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Magnetic Variation: possibly the most bogus theory of them all. When the Coast Guard put their name on this theory they neutered a lot of their credibility. No one had heard about this theory until the Coast Guard put out a little hastily written chit about 30 years ago, stating their position on the subject of the Bermuda Triangle.
   It reads, in part:

Countless theories attempting to explain the many disappearances have been offered throughout the history of the area. The most practical seem to be environmental and those citing human error. The majority of disappearances can be attributed to the area's unique environmental features. First, the "Devil's Triangle" is one of the two places on earth that a magnetic compass does point towards true north. Normally it points toward magnetic north. The difference between the two is known as compass variation. The amount of variation changes by as much as 20 degrees as one circumnavigates the earth. If this compass variation or error is not compensated for, a navigator could find himself far off course and in deep trouble.

This is a very misleading statement. For one, the area of no compass variation is a very narrow corridor, tantamount to a fraction of the overall Triangle. It also overlooks the fact that one cannot even plot a course without having a navigational chart, and all navigational charts have the amount of variation written on them for every degree of longitude. Before a navigator could even chart a course he would have to know the amount of variation. This also overlooks the large number of disappearances of pilots and skippers who were old hands in this part of the world, being charter pilots and the like. They were very familiar with local  variation.
   It also presupposes that the navigator was stupid enough not to compensate. Yet compensation in navigating is second nature to any navigator.   

   But lets expand on compass variation, since many do not understand it. Compass variation does not mean that the compass needle points somewhere else. The compass  always points to Magnetic North. The problem with this is Magnetic North is not at the North Pole, the absolute geographic northern spot on this planet; it is 1,500 miles away. As far as the compass is concerned, the absolute north of this planet is at Prince of Wales Island in the Northwest Territories of Canada.
   The magnetic field of the earth can be likened to a bar magnet running through the earth from north to south. Both ends of the bar would be the north and south magnetic poles. The bar itself would be the axis or, as it is called in geophysics, the Agonic Line.
  This would not pose any problem to the navigator were it not for the fact that Magnetic North is located 1,500 miles away from  the North Pole. Therefore, geographic north on the earth, the area we mentally consider absolute north, is not where the compass points. Following the N on your compass is not going to

The area of the Agonic Line marked in red, as it was when the Coast Guard drew up their statement 30 years ago.   Along this line there is no need to adjust one’s heading because Magnetic North and True North coincide. Already at Bimini island there is a 2 degree westerly variation. That means if a pilot wanted to head True West here, he would not steer 270o by his compass but 272o. It seems infinitesimal, but over time 2 degrees can lead to dozens of miles off course. In the short distances between the coast and the Bahama Islands, it doesn’t amount to much here.

lead you to the North Pole; it will lead you to Prince of Wales Island.  See illustration.  

The red dots indicate True North, that is, the absolute geographic north of this planet (North Pole); and Magnetic North, 1,500 miles in a southerly direction from it. The central axis (Agonic Line) of the magnetic field extends through the planet to the South Magnetic Pole at Antarctica. When off Florida, both the North Pole and the Magnetic Pole are in line. The Compass truly points to the North Pole here but only briefly. It is merely incidental because Magnetic North is directly due south of the North Pole here.

To compensate for this, the navigator must know the number of degrees of difference between Magnetic North and True North in his longitude. This changes according to one’s longitude around the earth. For instance, at the Azores Islands there is a 20 degree difference between True North and Magnetic North. Off the east coast of Florida, there is none. The compass is still pointing to Magnetic North. It just so happens that True North is directly north of here. See illustration.

Right: as the Compass sees the four cardinal points.  See what happens if you blindly follow your magnetic compass. Everything is tilted because it believes North is 1,500 miles south of the North Pole. West is slightly southwest; East is slightly northeast; North is slightly northwest; South: southeast. Wherever a navigator is, he must adjust his heading to maintain a true course. . . except at the Agonic Line.

Except for this narrow corridor, there is always some form of compensation the navigator must go through.* For example, at the Azores, if a navigator wanted to go straight north, he could not follow the N on his compass. If he did, he would end up in Canada and not in Greenland. So he heads 020 degrees and now he is heading True north. That is what Compass Variation means: the amount of difference between the North Pole and the Magnetic North Pole at a given location. The result is a simple navigational adjustment to stay on course.  

Right, what we imagine the Compass to reflect: the true North, East, West, and South of this geographic sphere. Far left, the Compass’ concept of where North, West, East, and South are located, if viewed from the Azores.  True North is actually 020o.

This amount of variation will decrease the further one travels West until one reaches the Agonic Line. Soon after, the amount of variation will increase again, with the compass pointing Easterly of True North.
  There is little reason to suppose that this has contributed to any loss. Failure to compensate the amount of variation correctly can cause a pilot to get lost anywhere in the world, whether there is no degree variation to compensate for or 15 degrees. One degree off can, over time, result in many miles in error, making a pilot miss his intended destination.
   But as I said this can happen anywhere in the world. The Triangle does not stand out as unique because there is no variation in degrees to calculate for a brief period in a very narrow corridor of it.
   I try and list theories objectively. But in this case a dead horse is a dead horse. There is no merit to this theory at all.
   A further factor contributing to this deduction is that the Agonic Line moves as the magnetic pole shifts, due to many factors in the rotation of the earth. Over time the Agonic Line can be miles from where it was. Actually every 2 months or so a flight is manned and sent to find the magnetic pole. The upshot is that the Agonic Line is not in the Triangle anymore. It is located in the Gulf of Mexico beyond Key West— to those who demand adherence to a strict shape to the “Triangle,” completely outside of it.
   The artwork and maps above show the Agonic Line where it was when the Coast Guard made up their little chit about 30 years ago. Magnetic Variation was not a satisfactory explanation before. It is even more passé now. Disappearances still occur in the same places as before, even though the Line is on the other side of Florida now.

 

*Yes I know it happens on the exact other side of the world; but that is not relevant here so we can dispense with it in this article.

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