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People telling north from south.... spontaneously...

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Leith
1044722.  Mon Dec 30, 2013 9:22 pm Reply with quote

Spud McLaren wrote:
Back to post 1044493 for a moment - interesting that a change of hemisphere throws the ability. It would seem to indicate that you're reacting to some aspect of the intensity of the magnetic field rather than its orientation. It doesn't matter which hemisphere you're in; the red half of a compass needle that points north in the northern hemisphere will still point north in the southern hemisphere. So I wonder what caused your orientation to reverse?


Perhaps not intensity, but inclination - the verticle angle at which the earth's magnetic field points into the ground (northern hemisphere) or out of it (southern hemisphere).

This study (mentioned on the QI J series) prompted the scientist behind it to speculate that foxes may use magnetic inclination as a range-finding device to help them pounce on hidden prey:
Discover Magazine: Foxes use the Earth's magnetic field as a targeting system

mis wrote:
The other interesting point... when I went to Singapore for several
weeks I could not detect either north or south at all.. results were
always varying.

My hypothesis is I can detect the closest magnetic pole and from that I
can extrapolate my position in the world. This is further proved by the
fact when I was in Brisbane my error rate (how far from correct I
was/the error deviation) was greater than it was in Melbourne, and that
was larger than when I was in the UK....


Here are some details of the Earth's magnetic field in London, and at the locations you specifically mention (data from http://magnetic-declination.com/*):

London
Magnetic declination: -1 8' WEST
Declination is NEGATIVE
Inclination: 66 27'
Magnetic field strength: 48695.1 nT

Singapore
Magnetic declination: 0 13' EAST
Declination is POSITIVE
Inclination: -14 56'
Magnetic field strength: 42114.2 nT

Brisbane
Magnetic declination: 10 58' EAST
Declination is POSITIVE
Inclination: -57 27'
Magnetic field strength: 53146.8 nT

Melbourne
Magnetic declination: 11 38' EAST
Declination is POSITIVE
Inclination: -68 49'
Magnetic field strength: 60039.7 nT

If you were able to subconsciously 'visualize' where a magnetic field line passing through you hit the ground, based on its horizontal and vertical orientation, that would give you a pretty good sense of north in the UK, but one that would be:
- reflected and a little out in Melbourne
- reflected and further out in Brisbane
- rather confused in Singapore

* Incidentally, magnetic declination, for those not familiar, is the difference between magnetic north and true north, which can vary quite considerably around the globe.

 
mis
1044754.  Tue Dec 31, 2013 6:28 am Reply with quote

Quote:
If you were able to subconsciously 'visualize' where a magnetic field line passing through you hit the ground, based on its horizontal and vertical orientation, that would give you a pretty good sense of north in the UK, but one that would be:
- reflected and a little out in Melbourne
- reflected and further out in Brisbane
- rather confused in Singapore


Which was exactly what I experienced.

I cannot visualise the pole/field, what I have to do is visualise my point of reference (my mothers kitchen, in Gt Yarmouth) and then turn slowly until the visualisation "locks on" to the turning.. when that happens I know where north is, I turn until I can point directly at the corner of my mothers pantry from the centre of the kitchen.

... and yes as a SCUBA diver, I have had to swim in straight lines with no references (at 40m below you can't even see the surface) for the first couple of years in Australia I nearly always swam the exact wrong way (much to the annoyance of my friend who was an instructor and boat hand.) After the first two years and I learned to trust the opposite I amazed people I took diving by my ability to swim dead straight and return to the surface within 5 meters of where I was supposed to be...

 

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