CHAPTER I. ASTRONOMY.
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THE EARTH AND OTHER PLANETS.
Fig. 1.
What is the shape of the Earth on which we live?
It is round like a ball.
What other names are given to the Earth?
It is called the World or Globe.
What else is it sometimes called?
It is called a Planet.
Are there any other planets?
Yes; some of the stars are called planets.
Is our earth or world a star?
It is a star.
Why do the other stars seem to us different from the earth?
Because they are so far away from us.
What gives light to the planets?
The Sun gives light to the planets.
Of what is the sun the centre?
The sun is the centre of the solar system.
Do the planets remain in one place?
The planets do not remain in one place, but are always moving.
How do the planets move?
They move around the sun.
Are some planets nearer the sun than others?
Yes; some planets are much nearer the sun than others.
Which planet is nearest the sun?
The planet called Mercury.
Which is next to Mercury?
The planet called Venus.
And which is third in distance from the sun?
Our own planet, the Earth.
Are there any planets still farther from the sun?
Yes; Mars, Jupiter, Saturn, Uranus, and Neptune, and many smaller planets.
How does each planet move?
It moves in its own track or orbit around the sun, as is represented in Fig. 2.
Fig. 2.
Does the earth always move in the same orbit around the sun?
Yes; the earth moves in the same orbit around the sun, year after year.
How long does it take the earth to move around the sun?
365 days, 5 hours and 49 minutes, or one year.
What makes a year to us?
A year to us is the time required by the earth to move around the sun.
If the earth is in a certain place at noon, on New Year's day, when will it be in that place again?
5 hours and 49 minutes after noon on New Year's day of the next year.
What, then, does the earth do every year?
The earth moves around the sun and comes back to the place whence it started, once every year.
Has the earth any other motion than the one around the sun?
It has; it turns over and over.
Does the earth stay in one place as it turns over and over?
It does not; it moves on in its track around the sun.
How many times does it turn over while going around the sun?
Three hundred and sixty-five times.
How many times, then, does it turn over in one year?
The earth turns over three hundred and sixty-five times in a year.
What is the time which it takes to turn over once called?
It is called a day.
How many days in a year?
There are three hundred and sixty-five days in a year.
What two motions, then, has the earth?
It turns over and over, and at the same time it moves around the sun.
What change is produced on the earth by its moving around the sun?
The change of Seasons.
Will you name the seasons?
Winter, Spring, Summer, and Autumn.
Do they follow each other in regular order?
They do; Spring follows Winter, Summer follows Spring, Autumn follows Summer, Winter follows Autumn, and Spring follows Winter again.
How often have we these seasons?
As often as the earth moves around the sun, which is once a year.
What change is produced on the earth by its turning over?
The change of day and night.
Where is it day?
It is day on that part of the earth which is turned towards the sun.
Where is it night?
It is night on that part of the earth which is turned away from the sun.
How often do we have the change from day to night?
As often as the earth turns over, which is once in twenty-four hours.
What is a day?
A day is the time from sunrise till sunrise again, from sunset till sunset again, from noon till noon again, or from midnight till midnight again.
What does a day include?
It includes the night-time as well as the day-time, of the twenty-four hours.
When it is day-time on one part of the earth, what is it on the opposite part?
It is night-time on the opposite part.
When it is morning to us, what is it to people living on the opposite side of the earth?
When it is morning to us, it is evening to them; when it is day-time to us, it is night-time to them; and when it is noon to us, it is midnight to them.
On how much of the earth is it always day?
It is day on one-half of the earth, while on the other half it is night.
The sun seems to move around the earth; does it really do so?
No; it does not move around the earth.
Does the earth move?
Yes; it turns over once every day.
Why does it not seem to us to be moving?
Because we move along with it. If we are on a railroad car, the trees and houses along the road appear to move, and the car to stand still; but the car really moves, while the trees and houses stand still.
In what direction does the earth turn on its axis?
The earth turns from west to east.
Where do the sun, moon, and stars rise?
The sun, moon, and stars rise in the east.
The teacher may, by means of a ball or small globe, readily make these things so plain that they can be understood even by small children.
When is it sunrise to us?
When the part of the earth on which we are, first comes into the sun's rays.
When is it sunset to us?
When the part of the earth on which we are, moves out of the sun's rays.
THE MOON.
We have been told that the earth moves around the sun; does any planet move around the earth?
Yes; one planet moves around the earth.
What is that planet called?
It is called the Moon.
Fig. 3.
How often does the moon move around the earth?
Once in 27 d. 7 h. 43 min.
How long is the time from new moon to new moon again?
It is 29 d. 12 h. 44 min.
How often do we have new moon?
Once every 29 d. 12 h. 44 min.
What is the period from one new moon to another called?
It is called a Lunar month.
Are the lunar months all of the same length?
Yes; they are all of the same length.
Is there any other kind of month?
Yes; the Calendar month, as it stands in almanacs.
How many calendar months in a year?
There are twelve calendar months in a year.
Are the calendar months all of the same length?
No; some are thirty-one days long, some thirty days long, and one only twenty-eight days long.
When can we see the moon and stars best?
We can see them best when it is night.
From what do the moon and the other planets get their light?
They get their light from the sun.
What do they do with this light?
They reflect it.
How do we see them?
We see them by the light which they reflect.
Why cannot we see the moon and stars in the day-time?
Because the bright light of the sun hides their light.
Are there stars in every direction around the earth?
There are stars in every direction around the earth.
How do we know this?
Because stars may be seen from every part of the earth, when it is night.
Stars are in every direction around the earth, just as we may imagine the apples to be in every direction around a boy who has climbed into a tree full of that fruit.
What planet moves around the earth?
The moon moves around the earth.
Upon what part of the moon does the sun shine?
It shines upon the part towards the sun.
What does the moon do with the light which it receives from the sun?
The moon reflects the light received from the sun.
What is this reflected light called?
It is called moonlight when reflected from the moon.
Is that part of the moon on which the sun shines always towards the earth?
It is not always towards the earth.
When all of the moon on which the sun shines is towards the earth, how does the moon appear?
The moon appears to be round, and the whole of it seems to shine.
What is the moon then called?
It is called the Full Moon.
When no part of the moon on which the sun shines is towards the earth, how does the moon appear?
We do not see the moon at all, and we say there is no moon.
When a small part of the moon on which the sun shines is first turned towards the earth, what is it called?
It is called the New Moon.
Does the lighted part of the moon grow?
It seems to grow larger and larger, until the whole of the moon is lighted.
What is it then called?
It is then called the Full Moon.
What then takes place?
It seems to grow smaller and smaller, until the whole of the lighted part is...
