Photo: Earth lights

Photo courtesy NASA

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NASA’s image of "Earth at Night" is familiar to most Americans. The image appears on posters and postcards, and in most geography textbooks. But how was this image made? And what does it tell us about where and how we live on Earth?

First of all, "Earth at Night" is not a single image, but rather a composite of hundreds of photos taken by low-altitude satellites that are able to detect light emitted by towns, cities, industrial sites, oil fields, and fires. Careful examination of the image reveals much about the distribution of people and their activities on Earth.

Examining the Image

a) Access the "Earth at Night" image online and project the image on a classroom screen, or alternatively, if a computer lab is available, have students working in small groups access the image. Provide students with blank world regional maps and world atlases.

b) Begin by clicking once to zoom in on the United States. (Clicking a second time will return the image to full size.) Have students compare the lights on the image to maps of the U.S. in the atlas in order to identify major urban areas. Have them label these urban areas on a blank map of the U.S., identifying major cities. Ask students to explain the uniform distribution of tiny dots of light in the Plains states (the grid pattern is a remnant of the township and range survey system used to divide land parcels in this area). Ask them to explain the dark areas on the image (dark areas are mountains, desert, or other areas with little or no population).  Have them refer to their atlases to identify and label these areas on their maps.

c) Assign different groups the following regions: South America, Europe, Africa, Southwest Asia, South Asia, East Asia, and Southeast Asia and Oceania. Have them repeat the exercise above for these regions, recording what they observe on the appropriate regional map.

Extending the Activity

Point out to students that not all visible light comes from urban areas. In fact, oil field burn-off flares and fires from slash-and-burn agriculture are also visible.

d) Access an updated version of "Earth at Night" and open the image. Point out the bright yellow and red areas on this image. Have students use maps in their atlases to identify these areas and speculate what the colors represent (yellow areas are oil fields; red areas are agricultural burning).

Millions of students participated in the National Geographic school Bees this year. Thank you to the 10,000 educators who organized school Bees!

Congratulations to the top 100 students from each state and D.C. who are advancing to their state Bee competition on April 1. To view the list of school champions who qualified for their state Bees, and information about your state's competition, visit the State Bee homepage.

State Bee Homepage

Key National Geographic Bee Dates

August 18, 2015 - December 18, 2015
Early bird registration ($100)
Check or credit card payment accepted

December 19, 2015 - January 18, 2016
Registration ($120)
Credit card payment accepted

February 5, 2016
Deadline for School Bee Champs to take online qualifying test by 11:59 pm EST.

March 4, 2016
State Bees qualifiers are announced.

April 1, 2016
State Bees are held in every state and Washington, D.C.

May 22-25, 2016
National Championship held in Washington, D.C.

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