Daylight and Darkness in High Latitudes: Encyclopedia Arctica 7: Meteorology and Oceanography
Daylight and Darkness in High Latitudes
EA-Met. (Edward M. Weyer, Jr.)
DAYLIGHT AND DARKNESS IN HIGH LATITUDES
The “long darkness of winter’” more than anything else except perhaps
the fear of cold, has prevented people from going to the Arctic. For ages,
the land “where the nights are six months long” baa been described as suit–
able only for Eskimos and other primitive people adapted to its extreme
conditions.
Only at the Pole, about; 800 miles farther north than the northernmost
Eskimos, does the extreme condition exist, and even there the sun shines
for about
^1 <formula>28 25 / 53 weeks ? 88</formula>
^
28 weeks each year and remains invisible for the remaining 25.
Moreover, the season of “useful light” is much longer than this would in–
dicate. Defining daylight as the amount of light enabling one to read
newspaper print out of doors under a clear sky, there are 32 weeks of con–
tinuous daylight at the Pole and over 8 weeks more during which there is at
least some twilight all the time. This leaves only about 80 days of real
night.
Where the northernmost Eskimos live, the sun is below the horizon
continuously for only a little over 16 weeks each year. Of this period,
only 11 weeks are without any twilight. And during these 11 weeks, the
landscape is brightened much of the time by the moon, which behaves in a
way that seems odd to people who live in lower latitudes, Among these
northernmost people the sun shines continuously for about 18 weeks in the
summer.
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About half of all the Eskimos in the world never see the midnight sun,
for they live too far south; neither do they see the sun go below the hor–
izon for a whole day even in the depth of winter. At the North Pole there
are actually about 140 more hours of sunlight each year than at the equator;
on the Arctic Circle there are about 230 more.
Sunlight has far-reaching effects on human, plant, and animal life, and
it is surprising that the influence of the cycle of illumination in high
latitudes, where the seasonal distribution is so unusual, has not been studied
more thoroughly.
Anyone accustomed to the rising and setting of the sun in the temperate
zone or the tropics will find interest in the midnight sun and other astron–
omical happenings peculiar to the Arctic and the Antarctic. Many an argument
has arisen on an Arctic expedition as to when and where the sun can be ex–
pected to set on a given day. As the expedition moves northward in summer
everyone agrees that the days are lengthening. But is the setting point of
the sun moving northward or southward? Sides are taken.
One man argues that at the equator the sun rises almost due east and
sets almost due west. As you go northward, he insists, you leave kthe sun
behind in the south. How, he asks, could the sun set farther north in the
Arctic than in more southerly latitudes, when it is straight overhead at the
equator?
Another man claims that it does just this. He admits that it seems
illogical that the sun should set farther north as you travel north, but he
has seen it do so. On May fifth he saw it set exactly northwest, when the vessel
was a few miles south of the Arctic Circle.
To understand how this can be so, you must remember that the earth is
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spherical and visualize its position in relation to the sun in summer. At that time the earth is tilted on its axis so that the North Pole is nearest to the sun. A person on the Arctic Circle is then on the side closest to the sun when it is noon, and he sees the sun well up in the sky. As the earth rotates, the observer travels on a circle corresponding to his circle of latitude, and, as midnight approaches, he has to look northward over the top of the spherical earth to see the sun — up over the North Pole.
If the sun rises and sets farther north the closer you get to the Pole
in summer, where does it set exactly at the Pole? The logical answer night
seem to be due north; but that is net correct. It actually sets due
south
;
for where else could it? All directions are due south at the North Pole.
And at the South Pole, all directions are due north. But anywhere between
65°30′ N. and the North Pole, as the summer sun circles the sky without
setting, it comes closest to the horizon when it is due north each day. And
when after the period of continuous sunlight it again sets, it does so in the
north. As the days become shorter, the situation is reversed. Instead of
dipping toward the northern horizon, it rises above the southern horizon.
The accompanying chart will show at a glance the direction in which
the sun will rise and set on any day in the year in any latitude from 0° to
75°N.
Duration of Sunlight
Another pair of charts reproduced here show quickly the number of hours
of daylight and twilight in the Northern Hemisphere on any day in the year
and in any latitude from 30° to the Pole.
An example will best show how the sunlight chart is used. Suppose you
want to know how many hours of sunlight there will be at Reykjavik, Iceland,
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on May 20. The latitude of Reykjavik is 64°N. On the sunlight chart find where the curve for 64°crosses the line for May 20. Where these two lines cross, set a ruler so that it is also lined up with the small X that is halfway between the figures for 85° on the horizontal line. This is always used as the pivot point in working the chart. The ruler will show on the circular scale at the top that there will be 18 hours and 50 minutes of sun– light at Reykjavik on May 20.
To compute this result mathematically would require considerable time
and a knowledge of the formulas of spherical trigonometry. This chart will
therefore save much time and simplify all problems connected with the season–
al sunlight cycle in high latitudes. It will prove useful in scheduling
airplane flights and various other activities where daylight is a considera–
tion. It also offers a rapid method of determining the effect of daylight
on seasonal color changes in animals and on other phenomena such as the time
of migration and hibernation, the ripening of seeds, and the rate of growth
in plants.
Because one half of the year repeats the other in reverse, the calendar
scale is half at the top and half at the bottom.
For the Southern Hemisphere, use a date half a year later and follow
the same method.
Equation Of Time
If the exact time of sunrise or sunset is wanted, longitude and the
Equation of Time must be taken into consideration. If there are ten hours
of sunlight on a given day, half of it will come before noon and half of it
after, as measured by
local sun time
. To convert this to the kind of time
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that the clock shows, add four minutes of time for every degree of longi– tude you are west of the meridian to which the clock is set, or subtract four minutes for every degree you are east of it.
For example, New York City is in longitude 74° W. and is on Eastern
Standard Time. This is 75th-merldian time. Therefore you have to subtract
four minutes from clock tine to get the time of sunrise or sunset. And if
there are to be ten hours of sunlight on a given day, the sun will really
rise at 6:56 instead of 7:00.
