Look to the north on a dark, moonless night, far, far from a major city, and you just might see a shimmering glow of light. Sometimes the light looks like waving curtains, sometimes it's just an amorphous glow. Sometimes the light is colored, other times it looks a greenish white. The mysterious light was named by the French astronomer Gassendi (1592- 1655) who, in reporting on a major display seen in Southern France on September 12, 1621, dubbed it aurora borealis: the northern dawn. Its counterpart in the southern hemisphere is called the aurora australis. Just what is this mysterious phenomenon and how long has it been around?
What is an aurora?
The sun is a hot ball of material whose surface temperature is some 10,000°F (5,500°C). Even though the sun's gravitational strength is 27 times that of the earth, because of the huge amount of energy there, material streams away from the sun at fantastic speeds. This flow of material is called the solar wind. Some of the particles making up the solar wind approach the earth and penetrate the atmosphere to a height of about 60 miles (100 kilometers) above the surface. Many of the particles are electrically charged and so they travel along magnetic lines of force. As a result, they travel to the north and south magnetic poles of the earth, where the lines of force produced by the earth's magnet enter into the earth. When these ions, as the charged particles are called, enter the air, they excite (ionize) the oxygen and nitrogen atoms in the upper air, causing them to glow in much the same way as electrons flowing through a fluorescent light causes the gas therein to glow. The amount of light emitted by the excited oxygen and nitrogen atoms depends on how active the sun is, that is, on how many solar particles hit the atmosphere. The degree to which the sun is active is reflected in the presence or absence of sunspots: regions of the sun which are cooler and thus darker than the surrounding area. When sunspots are at their maximum number, then the sun's activity is also at a maximum. The number of sunspots increase and decrease over an 11-year period, and so does the frequency and intensity of the northern and southern lights.
Historical evidence
D. Justin Schove of St. David's College, England, compiled the most
exhaustive collection of ancient records of sunspots and aurorae to date.1
He claimed that he was able to find the times of sunspot maxima for
every cycle back to A.D. 300, as well as many of the 11-year cycles back
to 649 B.C. He reports that the earliest known reference to a sunspot is
due to Theophrastus of Athens (ca. 370-290 B.C.), a student of Aristotle.
Chinese records of sunspots date from about 28 B.C. to A.D. 1638. From
his data, Schove found that the average period for a sunspot cycle is
11.11 years with individual cycles ranging in length from 9 to 14 years.
He also confirmed the so-called “Maunder minimum” in the latter half of
the seventeenth century when sunspots were virtually absent. Recent
speculation about the Maunder minimum involves the theory that the sun
is shrinking.
When it comes to ancient observations of the aurora in the Bible,
Schove interprets the following passages as sightings of the aurora:
Ezekiel 1:4: And I looked, and, behold, a whirlwind came out of the
north, a great cloud, and a fire infolding itself, and a brightness was
about it, and out of the midst thereof as the colour of amber, out of the
midst of the fire.
Zechariah 1:8: I saw by night, and behold a man riding upon a red
horse, and he stood among the myrtle trees that were in the bottom;
and behind him were there red horses, speckled, and white.
Other historic references to the aurora seem more realistic.
Anaximenes provides us with the earliest known Greek account in the
sixth century B.C. Anaxagoras (ca. 500 B.C.) and Aristotle (387-322
B.C.) also wrote about the aurora. Among the Romans who reported
aurorae are Cicero (106-43 B.C.), Livy (59 B.C.-A.D. 17) and Seneca (4
B.C.-A.D. 65). The latter describes an event in A.D. 37 when the people
in Rome thought that the colony of Ostia was on fire. During most of the
night, the heaven appeared to be illuminated by a faint light resembling
thick smoke. At low latitudes, aurorae are often red in color.
It is generally thought that aurorae do not occur at the equator, but on
September 25, 1909, aurorae were seen at Singapore (1°N) and Batavia
(6°S). On May 13, 1921, aurorae were sighted at Samoa (14°S) and Tongatabu
(21°S). So aurorae may be seen from any point on the earth.
Properties of the Solar Wind
The solar wind is a collection of electrons and protons which started
out as hydrogen atoms but which were stripped apart by the heat of the
solar corona (some 10,000,000 degrees) and ejected at speeds ranging
from 300 to 600 kilometers per second. When they reach the earth, the
temperature of the solar wind is between 18,000 and 180,000 degrees
Fahrenheit (10,000 to 100,000 degrees Kelvin or Celsius) and there are
from 1 to 30 protons or electrons per cubic centimeter (20 to 600 per
cubic inch).
