More on Magnetism (Article)

The Earth rotates on its axis like a giant top. The northernmost point of this axis of rotation is known as the geographic North Pole. The southernmost point of the same axis is the geographic South Pole.

The movement of metal fluids like iron and nickel in the outer core of the Earth is believed to generate the Earth's magnetic field according to the Dynamo Theory.

One can imagine a massive bar magnet or dipole running through the earth creating the magnetic North and South poles.

However the magnetic poles do not coincide with the geographic poles.

The magnetic North Pole, for example, is inclined about 11.5 degrees from the geographic North Pole. The magnetic North Pole is located near Ellesmere Island to the west of northwest Greenland.


Magnetic poles is offset from geographic pole by 11.5 degrees (Source: http://www.fas.org/irp/imint/docs/rst/Intro/Part2_1a.html)

The angle between the geographic and magnetic poles is the primary cause of magnetic declination, the difference between a magnetic compass reading for North and the true direction of geographic North.

The line where magnetic declination is zero is known as the agonic line, as explained in the previous blog entry. And again, because of magnetic anomalies this line is not easy to predict.

The agonic line can be thought of as a sort of magnetic meridian. A medieval Chinese text discusses such a central meridian where magnetic declination is zero.

The center of the Earth's magnetic dipole, or "bar magnet," also deviates from the center of the Earth's core from which it is offset by about 700 kilometers toward Southeast Asia.

The reason for this offset of the magnetic poles and center can only be guessed at, but the inequality results in differing strengths of the Earth's magnetic field.

Because the center of the dipole is closer to Southeast Asia, the magnetic field in Southeast Asia is stronger than anywhere else in the world. This is known as the Southeast-Asian Anomaly and it is the area of the Earth's surface closest to the dipole's center. The magnetic field is strongest along the magnetic equator in the Southeast-Asian Anomaly.

In the Western Hemisphere we find the South Atlantic Anomaly (SAA), which is the area of the Earth's surface furthest from the center of the dipole. Here the magnetic field is weaker than in other areas of the globe.

Because the Southeast-Asian Anomaly represents a stronger field it is known as a positive anomaly while the SAA is a negative anomaly.

The known practical effects of these anomalies is mainly found in space flight where they interfere with communications in the ionosphere. All communications are disrupted in the Southeast-Asian Anomaly and high frequency communications in the South Atlantic Anomaly.


The Southeast-Asian Anomaly and South Atlantic Anomaly (SAA) from Earth's Magnetic Field.

Biomagnetism and Magnetoreception

Research has clearly shown that many species are able to orient themselves and navigate using magnetoreception to detect the Earth's magnetic field.

There are two types of known magnetoreception -- one using detection of the poles, or polarity; and the other detects differences in magnetic inclination or "dip."

While magnetoreception is widely recognized in birds, bacteria and other species, the evidence for human magnetoreception has been more controversial with some political overtones.

Robin Baker first claimed to have found evidence for human magnetic orientation in tests he conducted in 1987. His methods though were questioned. In 1989, however, R. G. Murphy found evidence of human orientation that was disturbed when a magnet, but not a piece of brass, was placed on the head of the subject. This suggested that the orientation was magnetic in nature.

While Baker's research with other species was acclaimed, when he turned toward human study, he encountered resistance to his efforts. Helen Saul writes:

Sadly, Baker's research stopped before it got much further. When he shifted his interest from animals, birds, and fish to humans, it became so contentious that he lost the general support of the scientific community..."The stark contrast between positive results and negative interpretations remains an unexplained feature of the literature on human magnetoreception," he [Baker] wrote in 1987. He eventually left his post at Manchester University, and since then, the work has fallen by the wayside.

Henry H. Bauer writes in Science Or Pseudoscience: magnetic healing, psychic phenomena, and other heterodoxies:

Baker's heresy has been to study human sensing of magnetic fields, which attracts opposition for no obvious reason: “Every animal seriously tested has been found to have a magnetic sense, and it now seems that the final search will be for an animal that is magnetically blind. It would be more surprising to discover that Man just happened to be that animal than to discover he was not”...the “atmosphere surrounding the study of human magnetoreception has, both publicly and less publicly, been just a little unpleasant.”

