British Robin

Image by Diamonddavej at en.wikipedia

A perplexing property of quantum mechanics could be allowing birds to see and navigate the planet’s magnetic fields

One-fifth of Earth's 10,000 bird species migrate over great distances, crossing seemingly insurmountable obstacles as they follow the seasons.

Demoiselle Cranes fly to altitudes in excess of 20,000 feet as they pass over the Himalayan Mountains. The Arctic Tern travels from pole to pole in pursuit of an endless summer, a distance of some 40,000 miles.

Scientists have long speculated that certain animals are making use of magnetic fields to find their way, but biologists are mystified as to how they might do it.

Now some answers might be coming from one of the most perplexing interactions in physics.

Quantum entanglement dictates that if two electrons are created at the same time, the pair will be “entangled” so that whatever happens to one particle affects the other. Otherwise, it would violate fundamental laws of physics.

The two particles remain entangled even when separated by vast distances.

So if one particle is spin-up, the other must be spin-down, but what's mind-boggling is that neither will have a spin until they're measured.

That means that not only will you not know what the spin of the electron is until you measure it, but that the actual act of measuring the spin will make it spin-up or spin -own.

As difficult as entanglement is to believe, as well as understand, it is a well established property of quantum mechanics. And some physicists are suggesting that birds and other animals might be using the effect to see and navigate Earth's magnetic fields.

The process could work via light-triggered interactions on a chemical in bird’s eyes.

Light would excite two electrons on a molecule in the bird’s eye, switching one onto a second molecule, but the two would remain entangled even though they’re separated.

The Earth’s magnetic field would alter the alignment of the electron’s spins and in the process alter the chemical properties of the molecules. Physicists suspect that the reactions would leave varying concentrations of chemicals throughout the eye, possibly creating a picture of our planet’s magnetic field that would allow birds to orient themselves.

The theory is still in its infancy, but biophysicists already have their eyes on a few chemicals that might enable the birds to detect entanglement.

One such chemical is called cryptochrome and its potential effects already being studied.

It’s thought that that correlated pairs form in cryptochrome in the presence of blue light.

A group of physicists from the University of California at Irvine also studied the European Robin’s ability to sense small quantum changes by tampering with the magnetic field surrounding the birds.

A robin was placed in a cage during migration season and then the physicists switched the polarity of the magnetic field around it. The test indicated that changes on the level of one-thousandth the strength of Earth’s magnetic field would impact the birds’ abilities to orient themselves.

Perhaps even more fascinating is that European Robins might do a better job of detecting quantum entanglement than physics labs currently can. A group of physicists from the University of Oxford have proposed that entanglement could last in a bird’s retina for 100 microseconds, whereas physicists have only been able to make the interaction last for 80 microseconds – despite cooling their experiments to just above absolute zero.

The studies have implications beyond birds as well. A number of fish, reptiles, insects and even mammals are thought to use magnetic fields to navigate.

Resources:

Discover Blogs

How birds see magnetic fields – an interview with Thorsten Ritz

Wired Science

In the Blink of Bird’s Eye, a Model for Quantum Navigation

Biophysical Journal

Magnetic Compass of Birds Is Based on a Molecule with Optimal Directional Sensitivity

Letters to Nature

Resonance effects indicate a radical-pair mechanism for avian magnetic compass