THE SUN, THE BRIGHTEST OF ALL STARS
In naming over the stars of the first magnitude—that is, the stars that
shine the brightest—there is one star I did not mention and yet as we
see it it is brighter than all the other stars put together.
This great star is our _Sun_ and since we owe everything we possess on
Earth to him—light, heat, power and even life itself—he should and does
stand in a class by himself, though after all he is just as much of a
fixed star as the North Star, the Dog Star, or any of the thousands of
other stars which we see as mere points of light in the sky.
=How to See the Sun.=—You must never look directly at the Sun with the
naked eye, for he is so powerful that his light will injure your sight
for all time.
[Illustration: FIG. 28.—SMOKING GLASSES OVER CANDLE FLAME.]
[Illustration: FIG. 29.—SEEING THE SUN THROUGH SMOKED GLASSES.]
There are several ways, though, to observe the Sun without danger to
your eyes and as all of these are simple and cost nothing you can
easily try them. The most common way is to take a bit of window glass,
say an inch square, and smoke one side of it over the flame of a
candle, as shown in Fig. 28.
When this blackened glass is held closely to the eye, as shown in Fig.
29, and the latter is directed toward the Sun, a little circle of
light will appear on the film of smoke and the surface of the Sun may
be examined at length and without the least danger.
A decided improvement over the smoked glass idea is to use a piece of
red, or a piece of yellow glass, as an eyepiece, or, better, place the
red and yellow glasses together and bind the edges with paper. Another
plan to see the Sun without injury to the eyes is to make a hole with
the point of a needle in a visiting card and look through the hole
directly at the Sun.
A still better view of the Sun can be obtained if a pinhole telescope
is used. A telescope of this kind can be easily made without tools,
metals or lenses. It is described and pictured in Chapter IX.
To observe the Sun hold the pinhole end of the tube closely to your
eye, to cut off all the outside light, and sight the tube so that the
Sun shines directly into your eye through the pinhole, and you will get
a very brilliant view of the great yellow star which we call the Sun.
=What the Sun is Made of.=—When a candle is lit the wax of which it is
made begins to melt and this is drawn up the wick where it is changed
into gas and the burning gas forms the flame.
The flame of a candle is made up of four parts, which are really layers
of heated gas surrounding the wick, as shown in Fig. 30. In the center
of the flame is the wick; the first layer of gas is at the bottom of
the flame and this gives a greenish-blue light; the second layer is
the dark and cool part of the flame; the third layer is a cone of
heated gas which gives out the bright light, and surrounding this cone
is a faint blue light which can just be seen.
We know, of course, what the candle is made of and we also know why
it burns and in a way how it gives off light and heat because we have
examined it closely, but if we could get no nearer a candle flame than
a quarter of a mile it is very doubtful if we could ever be able to
learn anything about the real source of the flame—that is its greasy
wick.
[Illustration: FIG. 30.—A CANDLE FLAME SHOWING LAYERS OF FLAME.]
It is much the same with the Sun, for we can only examine it at a great
distance and know it by its action on our senses, for the flaming
layers of the Sun are so bright that no one ever saw through them,
so the real source of its light and heat—the core of the Sun—remains
unknown. Fig. 31 shows the Sun as seen with a field glass.
Since the Sun gives out light and heat it is easy to believe that it is
a great ball of very hot gases and from what astronomers have learned
of him with their wonderful instruments this idea seems to be pretty
well founded.
The Sun must be a tremendously hot body—for the iron and other metals
in it are not only melted but they boil away like water and are
changed into gases. Under certain conditions gigantic flames, called
_prominences_, shown in Fig. 32, can be seen to leap from the edge, or
_limb_, as it is called, of the Sun, and finally, great spots, called
_sun spots_, are formed on the Sun that are so large a dozen worlds the
size of our Earth could be dropped into any one of them and rattled
around like marbles in a cigar box. These are a few of the reasons we
are led to believe that the Sun is a seething ball of fire.
=The Sun’s Layers of Flame.=—Just as the wick of a candle is surrounded
with several kinds of flame, so the Sun has three layers of flame
around a central core.
The core of the Sun is believed to be formed of liquid gases which are
about as thick as New Orleans molasses.
Around this core, which is the real source of the Sun’s light and
heat—and which has never been seen—is a dark layer of flame usually
called the _Sun’s surface_; this layer, which is covered with numerous
dark spots like freckles on the face of a red-headed boy, is called the
_photosphere_, and it is this part of the Sun which gives out the most
light.
