July 1971 Popular Electronics
Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
Changes in Earth's magnetic field ~1500-2000.
If you read the physics and geographic news of the day, most likely you have
seen articles on the rapidly increasing migration rate of the geomagnetic "north pole" over
the past few decades. Magnetic north has never exactly lined up with geometric north
(as borne out in geological samples of rocks), and neither has it ever been uniformly
distributed across the globe. Ancient explorers on terra firma and at sea knew that
a magnetic compass needle did not align with the same stars, moon, or sun position
for every location, after accounting for difference in longitude. That is because
the earth's magnetic field is very nonuniform in strength and does not follow straight
lines from pole to pole as they more generally do from outer space. A correction
(aka declination) factor must be applied to any magnetic north indication based
on magnetic variation maps in order to establish your true geographical longitude.
It is the
magnetic variation (declination) that is changing
so rapidly. The Wikipedia page has a very cool animation of how it has varied over
The Magnetic North Pole Is Moving Fast Enough to
Earth's Magnetic Pole Is Wandering, Lurching Toward
Is Earth's Magnetic Field Flipping Soon?
Destiny and Geomagnetism
How Much Do We Know of the "Influences"
on Our Lives?
By Webb Garrison
"Everything that is, or that happens, in the sky is felt in some hidden fashion
by earth and nature ... "
Jeane Dixon? Zolar? The astrologer in the next block who has a standing cut-rate
price of $2 per reading? Who said that?
Actually, that testimony of belief in the influence of the sun, moon, and other
heavenly bodies came from the lips of the astronomer-mathematician Johannes Kepler,
who formulated the three basic laws of planetary motion. Kepler rejected the notions
of astrology. But more than 300 years elapsed before hard scientific evidence was
found to support his intuitive theory that movements of heavenly bodies have a profound
influence on creatures on earth.
Kepler's theory, greatly refined, provides a clue to the special character of
this wonderful spaceship called Earth. Most or all passengers aboard this craft
probably do receive some type of electronic or geomagnetic signals from space. These
signals from beyond our atmosphere help guide metabolism, reproduction, navigation,
migration, and many other basic activities.
Fifty years ago, all this would have sounded like nonsense. True, an occasion-al
man with ideas before his time had suggested that many activities are governed by
biological clocks. In 1759, J. G. Zinn found that some plants he studied showed
the same rhythm of activity and "sleep" regardless of variations in light and temperature.
Records dating from 292 BC supported the rather preposterous idea that some species
of bamboo produce flowers and seeds at intervals of 32 years.
Logic to the contrary, California fishermen swore that grunion know the precise
days and hours at which tides are highest. Years of observation showed that grunion
invariably spawn at high tide. They time their arrival at favorite beaches to coincide
precisely (not approximately) with the crest of the tide.
Dr. Frank A Brown, Jr., spent years searching for a biological
clock or "timer" before finding positive evidence that signals are from outside.
Biological Clocks. Long-range cycles of pinpoint accuracy, it
was found, are more spectacular but much less common than daily cycles. Dr. Franz
Halberg of the University of Minnesota coined circadian to designate those biological
rhythms that are "about a day" in length.
The reality of biological clocks that precisely govern circadian and other rhythms
proved a stimulus to new inquiries. Are the "clocks" intrinsic and wholly contained
within organisms that include them? Or, do they get the signals which govern them
from an outside (extrinsic) source or sources?
Most early believers in the reality and importance of biological clocks considered
them to be intrinsic. That viewpoint seemed logical, but some puzzling cycles didn't
fit into the behavior patterns that would be expected of self-contained "clocks."
At Yale, Dr. Burr found that, when opposite sides of a tree are connected by means
of a wire, a difference in potential causes a flow of current. Sometimes it flows
in one direction, sometimes the other. Burr studied massive records, but could find
no clue to these phenomena except in movements of the moon and sun. His findings
weren't taken very seriously however; how could movements of heavenly bodies have
any connection with wholly self-regulating activities of trees?