In addition to this correction, you must take into account the Equation
of Time. This is necessary because it is not exactly 24 hours from noon to
noon on two successive days. The interval varies because the earth is not
only rotating on its axis but revolving about the sun in a path that is not
exactly circular. The result is that our clocks are sometimes several min–
utes “behind the sun.” (behind the time as shown by a sundial), sometimes
ahead. The extreme amount is about 16 minutes, plus or minus. The accomp–
anying chart of the Equation of Time shows how to add or subtract this cor–
rection at any time of year to change “apparent,” or sun time, to “clock
time.” Note that during those seasons when the equation of time has a minus
value, the sun does not rise or set until that many minutes
after
the time
as reckoned from the sunlight chart. You would therefore
add
the time in–
dicated by this chart when the sign is minus to clock time to get the actual
time of sunrise or sunset, and vice versa.
Hours of Twilight
The twilight chart is used just like the sunlight chart. It shows the
length of time between the beginning of twilight at dawn and the end of twi–
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light at dusk. Thus it includes all the sunlit hours between. At Reyk– javit, for example, which is about 2-1/2 degrees south of the Arctic Circle, there is continuous twilight or sunlight for about 20 weeks, from April 11 to September 1. On March 1 there are about 15 hours and 25 minutes of twi– light and sunlight. The sunlight chart shows that 10 hours and 10 minutes of this are sunlight. This leaves 5 hours and 15 minutes of twilight, which is divided, of course, between morning and evening. So there will be about 2 hours and 37 or 38 minutes of twilight before sunrise, and the same amount after sunset.
Because twilight lasts so much longer in high latitudes, the periods of
full darkness are shorter than one might imagine simply from the hours of
sunrise and sunset. One must travel to within 6 degrees of the Pole to get
continuous darkness for 24 hours one day in the year. At the Pole, there are
only about 80 days without twilight.
Early in the history of astronomy, it was realized that the duration of
twilight depended upon the distance of the sun below the horizon, and cal–
culations were made to define the limits of twilight. Alhazen, Tycho Brahe,
and others concluded that l80° was the best figure. Thus, 18° is the standard
that comes down to us today for what is known as Astronomical Twilight. In
other words, Astronomical Twilight ends when the sun is more than 18° below
the horizon. This is the kind of twilight shown on the chart.
Actually, twilight is, of course, a variable condition. What might be
considered twilight to a sailor might not to a traffic officer. The sailor
may want to know when he can “shoot the stars” or when he should light his
running lights, while the officer may be more worried about when the street
limits should be turned on. Thus, two other kinds of twilight have come to
be recognized. Astronomical Twilight ends when the setting sun is more than
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18° below the horizon. Nautical Twilight ends when the setting sun reaches only 12° below the horizon. It is therefore brighter than Astronomical Twi– light. Even as far north as about 75°N. one does not find a complete 24-hour ^period^ period without Nautical Twilight at any time of the year. In latitude 80° there are about 37 days without Nautical Twilight, from about December 4 to January 10.
So-called Civil Twilight lasts as long as the sun is no more than 6°
below the horizon. If one were traveling northward he would still have about
an hour of Civil Twilight within 17-1/2° of the Pole on the darkest day of
the year. Three degrees farther north there is no Civil Twilight for a total
of over a month and a half in midwinter. And at the Pole there is none for
about 150 days. But all the rest of the year, about 215 days, there is
either sunlight or Civil Twilight at all times at the very top of the world.
Charts giving the duration of Civil Twilight from 65° to the Pole can be
found in
The American Air Almanac
.
At the North Pole the sun becomes visible on about March 19. Then for
about 190 days there is continuous sunlight. On September 24, the sun dis–
appears, and for 15 days there is continuous Civil Twilight. Then for 34
days there is either Nautical or Astronomical Twilight, until November 12.
Twilight again returns on January 30; and by about March 5 there is contin–
uous Civil Twilight. This increases for about two weeks, whereupon the sun
reappears.
The following observations indicate the amount of useful light during
the different kinds of twilight. They were made by the writer in gently
rolling, snow-covered country near sea level with excellent visibility under
a cloudless sky.
During the entire period of Civil Twilight there was plenty of light
for traveling over the snow-covered landscape. Indeed, travel was easier
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than during the day owing to the absence of glare on the snow. There was enough illumination in the shadows to show plainly every unevenness in the snow, and distant objects were clearly visible.
At the end of Civil Twilight there was plenty of light to read a news–
paper. Only one star, a planet, had come out by the end of Civil Twilight
on the night these observations were made. A pink glow from the setting sun
illumined a third of the horizon, where there was a low haze. A half moon
high in the sky made no appreciable contribution to the general illumination.
A second star became visible when the sun was about 7° below the horizon,
and seven others came faintly into view before it had sunk to 8°.
At this time (about one-third the way through Nautical Twilight) it
was possible to distinguish eight-inch tree trunks a mile away against the
western sky, and about one-fourth mile away against the darkest part of the
sky. It was still easy to travel over the ground.
It continued possible to read a newspaper until the sun was 9° below
the horizon, but it became difficult about that time, though there remained
enough light to write by. When the sun was between 9° and 11° below the
horizon, the light from the half moon took the ascendency and produced dis–
tinct shadows.
It is the writer’s opinion that one’s activity outdoors in snow-covered
country will depend largely on the moon when the sun is more than 11° below
the horizon. Thus on a moonless night, travel over rough or dangerous ground
will become difficult toward the end of Nautical Twilight. Contours in the
skyline may be distinguishable, but one would want moonlight in order to
negotiate steep grades. However, with no more than a half moon, travel would
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be possible over fairly rough ground.* Stall branches of trees would be distinguishable 100 feet away against the darkest part of the sky. The skyline would be clearly visible, though the intervening slopes might not.
