The Four SeasonsThe Four SeasonsWhat’s tilt got to do with it?What’s tilt got to do with it?

Vocabulary Vocabulary note how the terms compare in note how the terms compare in the opposite columns the opposite columns

Antarctic Circle Antarctic Circle Arctic Circle Arctic Circle

Tropic of CancerTropic of Cancer Tropic of CapricornTropic of Capricorn

autumnalautumnal vernal vernal

equinox equinox solsticesolstice

revolution revolution rotation rotation tilt tilt axisaxis

ObjectiveObjective The student can tell which factors

determine the four seasons.

The tilt of the earth, along with its 365 ¼ -day The tilt of the earth, along with its 365 ¼ -day revolution, results in our seasons.revolution, results in our seasons.

AxisAxis

The earth’s axis is an The earth’s axis is an imaginary line that runs imaginary line that runs through the middle of the earth through the middle of the earth from the North Pole to the South from the North Pole to the South Pole. The earth rotates on its axis Pole. The earth rotates on its axis which is tilted about 23 ½°. which is tilted about 23 ½°.

The earth’s tilt and its revolution causes the seasonsThe earth’s tilt and its revolution causes the seasons

A A solsticesolstice is either of the two times of the year when is either of the two times of the year when the sun is at its greatest distance from the equator: in the sun is at its greatest distance from the equator: in technical words, when the technical words, when the celestial equator and ecliptic reach their largest separation.

SolsticeSolstice

Stonehenge, England 2003Stonehenge, England 2003

Thousands gather here each year for Summer Thousands gather here each year for Summer and Winter Solstice celebrations. The and Winter Solstice celebrations. The widespread belief is that these rocks were set in widespread belief is that these rocks were set in ancient times to mark those days.ancient times to mark those days.

Pontiac SolsticePontiac Solstice

The summer solstice, The summer solstice, approximately June 21, approximately June 21, is the first day of summer is the first day of summer and the longest day of and the longest day of the year, occurring in the the year, occurring in the Northern Hemisphere Northern Hemisphere when the North Pole is when the North Pole is leaning more directly leaning more directly toward the sun than it toward the sun than it does on any other day. does on any other day.

Summer SolsticeSummer Solstice

The longest day…The longest day…

In June, the In June, the Northern Northern Hemisphere is Hemisphere is tilted toward the tilted toward the sun, so the sun, so the people in the people in the Northern Northern Hemisphere Hemisphere have longer and have longer and warmer days. warmer days.

Summer in the Northern Summer in the Northern HemisphereHemisphere

During the period marked by the During the period marked by the summer summer solsticesolstice, the Northern Hemisphere is warmed by , the Northern Hemisphere is warmed by more direct sunlight and days are long and hot.more direct sunlight and days are long and hot.

long long summer summer daysdays

land land of of the the midnimidnight ght sunsun

The Arctic region is unique because during June and The Arctic region is unique because during June and July each year, the sun literally does not set. There is July each year, the sun literally does not set. There is constant daylight for about 60 consecutive days. constant daylight for about 60 consecutive days. Similarly, in winter, the sun does not rise, and there is Similarly, in winter, the sun does not rise, and there is complete darkness for two months straight.complete darkness for two months straight.

winter winter solsticesolstice

Dowth, Ireland - It is these chamber Dowth, Ireland - It is these chamber stones, and the central one in particular, stones, and the central one in particular, which receive the beam of sunlight which receive the beam of sunlight during the time of during the time of Winter Solstice..

The first day of winter and the The first day of winter and the shortest day of the year. The shortest day of the year. The winter solstice in the Northern winter solstice in the Northern Hemisphere occurs when the Hemisphere occurs when the North Pole is leaning away North Pole is leaning away from the sun. from the sun.

The longest night…The longest night…

Many believe that Medicine Wheel, a Many believe that Medicine Wheel, a circular rock formation in Wyoming's circular rock formation in Wyoming's Bighorn Mountains, is a solar Bighorn Mountains, is a solar calendar built by the Plains Indians calendar built by the Plains Indians to track the sun throughout the year.to track the sun throughout the year.

