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WHY DO THE LENGTHS OF DAY AND NIGHT CHANGE WITH THE SEASON AND LATITUDE?. September 21. VIEW FROM OVER THE SUN LOOKING DOWN ON EARTH’S NORTH POLE. North Pole (Constant tilt). SUN. December 21. June 21. N. 66.5°N. March 21. Arctic C. Cancer. 23.5°N. Equator. 0°. Capricorn. - PowerPoint PPT Presentation
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WHY DO THE LENGTHS OF DAY AND NIGHT CHANGE WITH THE SEASON
AND LATITUDE?
SUN
March 21
December 21
N
s
Equator
Antarctic C.
Cancer
Arctic C.
Capricorn
June 21
September 21
66.5°N
23.5°N
66.5°S
23.5°S
0°
VIEW FROM OVER THESUN LOOKING DOWNON EARTH’S NORTH
POLE.
North Pole(Constant tilt)
SUN
March 21
December 21June 21
September 21VIEW FROM OVER THESUN LOOKING DOWNON EARTH’S NORTH
POLE.North Pole
(Constant tilt)
Half of Earth indarkness
Circle of IlluminationDay/Night
SUN
March 21
December 21 June 21
September 21
SUN
March & September 21
June 21December 21
N
s
Equator
Antarctic C.
Cancer
Arctic C.
Capricorn All places in the world spend equal lengthsof time in the dark (night) and lighted (day).
EQUINOXES
SUN
March 21
December 21
N
s
June 21
September 21
Places in northern hemisphere spend more than half a dayin darkness. Proportion of rotation in darkness increases to the Arctic Circle
Places in southern hemisphere spend more than half a dayin light. Proportion of rotation in daylight increases to the Antarctic Circle
December 21
Antarctic Circle
Arctic Circle
SUN
June 21
December 21
March 21
September 21
N
s
Places in southern hemisphere spend more than half a dayin darkness. Proportion of rotation in darkness increases to the Antarctic Circle.
Places in northern hemisphere spend more than half a dayin light. Proportion of rotation in daylight increases to the Arctic Circle.
Arctic Circle
Antarctic Circle
SUN
March & September 21
December 21
N
s
Equator
Antarctic C.
CancerArctic C.
Capricorn
N
s
June 21N
s
September 21
LatitudeDegrees
North
June SolsticeHours ofDaylight
March/SeptemberEquinoxHours ofDaylight
December SolsticeHours ofDaylight
90 6 months 12hr 0 hr
80 4 months 12hr 0 hr
70 2 months 12hr 0 hr
66.5 24 hr 12hr 0 hr
50 16 hr 12hr 8 hr
40 15 hr 12hr 9 hr
30 14 hr 12hr 10 hr
20 13 hr 12hr 11 hr
10 12.5hr 12hr 11.5 hr
0 12hr 12hr 12 hr
N
s
N
s
Equator
Antarctic C.
CancerArctic C.
Capricorn
N
s
THE BOTTOM LINE
THE BOTTOM LINE
• 1. All places at the equator receive 12hrs of daylight and 12hrs of darkness regardless of the season.
LatitudeDegrees
North
June SolsticeHours ofDaylight
March/SeptemberEquinoxHours ofDaylight
December SolsticeHours ofDaylight
90 6 months 12hr 0 hr
80 4 months 12hr 0 hr
70 2 months 12hr 0 hr
66.5 24 hr 12hr 0 hr
50 16 hr 12hr 8 hr
40 15 hr 12hr 9 hr
30 14 hr 12hr 10 hr
20 13 hr 12hr 11 hr
10 12.5hr 12hr 11.5 hr
0 12hr 12hr 12 hr
N
s
N
s
Equator
Antarctic C.
CancerArctic C.
Capricorn
N
s
THE BOTTOM LINE
• 1. All places at the equator receive 12hrs of daylight and 12hrs of darkness regardless of the season.
• 2. On March 21 and September 21 (Equinoxes) all places in the world receive 12 hrs of daylight and 12hrs of darkness regardless of their latitude.
LatitudeDegrees
North
June SolsticeHours ofDaylight
March/SeptemberEquinoxHours ofDaylight
December SolsticeHours ofDaylight
90 6 months 12hr 0 hr
80 4 months 12hr 0 hr
70 2 months 12hr 0 hr
66.5 24 hr 12hr 0 hr
50 16 hr 12hr 8 hr
40 15 hr 12hr 9 hr
30 14 hr 12hr 10 hr
20 13 hr 12hr 11 hr
10 12.5hr 12hr 11.5 hr
0 12hr 12hr 12 hr
N
s
N
s
Equator
Antarctic C.
