OUR NEAREST STAR--THE SUN
STARS are suns which lie at such vast distances that they seem no more
than twinkling points of light. Through the aid of the spectroscope we
have learned a great deal about these stars but so distant do they lie
that no telescope on earth can bring them close enough for us to see the
outline of a face.
There is one star, however, that lies so near that when it is in the sky
its light blots out that of all the other stars. This sun, which classic
poets call our "day star," lies only 93,000,000 miles away; the next
nearest star is over 200,000 times as far. This distance of 93,000,000
miles is close enough to enable us to examine the face of such a star as
ours with comparative ease, indeed, it is close enough to enable us to
feel the warmth of the fierce fires which rage upon its surface.
It is not at all a difficult matter to realize the distance from our
earth to the sun. A train traveling 60 miles an hour would reach the sun
in 176 years; an airplane flying at the rate of 200 miles an hour would
reach it in 50 years. Thus the distance seems to shrink as we adjust our
rate of speed. A ray of light crosses the same space in about 8 minutes.
The existence of all life upon the earth is absolutely dependent upon
the sun.
"It is perceived that the sun of the world, with all its essence, which
is heat and light, flows into every tree, and every shrub and flower,
and into every stone, mean as well as precious."
--_Swedenborg._
Equally dependent are the seven other planets which, with the earth,
whirl in elliptical orbits about this source of heat and light.
"The Sun the seasons of the year supplies
And bids the evening and the morning rise;
Commands the planets with superior force,
And keeps each wandering light to his appointed course."
--_Lucan's Pharsalia._
The planets are sometimes called the "family" of the sun, although his
family also includes the retinue of each planet, which in the case of
six of them at least, consists of from one to ten moons. Our sun is no
different than thousands of other stars in the sky; is it likely that
our star alone of all the countless millions which shine in our
universe, should be the only one to possess this additional charm of
maturity? One looks far out in the darkness to the hosts of radiant
stars--then wonders--how many stars have flocks of planets--how many
travel alone?
THE SURFACE OF THE SUN
Compared to a point of starlight, the disk of our "day star" looks most
exceedingly huge, and this at a distance of 93,000,000 miles. One is
therefore not quite so surprised to learn that this great sunball, which
rests like the hub of a wheel in the center of the solar system, has a
diameter of 886,000 miles. The 8000 miles which measures across the
earth seems quite inconspicuous when compared with such a diameter as
this.
Completely covering the sun's surface is a mass of intensely hot crimson
gases. These gases are like a turbulent upper atmosphere with a depth of
5000 to 10,000 miles. Raging and seething in long tongues of flame, they
swirl up for thousands of miles above the surface, or are thrown far
above it in titanic explosions. Formerly, these burning gases could only
be seen at the time of total eclipse when the black disc of the
moon passed in front of the glaring face of the sun leaving only the red
flames licking out beyond the dark edge. The invention of the
spectroheliograph now makes it possible to photograph these projections
when the sun is shining. One should never try to see them by looking at
the sun unless the glare is shut off either by the moon or by artificial
means, for the sun is so unbearably brilliant that the eyesight of an
observer would soon be ruined.
[Figure 133: SOLAR PROMINENCES.
Huge flames ejected from the surface of the sun, photographed at
Yerkes Observatory with the Rumford spectroheliograph attached
to the 40-inch refractor.]
This colorful gas which covers the surface of the sun, is called the
_chromosphere_ or color-sphere on account of the vivid color which it
acquires from the hydrogen and calcium of which it is largely composed.
The colossal flames which rise above its surface are called
_prominences_. Some of the prominences shoot up with a velocity ranging
from 300 to 600 miles a second, sometimes to a height of 200,000 miles,
and even higher. The largest so far recorded extended upward for 500,000
miles. Others extend horizontally for a distance of over 300,000 miles,
racing forward at the rate of a thousand miles a minute, although
sometimes they remain in an unchanged position above the surface of the
sun for days at a time. These flames seem tremendous compared to our
terrestrial standards, but they would not seem so large on the
globe of the sun which is 3,000,000 miles in circumference.
[Figure 134: HYDROGEN FLAMES ON THE SURFACE OF THE SUN.
Photographed with the aid of the spectroheliograph at the Mount
Wilson Observatory.]