It must be remembered that a good bit depends upon whether the eyes
have become accustomed to the darkness (an adjustment that takes longer than
might be imagined), and that individuals differ in their ability to see at
night. Also, the amount of light reaching the earth from the moon and stars
varies considerably depending upon the clarity of the atmosphere — its
freedom from mist or haze, as well as from dust and smoke, which are notably
absent in the Arctic.
Effect of Atmospheric Refraction
We have seen that the year at the Pole is by no means divided into two
equal periods of sunlight and darkness. The season of sunlight is more than
half of the year (190 or 191 days), because the sun is actually visible when
it is below the horizon. This is because the light rays curve as they pass
through air of different temperature and density. This happens in all lati–
tudes to varying degrees depending upon conditions. It is conventional to
evaluate this factor of refraction at 34′ of angle. This means that when a
star is 34′ below the horizon it will appear to be just on the horizon.
Since we consider that the sun has not set until its upper edge, or
limb, has disappeared, a correction must also be made for half its diameter,
2
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or 16′. In other words, from the time the center of the sun in at its highest point in the sky to the time when its upper edge passes below the horizon, the sun has actually gone through 90°16′. Adding to this the cor– rection for refraction, we get 90°50′ as the true zenith distance of the sun when it sets.
Refraction causes more extreme “mirage effects” under unusual circum–
stances, and of course it varies with seasonal weather conditions. But it
would scarcely be advantageous to take fluctuations of this sort into ac–
count when computing sunrise and sunset in the Arctic, because the weather
conditions during the sunnier part of the year do not differ radically from
those accepted as standard for the refraction factor used, and the difference
in the over-all picture would not be great in any case.
Effect of Observer’s Altitude
The figures given in this discussion and in the charts are for an ob–
server about 6 feet above sea level. There is considerably more sunlight
for an observer looking out to sea from a mountain top or from a plane. At
an altitude of 15,000 feet, for example, an aviator would see the sun for 77
minutes after it had “set,” in latitude 64° N. early in July. It would also
rise 77 minutes earlier. This difference varies widely with the seasons in
high latitudes. For tables giving it, the reader is referred to
The American
Air Almanac
. It scarcely need be pointed out, on the other hand, that the
sun appears to set earlier if there are mountains on the skyline and that the
light conditions may be altered considerably for a person in a deep valley.
Sun and Climate
Since there are more hours of sunlight in the Arctic than on the equator
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and since they are bunched much more in one half of the year, one may ask why it is not hotter in the Arctic. A partial answer is that the thermometer does sometimes go higher in the Arctic during the long days of sunlight than it ever does in certain parts of the tropics. This happens mostly inland, away from the moderating influence of water and ice. In general, however, summer temperatures in the Arctic become warm rather than hot. This is chief– ly because the sun, although visible for long periods, does not rise so high in the sky. Its rays consequently have to pass through a thicker blanket of atmosphere, which lessens their strength; and since they strike the earth at a lower angle, the same quantity of heat is spread over a larger area.
Sunlight and Animals
It is now well known that length of daylight determines the breeding
cycles and seasonal color changes in many animals and birds. As early as
1803, the Spanish are said to have used lights to increase the egg production
of hens, but they thought that the light simply kept the birds up in the
night and caused them to eat more. Today the practice of artificially
lengthening the daily period of light to increase egg production is so gen–
erally recognized that specially designed clocks for controlling illumination
are a standard commodity in the mail order catalogues.
Until about 1942 it was commonly argued that the increasing cold of
approaching winter caused the ptarmigan to don the white plumage which en–
ables it to escape the many enemies that otherwise might spot it against the
snow. By experimentally controlling the lighting, Per Höst induced the willow
ptarmigan to change its plumage regardless of high or low temperatures. He
caused the birds to whiten out of season and to lay eggs in winter. Indeed,
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they went through their molts and even skipped some depending upon the light schedule.
The ermine of regal reputation, more prosaically known as the weasel,
loses the whiteness of its pelt in the warmer season. Here again, the length
of daylight is the prime factor, as demonstrated by T. H. Bissonette, to whose
published works the reader is referred for further details. It was once
thought that cold or the “sight of snow” caused these animals to put on their
white coat for winter. Daylight is now known to be the explanation. Indeed,
it seems that female Bonaparte and New York weasels don theirs sooner than
the males even though the latter, being more venturesome, are out in the cold
more. The females, being more inclined to enjoy the security of the den, are
less exposed to daylight, and they change sooner.
In these changes, the
length
of daylight rather than its brightness is
believed to be the chief cause. The stimulus is received through the eyes
and affects the anterior pituitary gland, whose secretion causes the change.
On sixteen hours of light a day, weaver finches that do not normally
case into nuptial plumage until two years of age, have been caused to do so
the first year. Through artificial lighting, mallard drakes have been in–
duced in February and March to undergo the plumage change that usually takes
place in June and July.
The effect of day-length on birds does not stop with plumage and the
development of the reproductive organs, for this latter gives the urge to
migrate and sing. Even in Pliny’s time, the extreme regularity with which
birds migrate was noted, and fluctuations in temperature were too variable
to be held accountable. It is now known that the length of daylight controls
the migration dates of many birds. .And since the arrival of birds in spring
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and summer in the Far North is a spectacle of great magnitude, it is to be hoped that further studies will be made in the near future. All migrating birds do not respond to the length of day; some seem to be influenced by other factors, possibly temperature, food supply, or other forces too in– volved to discuss here.
The animals of the Arctic have not been studied adequately in this re–
spect, and a fertile field awaits investigation. From the lowest animals
to the highest, in the sea and on the land, the life of the Arctic will
probably show many strange adaptations to the sunlight cycle when fully
studied.
We know that in lower latitudes, animals can be classed according to
whether they are adapted to activity in the daytime (diurnal animals) or
during the darker hours (nocturnal animals). The diurnal group must become
adapted to meet or avoid relatively high temperatures, high evaporation rate,
bright light, and decreased conductivity of air for odors. The nocturnal
group must become equipped for decreased temperature, high humidity, dim
light, and increased conductivity of air for odors. Each group faces dis–
tinct problems in the securing of food and in the escape from enemies. The
animal’s sensory apparatus has sometimes undergone extreme specialization
in response to the conditions of life as determined by the sunlight cycle.
