edwardgeorge + magneticfield   1

Birds evolved compass 'head up display'
"Certain birds may have compass information mapped directly onto their vision, much as fighter pilots have ‘head up displays’ overlaying flight information on their view of the skies.'
"According to the new model, when a photon of light from the Sun is absorbed by a special molecule in the bird's eye, it can cause an electron to be kicked from its normal state into an alternative location a few nanometres away. Until the electron eventually relaxes back, it creates an ‘electric dipole field’ which can augment the bird's vision - for example altering colours or brightness.
"Crucially, the alignment of the molecule compared to the Earth's magnetic field controls the time it takes for the electron to relax back, and so controls the strength of the effect on the bird's vision.
"There are many such molecules spread throughout the eye, with different orientations. So from the patterns on top of its vision, and the change of these patterns as it moves its head, the bird learns about the direction of Earth's magnetic field."
science  nature  evolution  physics  birds  magneticfield  from:physorg.com 
march 2012 by edwardgeorge

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