Project 16
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This tilt not only accounts for why the length of daylight varies, it also gives us a changing of seasons from spring, summer, fall, and winter.
The Sun rises in the east and sets in the west, but the path it travels across the sky changes as the seasons change. The altitude (its height above the horizon) of the Sun reaches a higher angle during the day in the summer than in the winter.
Does the Sun reach its highest point in the sky (its zenith) during the day at the time that is halfway between sunrise and sunset for that day?
Knowing the position of the Sun at all times during the day throughout the year at a particular location is important to architects who design buildings. They need to know how much sunlight will enter through
windows because this will affect their designs for lighting, heating, and air conditioning.
Hypothesis
Hypothesize that the Sun reaches its zenith during the day at the time that is equally between sunrise and sunset.
Materials’ List
• Time of sunrise and sunset for that day (available from a daily newspaper, the Farmers’ Almanac, your local radio station, or a National Oceanic and Atmospheric Administration (NOAA) weather radio)
• Possible adult supervision needed
Procedure
First, be sure you never look directly at the sun!Next, find the time of sunrise and sunset for the day you do this project. These times can often be found in a local daily
newspaper, from an almanac, from the news on a local radio station, or from a NOAA weather radio.
Then, calculate the total number of minutes between sunrise and sunset. Divide that number by two. Convert the answer to hours and minutes. Add that to the time of sunrise to arrive at a time that is midpoint between sunrise and sunset.
Now, mount a protractor on a small piece of plywood, so it stands perpendicular to the board. Modeling clay can be used to secure the protractor.
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Project 16: Zenith Is Not a Radio
Next, set the protractor device outside in an area that receives unobstructed sunlight all day. Lay a carpenter’s level lengthwise, and then widthwise, to level the board. Pile a little sand or small stones under the board to level it.
The reference point of zero on the
protractor will be held constant (the plywood and protractor will be kept level horizontally with the ground). The movement of the Earth is the variable in this project.
About two hours before midday, begin measuring the angle of the Sun’s altitude by placing the point of a pencil by the base at the middle of the protractor, and raising the pencil up or down until no shadow of the pencil is cast. Remember, do not look
directly at the sun during this project.Check the angle of the pencil by reading the
increments on the protractor.
Make these measurements at ten-minute intervals. Write down the angle of the Sun’s height.
Continue making measurements until one hour after the Sun’s angle begins to decrease.
Did the Sun’s peak height occur at about the time you calculated the midpoint between sunrise and sunset?
Results
Write down the results of your experiment.
Document all observations and data collected.
Conclusion
Come to a conclusion as to whether or not your hypothesis was correct.
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Project 16: Zenith Is Not a Radio
North Pole
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Project 16: Zenith Is Not a Radio
Something More
1. Is the Sun always at zenith at 12 o’clock noon?
2. Determine the azimuth(the angle between sunrise in the east and sunset in the west) of the Sun. Thumbtack a piece of white paper onto a piece of plywood, and slightly hammer a nail in the center through the paper and into the plywood, just deep enough for the nail to hold. At sunrise, draw a line tracing the shadow cast by the nail. Just before sunset, when the shadow cast by the nail is about to disappear, draw a line tracing the shadow. Measure the angle. Repeat this once a week for a month. Does the angle change? Is the angle increasing or decreasing in size?
Which season are you headed toward?
Does the peak height of the Sun in its path across the sky change from week to week?
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Suggested Entry Categories
• Biochemistry
• Environmental
• Microbiology
Purpose or Problem
The purpose is to identify several
environmental factors in the home that affect the rate at which mold grows on food, spoiling it. By controlling how food is stored, we can extend its edible life.
Overview
Have you ever been hungry for a sandwich, only to discover that the last two slices of bread in the house have green mold on them?
Yuck! Finding mold on your bread in the bread box, mold on your cheese in the refrigerator, or mold on your peaches in the fruit basket can be unpleasant and irritating.
Mold, and another member of the fungi kingdom, mildew, can even attack books. You may have picked up a book that has been stored in a damp basement and found it covered with a powder-like substance.