Seasons

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Seasons

• What do your students think causes the seasons?

Images at http//nix.ksc.nasa.gov/info
Created by the Lunar and Planetary Institute For
Educational Use Only LPI is not responsible for
the ways in which this powerpoint may be used or
altered.
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Lets Look at Some Data!

• Temperatures around the World
• Daylight hours

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Average Daily Temperatures (F) in Tourist
Cities (from http//www.infoplease.com/ipa/A000458
7.html ))  
  January April July October
Cape Town (South Africa) 69 66 60 65
Caracas (Venezuela) 75 81 78 79
London (United Kingdom) 44 56 73 58
Mexico City (Mexico) 66 77 73 70
Montreal (Canada) 22 51 79 56
Moscow (Russia) 21 47 76 46
Nairobi (Kenya) 77 75 69 77
Paris (France) 42 60 76 59
San José (Costa Rica) 75 79 77 77
Seoul (Korea) 33 62 84 67
Singapore 86 89 87 88
Stockholm (Sweden) 31 45 70 48
Sydney (Australia) 79 73 62 72
Tokyo (Japan) 48 64 84 70
 
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True color images
December
March
June
September
Images at http//www.nasa.gov/vision/earth/feature
s/blue_marble.html
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Animation-Earths Life through Seasons
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Daylight Hours Across the GlobeTime is indicated
as number of hours (h)

• Jan Feb Mar Apr May
  Jun Jul Aug Sep Oct
  Nov Dec
• 10.5 h 11 h 12 h 12.5 h 13 h
  14 h 14.5 h 14 h 12.5 h 12.5 h
  11 h 11.5 h
• 14.5 h 13.5 h 13.5 h 12.5 h 11 h
  11 h 11 h 11.5 h 11.5 h 12.5 h
  14 h 14.5 h
• 12 h 12 h 12 h 12 h 12 h
  12 h 12 h 12 h 12 h 12 h
  12 h 12 h
• 17.5 h 15.5 h 13.5 h 11.5 h 10 h
  8.5 h 8.5 h 9.5 h 11.5 h 13 h
  15 h 16.5 h
• 5 h 7 h 10 h 13.5 h 17.5 h
  21.5 h 22 h 18 h 15.5 h 11.5 h
  8.5 h 5.5 h
• 12 h 12 h 12 h 12 h 13 h
  13 h 12 h 12 h 12 h 12
  h 12 h 12 h
• 15 h 14 h 13.5 h 12.5 h 11.5 h
  10 h 10.5 h 11 h 11.5 h 12.5
  h 14 h 14 h
• 9 h 10 h 11 h 13.5 h 15 h
  17 h 16.5 h 15.5 h 13.5 h 11.5 h
  10.5 h 9.5 h
• 24 h 24 h 19 h 14.5 h 0 h
  0 h 0 h 0 h 7 h
  15 h 24 h 24 h

Miami Brisbane Nairobi Punta
Arenas Nome Singapore Cape Town Seattle Vosto
k
http//www.lpi.usra.edu/education/skytellers/seaso
ns/activities/light.shtml
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Lets Start with some Observations

• Using free downloaded computer program,
  Stellarium http//www.stellarium.org/
• Stellarium is planetarium software that shows
  exactly what you see when you look up at the
  stars. It's easy to use, and free.
• Lets look at sunrise sunset, and Suns height
  in the sky.

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Height of Sun for USA
Winter The Sun rises in the southeast, stays low
in the sky, and sets in the southwest. Spring
The Sun rises due east, moves higher in the sky
than in winter, and sets due west. Summer The
Sun rises in the northeast, travels high (near
zenith), and sets in the northwest. Fall The
Sun rises due east, travels to a medium-height in
the sky, and sets due west.
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What Causes Earths Seasons?

• Earths axis is tilted 23.5 degrees it always
  points in the same direction (Polaris, the North
  Star) as we orbit our Sun once a year
• This tilt causes the hemispheres to alternate in
  the amount of our Suns light and heat they
  receive through the year

Image at http//www.lpi.usra.edu/education/skytell
ers/seasons/about.shtml
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Northern Hemisphere Summer
More daylight hours, more direct sunlight
Image at http//www.lpi.usra.edu/education/skytell
ers/seasons/about.shtml
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Earths orbit is almost a perfect circle

• Earth is CLOSEST to our Sun (91 million miles)
  in winterJanuary 3
• Earth is farthest from on our Sun (94 million
  miles) in summer July 4

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Seasons on Other Planets

• In some cases, the changing distances from the
  Sun will affect the seasons.
• In others, the axial tilt will make a huge
  difference!

Image at http//photojournal.jpl.nasa.gov/catalog/
PIA01589
Image at http//photojournal.jpl.nasa.gov/catalog/
PIA02963
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Seasons on Planets

• Planet Axial Tilt Eccent.
  Orbit Perihelion Aphelion
• Mercury 0 0.21 88 days 28 mill.
  Miles 43 mill. miles
• Venus 177 0.01 224 days
• Earth 23 0.02 365 days 91 mill.
  miles 94 mill. miles
• Mars 25 0.09 686 days 129 mill.
  miles 155 mill. miles
• Jupiter 3 0.05 12 years
• Saturn 27 0.06 30 years
• Uranus 98 0.05 84 years
• Neptune 30 0.01 165 years

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Mars Orbit and Seasons
At vernal equinox, Mars is 145 million miles from
the Sun
At winter solstice, Mars is 128 million miles
from the Sun
At summer solstice, Mars is 153 million miles
from the Sun
At autumnal equinox, Mars is 134 million miles
from the Sun
Original images from http//photojournal.jpl.nasa.
gov/index.html