University of Hawai'i anthropologist Ben Finney picked up on Baker's research by discussing the subject with modern navigators trained in traditional Pacific Islander (Micronesian) navigation.

Finney came to the conclusion that magnetoreception might be employed by navigators on an intuitive basis:

Taken together with experimental findings about magnetoreception in various species, these reports suggest that skilled noninstrument navigators may be able to turn to magnetoreception for orientation cues of last resort and that this magnetic sense of direction may also play an unconscious role in dead reckoning. In the light of experimental evidence on the hierarchy of directional senses, it is not surprising that noninstrument navigators would refer the more exact cues available from the passage of the sun and stars across the sky to any feelings they might have about their bearings but be open to following those feelings whenever the situation demands.

Finney suggests, as I have also in my own writings, that magnetoreception may be a latent ability in humans that must be learned much like humans must learn how to swim.

The subjects-typically students-usually employed in magnetoreception experiments have been navigationally naive in comparison with such Pacific island masters as Mau Piailug and Nainoa Thompson. If there are striking differences in performance between young birds without navigational experience and veterans of migrational or homing flight, might not this also be the case for humans?

Regards,
Paul Kekai Manansala
Sacramento

References

Baker, Robin. Human navigation and magnetoreception, Manchester:
Manchester University Press, 1989.

Bauer, Henry H. Science Or Pseudoscience: magnetic healing, psychic phenomena, and other heterodoxies, University of Illinois Press, 2001.

Gehmeyr, Michael. Earth's Magnetic Field, Boston University, 2005.

Finney, Ben . "A Role for Magnetoreception in Human Navigation?" Current Anthropology, Vol. 36, No. 3. (Jun., 1995), pp. 500-506.

Murphy, RG. The development of magnetic compass orientation in children. Paper presented at the Royal Institute of Navigation Conference, 1989.

Saul, Helen. Phobias: Fighting the Fear, Arcade Publishing, 2004.

"Dragon's Triangle" and the Magnetic Mountain (Article)

Many people are aware of the Bermuda Triangle, a wedge-shaped area of the western Atlantic Ocean where ships and planes are said to mysteriously disappear.

The same author who popularized the existence of the Bermuda Triangle, Charles Berlitz, also developed a lesser known theory of the Dragon's Triangle. This latter area was nearly antipodal, on the other side of the earth, in relation to the Bermuda Triangle and, according to Berlitz, hosted the same unusual phenomenon.

Supporters and skeptics have long battled over the Bermuda Triangle theory. Some have claimed that the first record of mysterious activity in this area was recorded by Christopher Columbus. Many fantastic reasons are given for the disappearances that occur in the area including UFOs and black holes. There are also more scientific reasons offered such as the existence of magnetic anomalies.

Skeptics counter that the number of lost ships and planes in the region is not that unusual. They note that authorities have not classified the region of the Bermuda Triangle as especially dangerous.


Dragon's Triangle has older pedigree

While some claim that Columbus was the first to hint about something strange in the Bermuda Triangle region, it was really in 1950 that the legend as we know it first came to light in an Associated Press article by E.V.W. Jones.

However, Berlitz's suggestion of a similar anomalous region in the Philippine Sea does link into more ancient local legends.

The most common form of this legend was that of the Magnetic Mountain, which was said to pull out iron nails and other iron parts from ships that passed nearby. The Chinese classic Huainanzi of the 2nd century BCE mentions "the lodestone that makes [iron objects] fly," without however describing any lodestone mountain.

In the 2nd century CE, the Greek geographer Ptolemy describes a magnetic mountain located near the Isle of Satyrs somewhere off the Indochinese coast. About two centuries later the Nan Zhou Yi Wu Zhi mentions a similar location off the coast of Central Vietnam where only wooden ships should sail.

