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How do animals navigate using the earth's magnetic field?

Butterfly

20 Nov 2014

How do animals navigate using the earth's magnetic field? On 6 November 2014, SCI's Thames & Kennet Regional Group and the Chemistry Society of Charterhouse School held an event of the same title to look at the answer – quantum biology. We were very honoured to have Dr Alex Jones from the University of Manchester to give a talk on his research interests, titled 'The Quantum Mechanics of Animal Navigation'. Dr. Alex Jones' current research interests are in quantum biology, and thus it is no surprise when he started by discussing the behaviour of animals.

Monarch Butterflies migrate every year from America to Mexico, and by plotting their movements it's apparent that they migrate South collectively from all over America. They do so by navigating the Earth's magnetic field, and Dr Jones' research is tackling the question that arises from this – the mechanism by which the butterflies navigate through the Earth's magnetic field.

As with all good story tellers, letting us know how the story ends in no way diminishes the story. From here Dr Jones goes back to the start of the story, how he was a photochemist, and it was during his training as a physical chemist that he studied radical reactions – radicals can be created by the energy from incoming photons. If we consider the creation of radical pairs through electron transfer, then there are two possible outcomes – the radical pair could have electrons of different spins, called a singlet radical pair, or electrons with the same spin, a triplet. Due to Pauli's Exclusion Principle, a triplet could not recombine, thus have to stay triplet, and therefore are easy to remove from the system by reacting the triplets with other radicals, forming escape products.

It is at this point where magnetic fields come into play. By having an external magnetic field, the spin of the electron can be made to align with the external field (since this is the most energetically stable configuration) and thus favour the formation of triplets in the equilibrium between singlets and triplets. This results in the increased production of escape products. In an animal, the magnetic field affects protein radical pairs created by energy from photons. This explains why the 'magnetic compass' in the Monarch Butterflies are light-dependent – if red light is shone at them their magnetic compasses do not work as red light has low energy.

Apart from being a fascinating talk captivating biologists, chemists and physicists present at the talk, it was a very unique occasion as Dr Jones tells us about how he went from a physical chemist, to what some might consider physics, and then make a huge leap into biology. This reflects the nature of scientific research – it is a collaborative effort from traditionally different fields and expertise from all areas of science are needed. As with all things, there is also the touch of serendipity – Dr Jones got into this research after attending a lecture by his biologist colleague in Manchester University which involved the same chemicals and mechanisms that Dr Jones has previously researched on. It gave us an invaluable insight into modern research.

Anthony Wong,
Charterhouse

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