Nalini Chandra & John Percy, University of Toronto
Activity 3: Measuring the Position of the Sun in the Sky
Purpose: To give students the opportunity to measure the position of the Sun in the sky using simple tools and methods.
Note: For safety reasons you may choose to use this exercise to have students measure the position of the Moon in the sky.
Materials: a hand (preferably, your own)
a) Read the Inuit example above to students.
b) Define horizon as the line along which the sky and land appear to meet.
c) Choose one part of the horizon to observe. Try to choose one with landmarks, to give students a common reference point.
d) Have them stretch out their arm and make a vertical fist (with the thumb on top), while looking directly at the horizon. (Their outstretched arm should be perpendicular to the horizon, and the imaginary lines, one running along their arm and one running from their neck to the top of their head, should make a 90 degree angle).
e) This discussion provides a good opportunity to review geometry terminology, since the bottom of the fist on the horizon to the top of the fist makes an angle of ten degrees.
f) Have students count how many fists they can fit between the horizon and the bottom of the Sun's disk.
When deciding when to make further observations, you should discuss the importance of keeping variables constant. For instance, the time of the day and the place from which they measure the angle and position of the Sun should be the same.
Alternatively, you may have students devise their own methods of relative measurement and apply them to measuring the position of the Sun in the sky.
Observing the Changing Position of the Sun To Establish a Seasonal Calendar in the Southern Hemisphere
The following example illustrates the reversal of the seasons in the southern hemisphere compared to the northern hemisphere. Considering that children have deep misconceptions about the Sun's motion in the sky, this story requires some discussion about how the Earth's rotation is the cause of the apparent motion of the Sun.
The New Zealand Maori display their understanding and observations of the connection between the solstices, the seasons and the position of the Sun in the sky in the following story. They say that "during the year the Sun roams from Rangi's head to his toes and back again. Rangi is the sky, and when the Sun is near Rangi's head it is summer in New Zealand. The Maori also say that the Sun is spending time with the Hine-raumati, the Summer Maid. He leaves her in December, around the time of the Summer solstice to go and live with Hine-takurua who is the Winter Maid. The Sun enjoys the company of Hine-takura until the June solstice, when it's time for him to head back to the land. There the Summer Maid is cultivating crops and preparing the game of the forest for the summer hunt. There are two things that should be highlighted for students in this story. First, the position of the Sun changes from high to low in the summer and winter respectively. Second, children should note that the months of summer and winter in New Zealand are opposite to those of the Northern Hemisphere. In the northern hemisphere the summer months are in June to August in the southern hemisphere the summer months are December to February.
Activity 4: The Sun and the Seasons at Different Latitudes
Purpose: To understand the difference between seasons and the position of the Sun in the northern and southern hemispheres.
Halfway between the celestial poles is the celestial equator, this is a projection of the Earth's equator onto the sky. The stars on the celestial equator will rise due east and set due west. The stars that form the "belt" of Orion are an example of stars that travel this path. Early navigators learned to use the rising and setting of these stars to find their way. They were particularly important to the Pacific Islanders when they were surrounded by water, and land could not serve as a reference point. Over time, the observations and records of these star patterns provided a method for navigation that would be communicated to others.
In the northern hemisphere, the star Polaris is quite close to the direction of the North Celestial Pole - the point in the sky directly above the North Pole. Polaris is circumpolar, which means that it never rises or sets; it makes a very small circle around the North Celestial Pole. Other stars, like the Big Dipper also circle around this "pole star" but they do so in much larger circles. From more northerly latitudes, they also never set. Those stars in the sky that are circumpolar depend on one's latitude. For example, if you were standing on the North Pole, all the stars that were visible would be circumpolar and would just move horizontally, circling around the celestial pole overhead. If you are between the North Pole and the equator, the direction of the North Celestial Pole is tilted away from the point directly above you. In fact, the angle of Polaris above the horizon is approximately equal to your latitude. Having students learn to identify Polaris in the sky, hence the direction north can be a short but useful lesson in celestial navigation for them to learn.
Polaris became a symbol of freedom to slaves as well as a guide star for those who would flee north. Children were taught to identify Polaris by finding the Big Dipper. Slaves passed the travel instructions from plantation to plantation by singing the song "Follow the Drinking Gourd". In the song, The Big Dipper was the drinking gourd, which was a spoon shaped utensil with a curved handle, which the slaves would use to drink water.
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