Sun, Moon, and Stars: Astronomy for Beginners · Part I, Ch. II · Part 1: Part I: Our family in the sky, and its neighbors
2. The head of our family: the Sun
Goal: Your child can describe how far away and how big the Sun is, using the book's train and model comparisons, and knows the Sun must never be looked at directly.
You'll need
- The book, open to Part I, Chapter II
- A tape measure or yardstick
- A pea or a bead (about a quarter-inch) and a large ball
- For the pinhole viewer: two pieces of stiff white card and a pin
What's in the book
This chapter gives the Sun's distance (about ninety-two million miles) and size (865,000 miles across), with a train ride and a field-sized model to picture them. Then it tells of the first sunspots and describes the Sun's shining surface, its fiery edge, the red prominences and the pale corona seen in an eclipse.
The lesson, step by step
Safety first
Safety first: never look at the Sun, not even for a moment, and not through sunglasses, smoked or darkened glass, film, binoculars or a telescope. It can hurt your eyes for good, and it does not hurt while it happens.
SayIn this chapter a man stares at the Sun until he is too dazzled to go on. That was dangerous, and we will never copy it. Today we will learn a safe way to see the Sun's shape.
Read together
Read the chapter aloud. Stop at the big numbers and say them slowly together:
ninety-two millions of MILES.
Then read the train journey: going at 60 miles an hour without stopping, a traveler would take about 175 years to get there.
Picture the size
The book says the Sun is about 108 times as wide as the Earth. Shrink the Earth to a one-inch ball, and the Sun becomes a globe nine feet across, set 320 yards away.
Measure nine feet along the floor with the tape measure, and lay a one-inch object beside the end. Say: That little thing is the Earth. The whole nine feet is the Sun.
Make a pinhole viewer (the safe way)
Poke one small, neat hole in a card with a pin. Stand with your back to the Sun. Hold the pierced card up so sunlight passes through the hole, and let the light fall on the second card held about three feet below it.
You will see a small round image of the Sun. Look only at the image on the card, never up through the hole.
SayThis is how we look at the Sun: with our backs to it, at its picture.
What we know now
The book calls sunspots huge storms, perhaps holes. We now know they are cooler, darker patches made by the Sun's powerful magnetism.
The Sun is not made of molten metal clouds. It is a ball of extremely hot gas, mostly hydrogen and helium, about 10,000 °F at its surface.
The book says little was known about the corona. We now know it is a very thin, extremely hot outer layer, over a million degrees, that streams out into space as the solar wind.
The Sun's average distance is about 93 million miles, very close to the book's number.
Tell it back
Ask your child to tell you:
How long a nonstop express train would take to reach the Sun.
What sunspots taught astronomers about the Sun's turning.
What prominences are, and when people used to be able to see them.
Check questions
About how many times wider than the Earth is the Sun?
How long does the Sun take to turn once on its axis?
Why is it never safe to look at the Sun?
Notice it this week
Look at the shadows of leaves under a tree on a sunny day. The little round spots of light on the ground are pinhole images of the Sun, made by gaps between the leaves.
Afterwards
Ask a grown-up to help you look up today's photo of the Sun taken by a NASA space observatory, and count the sunspots. Check again a few days later to see that they have moved across the Sun.
Tip
The book mentions looking at the Sun 'through darkened glass'. That is not safe. Only the pinhole method (or special certified eclipse glasses, worn under adult supervision) is safe, and the pinhole is all you need here.
Answers to the book's problems
About 108 to 109 times wider. About twenty-five days (the book's figure). Because its light can burn the back of the eye and cause lasting harm, without any pain while it happens. Train: about 350 years at 30 miles an hour, about 175 years at 60. Sunspots move across the Sun, vanish round one edge and come back on the other, which showed the Sun turns. Prominences are huge red tongues of glowing gas, mostly hydrogen, rising from the Sun's edge; once they could be seen only in a total eclipse.
Worked out for this site from the scan. If a number in your copy differs, trust the book.