Chinese writer Sung So between 1023 and 1063 says that "at the capes and at the points of Chang-hai (South China Sea), the waters are low and there are many magnet stones, so that if the great foreign ships which are covered with iron plates approach them, they are arrested, and none of them can pass by these places."

Other Chinese accounts suggest that in this same region the magnetic compass often erred throwing ships off course into certain doom. In 1438, Fei Xin mentions such phenomenon near Kunlun Island:

To the north we are afraid of the Seven Islands; to the south we fear the Kunlun. At these places the needle may err, and if that happens, or the steering is inaccurate, both men and ships will be lost.

Later the Dan Shui Ting Zhi dated about 1871 mentions rocks around Taiwan that 'bewilder' the magnetic compass.

As accounts of compass failures and the supposed linked magnetic anomalies form part of the mystery of both the Bermuda and Dragon's Triangle, the older Chinese testimony is interesting.

There are numerous other tales of the dangers of the Magnetic Mountain in the medieval period especially starting from the 11th century found in Chinese, Indian, Muslim and European works. The theme generally involved the mountain violently pulling iron nails from ships sending them flying toward the mountain.

The location of the Magnetic Mountain was generally placed somewhere in the "Indies," usually the most eastern parts. John of Mandeville, for example, locates the mountain on the "Adamant Isles" in Prester John's empire, while Roman de Ogier le Danois says that the "Great Lodestone" is located "not far on this side of the terrestrial paradise, whither were rapt in a flame of fire Enock and Helios."

Berlitz, on the other hand, located the Dragon's Triangle more to the east and north in the Philippine Sea.

In the One Thousand and One Nights, a king neutralizes the dangers of the Magnetic Mountain by shooting lead arrows at a brazen horsemen with a lead tablet on his chest. This causes the island to sink, rendering the mountain harmless, and the king is rescued by apparently the same brazen horseman, this time riding a boat.

The story of shooting arrows on the Magnetic Mountain and also of the latter causing iron nails to fly toward its magnetic influence may have some link to practices found more recently.

Early Spanish observers described an indigenous rite in the Philippines of ship crews shooting arrows into promontories and cliffs that jutted into the sea to propitiate the spirits involved. Following is a description of one such practice from Pedro Chirino (1604):

In the island of Mindanao between La Canela and the river, a great promontory projects from a rugged and steep coast; always at these points there is a heavy sea, making it both difficult and dangerous to double them. When passing by this headland, the natives, as it was so steep, offered their arrows, discharging them with such force that they penetrated the rock itself. This they did as a sacrifice, that a safe passage might be accorded them. I saw with my own eyes that although the Spaniards, in hatred of so accursed a superstition, had set a great many of these arrows on fire and burned them, those still remaining and those recently planted in the rock numbered, in less than a year, more than four thousand arrows; they certainly seemed as many as that, to all of us who passed that point.

Arrowheads in the Philippines were generally of two types -- ones made of palmwood and/or bamboo, and iron arrowheads. Given that the arrows mentioned above penetrated into the rock, we can surmise that they had iron arrowheads.

While no reason is given as to why shooting iron arrows into the cliff would have such an effect, we are still led to believe that the locals believed this would afford safe passage. We could possibly interpret the iron in the arrows as a substitute for iron or other metals on-board the ship in a ritual whose meaning had been forgotten?

In the Arabian tale, shooting the brazen horseman with the lead tablet off his horse with lead arrows also makes the sea safe and interestingly the horseman eventually saves even the one who shoots the arrows.

Another tale from Japan tells of Urashima, a fisherman who is brought to the underwater Dragon's Palace in the region of Tokoyonokuni generally thought of as in the South Seas. The story is often connected with modern Dragon's Triangle lore especially by those who like to believe in black holes and time warps as it contains the theme of "lost time." Here is a synopsis of the story from Answers.com:

Urashima Taro was fishing one day when he sees a turtle in distress. Urashima saves the turtle, in gratitude the turtle takes Urashima to the Dragon Palace. He spends many days in happiness at this underwater kingdom, however soon becomes homesick and asks to be allowed home. The queen of the palace allows him to go home and gives him as a gift a jewel encrusted box with explicit instructions never to open it. Upon arriving home Urashima discovers that over 300 years have passed in the real world and no one can remember him or any of his contemporaries. Wallowing in self-induced depression, he heads to the beach and remembers the box he was given. He opens it and a white cloud is released and he suddenly ages and dies - the box having contained his true age. Variants of this story have developed throughout Oceania and the actual origin is unknown.