L. C. Cole, a vociferous critic of early theories about possible outside sources
of signals received by biological clocks, believed that statistical errors were
involved. He joked that by juggling numbers he had "discovered the exogenous rhythm
of the unicorn." But he was not joking when he underscored his verdict that "so-called
exogenous rhythms are as imaginary as the unicorn itself."
Long before the controversy was settled, an extraordinary man, Frank A. Brown,
Jr., had turned his attention to the riddle of biological clocks. Brown had earned
his Ph.D. at Harvard in the field of biology. After brief terms at Harvard and Illinois,
he joined the faculty of Northwestern University in 1937 at the age of 29. He investigated
such matters as conditioned behavior in lower animals, color perception in fishes,
and plumage changes in birds.
Some at the phenomena he studied were dependent upon existence of biological
clocks, Much evidence suggested that just as humans periodically set their clocks
by means of information from radio time signals, so organisms receive signals from
points beyond their immediate environment.
Brown probed the activities of organisms ranging from potato sprouts to oysters.
Then he found a particularly valuable experimental animal - the fiddler crab that
goes through elaborate daily cycles of change in color.
In nature, fiddler crabs are pale silvery gray at sunset. Next morning when the
sun rises they begin to grow darker. Color changes, plotted on a chart, show astonishing
regularity. And crabs maintained in a photographic darkroom continue for weeks to
change color in synchrony with others of their kind exposed to the day-night pattern
Mud snail emerging from gate pointed to magnetic south pole veers
to the left at noon. Morning and evening he goes to right. (Courtesy Dr. F. Brown.)
Cosmic Radiation Effects? A major break came in 1954. By chance,
Brown noticed that the chart showing daily metabolic changes in the fiddler crab
was almost an exact mirror image of charts showing the intensity of cosmic rays
for the same period.
Correlations such as this are extremely rare. They do not constitute proof of
a cause-and-effect relationship. Brown was interested - and puzzled. He was well
aware that primary cosmic radiation seldom gets within miles of the Earth's surface.
That being the case, how could particles from the sun and distant space have any
effect on color changes of crabs?
For practical purposes a natural "electronic ear," would have to be extremely
sensitive. It would have to be capable of responding to lunar cycles, solar cycles,
sunspots, and possibly many other phenomena.
The Earth's natural magnetic field met all these requirements. But the strength
of the geomagnetic field is puny compared with fields produced in laboratories.
It had always been assumed that Earth's magnetism couldn't possibly affect living
things - to say nothing of feeding intricate information to them about positions
of the moon, sun and other bodies.
Frank Brown decided to embark on a series of daring experiments. Instead of using
very strong magnetic fields, he worked with weak fields.
The results were hard to believe. Slow moving slug-like mollusks (Nassarius)
forced to leave a "corral" in single file proved sensitive to changes in magnetic
fields. By the time thousands of slugs had been observed, Brown and his colleagues
reached a clear conclusion. The Nassarius is equipped to "measure" the lunar month
as accurately as instruments used by geophysicists!
Additional experiments with flatworms (Planaria) confirmed and amplified these
findings. When orientation of a field was artificially changed, worms could still
ascertain the geomagnetic field within 15°.
Thousands (not simply hundreds) of experiments have been made since then. To
the satisfaction of most (but not all) specialists, it has been shown that practically
all organisms on Earth have a built-in capacity to sense changes in the magnetic
This capacity had been overlooked, partly because of the ever-present and totally
pervasive nature of this feature of our environment; and partly because experiments
with relatively strong fields have proved futile - by exceeding reaction levels
to the point where "flooding" resulted.
Today it is generally recognized that creatures ranging from insects to men really
do perceive both strength and direction of geomagnetic fields. These fields are
constantly involved in complex cycles of change. Earth's magnetism at a given point
at a particular moment is affected by the solar wind, position of the moon, position
of the sun, and many other factors. As a result, the geomagnetic field is continually
monitoring signals from space, literally (not simply figuratively) talking to slugs,
birds, worms, oysters, men, and even bean sprouts.
