Handbook of Nature-Study · Lesson CCXXXII · Topic 38: The Sun and the Moon
232. The Sun and the Earth
Goal: Your child can show with a shadow stick that the Sun's path is higher in summer than in winter, and can explain that this brings the seasons.
You'll need
- A board and a peg or pencil 2 or 3 inches tall stuck upright in clay
- A sunny south window or a sunny spot outdoors
- A pencil or chalk and a ruler
- A nature notebook and a pencil (colored pencils if you have them)
What's in the book
A chapter on the Sun comes first. The lesson has a leading thought and fourteen observations on the Sun's heat, sunrise and sunset, the shortest and longest days, where the Sun rises and sets through the year, gravity on the Sun, and a shadow stick, with topics for writing.
The lesson, step by step
Safety first
Never look at the Sun, not even for a moment, and not through sunglasses, binoculars or a telescope. In this lesson we study the Sun only by its shadows. To see the Sun itself, make a pinhole projector: a pinhole in a card lets a small image of the Sun fall on a sheet of paper while your back is to the Sun.
The leading thought
The sun which is the source of all our light and heat and, therefore, of all life on our globe travels a path that is higher across the sky in June than the path which it follows in December, and hence we experience changes of seasons.
Talk about it
What does the sun do for us?
Is the sun equally hot all day? Why does it seem hotter to us at one time of the day than at another?
The shadow stick
Place a peg two or three inches high upright in a board and place the board lengthwise on the sill of a south window or where it will get the south light.
Every hour of a sunny day, mark the tip of the shadow and write the time. Join the dots.
Make a similar outline a month later and again a month later and note whether the shadow traces the same line during each of these days of observation. Note especially the length of the shadow at noon.
Sunrise and sunset
Standing in a certain place, mark by some building, tree or other object just where the sun rises in the east and sets in the west on the first of February.
Look at the horizon near sunrise or sunset, not at the Sun, and note the landmark. Do it again on the first of each month.
Long and short days
Which is the shortest day of the year, and how long is it?
Which is the longest day of the year, and how many hours and minutes are there in it?
Find sunrise and sunset times for your town in a newspaper or weather website and work out the day's length.
A weighty question
The sun is so much larger than the earth that its force of gravity is twenty-seven and two-thirds times that of the earth.
How much would you yourself weigh if you were there?
Work it out with your child's weight.
Nature notebook
Draw the shadow-stick board with the day's curve of dots. Next month, add the new curve in another color. Write the noon shadow length each time.
Afterwards
Repeat the shadow stick on the same date each month, and note the sunrise or sunset landmark on the first of each month.
Answers to the book's problems
We get the least heat soon after sunrise and the most in the early afternoon. The Sun feels hotter at midday because its light comes down more directly. In the Northern Hemisphere the shortest day is about December 21 and the longest about June 21 (their lengths depend on your latitude). The noon Sun is highest about June 21 and lowest about December 21. The Sun rises due east and sets due west about March 20 and September 22. Noon shadows are longest in December and shortest in June. Weight on the Sun: a 60-pound child would weigh 60 x 27 2/3 = 1,660 pounds (today's figure is about 28 times). What we know now: the seasons come from the tilt of the Earth's axis, which makes the Sun's path higher and the days longer in summer.
Worked out for this site from the scan. If a number in your copy differs, trust the book.