To construct a line graph showing the changing times throughout the year for sunrise and sunset at your location
The graph will take at least 40 minutes to construct. Because it is based on charts that are always available, it can be done at any time during the year.
- Using the data from an ephemeris or almanac, find and list the times of sunrise and sunset for the 22nd day of each month for the latitude closest to yours.
- Help the students to make graphs. On the vertical axis list the hours by the 24-hour system. On the horizontal axis list the months of the year.
- Plot the hours of sunrise and the hours of sunset to the nearest half hour on the graph. Connect all the points for sunrise with one line; all the points for sunset with another line. Locate and label the equinoxes and solstices on the graph.
- The graph will clearly show that the hours between sunrise and sunset increase as the year goes toward summer and are at their greatest at the time of the summer solstice in June. Conversely, the shortest days are in the winter and are shortest at the time of the winter solstice.
- If the students count the lines on the graph, they will find that at the time of the equinoxes, there are 12 hours of daylight between sunrise and sunset. Since there are 24 hours in any one day, that leaves 12 hours for night. These are the times when day and night are equal.
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