Magnetic polarities of 64 volcanic rocks and their potassium-argon
ages. Geomagnetic declination for moderate latitudes is indicated schematically.
(A. V. Cox, et al., from the magazine Science, 144:1541, used here with permission.)
The Electronic Ear. Just how this natural "electronic ear" feeds
information into bio-electric systems, no one knows. There are several theories,
each of which may contain a bit of truth. Liquid crystals (abundant in many living
organisms) are so sensitive that they may respond to magnetic fields of low strength.
Many, or most, "higher organisms" probably have elaborate dc systems whose sensitivity
to magnetism is largely masked by extraneous electrical activity.
Until comparatively modern times, no one knew that a geomagnetic environment
existed. William Gilbert, the 16th-century English physician who discovered it,
thought the Earth's interior might include an enormous bar magnet. This naive notion
was soon quashed, but the precise systems that operate to give our planet a vast
magnetic shield are still unknown. Turning on its axis, the planet may operate as
a dc generator. James Van Allen (for whom the Van Allen radiation belts are named)
supports this theory. According to him, the "generator effect" has a potential of
approximately 50,000 volts.
On the morning side of the earth, thinks Van Allen, protons are extracted from
the solar wind. At the same time, electrons are exiting from the evening side.
Instead of being stable, the geomagnetic field varies from hour to hour and even
from minute to minute. The shape of the field that reaches about 40,000 miles into
space is greatly influenced by movements of the moon and the Earth. An immense magnetic
tail trails behind the Earth, somewhat like the tail of a comet. Until unmanned
satellites were put into orbit, the contemporary concept of the geomagnetic field
Unconsciously monitoring the celestial movements that affect the shape and strength
of the geomagnetic field, earth-bound organisms are given time coordinates. This
information fosters navigation by birds, fishes, and insects. It is an essential
factor in seasonal migration (which may involve a 2000-mile trek to a target destination
that is very small). It fosters reproduction by telling creatures when it is time
to mate - and how to reach the mating grounds of the species.
Other cues and clues (from light, temperature, relative humidity, and the like)
are fed into the "organic computer" that is ceaselessly receiving and analyzing
magnetic data. Geomagnetic signals, alone, do not account for the myriad complex
rhythms of nature. But they seem to be essential ingredients in the complex that
forms a foundation for life.
The stream of evolution itself may have been profoundly affected by our planet's
natural magnetic field - and changes in it.
For more than 30 years it has been known that the vast Pilandsberg dyke system
in South Africa (1290 ± 180 million years old) is reversely magnetized. Geologists
now recognize that, when ferromagnetic minerals in lava cool below their Curie points,
they acquire thermo-remnant magnetization.
During the last decade, the study of paleomagnetism has become worldwide. Evidence
from every part of the globe confirms early hints that the Earth's magnetic poles
have repeatedly reversed themselves. This reversal has taken place at least nine
times in the past 3.6 million years.
Dr. James D. Hays, Lamont-Doherty Geological Observatory checks
deep-sea sediment in his study of magnetic reversals. (Photo by H. C. Wehner.)
Polarity Reversals. Duration of geomagnetic epochs varies widely.
All known reversals of polarity have occurred during relatively brief periods -
10,000 years or so. Several theories seek to account for sudden switching of the
poles; none is supported by conclusive evidence.
Whatever the cause, paleomagnetic evidence indicates that life on Earth has been
greatly affected by influences that accompany pole reversal. Sedimentary cores recovered
from deep-sea drilling show a striking correlation between the last reversal (about
700,000 years ago) and disappearance of many forms of life.
At Columbia University's Lamont-Doherty Geological Observatory, Dr. James D.
Hays has pinpointed seven instances in which extinction of radiolaria (marine plankton)
has been linked with magnetic reversals.
Geomagnetic field strength presumably diminishes over a period of centuries (a
mere instant, in terms of planetary history). For a thousand or so years, our whirling
space ship has no magnetic field at all. During such a period, primary cosmic radiation
is no longer deflected or modified by the magnetosphere. Whether this relatively
sudden shower of powerful radiation serves to bring about genetic changes is a subject
still widely debated.