CancerArctic C.
Capricorn
N
s
THE BOTTOM LINE
• 1. All places at the equator receive 12hrs of daylight and 12hrs of darkness regardless of the season.
• 2. On March 21 and September 21 (Equinoxes) all places in the world receive 12 hrs of daylight and 12hrs of darkness regardless of their latitude.
• 3. All places lying north of the Arctic Circle (66.5°N) or south of the Antarctic Circle (66.5°S) will experience at least one day of total darkness and one of total daylight.
LatitudeDegrees
North
June SolsticeHours ofDaylight
March/SeptemberEquinoxHours ofDaylight
December SolsticeHours ofDaylight
90 6 months 12hr 0 hr
80 4 months 12hr 0 hr
70 2 months 12hr 0 hr
66.5 24 hr 12hr 0 hr
50 16 hr 12hr 8 hr
40 15 hr 12hr 9 hr
30 14 hr 12hr 10 hr
20 13 hr 12hr 11 hr
10 12.5hr 12hr 11.5 hr
0 12hr 12hr 12 hr
N
s
N
s
Equator
Antarctic C.
CancerArctic C.
Capricorn
N
s
THE BOTTOM LINE• 1. All places at the equator receive 12hrs of daylight and
12hrs of darkness regardless of the season.• 2. On March 21 and September 21 (Equinoxes) all places in
the world receive 12 hrs of daylight and 12hrs of darkness regardless of their latitude.
• 3. All places lying north of the Arctic Circle (66.5°N) or south of the Antarctic Circle (66.5°S) will experience at least one day of total darkness and one of total daylight.
• 4. As one moves geographic position from the equator to the poles the differences in summer and winter lengths of day and night become more extreme.
Fairbanks, Alaska,Midday, December 21.
Spitzbergen, Norway,Midnight, June 21.
Sun Rise - Sun Set, DaylightGainesville, Florida, 29°N
DarknessHours of Daylight
Julian Day0 30 60 90 120 150 180 210 240 270 300 330 360
Tim
e of
Day
(24h
r. cl
ock)
and
Day
light
(hrs
)
0
4
8
12
16
20
24
0
4
8
12
16
20
24J F M A M J J A S O N D
Sun Rise - Sun Set, DaylightGainesville, Florida, 29°N
DarknessHours of Daylight
Julian Day0 30 60 90 120 150 180 210 240 270 300 330 360
Tim
e of
Day
(24h
r. cl
ock)
and
Day
light
(hrs
)
0
4
8
12
16
20
24
0
4
8
12
16
20
24J F M A M J J A S O N D
Sun Rise - Sun Set, DaylightGainesville, Florida, 29°N
DarknessHours of Daylight
Julian Day0 30 60 90 120 150 180 210 240 270 300 330 360
Tim
e of
Day
(24h
r. cl
ock)
and
Day
light
(hrs
)
0
4
8
12
16
20
24
0
4
8
12
16
20
24J F M A M J J A S O N D
Sun Rise - Sun Set, DaylightGainesville, Florida, 29°N
DarknessHours of Daylight
Julian Day0 30 60 90 120 150 180 210 240 270 300 330 360
Tim
e of
Day
(24h
r. cl
ock)
and
Day
light
(hrs
)
0
4
8
12
16
20
24
0
4
8
12
16
20
24J F M A M J J A S O N D
Sun Rise - Sun Set, DaylightSan José, Costa Rica, 10°N
DarknessHours of Daylight
Julian Day0 30 60 90 120 150 180 210 240 270 300 330 360
Tim
e of
Day
(24h
r. cl
ock)
and
Day
light
(hrs
)
0
4
8
12
16
20
24
0
4
8
12
16
20
24J F M A M J J A S O N D
Sun Rise - Sun Set, DaylightSouthampton, England, 51°N
DarknessHours of Daylight
Julian Day0 30 60 90 120 150 180 210 240 270 300 330 360
Tim
e of
Day
(24h
r. cl
ock)
and
Day
light
(hrs
)
0
4
8
12
16
20
24
0
4
8
12
16
20
24J F M A M J J A S O N D