The days are The days are longer in summer longer in summer and shorter in and shorter in winter the further winter the further you move from you move from the equator. It’s the equator. It’s generally dark on generally dark on a summer night in a summer night in Florida by 8:30 Florida by 8:30 p.m., but in p.m., but in Vermont, there Vermont, there will still be some will still be some light at 10:00 p.m.light at 10:00 p.m.

burning daylightburning daylight

When the North Pole is When the North Pole is pointing away from the pointing away from the sun, the Northern sun, the Northern Hemisphere receives only Hemisphere receives only indirect sunlight; that is indirect sunlight; that is why winter is so much why winter is so much colder than summer.colder than summer.

colder weathercolder weather

EquinoxEquinox

Equinoxes occur during transition periods when the Equinoxes occur during transition periods when the North Pole is pointing neither directly toward nor North Pole is pointing neither directly toward nor directly away from the sun; these days are marked by directly away from the sun; these days are marked by equal periods of light and darknessequal periods of light and darkness

This image photographed inside Cairn T at This image photographed inside Cairn T at 6:51am shows the shaped beam of equinox 6:51am shows the shaped beam of equinox sunlight illuminating the back stone. Over a sunlight illuminating the back stone. Over a period of about 30 minutes the beam moves period of about 30 minutes the beam moves to the bottom right corner of the backstoneto the bottom right corner of the backstone..

The first day of springoccurs when the North Pole begins to lean toward the sun again.

Vernal EquinoxVernal Equinox

Is it true that you can stand an egg on end Is it true that you can stand an egg on end during the Spring Equinox?during the Spring Equinox?

The answer is YES. However, The answer is YES. However, you can stand an egg on end, you can stand an egg on end, with a large amount of patience, with a large amount of patience, on any day of the year. This myth on any day of the year. This myth seems to pop up every year seems to pop up every year around the equinox, with the around the equinox, with the regularity of the grass greening regularity of the grass greening up in the spring. up in the spring.

This image shows the shaped beam of equinox sunlight This image shows the shaped beam of equinox sunlight illuminating the back stone. The symbol on the top left of illuminating the back stone. The symbol on the top left of the illuminated area clearly represents the sun and the the illuminated area clearly represents the sun and the symbols with the horizontal markings symbols with the horizontal markings may be measuring scales.may be measuring scales.

The first day of The first day of autumn occurs autumn occurs when the North when the North Pole begins to Pole begins to lean away from lean away from the sun.the sun.

Autumnal EquinoxAutumnal Equinox

AutumnAutumn

Equinox Equinox celebrationscelebrations

A thousand years A thousand years ago the Maya ago the Maya gathered around gathered around the El Castillo the El Castillo pyramid at the equinox to celebrate a myth with pyramid at the equinox to celebrate a myth with the setting sun.  This symbolic mixture of sun, the setting sun.  This symbolic mixture of sun, shadow and stone is a representation of the shadow and stone is a representation of the arrival of the great Maya god Kukulkan to the arrival of the great Maya god Kukulkan to the Earth. Earth.

Chevrolet EquinoxChevrolet Equinox

At whichAt which date would date would there be no there be no sunrise in Antarctica?sunrise in Antarctica?

Antarctic Antarctic CircleCircle

links http://www.tea.state.tx.us/ssc/teks_and_taas/teks/glossworldgeo.htm#earthsun http://geography.miningco.com/library/weekly/aa031897.htm http://www.nationalgeographic.com/xpeditions/activities/07/season.html http://www.ems.psu.edu/~fraser/Bad/BadCoriolis.html http://www.wrh.noaa.gov/Flagstaff/science/seasons.htm http://www.windows.ucar.edu/cgi-bin/tour_def/earth/Water/water_cycle.html http://www.windows.ucar.edu/tour/link=/earth/Water/ocean.html http://www.windows.ucar.edu/tour/link=/earth/interior/RIM_of_FIRE.html http://www.windows.ucar.edu/tour/link=/earth/Atmosphere/precipitation.htmll http://www.colorado.edu/geography/gcraft/notes/mapproj/mapproj_f.html http://www.windows.ucar.edu/tour/link=/earth/images/low_high_pressure_jpg_im

age.html http://members.tripod.com/~Stipanovic/Wallpaper15/Autumn.jpg http://www.piramideinn.com/equinox.htm http://www.graphics-galore.com/images/Landscapes/Landscapes-2/Summer%20

Softness.jpg http://oshihan.org/images/Winter_Solstice_NASA.gif