Even if no genetic changes are involved, the weakening, disappearance, and subsequent
reversal of the natural magnetic field could have profound effects. Creatures dependent
on signals received by way of that field could become completely disoriented - in
time, space, and bodily function. This factor alone could account for the puzzling
fact that animal extinction (and emergence of new families) has proceeded by periodic
bursts rather than along a gradual curve.
If reversal of geomagnetic polarity, with accompanying drop in field strength,
really does test the survival capacity of organisms, men of the future may face
A Reversal Coming? The Earth's magnetic moment is now decreasing. Physicist Keith
McDonald estimates that it has dropped 15% in the last three hundred years. If the
present rate of decrease continues, our planet will become nude (in terms of its
magnetosphere) about 4000 AD. The Earth's surface is likely to be pelted with protons
- known to be capable of splitting atoms and causing genetic mutations. In the absence
of our geomagnetic signals, hundreds of human bodily rhythms may be affected.
Long before this magnetic Doomsday, we are likely to know a great deal more about
its potential impact. Once we begin truly long-distance space flights (as opposed
to neighborhood jaunts such as flights to the moon) aerospace scientists will have
new data about effects of lengthy stays in environments that lack magnetic clues.
Physicist Keith McDonald of the Environmental Science Services
Administration points to magnetic map indicating drop in field intensity from 1835
to 1965. With Robert Gunst of the U. S. Coast and Geodetic Survey, McDonald has
calculated that if the rate of drop continues, the earth's magnetic field will fade
away completely by year 3991. (This photo courtesy ESSA.)
We know a little - a very little - about this matter already. On journeys to
the moon, astronauts have found that some bodily cycles change significantly. Others,
such as the all-important cycle marking daily excretion of potassium, remain constant
or practically constant for the duration of brief flights.
Astronauts have the tremendous (and perhaps vital) advantage of being able to
receive information through man-made channels. Lacking radio and TV contact, members
of a crew would quickly lose all sense of time. How effectively even highly trained
persons could function in such a chaotic, formless environment is open to serious
Your own body is affected by hundreds of cycles that are guided by biological
clocks. One of the most conspicuous of these cycles is body temperature - which
is about 2°F lower at midnight than it is at noon. Sweating of the palms, rise
and fall of blood pressure, reflex time, excretion of sodium, and great numbers
of equally complex activities are "set" to follow daily, or circadian, cycles.
Other cycles are longer and more puzzling. There is at present no direct causal
relationship between length of the lunar month and the 28-day menstrual cycle of
women. But is the correlation accidental? Does it represent a biological carry-over
from the infancy of the race, during which the moon set the clock that governs fertility?
Positive evidence is lacking - but the recent discovery that human males have 28-day
cycles of sex hormone production strengthens the theory that movements of the moon,
monitored by the geomagnetic field, may have permanently molded man.
Frank A. Brown minces no words, "The evidence at hand suggests strongly that
diurnal, or 24-hour rhythmicity is as fundamental a characteristic of life on the
Earth as are respiration, reproduction, growth, differentiation and excitability."
Indisputable evidence suggests that most or all creatures on Earth "listen" to
electronic signals fed into their system by the geomagnetic field and - in the absence
of all other information - can remain biologically informed about days, months,
years, tides, and other factors.
Results obtained from space probes suggest that this state of affairs doesn't
prevail on other planets of our solar system. Earth's dipole moment ranges slightly
above or below 8 X 1025 gauss cm3. That of Venus is only about
3.4% as strong and Mars only 0.3 %.
Earth, then, is unique among known heavenly bodies. Passengers on it are protected
by a vast and complex magnetosphere. Because it is subject to periodic cataclysmic
change, it may have played a major role in eliminating or modifying many forms of
life. Now in a period of rapid decline in strength, it may give space-age man one
of his biggest tests. Meanwhile, the magnetosphere (along with light, temperature
and other factors) "is an omnipresent factor with which life steadily interacts."
Posted June 14, 2019