An example from the temperate zone is the rattlesnake. Being unable
to endure the high temperatures of the desert during the day, it hunts largely
at night and depends not so much upon eyesight to locate its prey, as upon
a pair of heat receptors, located on the head, These are so sensitive that
a blindfolded rattlesnake can search out and strike a small warm-blooded
animal with remarkable precision.
Many animals adapted to activity in the daytime, on the other hand, have
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poor sensory equipment for seeing at night and are relatively helpless.
Specialization in either of these directions follows a recognizable
pattern in moderate latitudes, where daylight and darkness succeed each other
with what we are accustomed to think of as normal rapidity. Rest alternates
with activity on a 24-hour cycle. North of the Arctic Circle, nocturnal spec–
ializations are of course valueless at the season when there is continuous
daylight. No animal depending upon nighttime prowling could survive long in
this situation. Nor could the diurnal animal conceal itself by the same methods
that are used when the cover of darkness can be depended upon in each 24-hour
period.
In winter, the sun disappears for more than 24 hours everywhere north
of about 67-1/2°. At the North Pole it disappears for about 175 days. She
animals living in these high latitudes must to greater or less degree be equip–
ped to forage during twilight, if they do not hibernate or live on stored
food.
Biologists have become increasingly aware in recent years of the import–
ance of the daylight-darkness cycle in causing anatomical and physiological
adjustments for rhythmic or periodic activity. Many basic tests have been
made, but few studies have been carried out on the creatures living where the
midnight sun imposes the most interesting and extreme conditions.
Moonlight in the Arctic
Another reason why the Arctic night is not so black as it has been painted
is that the moon remains above the horizon for long periods during its bright–
est phases. Also, the lack of dust in the atmosphere and the reflective power
of snow-covered land make moonlight especially bright.
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At the poles the moon remains above the horizon continuously for about
two weeks each month. Then it disappears below it for a period that is some–
shorter. Its monthly schedule is therefore comparable in general to the sun’s
yearly cycle. It is above the horizon longer than it is below it because of
atmospheric refraction and because its upper edge, rather than its center, has
to disappear before it has actually set. The apparent diameter of the moon is
about the same as that of the sun, as anyone can see during a total eclipse.
However, the moon’s motions are not as simple as the apparent movement of
the sun. For this reason and because our calendar is geared to the sun rather
than to the moon, it is not possible to chart the cycle of moonlight as simply
as we have done for sunlight.
More important to the hunter and traveler than slight variations in the
length of time the moon remains above the skyline is the question of whether
it is full, quarter, or new. The moon goes through its phases in the Arctic
on the same schedule as elsewhere in the world. But this schedule is related
to its time of rising and setting in such a way that the situation is peculiar–
ly favorable for those who dwell in high latitudes. To understand this, one
must picture the relative positions of the sun, earth, and moon as shown in
the accompanying drawing.
The earth travels in a curved path around the sun, rotating on its axis
as it does so. But it is inclined on its axis so that in the middle of winter
(December 22) the North Pole is tipped away from the sun at an angle of about
23-1/2°. This is the time of greatest darkness in all high northern latitudes.
Continuous night or twilight exists for one or more days north of about 65-1/2°.
The sun cannot shine over these regions even at “noonday.” The tilting of the
axis of the earth has taken them into the shadowed side. This tilting is what
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makes it winter in the Northern Hemisphere. It also is what determines that there shall be the most favorable distribution of moonlight at the season when it is most needed.
The moon continually revolves around the earth, completing the circuit
once every month. When the moon is between the sun and the earth, we have
new moon, when it is out at the side, approximately a week later, we have
“quarter” moon. And when it is on the opposite side of the earth from the
sun, we have full moon. At this time of the year, the arctic regions are
tilted away from the sun. They are therefore tilted
toward
the moon when
the moon is full. This means that in winter the moon will always be highest
and longest in the sky when it is fullest. New moon and crescent moon will
not appear above the horizon at the Pole in midwinter. The two weeks when the
moon is above the horizon in midwinter are the two weeks when it is at its
brightest.
The same seasonal relationship favors the Antarctic, though at the
opposite time of year, of course, because it is winter there when it is summer
in the Arctic.
When it is summer in the North, the moon does not waste its light in
competition with the midnight sun. At that season, the axis of the earth is
tipped so that the North Pole is nearest to the sun and the South Pole forth–
est away. The light of the sun shines over the North Pole and down the far
side of the earth. The nearest thing to night for a person on the Arctic Circle
comes when the earth, in its daily rotation, takes him around to the side that
is farthest from the sun. He then has to look up over the North Pole to see
it, but the sun remains visible above the horizon. Whether or not the observer
can see the full moon in this position will depend upon what year it is, but
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we shall discuss this later. In any case, he will not see it for long each day. Latitudes north of about 70-1/2° never do see the full moon exactly in midsummer (unless more than normal atmospheric refraction produces a mirage effect). Right at the North Pole, the moon is continuously below the horizon for about two weeks during its brightest phases in midsummer.
As the moon wanes, it shows itself more and more above the horizon during
the northern summer. Since by the very nature of its motion it has to be be–
low the horizon almost half of the time each month at every season, it is for–
tunate that it gives the Arctic its weaker phases in summer when there is so
much sunlight and that it reserves its stronger phases for the season when the
sun provides the least light.
In this explanation we have pretended for the most part that the path of
the moon around, the earth lay in the same plane as the path of the earth around
the sun. Actually, the moon’s orbit is tipped at an angle of about 5° from the
earth’s. And the “high” and “low” points of its orbit are slowly but contin–
ually moving around in relation to the inclination of the earth on its axis.
