 
• This gives us fall and spring seasons.

SEASONS
10
DECEMBER

• Lastly, near December 21st, the Sun is positioned
  directly over the Tropic of Capricorn (WINTER
  SOLSTICE). 
• The southern hemisphere is therefore receiving
  the direct sunlight with less scattering of the
  sun's rays and a high sun angle producing long
  days.  (SUMMER)
• The northern hemisphere is tipped away from the
  Sun, producing short days and a low sun angle.
  (WINTER)
• June 21st marks the beginning of summer
  SUMMER SOLSTICE

SEASONS
11
SEASONS
SEPTEMBER
SEASONS
DECEMBER
JUNE
MARCH
12
Earths Yearly Trip

• The changes in temp. in length of daylight that
  accompany seasons differ greatly at diff.
  latitudes.
• POLES summer is 6 months of daylight and winter
  is 6 months darkness
• EQUATOR days/nights remain about 12hours
  light/dark yr around.
• ARCTIC/ANTARCTIC CIRCLES (66 1/2N 66 1/2S)
  Mark farthest points from poles at which there
  can be 24 hrs of daylight/darkness.
• MIDLATITUDES (midway btwn. Poles high latitudes
  and equator low latitudes) the length of
  daylight varies from about 8 hrs in winter to
  about 16 hrs in summer

LATITUDE
13

• What causes day and night?What causes seasons?
• What latitude do you live in and how are you
  affected by the tilt, rotation, and revolution of
  the earth?

Reflection