First Lessons in Natural Philosophy for Beginners — A Closer Reading

CHAPTER I. Astronomy.

The Earth and Other Planets.

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?

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.

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?

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.

It is day on that part of the earth which is turned towards the sun.

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.

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.

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.

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?

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.

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 gone.

Just before the last part is gone, what is it called?

It is called the Old Moon.

How long is it from one full moon to another full moon?

How many full moons are there in a year?

There are thirteen full moons in a year.

Is the sun much larger than the moon?

The sun is many thousand times larger than the moon.

Why does the moon appear nearly as large as the sun?

Because it is so much nearer to us.

How far is the moon from the earth?

The moon is nearly 240,000 miles from the earth.

How far is the sun from the earth?

The sun is nearly 92,000,000 miles from the earth.

How long does it take the light of the sun to reach the earth?

It takes about eight minutes; therefore, the light of the sun must travel about twelve millions of miles in a minute, or two hundred thousand miles in a second of time. At this rate, the light would come from the moon to the earth in a little more than one second of time. It would take no longer for it to come than it does for the pulse to beat once, or the clock to make one tick.

How do we know that the earth is round, like a ball?

We know that the earth is round like a ball, because its shadow is similar to the shadow of a ball.

How else do we know that the earth is round?

We also know that the earth is round, because we can circumnavigate or sail around it.

Where can we see the shadow of the earth?

We can see the shadow on the moon, when the moon is eclipsed.

What is the shadow on the moon like?

It is round, like the shadow of a ball.

When the Earth comes between the sun and the moon, where does the shadow of the earth fall?

The shadow of the earth falls on the moon, as is represented in Fig. 4.

What is this shadow on the moon called?

It is called an Eclipse of the moon.

How do we know that the moon is round?

We know that the moon is round, because its shadow is similar to the shadow of the earth.

When is the moon eclipsed?

When it comes into the earth’s shadow.

When the moon comes fully into the earth’s shadow, what is it called?

It is called a total eclipse of the moon.

When it comes partly into the earths shadow, what is it called?

It is called a partial eclipse of the moon.

When the moon comes between the sun and the earth, where does the shadow of the moon fall?

The shadow of the moon falls on the earth, as is represented in Fig. 5.

What does this produce?

It produces an eclipse of the sun.

When the moon is between the sun and the earth, can we see the sun?

No; we cannot see the sun, because the moon prevents the rays of the sun from coming to us.

When the moon prevents the sun’s rays from falling on us, what is it called?

It is called an eclipse of the sun.

When the moon prevents _all_ the sun’s rays from falling on us, what is it called?

It is called a total eclipse of the sun.

When the moon prevents only a part of the sun’s rays from falling on us, what is it called?

It is called a partial eclipse of the sun.

When will the _sun_ be eclipsed?

Whenever the moon comes between the sun and the earth.

When will the _moon_ be eclipsed?

Whenever the earth comes between the sun and the moon.

Who made the sun, the moon, and the stars?

God, the creator of all things, made the sun, the moon, and the stars. He placed them in the heavens, where they remain in obedience to His will. He made the bright rays from the sun to light up the day, and give beauty to the world; but the feebler rays of the moon and the stars are seen best at night, when the sun is hid.

In what way is the sun useful to us?

It gives heat, which makes us warm, and it gives light, so that we can see.

Is it useful in any other way?

It gives light and warmth to all animals as well as to all plants.

What make the flowers and leaves so beautiful?

The light and heat from the sun make them beautiful.

What do the light and heat from the sun ripen?

They ripen the apples, cherries, and other fruits; also, the wheat, corn, and other grains, and make them fit for food.

When it is night-time or dark, can we distinguish objects?

No; because all things are then without color, and they cannot be seen.

As it grows light in the morning, what takes place?

At first, we see the objects around us faintly; but as it grows lighter, we see them more distinctly.

Do they all show the same color in the light?

They do not; they show different colors.

What enables us to see the color of different things?

Light enables us to see the color of everything.

What kinds of light have we?

We have the light of the sun, moon, and stars; also, the light from the burning of any substance.

Does the light show many colors?

It does show many colors or shades of color.

How may some colors be made?

They may be made by mixing other colors together.

How can we make a purple color?

By mixing a red and a blue color together.

How can a green color be made?

By mixing a blue and a yellow color together.

How can an orange color be made?