This does not materially modify the seasonable relationship we have been dis–
cussing. But it does change the height to which the moon rises in the sky at
any one time and place from year to year. And it determines how far north one
has to travel, to see the lunar equivalent of the midnight sun.
If the orbit of the moon lay in the plane of the earth’s orbit, an ob–
server at the Pole would see the moon rise above the horizon to a height of
about 23-1/2° each month, year-in and year-out. But because the moon’s orbit
is tilted about 5°, a man at the Pole would sometimes see the moon rise to about
28-1/2° and at the opposite extreme only to about 18.1/2°. This is because the
5-degree tilt of the moon’s orbit is sometimes added to the earth’s 23-1/2-degree
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tilt and sometimes subtracted from it. This cycle is completed about every 18.6 years.
In 1932 the moon reached its peak altitude. About nine and a third years
later, in 1941, it rose only to 18-1/2° at the Pole. In September of 1950,
it again reached its highest altitude. The exact height varies slightly from
one peak to the next but not enough for us to consider here.
Tracing the circle back through history, we see that the noon was at about
its lowest point in the sky at the time Sir John Franklin’s expedition of over
100 men perished in the central Canadian Arctic. Pure coincidence certainly,
but tragedy also overtook the Greely expedition in northern Greenland when
the moon was approaching its lowest point. Peary made his famous polar hourney
when the condition was about average. It was considerably better when Roald
Amundsen and Robert Falcon Scott both reached the South Pole. The moon hung
high when Vilhjalmur Stefansson began his celebrated expedition of 1914-18,
and he completed it under an average moon. Five years later, when the Wrangel
Island expedition perished, the moon was again at its worst.
What this means is that at the Pole during What we have been calling
favorable periods, the moon rises more than 50% farther above the horizon
in its circuit of the sky than it does at the opposite point in the 18.6-
year cycle, As a result, It rises more rapidly and is higher and therefore
brighter for a greater percentage of the time. It is not visible appreciably
longer each month. But even so, it is more useful for certain types of hunt–
ing and, other sorts of activity than when it is not rising so high.
One has only to travel to about 60-1/2° north latitude to see the lunar
equivalent of the midnight sun when the soon is rising to a height of 28-1/2°
at the Pole (allowing case degree for atmospheric refraction). At the opposite
time in the 18.6-year cycle, when the moon is rising lowest over the Pole, it
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is necessary to go about 650 miles farther north - to about 70-1/2° N. - to witness this. The sun, it will be recalled, offers its midnight display in a latitude of about 65-1/2° every year.
Value of the Moon
Though the full moon gives only about a half a millionth as much light
as the sun, its illumination is very important to those who live in the Arctic.
In winter, when both direct and indirect sunlight are absent much of each day,
the ground is usually snow-covered, and it therefore reflects ouch more light.
Also, there is a minimum of dust in the air in arctic regions, because most
of the surface is sea, lake, or swamp. Smoke is rare so far from factories
and forest fires. These things make the air in the Arctic especially clear
and cause the moan to shine with special brilliance unless there are clouds
or fog.
Vilhjalmur Stefansson consulted a number of polar travelers and found
them to agree that on a cold midwinter night you get more useful light from
half a moon on a snowy landscape than from a full moon shining on a green
landscape. It is his opinion that, with a clear sky, you can see a mountain
range as far by the light of the stars and half a moon as you can by sunlight.
Several arctic pilots he wrote to agreed that you can land an airplane about
as safely with half an arctic moon as with daylight. Some informants have said
that half a moon does not give quite as much light as you would ideally want
but that freedom from glare compensates for the brighter light of a daytime
landing on snow.
Quoting Stefansson further, “Some experienced flyers disagree that the
light of half a moon is adequate for safe landings, and. feel that moonlight
really sufficient is available only for the two or three nights at the immediate
EA-Met. Weyer: Daylight and Darkness
full. These flyers, however, are all from Alaska, all have their main exper– ience in the Yukon valley, not on the prairie north of the Brooks Range or on the Arctic coast. This brings out an important thing — that clumps of forest scattered here and there about an otherwise snowy landscape detract from the total reflecting effectiveness more than you would expect. For one thing, the moon is usually at a slant so that the trees not only absorb the light which strikes them directly but also throw a shadow over same more of the landscape. Then there are like shadows thrown by rocks and cutbanks, while cliffs are usually dark because they are steep. Mountain slopes are not on the average as effective with moonlight as are horizontal landscapes....
“An advantage of moonlight over sunlight, connected with the absence of
glare, is that it throws more sharply defined shadows or appears to do so; and
shadows give an airman his one possibility of telling the difference between a
level and a rough snow or ice surface when he is coming down for a landing.”
Northern lights, of course, sometimes add considerably to the illumination
(See “Aurora Borealis” in Vol. I of this Encyclopedia), though they do not
give these sharp shadows and are not predictable.
Moonlight and Hunting
If the Eskimos had to stop hunting when the sun went down, a great many
of them would starve. Stores of meat and fuel laid aside for winter help greatly,
but these people secure a significant share of their provisions during twilight
and moonlight. The first brilliant moonlight after the winter ice has formed
is a favorite time for hunting the polar bear among the Eskimos of northern
Greenland. The principal sealing season among many groups of Eskimos is during
the arctic night. Hunting is brought practically to a standstill in midwinter
EA-Met. Weyer: Daylight and Darkness
chiefly among the groups farthest north, like the Polar Eskimos of Smith Sound, and even there only when the moon does not brighten the landscape. And if stores have been secured in the normal course of events to tide over this season, the natives enjoy many activities less ardently pursued at other times, such as visiting, dancing, and ceremonial festivals.
Stefansson points out that sealing is easier under waning illumination
than caribou halting is, for in the latter, field glasses are as important
as the rifle, and this makes daylight necessary for any considerable success.
It is interesting that one type of sealing - that with nets placed under the
ice - is practical only during darkness. Even the moon interferes with this
type of hunting, and a bright aurora is said to be unwanted.
