42
WORK AND EXPERIMENTATION TECHNIQUES
1.
At what time was the shadow the shortest?
2.
Between sunrise and solar midday, does the shadow get bigger or smaller? Between solar midday and sunset,
does the shadow get bigger or smaller?
3.
What angle is formed by the shadows of two consecutive hours?
4.
Which cardinal point does the shadow point to at sunrise? Which cardinal point does it point to at sunset?
5.
Considering your answer to question 4, which cardinal point does the Sun seem to move from and towards?
Make a sundial
1.
Place the paper or card over the piece of wood.
2.
Put the nail in the middle of a long side of the piece of wood.
3.
Use the spirit level to place the piece of wood on a flat surface in a sunny
area (figure 1).
4.
Using the compass, place the piece of wood facing north, with the nail
in the south.
If you don’t have a compass, observe the shadow when the Sun is at
its highest (solar midday); this indicates approximately north. Take into
consideration that solar midday in the winter is at 13:00 and in the
summer at 14:00.
5.
On the paper or card, draw the lines that represent the cardinal points
(figure 2).
6.
Mark the shadow produced by the nail every hour (figure 3).
Procedure
Materials
❚
Compass
❚
Piece of wood (100 x 60 cm)
❚
20 cm long nail
❚
Hammer or glue
❚
Paper or card
❚
Spirit level
The Ancient Egyptians used sundials to measure time 1500 years
B.C. In this science practical you will build a sundial. You will also
learn how it works and how to use it.
The sundial will help us to:
• Orient ourselves with the help of the Sun and shadow.
• To distinguish the direction and length of the shadow at each hour of the day.
Figure 1
Figure 2
Figure 3