[Illustration: FIG. 31.—THE SUN AS WE SEE IT.]
The second layer, which is called the _chromosphere_, is about 5,000
miles thick, and if you could imagine the whole world afire you would
then have but a faint idea of what a mighty seething sea of flame
this layer is. It is in this layer of luminous gases that terrific
explosions take place and red tongues of flame, or _prominences_, are
shot out for upwards of 300,000 miles.
Around the chromosphere is another layer of flame which extends for
hundreds of thousands of miles in all directions. This last layer is
called the _corona_, and it is as thin as the stuff of which dreams are
made. It is formed of the gas coronium and since it is so thin it can
never be seen except when there is a total eclipse, that is, when the
Moon passes between us and the Sun, which will be explained in Chapter
VII, and so shuts out the intense light of the other two layers. A
cross section of the Sun is shown in Fig. 33.
[Illustration: FIG. 32.—PROMINENCES OF THE SUN COMPARED WITH THE SIZE
OF THE EARTH.]
=Sun Spots and Their Effect on the Earth.=—Very often great spots are
seen on the Sun’s surface. These purplish black spots appear to be
holes, like the craters of volcanoes, in the photosphere, or layer of
flame next to the core of the Sun. The sun spots are caused by great
eruptions which take place in the core of the Sun, and these sun
spots are sometimes over 100,000 miles in diameter, when they can be
easily seen with the naked eye; indeed if a sun spot has a diameter
only as large as that of our Earth, it can be seen with the naked eye,
protected, of course, with either a smoked or a colored glass, or
better, with a pinhole telescope; in any case it will look like a black
speck about the size of a pinhead. Fig. 34 shows a view of a sun spot
made through a large telescope.
[Illustration: FIG. 33.—CROSS SECTION OF THE SUN.]
Whenever the sun changes his spots _magnetic storms_ take place on the
Earth, when compass needles, telegraph and telephone apparatus and
wireless systems are disturbed. When a large number of spots appear at
the same time on the Sun the _Northern Lights_ are often very bright.
Sun spots have something to do with our weather, but the effects are
not yet well understood.
=The Sun and the Weather.=—Of course the Sun has everything to do with
the weather, but to be able to predict the kind of weather we shall
have even the next day is a very hard thing to do.
The changes in the weather are caused by the heat of the Sun alone.
The heat of the Sun produces clouds by vaporizing the water of rivers,
lakes and oceans. He causes hot and cold weather by heating some parts
of the air more than other parts, and this sets the air in motion and
we call this movement of the air the wind.
[Illustration: FIG. 34.—SUN SPOT IN PHOTOSPHERE.]
Changes of heat, moisture and wind are the cause of all the kinds of
weather we have, and we have a good many kinds, be it hot or cold, dry
or wet, calm or windy, clear or stormy, good, bad and indifferent.
=To Forecast the Weather by a Barometer.=—The best way to tell what the
coming weather will be in the next few hours is by the rise and the
fall of the _pressure_ of the air, or _barometric pressure_, as it is
called.
A simple _barometer_ for showing the changes in the pressure of the air
can be made of a glass tube about 3 feet long, ½ inch in diameter, and
closed at one end as shown in Fig. 35. Fill the tube with mercury and,
placing your finger over the mouth of the tube, turn it upside down and
put the open end into a cup, or other vessel, which is half full of
mercury; in placing it into the cup be careful that no air gets into
the tube.
Only a small part of the mercury in the tube will run into the cup
and this will leave a space in the top of the tube. Now fasten a
yardstick, the purpose of which is to show the changes in the height of
the mercury in the tube, with a string or wire to the tube, and your
barometer will be complete, as shown in Fig. 36.
Since the air presses on the mercury in the cup but not in the tube,
the pressure of the air on the mercury in the cup just balances the
weight of the mercury in the tube and, hence, any increase or decrease
in the pressure of the air, which ordinarily is about 15 pounds to the
square inch, is shown by the rising or the falling of the mercury in
the tube.
The barometer in helping to forecast the weather shows that: (1) when
the mercury _rises_ in the tube, that is when it is high, the weather
will be _fair_; (2) when the mercury _falls_ in the tube, that is
when it is low, _bad_ weather may be looked for; (3) when the mercury
_suddenly falls_ in the tube a _storm_ is coming, and (4) when the
mercury continues at a _high point_ the weather will remain _fair_.
