Seasons and Earth’s Distance to the Sun
Environmental Science
Name: _______________________________________________ Period: _____ Date: ______________
Essential question: How do we have seasons on Earth?
What do you think? Many people believe
that Earth is closer to the Sun in the
summer and that is why it is hotter. And,
likewise, they think Earth is farthest from
the Sun in the winter. Although this idea
makes sense, it is incorrect.
It is true that Earth’s orbit is not a perfect
circle. It is a elliptical ( Kepler’s 1st law).
Yes! The orbit of Earth around the Sun is
elliptical or oval shaped. During part of
the year, Earth is closer to the Sun, called
Perihelion, than at other times. However,
in the Northern Hemisphere, we are having winter when Earth is closest to the Sun and summer when it is
farthest away! Compared with how far away the Sun is, this change in Earth's distance throughout the year does
not make much difference to our weather. Earth’s tilt on its axis and its revolution around the barycenter of the
Solar System causes seasons. Not the distance!
Earth's axis is an imaginary pole going right through the center of Earth from "top" to "bottom." Earth spins or
rotate around this pole, making one complete turn each day. That is why we have day and night, and why every
part of Earth's surface gets some of each.
Earth has seasons because its axis doesn't stand up straight. Long, long ago, when Earth was young, it is thought
that something big hit Earth and knocked it off-kilter. So instead of rotating with its axis straight up and down, it
leans over a bit.
By the way, that big thing that hit Earth is called Theia. It also blasted a big hole the
surface. That big hit sent a huge amount of dust and rubble into orbit. Most
scientists think that rubble, in time, became our Moon.
http://spaceplace.nasa.gov/seasons/
Remember! We have season because of Earth’s
tilt and its revolution around the barycenter of
the Solar system and not the distance to the
Sun. The uneven distribution of sunlight is the
main reason why we have season. This happens
because Earth is tilted at 23.5 degrees on its
axis. When the Northern hemisphere is tilted
away from the Sun it is winter and Summer in
Australia, which is in the Southern hemisphere.
It is summer in June in the Northern
Hemisphere because the Sun's rays hit that part
of Earth more directly than at any other time of
the year. It is winter in December in the
Northern Hemisphere, because that is when it is
the South Pole's turn to be tilted toward the
Sun.
http://vnatsci.ltu.edu/s_schneider/astro/wbstla2k/mytalk/seasons.shtml http://www.pa.msu.edu/sciencet/ask_st/110691.html
Clarifying questions:
1. What do many people believe about seasons and the distance of Earth to the Sun? Is this correct?
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2. What is the shape of Earth’s orbit?
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3. What does it mean by Perihelion?
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4. What kind of season do we have in the Northern hemisphere when Earth is farthest from the Sun?
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5. Does Earth’s distance to the sun throughout the year has any effect with our seasons? Why?
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6. What is Earth’s axis?
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7. Why do we have day and night?
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8. Why is Earth tilted?
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9. What do you call the thing that hit Earth and caused it to tilt?
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10. How did the moon form?
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11. What cause Earth’s seasons?
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12. What is season in the Northern hemisphere when it is tilted away from the Sun?
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13. What is season in the Northern hemisphere when it is tilted towards the Sun?
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14. What is the season when the Sun's rays hit that part of Earth more directly?
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15. Why is it winter in December-January-February? Think!
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Completion: Get the answers from the charts on the front page.
16. The Northern hemisphere points towards the Sun, causing ____________days and __________
direct sunlight. The Northern hemisphere points away the Sun, causing ____________ days and
_________ direct sunlight.
17. Write the dates of the following: Get the answers from the charts on the front page.
a. Autumnal equinox ________________________________________________
b. Winter solstice ____________________________________________________
c. Vernal equinox ____________________________________________________
d. Summer solstice ___________________________________________________
Remember: Spring: Time Forward 1 Hour; Fall: Time Backward 1 Hour
Spring forward, Fall back
During DST, clocks are turned forward an hour, effectively moving an hour of daylight from the morning to the evening.
United
States
European
Union
Year
DST Begins
at 2 a.m.
DST Ends
at 2 a.m.
Summertime
period begins
at 1 a.m. UT
Summertime
period ends
at 1 a.m. UT
2009
March 8
November 1
March 29
October 25
2010
March 14
November 7
March 28
October 31
2011
March 13
November 6
March 27
October 30
2012
March 11
November 4
March 25
October 28
2013
March 10
November 3
March 31
October 27
2014
March 9
November 2
March 30
October 26
2015
March 8
November 1
March 29
October 25
March 13
November 6
March 27
October 30
2016
US calculator valid 1976-2099; EU 1996-2099. Change with up/down key.