It seems strange to think that the "tranquil stars" must also be
seething in such wild commotion,--blazing orbs torn by terrific
tornadoes of fire. It is fortunate that we cannot hear the terrible roar
as well as see the light of their conflagrations. Since sound waves do
not travel through space like the waves of light and heat, the
tumult on even our nearest star could never reach us; yet sound is such
a laggard traveler compared with fleet-winged light, that light could
cover the distance of 93,000,000 miles in less than 8 minutes while
sound would require over 14 years to travel over the same space. Thus,
even if we could hear the voices of these explosions, they would never
coincide with the scenes enacted.
The bright yellow surface of the sun which every one sees, is called the
_photosphere_ or light-sphere. If strongly magnified through a
telescope, this surface is seen to have a decided "mottled" appearance,
like a layer of little clouds with dark spaces between, spread over the
whole face of the sun. These are now known to be masses of calcium gas.
Practically all that is known of the physical constitution of the sun
has been discovered through the study of the fine, dark lines in the
solar spectrum. Through the aid of the spectroscope, many terrestrial
elements have been discovered, among these being calcium, sodium,
magnesium, potassium, aluminum, silver, iron, nickel, copper, zinc, tin,
lead, hydrogen, oxygen and carbon. All these elements are either in the
form of permanent gases or metallic vapors.
The _photosphere_ or light-sphere lies below the _chromosphere_ or
color-sphere. Beyond the crimson color-sphere lies another envelope of
very delicate light called the _corona_. This may only be seen at the
time of total eclipse. It was once thought to belong to the moon but it
is now known that the moon has very little atmosphere. Besides, the
moon's black disk may be seen floating across this beautiful halo of
light.
The corona has been described by those who have seen it, as having a
"soft, pearly radiance" "tinged with green"; its form is quite irregular
and varies at different times, extending from 1,000,000 to 3,000,000 and
sometimes even 9,000,000 miles beyond the surface of the sun. In the
eclipse of 1879 the streamers were quite extensive in the
equatorial plane of the sun where they united in a formation like the
petals of a narcissus while at the solar poles they were shorter and
extended in well-defined rays. Yet no matter what its form, it is a
magnificent background during the sun's eclipse for the narrow rim of
deep crimson projects beyond the inky edges of the moon.
The corona seems to be caused by electrical discharges in a medium of
fine dust and rarefied gases, chiefly coronium and protofluorine.
Various electrical phenomena take place in the strong magnetic fields of
the sun as a whole and in the sun-spots, and the changing fields of
magnetic force cause the changing appearance of the corona.
The sun-spots, however, are of the greatest interest to amateurs for
these may often be seen with very little optical aid. These dark,
movable spots were first noted by Galileo, although the idea that the
sun could have spots upon its surface was ridiculed by the scholars of
the medieval schools who argued in the fervid language of scholastic
philosophy and medieval dogmatism, that the sun was a sphere of pure
fire undefiled by any spots.
Sun-spots are, as a rule, thousands of miles across and usually appear
in groups which cover an immense area on the surface of the sun, but,
since the sun lies 93,000,000 miles away, a spot large enough to contain
the earth would appear to us about the size of a pinhead on a
pincushion. Right here one should be warned again not to attempt to look
at the sun without adequate protection (such as smoked glasses) for the
eyes. A photograph taken through a large telescope is the most
satisfactory. Although these dark blotches--which are only comparatively
dark--were called "spots" and were later drawn as saucer-like
depressions, modern research and increased power in the telescopes has
revealed them as gigantic solar tornadoes. These tornadoes usually last
from a few days to several months, and are especially numerous in
cycles of 11 years. During sun-spot activity eruptive prominences rise
to heights of many thousands of miles and streams of electrons are shot
forth with such force that they may possibly even penetrate deeply into
our own atmosphere causing disturbances such as magnetic storms and
auroras.
[Figure 135: SUN-SPOTS.
The earth is so small compared with the huge bulk of the sun that
it would be lost in one of these "spots." Photograph by the Mount
Wilson Observatory.]
If a total solar eclipse occurs at a time when these great magnetic
storms are raging in particular fury on the sun's surface, the corona
always appears brighter and more intricate than when the sun is
peaceful.
Sun-spots were very numerous in 1915 and 1916. The next spot maximum
will occur about 1926, then in 1937 and so on. For three years or four
years they appear with great frequency, then declining to a minimum for
three or four years, rise to a maximum again; thus the period from
maximum to maximum is about 11 years.
Through watching these black spots disappear around one edge of the sun
and then reappear after an interval of time on the other side, Galileo
discovered that the sun turned completely around on its axis in 25 days.
[Figure 136: SUN-SPOTS, DIRECT PHOTOGRAPH.