Summarizing, the moon goes through its phases each month in the Arctic
as it does elsewhere. But whereas in moderate and tropical latitudes it is
below the horizon about half the time whether it is new or full, in the Arctic
it remains above the horizon continuously for long periods when it is bright–
est and most needed. Even a half moon is a welcome aid to the traveler and
hunter. At its brightest its light, reflected through clear air
^
^
by the snow
cover, exceeds anything oriinarily seen in the tropics. It is of considerable
practical value to those living in the north; and its silvery brilliance, fall–
ing upon, mountain peak, crevassed glacier, and nestling hamlet has caused many
to extol Its esthetic qualities.
Water Sky, Land Sky
Under certain light conditions, especially when the sky is uniformly over–
cast with reasonably high clouds, the navigator or sledge-traveler in the Arctic
Sea can make good use of their reflective power in setting his course. They
show him where there is open water, where ice, and where land of different sorts.
EA-Met. Weyer: Daylight and Darkness
Indeed, the sky becomes like a map of the territory beneath.
The sailor is particularly anxious to find open water or lanes in the
ice wide enough for him to navigate. These appear on the sky map as dark areas
between white patches. The sun, shining through the clouds on areas different–
ly colored or lighter or darker, produces this effect. Even the character of
the ice can be ascertained. Quoting from Stefansson, “Broken surfaces with
many pressure ridges can themselves never be quite uniformly white and are,
therefore, represeneed above by a slightly mottled appearance. One kind of
surface ice, the paleocrystic, has been converted by many summers of rains and
thaws into a small-scale equivalent of an undulating prairie. The hollows are
choked with snow, the hills that have been swept free of snow are blue in ap–
pearance, because, as elsewhere explained, old ice is always fresh and glare.
Paleocrystic floes are, then, reflected to the sky by round, oval, or at least
not angular, dark patches in a matrix of white.
“The sky map shows leads in their full variety of manifestations. Those
which are several weeks or months old are smoothly snow covered and are there–
fore shown by the clouds more uniformly white than any other ice; and so you
will discover long ribbons in the sky representing them cleanly. Other leads
have ice from one to several days old, and they are represented by sky ribbons
of various degrees of darkness. Those leads in which the water is still un–
frozen are shown the darkest of all, practically black….
“When you approach land [when traveling over white sea ice] in winter or
early spring you see first a general darkening of the sky. This is not as pro–
nounced as if caused by open water. There are certain patterns in the sky map
now which you recognize as showing land formations, and there is an amber or
yellow tinge due to the bleached grass which sticks up here and there through
the snow. If there are in the land sky a few patches as dark as over water,
EA-Met. Weyer: Daylight and Darkness
you know they are sandy or rock stretches — at any rate land where the wind has swept all the snow away.
“A modification of land sky is something found at sea in that strong off–
shore winds have carried dust and fragments of rock out upon the ice. There
will then be belts and tongues of gradually fading darkness stretching out in
the sky map from the denser drabness of the land.”
A special pinkish effect is seen in the sky map when the tiny plant known
as “pink snow” has formed on the surface. This occurs in late spring when the
temperature is ranging between about 20°F. at night; and 20° in the daytime.
Sun Dogs
An interesting sight that can be seen in the Arctic because it is caused
by crystals of ice in the atmosphere is the phenomenon known as sun dogs, or
parhelia. These are mock suns, appearing at about the same height as the sun
and connected with it by a white arc or halo. There are also halos surrounding
the sun (or moon) at definite distances of about 22° and 46°. These distances
tire determined by the fact that the ice crystals suspended in the air have defin–
ite angles of 60°and 90°. The luminous arcs exhibit the colors of the rainbow
but not in a well-defined manner. The only definite tint is the red on the
inside of the circle. In addition to these two arcs, there may be others form–
ing a definite pattern but not completely visible all at once, as a rule.
The brightest sun dogs are usually seen at the intersections of the two
halos with the luminous are paralleling the horizon through the true sun. They
are most brilliant when the sun is near the horizon. Mock moons are formed in
the same way and are called
paraselenae
instead of
parhelia
. As the sun rises,
the sun dogs may pass a little beyond the halo and acquire flaming tails. There
is sometimes a vertical circle passing through the sun.
EA-Met. Weyer: Daylight and Darkness
Though more recent studies have added to our knowledge of these phenomena,
the reader is referred especially to the celebrated memoir by Auguste Bravais,
Sur les Halos et les Phenomenes Optiques qui les Accompagnent
(1847), in the
Journal de l’Ecole Royale Polytechnique
, vol. xviii.
The Sun and Human Life
One is perhaps most curious to know the effects of the northern sunlight
cycle on human life. Of course, the most obvious thing is that you can get a
terrific sunburn, owing to the intense reflection of the sun’s rays from sur–
faces of ice, snow, or water. The Eskimos wear snow goggles made of wood,
bone, or ivory with narrow horizontal slits cut in them.
Many peoples throughout the world have worshipped the sun, both in trop–
ical and temperate latitudes. Elbaroate rituals have been developed to cele–
brate the “return of the sun” and the summer solistice. We see relics of such
ceremonies even in central Europe in our own time. We are somewhat surprised,
therefore, to find that the Eskimos, who are exposed to the extremes in the
sunlight calendar, express little religious concern for the sun. Nor can this
be explained by any failure to develop an elaborate religious philosophy in
other directions.
To be sure, among the Iglulik Eskimos, when the sun first reappears after
the period of darkness, the children must run into the snow huts and put out
the lamps. The new sun must be attended by new light. And at Point Barrow it
was customary in pre-Christian times when the sun returned, to chase the evil
spirits out of the house with knives, shouts, and frantic gestures. In West
Greenland there was customarily a feast and dance at the time of the winter
solstice, but we cannot be sure that it was not instituted by the medieval
Europeans who began occupying the west coast of Greenland following 982.