By mixing a red and a yellow color together.

How does the light come from the sun?

It comes in rays or straight lines.

What may be done with a ray of light?

It may be separated into different colors.

Into how many colors may a ray of light be separated?

Into _seven_ colors, like the colors of the rainbow.

What names are given to these colors?

Red, orange, yellow, green, blue, indigo, violet.

How may these colors be separated?

By a prism, or three-sided piece of glass.

How may this be done?

If a sunbeam, shining through a hole in the window-shutter of a dark room, should fall upon a prism, it will be broken up as it passes through the prism, and be shown on the opposite wall, in the seven rainbow colors.

In Fig. 6, D is a sunbeam passing through a shutter. When it passes through the prism, at E, it is separated into the seven rainbow colors, as is shown on the opposite wall.

In what order will these colors appear?

They will always appear one above the other, in the order named.

How may this order be remembered?

By the word Roy-g-biv, made from their initial letters, beginning at the bottom.

From what are the colors of the rainbow made?

From the rays of light coming from the sun.

When is a rainbow seen?

A rainbow is seen when the sun shines through the drops of water as they fall through the air.

How do the drops of water help to make a rainbow?

The drops of water act like little prisms, and separate the rays of light passing through them into the colors of the rainbow.

What two things, then, are needed to make a rainbow?

A shower of water, and a bright sunshine.

In what part of the sky does the rainbow appear?

In the part opposite to that in which the sun is, at the time of the shower.

How does the rainbow appear?

It appears like a great arch, spanning the sky, and its splendid bright colors are very beautiful.

What may we remember in reference to the rainbow?

We may remember that God set his “bow” in the cloud, as a token that the world should no more be destroyed by a flood of waters.

Where else may we see a variety of colors?

Why are these colors constantly changing?

Because the walls of the bubble are constantly growing thinner, and different colors are, therefore, reflected from them.

Why do the walls of the soap-bubble grow thinner?

Because the water runs to the bottom of the bubble until its top becomes so thin as to burst.

Can we tell the color of any object by touching it?

No; we must see it in order to tell its color.

If there are two coats, one blue and the other black, we cannot tell which is the blue one or which is the black one, by feeling them.

What is necessary in order to see the colors?

Light is necessary; because all colors come from the rays of light.

Can we see the different colors in the ray itself?

We cannot; because God has so blended them together that they cannot be seen by us.

When most of the rays of light pass through a substance, what is said of it?

The substance is said to be _transparent_.

Name some transparent substances.

Glass, ice, diamonds, air, and clear water.

When only a few rays of light pass through a substance, what is said of it?

The substance is said to be _translucent_.

Name some translucent substances.

Flint, isinglass, scraped-horn, and china-ware.

When no rays of light pass through a substance, what is said of it?

The substance is said to be _opaque_.

Name some opaque substances.

Wood, iron, coal, and granite.

Can we see through a glass window?

Yes; because the glass is transparent, and the light passes through it.

Can we see through a looking-glass?

No; because the back of the looking-glass is covered with quicksilver, which prevents the rays of light from passing through it.

What becomes of the light falling on the looking-glass?

It is thrown back from the glass.

It is called _reflection_.

What objects are good reflectors of light?

Those having smooth and polished surfaces; such as tin, silver, gold, and quicksilver.

What objects are poor reflectors of light?

Those having dull, uneven surfaces; such as iron, wood, cloth, leather, and calico.

Of what is every ray of sunlight composed?

It is composed of the seven colors of the rainbow.

What does a looking-glass do with these colors?

A looking-glass throws them all back from its surface.

What does a glass window do with these colors?

A glass window permits all these colors to pass through it.

What do opaque substances do with these colors?

They throw back or reflect some of them.

Do they all reflect the same color?

No; some reflect one color, and some another color.

What color does the grass reflect?

It reflects the green color; therefore, the grass is green.

What does the grass do with the other colors?

It absorbs or hides them in itself.

How do we know the color of anything?

We know it by the color which it reflects.

Because it reflects the red color, and absorbs or hides the other colors in itself.

When anything _absorbs_ all the colors of a ray of light, what color is it?

When it _reflects_ all the colors of light, what color is it?

Why are the letters on this page black?

Because they absorb all the colors of light, and reflect none.

Why is the paper white?

Because it reflects all the colors of light, and absorbs none.

Why are all things black in the dark?