Agonic Lines and the Magnetic Equator

At most locations on Earth, the magnetic compass does not point directly toward the North but at Magnetic North instead.

The difference between True North and Magnetic North is known as magnetic declination. This difference varies in quantity depending on location and time.

Chinese texts first record the existence of magnetic declination and they also track differences in declination that occur over time.

At certain points on the globe, the difference between True North and Magnetic North becomes zero. These points form an undulating boundary known as the agonic line. The agonic line occurs in the Eastern Hemisphere and is roughly antipodal to the agonic line in the Western Hemisphere.

In 1189, Zeng San Yi suggested that there was a central meridian where the magnetic needle pointed toward True North without any deviation, the first mention of what we know today as the agonic line. When one moves east of the agonic line, the needle points west of north, and if one moves west of the same line the needle points east of north.

The variations in the Earth's magnetic field are believed to be caused by movement of conducting fluids at the core-mantle boundary, magnetohydrodynamic waves and other factors. Below we have a graphic showing the position of the agonic line over different time periods starting in the 16th century.

Agonic Line (in red) at dates 1590, 1690, 1790, 1890 and 1990 (Chapter 1 Earth’s magnetic field, http://www.diss.fu-berlin.de/2005/70/chapter-1.pdf).



As can be seen above, the agonic line drifts over time and this drift is thought to have a westward bias. One can also see that the Eastern Agonic Line does tend to pass through or near the Philippines and the Philippine Sea.

In addition to magnetic declination, which causes a clock-like variation of the compass, there is another influence known as magnetic inclination. This is caused by the opposing pole, the South Pole in the Northern Hemisphere and the North Pole in the Southern Hemisphere. The opposing influence of the poles causes a vertical "dip" of a magnetic needle.

Georg Hartmann apparently discovered magnetic dip in 1544. The quantity of dip depends on one's latitude and it is possible to get a vague idea of one's latitude by measuring the dip. Also, as with the agonic line, there is a point where the dip becomes zero. This point is known as the magnetic equator.

The magnetic equator undulates north and south of the true equator and also varies with time and place like the agonic line. At any period, there are at least two points on earth where the agonic line and magnetic equator intersect -- at least one in the Eastern Hemisphere and one in the Western Hemisphere.

The figures below show the approximate intersection points for three periods: 1590, 1690 and 1790.

Agonic lines and magnetic equator, red curve shows agonic line, bold black curve is magnetic equator, blue dot is intersection point of Eastern Agonic Line.


The area where the agonic line and magnetic equator intersect would cause the compass to give "centered" readings but there is no reason to associate them with magnetic anomalies that would cause errant readings.

However local compass disturbances caused by magnetic rocks both on land and at sea is documented. Such disturbances would vary based on local magnetism which is greatly influenced by volcanism.

So the magnetic aberrations documented in the South China Sea and northward could certainly have factual basis. Possibly the knowledge of strange magnetic forces in the area could have given rise to the practice of offering metal arrows to rocks by seafarers, something that again could potentially have mutated into the legend of the perilous Magnetic Mountain.

Regards,
Paul Kekai Manansala
Sacramento

References

Berlitz, Charles. The Dragon's Triangle, Fawcett, 1999.

Jonkers, A. R. T. Earth's Magnetism in the Age of Sail, Johns Hopkins University Press, 2003.

Ronan, Colin Alistair and Joseph Needham. The Shorter Science and Civilisation in China: An Abridgement of Joseph Needham's Original Text, Cambridge University Press, 1994.