Compare with photograph on page 214, also made on same day by
the Mount Wilson Observatory.]
Further study disclosed the still stranger fact that the sun does not
turn around in a solid body. Areas near the equator were found to
complete a revolution in 25 days, but they were seen to forge ahead of
those regions in higher latitudes; 45 degrees north and south latitude,
the rotation period is 27½ days; 60 degrees north and south latitude,
the period is 31.2 days, and in 80 degrees north and south latitude, the
period is 35.3 days. This alone can be regarded as proof that the sun's
apparent surface is not solid but is either in a liquid or gaseous
state.
AN ECLIPSE OF THE SUN
A _total_ eclipse of the sun is caused by the moon passing between the
earth and the sun, and since the moon is apparently the same size as the
sun in the heavens, it hides the bright face of this luminary from our
view; but the long shadow which trails behind the moon must touch the
earth. The shadow moves along a narrow strip as the earth revolves and
only those who are in this shadow can see the sun totally eclipsed.
If the shadow of the moon does not quite touch the earth, the moon's
disk does not quite cover the sun.
[Figure 137]
Then the dark body of the moon is seen surrounded by a ring of light.
This is called an _annular_ eclipse.
In a _partial_ eclipse, the sun's disk suddenly becomes indented on one
side, the indentation slowly increasing for some time, and then
diminishing until it disappears altogether.
Total solar eclipses are extremely infrequent in any one place because
of the smallness of the cone of the moon's shadow. This shadow draws a
black streak across the earth, which, under favorable circumstances, may
have a breadth of a little more than 160 miles and a length of 10,000 to
12,000 miles. The width of the shadow depends upon the nearness of the
moon for if its shadow just touches the earth, the streak will have no
sensible width. A partial solar eclipse is visible 2,100 miles or more
on either side of the region where the eclipse is total.
[Figure 138: RELATIVE POSITION OF THE SUN, MOON AND EARTH
AT THE TOTAL SOLAR ECLIPSE OF SEPTEMBER 10, 1923.
(The two words at the point of the shadow's contact with the Earth
are "Catalina" and "San Diego.") Drawing by Dr. Mars F. Baumgardt,
Curator of Clark Observatory, Los Angeles, Calif.]
Since the shadow of the moon passes across the earth at the furious rate
of 1300 miles an hour, a total eclipse of the sun lasts for only a few
minutes,--and for this length of time, short as it is, some thanks is
due to the fact that the earth, in revolving upon its axis, carries the
observer and the ground upon which he stands along the same direction in
which the shadow is moving. Total eclipses are of extremely rare
occurrence and only happen about once in every three hundred years for
any selected spot on the earth's surface.
An interesting description of a total eclipse may be found in
Flammarion's "Astronomy for Amateurs":
"The luminous disk of the sun is gradually corroded. Another disk, as
black as ink, creeps in front of it and little by little invades it
entirely. The atmosphere takes on a wan, sepulchral hue; astonished
nature is hushed in profound silence; an immense veil of sadness spreads
over the world. Night comes on suddenly, and the stars shine out in the
Heavens. It seems as though by some mysterious cataclysm the Sun had
disappeared forever."
Professor Moulton in his "Astronomy" gives another splendid
description:
"It always occurs precisely at new moon, and consequently the moon is
invisible until it begins to obscure the sun. Steadily the moon moves
over the sun's disk; and, as the instant of totality draws near, the
light rapidly fails, animals become restless and everything takes on a
weird appearance. Suddenly a shadow rushes across the surface of the
earth at the rate of more than 1300 miles an hour, the sun is covered,
the stars flash out, around the apparent edge of the moon are rose-colored
prominences of vaporous material forced up from the sun's
surface to a height of perhaps 200,000 miles, and all around the sun
extending out as far as half its diameter are streamers of pearly light
which constitutes the sun's corona. After seven minutes at the very
most, the western edge of the sun is uncovered and daylight suddenly
appears."
In "New Astronomy," Langley tells of the sensations of an observer
as the moon's shadow passes furiously on its way:
"The bright cloud I saw distinctly put out like a candle. The rapidity
of the shadow, and the intensity produced a feeling that something
material was sweeping over the earth at a speed perfectly frightful. I
involuntarily listened for the rushing noise of a mighty wind."
On June 8th, 1918, September 10, 1923, and on January 24th, 1925, many
people in the United States were privileged to view the wonderful
spectacle of a total eclipse. Scientists came from all over the world to
witness the solar eclipse of 1923, for not only was it visible from an
attractive corner of our country at a pleasant time of the year, but the
sun was at a convenient altitude for observation. Many photographs were
taken of the great flaming corona, some even from airplanes.
