The Reason for the Seasons - University of Chicagomath.uchicago.edu/~grodnick/seasons.pdfAfter...

The Reason for the Seasons

SESAME AstronomyWeek 1 - January 12th, 2010

Thursday, January 13, 2011

the year

takes 1 day for earth to make 1 rotation (to rotate once) on its axis

takes 1 year for earth to make 1 complete orbit (revolution)

rotation axis tilted with respect to orbit

rotation axis tilted in the same direction with respect to the background stars, no matter where in orbit earth is

Huh?Thursday, January 13, 2011

the year

takes 1 day for earth to make 1 rotation (to rotate once) on its axis

takes 1 year for earth to make 1 complete orbit (revolution)

rotation axis tilted with respect to orbit

rotation axis tilted in the same direction with respect to the background stars, no matter where in orbit earth is

Huh?


direct vs. indirect light


Summer solstice - June 21stlongest day of yearsun as high as it gets in the skyEarth tilted toward sun

Winter solstice - December 21stshortest day of the year sun as low as it gets in the skyEarth tilted away from sun

Equinoxes - March 21st/September 21stequal number of hours of light and darkelevation of sun at noon equal to latitudeEarth tilted neither toward or away from sun


So why is the winter solstice near the

beginning of winter, and not the middle of

winter?


There’s A LOT of water!

Water takes a long time to cool off

As the water cools off, it warms up the air (so air stays warm longer than sunlight can account for)

Water takes a long time to heat up

As the water heats up, it cools off the air (so air stays cool longer than sunlight can account for)

After summer solstice After winter solstice


Activities

Play with computer demos

Do sunrise/sunset activity

Come back for summation and discussion of homework and projects


Summary

Earth rotates on an axis once per day

This axis is tilted with respect to Earth’s orbit around the sun

When the Earth is tilted toward the sun, sunlight is “direct” (meaning: more concentrated)

This concentrated sunlight heats up the part of Earth tilted toward the sun


Summary

As the Earth moves around its orbit, the tilt faces away from the sun

When the Earth is tilted away from the sun, sunlight is “indirect” (meaning: watered down)

This watered down sunlight can’t keep the Earth warm, and the part of Earth tilted away from the sun cools off


Summary

June 21st: summer solstice - most sunlight

June 22nd: Earth moves away from summer solstice

July-August: Earth still moving away from summer solstice, but water cools off and warms up air at same time to keep Earth warm through summer

December 21st: winter solstice - least sunlight

December 22nd: Earth moves away from winter solstice

January-February: Earth still moving toward summer solstice, but water warms up and cools air at the same time to keep Earth cool through winter


AssignmentsRead through http://www.astronomy.org/programs/seasons/

This website gives 2 common misconceptions about why we have seasons. For each misconception, imagine that one your students made that claim. Write what your response to the student would be. Please type your assignments. (You may draw diagrams, though.)

Finish worksheets started in class

Start sun project and moon project - have ready for project checks next Wednesday


http://www.astronomy.org/programs/seasons/




Resources





The Reason for the Seasons - University of Chicagomath.uchicago.edu/~grodnick/seasons.pdfAfter...

Documents

Transcript of The Reason for the Seasons - University of Chicagomath.uchicago.edu/~grodnick/seasons.pdfAfter...