EA-Met. Weyer: Daylight and Darkness
The sun does play a part in Eskimo mythology, as distinct from cultic
ceremony. The sun is a girl who is constantly being chased about the sky by
her brother, the moon. (The moon-man, indeed, is a more important spirit than
the sun, particularly in Alaska.) But the sun-girl is not an important deity.
Eskimo religious ceremonies are directed largely toward the obtaining of food
and other necessities. Yet in spite of the fact that the sunlight season is
associated with plenty and the sunless time with difficulties in securing these
necessities, the sun-girl is not worshipped. The honors go to a goddess who
lives down under the sea and is thus as far from the sun as she could get.
The respect they pay the moon-spirit is not for the light he sheds, either,
but rather for the ways he can help people indirectly through magical powers.
It is as though the Eskimos recognized the orderly processes of astron–
omy as unchangeable. Weather they will try to alter. But who could change
the heavenly bodies in their courses? Their philosophy here appears to differ
from that of more advanced peoples who have put much store in the supernatural
influence of astronomical movements.
In some sections the Eskimos do practice a semireligious pastime of making
cat’s cradles with string in the autumn “to delay the disappearance of the sun,”
but the commoner rule seems to be that the gams is tabooed except during the
dark days “when the sun cannot see.” So the attitude in this observance, while
linked with the sun, does not seem well defined.
The northern lights are believed to be a manifestation caused when the
spirits of the dead play football with a walrus head.
One finds many descriptions in arctic literature of the miseries the Eski–
mos endure during the darker season. If sufficient stores of food, clothing,
and fuel have not been laid aside, the people do suffer. But it must not be
EA-Met. Weyer: Daylight and Darkness
assumed that this is the fate of every village every winter. There is also much merriment during the time of darkness, with games, supernatural ceremonies, and story telling. The “gloom of winter” has not prevented the Eskimos from having a reputation for unusual cheerfulness.
An observer from more southerly regions usually searches for psychological
effects that can be attributed to the environment he finds so different from
his own. Stefansson points out that the impressions and reactions of a person
during his first year in the Arctic are apt to reflect the “un-Arctic” ideas
he brought with him rather than the actual state of affairs. If his mind is
full of the dramatic episodes of arctic exploration, it is a shock for him to
realize that people from moderate latitudes have lived in the Arctic year-in
and year-out, raising families and vegetables, and, for that matter, enjoying
recreational activities not possible in our sore heavily populated areas. If
by background and nature a man is the sort of person who would rather live under
the tracks of an elevated train than under the northern lights, he will probably
return to his noisy canyon as soon as he can. He may no longer feel, in all
honesty, that he is something of a hero simply for having ventured into the
Arctic Zone, He will probably only consider himself more fortunate staying
right back where he came from for the rest of his life. If, however, he remains
in the Arctic, either through desire or necessity, he may give a more balanced
view of the conditions there, and he may come to love the land.
The writer would point out that life in the so-called Temperate Zone in
winter would be far from comfortable were it not for our equipment for living
there. Few of us wrest our food, clothing, shelter, fuel, and other necessities
from nature as the Indians did before the coming of white men. As a result, we
cannot easily think of the climate in the same terms as our pioneer ancestors
did.
EA-Met. Weyer: Daylight and Darkness
Man carries with him an environment of his own making, compounded of all
the things he has invented or acquired to modify the effects of the natural
world. When we cay that a man enjoys nightlife, we do not mean that he craves
darkness like some nocturnal animal, poorly equipped far life abroad at any
other time. We mean that he enjoys the activities that the world of entertain–
ment provides — with plenty of bright lights. Another will prefer the pleas–
ures of the beach, even if he has to plaster himself with grease to avoid pain–
ful and dangerous consequences.
These are the things we must hold in mind when trying to evaluate the
climate of any part of the world. We must separate fact and opinion. The
facts of climate, of which the daily and seasonal distribution of sunlight
forms a part, can be agreed upon. But, since human temperament differs as
widely as it does, there is room for difference of opinion among reasonable
persons.
It is therefore no surprise that we get divergent interpretations regard–
ing the effect of winter darkness on human beings. From his personal experience,
Stefansson refutes the thesis that darkness must of itself produce melancholy.
Bertelsen, on the other hand, writes of the situation in Greenland as follows:
“Of the greatest importance in respect to health is, however, the influence of
the country on the nervous system of those who have come to live there. The
long distance from the mother country, the formed associations with the same
few people or the absolute loneliness, the lack of suitable variety, the com–
parative inactivity, the monotomy which often makes life feel curiously unreal
and shadowy, an existence limited essentially to daily metabolic process, the
journeys, frequently with a distinct element of danger, the close contact with
the forces of nature, the illimitable space, the stillness and darkness, oper–
ate strongly on the mind. During the first part of the stay all of these fac–
EA-Met. Weyer: Daylight and Darkness
tors not infrequently result in an increased irritability and a morbid dis– trust of the surroundings; later on a certain dullness of the initiative and a coarsening of the whole mental life are the most conspicuous symptoms. In certain cases, with special mental predispositions, the reaction may set in far more strongly, ending in pronounced insanity.”
It is the writer’s belief that we might find a comment quite comparable
to this if we searched the literature of England in early colonial times, de–
scribing, let us say, the region of Atlantic City. In natural beauty, one
hesitates to compare Greenland with Atlantic City.
“
Arctic Hysteria
”
Knud Rasmussen, the well-known explorer and ethnologist, wrote of the
natives of King William Land as follows: “Then it was that I observed the
same thing as so often before at Thule in North Greenland, that the approach–
ing darkness and the long stormy night affected the nerves and minds of the
Eskimos. Almost every evening the camp was scared by the imaginary visits of
spirits which, they said, could only be heard or felt, and with which the local
shamans...were consequently compelled to combat incessantly.”
H. P. Steensby, writing of the Polar Eskimos of northern Greenland, stated
that “....a peculiar form of hysteria, more frequent among women than among men,
is said to be strikingly common late in the autumn, when the winter darkness
is just coming an. Such attacks last for some minutes to about half an hour...”