[Illustration: FIG. 35.—BAROMETER TUBE.]
[Illustration: FIG. 36.—BAROMETER COMPLETE.]
To remember these forecasts easily they may be briefly stated thus:
(1) A _high_ barometer shows _fair_ weather.
(2) A _low_ barometer shows _bad_ weather.
(3) A _sudden fall_ of the barometer shows a _coming storm_.
(4) A _constant high_ barometer shows continued _fair_ weather.
=To Forecast the Weather by Signs.=—It will seldom happen that a boy
who goes camping, or one who otherwise wants to know what the weather
is likely to be on the morrow, will have a barometer to consult, so the
next best thing is to know how to read the weather signs:
(1) “Red at night is the sailor’s delight” is an old
forecast, and means that the morrow will be a fine
day.
(2) “Red in the morning is the sailor’s warning,” which
means that rain is coming.
(3) A golden sunset is a sign that a high wind is
coming.
(4) A yellow sunset is a sign that rain is coming.
(5) When the Sun sets clear it is a sign of a fine day
on the morrow.
(6) When the Sun sets behind a cloud it is a sign that
the next day will be cloudy or rainy.
(7) A misty dawn shows the coming of a fine day.
(8) A low dawn, that is when the Sun shines clear on
rising, shows the coming of a fine day.
(9) A high dawn, that is when the Sun rises over a
haze, or clouds, shows wind.
=To Light a Fire with the Heat of the Sun.=—A small _magnifying glass_,
or burning glass, is simply a convex lens. It is a little piece of
apparatus that every boy should always carry with him just as he does
his pocket knife and compass. A lens 1½ inches in diameter and having a
4-inch focus may be bought for 25 or 30 cents.
A lens of this kind will be found very useful in many ways, for it
will greatly magnify any object such as cloth, leaves, insects,
finger-prints, in fact anything you may wish to see better than you
could with your naked eye, though you cannot use a single lens for a
spyglass. A magnifying glass will also frequently come in handy for
lighting fires, by using the Sun’s rays when matches are scarce.
While a Boy Scout would disdain to use paper to kindle a fire, yet if
a scrap of paper is at hand it will prove a good medium on which to
direct the rays of the Sun with a burning glass. If you have no paper
focus your glass on some _punk_ or very dry leaves, as shown in Fig.
37.
To focus the glass means to hold it away from the paper or leaves so
that the rays of the Sun are brought to a point like the sharpened end
of a lead pencil; when all the rays of sunlight, each of which carries
a little heat, are brought to a point, they will make enough heat to
light a piece of paper or a dry leaf.
[Illustration: FIG. 37.—BOY FOCUSING BURNING GLASS ON LEAVES TO MAKE
FIRE.]
=Signaling with the Sun’s Rays.=—There are many ways of sending a
signal or a message across space by day, as, for instance, by means of
smoke, by flags and flashes of sunlight; by bonfires, pine-knot flames
and burning arrows by night, and by wireless, which can be used either
by day or by night.
A simple and effective way to signal in the daytime when the Sun is
shining is by using a mirror, that is, a looking-glass, as it is
commonly called. Every boy knows how to make flashes with a mirror, so
it will be enough to say here that the glass is held in the hand in
such a position that the sunlight falling upon it will be reflected in
the direction you wish to send the signals. Fig. 38 shows how it is
done.
[Illustration: FIG. 38.—BOY SENDING FLASH SIGNAL WITH MIRROR.]
[Illustration: FIG. 39.—CONTINENTAL MORSE CODE.]
Any sort of a code can be used, but it is far more interesting and will
prove very useful if you are able to send and receive messages in the
dot and dash alphabet, or Morse telegraph code, which is given in Fig.
39. A short flash represents a dot, a long flash a dash and short and
long flashes represent letters. This is the same code that is used for
wireless telegraphy.
=How to Make a Simple Heliograph.=—A _heliograph_ is merely a mirror
mounted on a baseboard, but this is a big improvement over holding the
mirror in the hand, for to send and receive flashes over long distances
the mirror must be carefully aimed and kept in position.
To make a heliograph, get a board 12 inches long, 4 inches wide and
1 inch thick and cut a piece out of one end 4 inches long and 1 inch
wide, as shown in Fig. 40. Bore a ¼inch hole through the slotted end
and another ¼ inch hole 4½ inches from the slotted end, as shown in the
cut.