Since the protons and electrons are free from each other, the plasma,
as the solar wind is called, is highly conductive. As a result, it retains
part of the sun's magnetic field and is subject to the earth's magnetic
field, too. The earth's field acts as an obstacle to the solar wind and the
effect is to deform and compress the terrestrial field's lines of force. The
deformation results in the construction of a boundary between the solar
wind and the earth's field, which boundary is called the magnetopause
(Figure 1). The magnetopause begins about 40,000 miles (64,000 km)
from the earth in the direction toward the sun and extends more than
2,000,000 miles (3,200,000 km) in the “downwind” direction. Also,
since the speed of the solar wind is about 10 times the “speed of sound”
near the earth, a shock wave (akin to a sonic boom) is permanently in
place upstream from the magnetopause. The shock slows down the solar
wind and heats it up to a temperature of over a million degrees Kelvin
(1.8 million Fahrenheit). The shocked, slowed gas then flows over the
magnetosphere where, in the process, a small fraction is trapped and becomes
part of the gas in the reservoir called the plasma sheet. The temperature
there ranges is from 20 million to 200 million degrees Fahrenheit
(10 to 100 million Kelvins).
The plasma sheet is not a simple sheet in form. Instead, it is shaped
more like that of a glass tube at the end of which some gigantic glass
blower has started to blow a bubble. Yet the bubble's end looks like a
pair of pincers pinching the earth near its poles (Figure 1). It is from
these “pincers” that electrons rain down from the plasma sheet into the
earth's upper atmosphere to produce the aurorae. During solar storms,
the plasma sheet moves closer to the earth, causing the aurora to move
closer and closer to the equator. That motion stops at the edge of yet
another collection of particles called the plasmasphere. The plasmasphere
is the upward extension of the earth's ionosphere and is composed
of ionized atoms (atoms stripped of one or more of their electrons),
mainly hydrogen, from the earth's atmosphere. Compared to the plasma
sheet, the plasmasphere is cold and dense.
The plasmasphere is in the shape of a doughnut (toroid) with the earth
filling the hole in the middle. It has a sharp upward boundary called the
plasmapause, which is caused by a wind in the magnetosphere which at
that point sweeps away particles faster than the ionosphere produces
them. The shape of that boundary is dictated by the earth's magnetic
field. On the average it is 20,000 miles (30,000 km) from the earth at the
equator, and it reaches the top of the atmosphere at about 63 degrees
north and south latitudes. These are the auroral latitudes.
Although the densities may not sound like much, the pinching effect
of the plasmasphere can produce dramatic currents. One of the greatest
magnetic storms occurred on September 1, 1859. It was observed in
Honolulu, Cuba, Jamaica, Guadalupe and, in the southern hemisphere at
Santiago and Sydney. The solar flare which spawned it was the first ever
observed, being visible as a white spot on the face of the sun, an extremely
rare event. The storm disrupted telegraph communications in
France where isolated cables would spark to grounded objects brought
near the wire. Elsewhere, the storm aided communication. For example,
the telegraph between Boston and Portland ran for two hours without a
battery, using only the current induced by the storm.
Conclusion
At this point there is nothing inherently geocentric or even creationistic
about the aurorae. Perhaps the reference to stretching the heavens as a
curtain in Isaiah 40:22 refers, in part, to the aurorae; but I doubt it.
Others have speculated that the center of the aurorae, above the magnetic
poles of the earth, are the sides of the north referred to in Isaiah 14:13,
but I doubt that, too; for Psalm 48:2 relates those sides to mount Zion and
”the city of the great King.” Future generations may find the solar wind
and the magnetosphere to be a useful source of energy; but for the time
being it is still a pristine phenomenon untouched by human hands. 1 2Jeremiah 1:13: And the word of the LORD came unto me the second
time, saying, What seest thou? And I said, I see a seething pot; and
the face thereof is toward the north.
To interpret these as references to the aurora is stretching it, especially
Zechariah 1:8 where the phenomenon is described as a man on a red
horse standing among the myrtle trees. A “seething pot?” maybe, but it
should say “a seething sky,” instead, to be more correct. To interpret the
seething pot as an aurora would require human corruption of the text and
a low view of inspiration. As for the whirlwind in Ezekiel 1:4,
whirlwinds are common in the Mid-East, so why not take it at face value?
Besides, all of these are prophetic visions and, as visions, are not required
to have any physical substance.
14 Then the LORD said unto me, Out of the north an evil shall break
forth upon all the inhabitants of the land.
Figure 1: The Magnetosphere and its plasmic parts and
currents.2
___________, 1962. “Auroral Numbers Since 500 B.C.,” J. of the
British Astron. Assoc., 72:30.
___________, and P.-Y. Ho, 1967. “Chinese Records of Sunspots
and Aurorae in the Fourth Century A.D.,” J. of the American Oriental
Society, 87:105.