Jenness likewise wrote: “Hysteria is particularly common around the Polar basin;
the long winter darkness and the loneliness and silence of the hunter’s life
make the Arctic people more susceptible to this disorder than the rest of the
human race.” And Novakovsky reported that “arctic hysteria” was prevalent in
northeastern Asia. The women
^
there
^
likewise seemed more susceptible than the men, and
EA-Met. Weyer: Daylight and Darkness
it was suggested that the tribes that have been in the region longest appear more immune to it than those that have arrived more recently.
Kaj Birket-Smith, on the other hand, did not notice any “arctic hysteria”
on his extensive travels in the central Canadian Arctic. And Margaret Lantis
did not find a single case of it on Nunivak Island daring her stay there in
1939-40, nor was there any report of it from recent years. She concluded that
it may have existed in the far past but that it was not in any case common.
Perhaps the best summary of the evidence and opinions regarding “arctic
hysteria” is given in
The Science of Society
, by Sumner, Keller, and Davie
(1927), Vol. IV, pages 514 ff.
It seems that little if any difference can be detected between “arctic
hysteria” and hysterical phenomena observed widely throughout the world. Is it,
therefore, caused by some factor peculiar to the Arctic, or is it merely the
outsider’s name for something that occurs almost everywhere? In the absence
of consistent statistical evidence, we can only express uncertainty and skep–
ticism and place the matter squarely in the lap of the psychologists as a
problem deserving further inquiry. Those who investigate the subject as spec–
ialists will, of course, recall that monstrous outbursts of hysteria have oc–
curred in lands where the sun rises and sets in a perfectly conventional way,
and that the shamans of Siberia have not been content with letting darkness do
the trick but have employed all manner of methods to induce the condition.
Sunlight and Agriculture
Pursuing the thesis that man’s natural environment is one thing and what
he makes of it another, this discussion would not be complete without mention
of the advances made in recent decades in agriculture in the Subarctic and
Arctic. White man’s earliest interest in this part of the world was based upon
EA-Met. Weyer: Daylight and Darkness
its pastoral and agricultural opportunities. From shortly before the year 1000 to sometime in the fifteenth century, thousands of persons from Europe made Greenland their home and established farms there. These colonies devel– oped a successful social, economic, and religious life. They had their own bishops and ^ ^ helped to support the Crusades. After the mysterious disappearance of these colonies, apiculture in the Arctic [or, rather animal husbandry re– lying on the common domestic animals of Europe] went into eclipse for almost five centuries, and other objectives like the fur trade and mineral exploita– tion gained popularity.
In most parts of the Arctic where civilization has penetrated, farming of
one sort or another is now looked upon as a practical activity and a desirable
adjunct to other pursuits. The results are sometimes more impressive than the
world of a century ago would have thought possible. The abundance of summer
sunlight is, of course, the reason why food plants flourish there.
Without many years of scientific interest in arctic agriculture, we have
records of 14-pound cabbages from 80 miles north of the Arctic Circle, at Thunder
River, Northwest Territories. At the same place, 985 pounds of potatoes have
been grown from 42 pounds cut to one-eye sets; and 46-inch barley has ripened
an August 18th. (See articles on Agriculture in Vol. VI, Plant Sciences, for
further information.)
Within certain limits, wheat and oats grow more rapidly in high latitudes
than farther south. In tests carried out over an 8-year period, wheat at Fort
Vermilion matured 16 days sooner than at Beaver Lodge 220 miles farther south,
and 1-1/2 days sooner than at Lethridge 600 miles farther south.
The researches of John M. Arthur have led him to conclude that the potato
produces most abundantly when grown at a high light intensity on the longest
EA-Met. Weyer: Daylight and Darkness
possible days and at a low temperature (about 68° F.).
With plants of many species it is the length of sunlight more than any
other factor that determines when the flowers and seeds shall be produced. The
size, shape, and vigor of the leaves and stems are affected by temperature and
moisture, as well as by the intensity of the light; but the time of flowering
depends primarily upon the length of daylight. For this reason, many of the
common vegetables of the temperate zone will not produce seeds in the tropics,
where sunlight never lasts much longer than twelve hours. It follows that
^
^
if
the farmer in the Arctic wants vegetative growth, he will often do best with
the plants that require long hours of sunlight before flowering occurs, there
is wide opportunity for experimentation in the selection and development of
plants best suited to growth in the Arctic. (See “Thermoperiodism, Vernaliza–
tion, and Photoperiodism in the Arctic” in Vol. V, Plant Sciences.)
Stefansson has pointed out that through the ages man has perversely clung
to domestic animals that were originally native to the tropics instead of domes–
ticating ones that are better adapted locally to conditions in other climatic
zones. Though it cannot be said that the native plants of the Arctic will nec–
essarily produce the greatest food crops, somewhat the same argument can profit–
ably be applied to future research in arctic agriculture. We cannot expect to
make the best progress unless the factors influencing the growth of the useful
part of the plant are analyzed with a view to selecting the varieties and species
that will respond to the special conditions encountered there.
Many things are destined to Change in the Arctic in the next few years and
decades. Occupations attractive to persons in many walks of life will beckon.
Airplanes, tractors, roads, and el
^
e
^
ctrical generating plants are hastening the day
when there will be “a radio in every Eskimo snowhouse.” Man’s complex culture
will seem to overshadow the true Arctic in many ways and to rob it of much of its
EA-Met. Weyer: Daylight and Darkness
traditional mystery and romance; and the ingenuity with which we apply our– selves to the problems peculiar to the Arctic will determine how rapidly the land will be made useful for more people.
But above all, the sun and moon will continue on their accustomed courses,
shedding their light according to their strange schedule, regimenting the seasons.
ripening plants, affecting directly or indirectly every creature of land and
sea and time controlling the vital processes of nature which provide man with
his basic needs and spell plenty or famine in any part of the world.
Edward Weyer, Jr.
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