[Illustration: FIG. 40.—BASE FOR HELIOGRAPH.]
[Illustration: FIG. 41.—BACK VIEW OF HELIOGRAPH.]
Make a block of wood 4 inches long, 1 inch wide and 1 inch thick and
bore a ¼ inch hole through it near one end. To the other end of this
stick fasten a mirror about 4 inches square. This mirror should be
perfectly smooth—a plate glass mirror is the best—and have a hole
¹/₁₆ inch in diameter drilled through the center of the mirror for
sighting the heliograph, as shown in Fig. 41. Any optician will drill
the hole for you for a quarter or less. Fig. 42 shows a top view of the
heliograph and Fig. 43 shows a side view of it.
Make a wood frame so that the mirror can be fastened in it and screw
the frame to a stick of wood. Get a bolt 5 inches long and ¼ inch
in diameter and have a thumb screw fitted to it. Set the end of the
stick which has the mirror fastened to it into the slotted end of the
baseboard, push the bolt through the holes and after slipping on the
washer put on the thumb screw. The mirror can now be moved to and fro.
[Illustration: FIG. 42.—TOP VIEW OF HELIOGRAPH.]
[Illustration: FIG. 43.—SIDE VIEW OF HELIOGRAPH.]
Into the hole in the front part of the base put a wire or a thin round
stick to sight the mirror by. The heliograph is now ready for use.
After sighting the mirror at the place where the signals are to be
received, set the mirror so that the reflected beam of sunlight shines
directly on the place. To send signals in the Morse code all you need
to do to make dots and dashes is to place a sheet of cardboard before
the mirror and take it away; the length of time the mirror remains
uncovered determines whether it is a dot or a dash. The heliograph
complete is shown in Fig. 44.
[Illustration: FIG. 44.—HELIOGRAPH COMPLETE.]
=How to Make a Simple Sundial.=—To make a sundial of the usual kind
that will give the correct Sun time is not an easy matter, for the
spaces marking the hours on the dial are not equal as they are on the
face of the clock and this will make it hard to figure out.
A kind of sundial that will give the correct Sun time though, can be
easily made and at little cost. Get a strip of tin 2 inches wide and 24
inches long; mark it off into 24 equal spaces like those on a two-foot
rule, and beginning at one end with the number 1, number each space
to 24, as shown in Fig. 45. This done, bend the strip of tin into a
perfect ring with the numbers inside and solder the joint, as shown in
Fig. 46.
[Illustration: FIG. 45.—NUMBERED STRIP FOR SUNDIAL.]
[Illustration: FIG. 46.—TIN RING FOR SUNDIAL.]
Next get a strip of iron or brass ¼ inch wide, ¹/₁₆ inch thick and 13
inches long; drill a ¹/₁₆ inch hole through each end and a ⅛ inch hole
4 inches from one end; bend this strip into an exact semi-circle, as
shown in Fig. 47 and solder the tin ring, at the point where numbers 1
and 24 meet, to the middle of the brass semi-circle. Through the holes
in the ends of the brass semi-circle fasten a wire, and this wire must
run exactly through the center of the tin ring. Now screw the brass
semi-circle to a baseboard (see Fig. 48), so that the angle made by the
wire and the surface of the board will be equal to the latitude of the
place where it is to be used; in other words, when the board is level
the wire should point directly to the North Star and when this is done
it will be adjusted to the proper angle. The board should be about 12
inches square and 1 inch thick.
[Illustration: FIG. 47.—BRASS SEMI-CIRCLE WITH SHADOW WIRE.]
[Illustration: FIG. 48.—SUNDIAL COMPLETE.]
Since the shadow of the wire made by the sunlight will fall on XII
at noon, it will be plain that the shadow of the wire falling on the
numbers on one side or the other of the ring will mark the Sun time. To
change Sun time to _mean solar time_, or ordinary time, see _Equation
of Time_, Appendix M.
[Illustration: FIG. 49.—TO FIND THE NORTH BY A WATCH.]
=To Find the North by a Watch=.—To use a watch as a compass, that is to
find the north by means of a watch, is easy if the Sun is shining. The
watch should be held face upward; then turn the watch around until the
hour hand points in the direction of the Sun. Draw an imaginary line
from the hour XII to the center of your watch.
If, now, in the middle between this line and the hour hand you draw
another line from the center of the watch and produce, or extend it,
the middle line will point just about north, all of which is clearly
shown in Fig. 49.