Transcript Reasons for the Seasons

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Reasons for the Seasons
Chapter 17.1
Nearly 150 million kilometers separate the sun and
Earth, yet solar radiation drives Earth's weather.
Figure 1.1
Does the distance from the Sun make the
Seasons?
• NO
• The Earth is actually farther away from the
Sun when we have our Summer.
Perihelion- Earth is closer to the Sun
January 3rd
Aphelion- Earth is farthest from the Sun
July 6th
Reason for the Seasons
1. The Earth’s tilt causes the seasons
• It is tilted at 23.5 degrees
• The angle of the sun’s
radiation (Insolation) hitting
the Earth impacts the
climate or temperature.
If the tilt were the only factor, then every
location on Earth would have one season
and it would never change.
2. Earth’s Revolution
• Causes the Suns rays to strike at different locations
as the Earth orbits the Sun.
When northern hemisphere is facing the sun:
•Summer Solstice (June 21st or 22nd )
SUMMER SOLSTICE
• Most direct rays over Northern Hemisphere
• •Striking at Tropic of Cancer 23.5° N.
• Light = 15 hours (about 14.27 (NC) Dark = 9 hours
Antarctica is completely dark for 24 hours and
the Arctic is completely light for 24 hours!!!
Fall Equinox (September 22 or 23)
• EQUAL amounts of daylight and darkness everywhere.
• Direct rays over Equator:
• Light = 12 hours
Dark = 12 hours
• Winter Solstice - December 21-22
• SHORTEST DAY !!!
• Most direct rays over Southern hemisphere
•Striking at Tropic of Capricorn 23.5°S
• Light = 9 hours
Dark = 15 hours
Spring Equinox (March 21 or 22)
• EQUAL amounts of daylight and darkness everywhere.
• Direct rays over Equator:
• Light = 12 hours
Dark = 12 hours
The Southern Hemisphere has opposite
Seasons than us . . . WHY?
Light - Year
– The unit used to measure
stellar (star) distance.
• The distance that light travels
in one year.
– 9.5 x 1012 kilometers a year.
– 180,000 miles per second.