Remember, the relationship between the tilt of the Earth's axis and its yearly orbit around the sun produces the seasons.

Description: Your goal will be to use collected data and compare patterns of seasonal daylight changes.

Student Information: To solve problems scientists usually go through the same process. First, they develop a good answer to the problem they are working on (hypothesis), and then data needs to be collected in a controlled procedure or acquired from a reliable source. Data is often organized in a table or chart to aid in analysis of the information.

Procedure: Look closely at the data table below. It shows the rising and setting times of the sun in Salt Lake City. Details for this data can be found at the U.S. Naval Observatory. (You may use this site to create the data for almost any location in United States.)

 Sunrise (p.m.) Sunset (p.m.) January 1 7:52 5:11 15 7:50 5:25 February 1 7:38 5:45 15 7:21 6:02 March 1 7:01 6:19 15 6:39 6:34 April 1 6:11 6:52 15 6:49 8:07 May 1 6:26 8:24 15 6:10 8:38 June 1 5:58 8:53 15 5:56 9:01 July 1 6:00 9:03 15 6:09 8:57 August 1 6:24 8:43 15 6:38 8:25 September 1 6:54 8:00 15 7:08 7:36 October 1 7:24 7:10 15 7:39 6:47 November 1 6:58 5:24 15 7:14 5:09 December 1 7:32 5:01 15 7:45 5:01

Analysis

1. Explain the pattern of sunrise times during the year.
2. Is the pattern the same for sunset times during the year?
3. During which month is the number of daylight hours the longest?
4. Use the data to make a line graph showing the changes in time of sunrise and sunset for the year. (Drag your mouse over the link to see an example of a line graph.)
5. Which season has the greatest number of daylight hours?
6. Which season has the lowest number of daylight hours?

Extension Activity:

When the sun is overhead and the rays are directly hitting the Earth, the energy reaching a given area is at the maximum. When it is low in the sky and the rays are slanted, this same amount of energy is spread out over a larger area. The angle at which the sun’s rays hit the Earth also causes a change in the number of daylight hours, which means the sun rises and sets at different times each day.

Image courtesy of NASA

Study the chart below to answer this question: What happens to the number of daylight hours through a year?

 Day Hours of daylight January 22 9 February 22 10.5 March 22 12 April 22 13 May 22 14.5 June 22 16 July 22 14.5 August 22 13 September 22 12 October 22 10.5 November 22 9 December 22 8

Analysis:

Look closely at the graphs below. Which shows the correct pattern of change in daylight hours through the year? Click to check your answer.

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