Although people now travel halfway across the earth in order to be able
to witness an eclipse, in olden days such an occasion was marked by the
greatest terror.
[Figure 139: THE SOLAR CORONA.
Photographed during the eclipse of June 8, 1918, at Green River,
Wyoming, by the Mount Wilson Observatory Expedition.]
To the ancients they were without the order of nature, and in Rome, at
one time, it was blasphemy, and punishable by law, to talk publicly of
their being due to natural causes.
The Chaldeans believed the sun and moon to be black on the hidden side,
and upon the displeasure of the Gods, the darkened side was turned to
the earth thus causing an eclipse.
[Figure 140: SUCCESSIVE STAGES OF AN ECLIPSE OF THE SUN, RECORDED
WITH THE AID OF A KODAK.
Photographed by Edith Carlson at Palo Alto, California, September
10, 1923.]
Many people among the European nations covered their wells and fountains
for fear that the water would become contaminated by the poisonous,
mists which arose during an eclipse. The notion was probably due to the
fact that the drop in temperature is often accompanied by a fall of dew.
The Peruvians thrashed dogs during an eclipse so that their howling
would keep evil spirits away, and for the same reason, the Romans beat
their pots and pans, lifted up torches and fire-brands into the air. The
people of the Northern nations also created a great din, for they
imagined that the sun was pursued by fierce wolves (Skoll and Hati), who
tried to swallow their brilliant prey so that the world would return to
its primeval darkness.
Crooke, in "Popular Religion and Folk-Lore," says that
"A high-caste Hindu will eat no food that has remained in the house
during an eclipse, and all earthen vessels which are in the house at the
time, must be broken. During an eclipse all household business is
suspended, and eating and drinking is prohibited, even sleep at such
times is forbidden, for it is then that the demons and devils are most
active. The most effectual way of scaring the demon Rahu and releasing
the afflicted planets is to bathe in some sacred stream and for
protection, a Brahman should stand in the water beside the worshipper
and recite the Gayatri."
It is said that at such times the rivers are covered with human
heads.
Some barbarian tribes imagined that when the sun or moon began to lose
its light, the orb was sickening under the arts of a wicked magician and
they danced and screamed and beat their tomtoms in a wild frenzy so that
the wicked one might become afraid and steal away. The well-known idea
of the Chinese, however, is the most interesting of all, for there are
records showing that for several thousand years these people believed
that an eclipse was caused by the attempt on the part of a huge black
dragon to seize the burning ball and swallow it. The dread of such
a catastrophe so preyed upon the minds of the populace that it is
reported in the "Tshu-King," one of the oldest chronicles in existence,
that the ancient astronomers Ho and Hi had their heads laid before their
feet for failing to predict an eclipse of the sun. Plenty of time to get
out drums and kettles and to make the deafening noise which had always
caused the monster to drop the sun was always given after this little
incident. Douglas, in "History of China," relates that at this time, the
intervention of every official in the country is called upon to save the
sun from being destroyed.
"Some months before the expected eclipse the board of astronomers
notifies the exact date of its appearance to the officials of the board
of rites, who in their turn announce its appearance to the viceroys and
governors of the provinces. They transmit the message to all their
subordinates, so that, when the time arrives, an army of mandarins stand
prepared to avert disaster. Their procedure is simple and as neither the
sun nor the moon have ever been devoured, it is regarded as efficacious.
At the appointed time the mandarins assemble at the yamen of the senior
official, and arrange themselves before an altar set up in the
courtyard, on which incense is burning. At a given signal, they fall
down on their knees and perform Ko-t-ow, after which the attendants beat
drums and gongs to frighten away the oppressive monster, while the
priests move in a procession round the altar chanting prayers and
formulas. To assist the mandarins in their patriotic efforts, the people
mount to the roofs of their houses, and add to the din which issues from
the yamen by beating everything capable of emitting resounding noises."
The Grecians, however, ascribing all things to the gods, thought that
the phenomenon was due to Jupiter, who, sometimes wishing to keep his
business on earth secret from the other immortals on Mount Olympus, kept
them from seeing him by hanging a little covering over the sun.
"The Olympian Father hangs a noon-day night
O'er the sun's disk and veils its glittering light,
Fear falls on man. Hence miracles, before
Incredible, are counted miracles no more."
--_Archilochus._ (_Trans. by_ SIR CHAS. ABRAHAM ELTON.)