Seeing our world through the eyes of a migratory bird would be a somewhat frightening experience. Something about their visual system allows them to „see“ the magnetic field of our planet, a clever trick in quantum physics and biochemistry that helps them travel vast distances.

Now, for the first time ever, scientists from the University of Tokyo have observed a major interaction that is supposed to be behind the talents of birds and many other creatures to sense the direction of the planet’s poles.

Importantly, this is evidence that quantum physics directly affects a biochemical reaction in the cell – something we assumed long ago but never witnessed before.

Using a specially designed microscope sensitive to faint flashes of light, the team observed a culture of human cells containing a special light-sensitive substance that dynamically responds to changes in the magnetic field.

The fluorescence of the cell darkens as a magnetic field passes over it. (Ikea Woodward, CC BY)

The change the researchers observed in the laboratory matches what would be expected if the quirky quantum effect were responsible for the luminous reaction.

„We have not modified or added anything to these cells,“ Says Biophysicist Jonathan Woodward.

„We think we have very strong evidence that we observed a purely mechanical quantum process affecting chemical activity at the cellular level.“

So how can cells, especially human cells, respond to magnetic fields?

While there are many hypotheses, many researchers believe that this ability is due to a unique quantum interaction involving photoreceptors called cryptochromes.

Cyrptochromes are found in the cells of many species and are involved in regulating circadian rhythms. In bird, dog, and other migratory species, it is associated with the mysterious ability to sense magnetic fields.

In fact, while most of us cannot see magnetic fields, our cells certainly do Contain cryptochromes. And there is evidence that although unconscious, humans were still able to discover the Earth’s magnetism.

To see the reaction inside the cyrptochromes in action, the researchers doused a culture of human cells containing cryptochromes in blue light causing them to fluoresce weakly. As they glowed, the team repeatedly traversed magnetic fields of different frequencies above the cells.

They found that every time a magnet passed over the cells, their fluorescence decreased by 3.5 percent – enough to show a direct reaction.

How can a magnetic field affect photoreceptors?

It all comes down to something called spin – an innate property of electrons.

We already know that rotation is greatly affected by magnetic fields. Arrange the electrons in the correct way around the atom, and collect enough of them together in one place, and the resulting mass of matter can be made to move using anything more than a weak magnetic field such as the one surrounding our planet.

This is all well and good if you want to make a navigational compass needle. But with no clear signs of magnetically sensitive parts inside the skulls of pigeons, the physicists had to think smaller.

In 1975A researcher at the Max Planck Institute called Klaus Schulten has developed a theory about how magnetic fields affect chemical reactions.

It included something called a root pair.

A garden variety root is an electron in the outer shell of an atom that does not bind to a second electron.

Sometimes these celibate electrons can adopt the winged bird of another atom to form a root pair. The two remain unpaired but thanks to a shared history they are considered intertwined, which means quantitatively that their rotations will coincide frighteningly regardless of the distance between them.

Since this correlation cannot be explained by continuous physical connections, it is purely quantitative activity, something Albert Einstein considered „frightening“.

In the bustle of a living cell, their entanglement will be fleeting. But even these interconnected spins for a short period must last long enough to make a subtle difference in the way their parent atoms behave.

In this experiment, as the magnetic field passes over the cells, the corresponding decrease in fluorescence indicates that the generation of root pairs was affected.

One of the exciting findings of the research could be how weak magnetic fields can indirectly affect other biological processes. While the evidence for magnetism affecting human health is weak, similar experiments could be another means of investigation.

„The interesting thing about this research is that we see that the relationship between the rotation of two individual electrons can have a huge impact on biology.“ Says Woodward

Of course birds aren’t the only animal to rely on our magnetosphere for direction. Types of fish and worms InsectsAnd even some mammals have a knack for it. We humans may be cognitively affected by the Earth’s faint magnetic field.

The development of this ability could have introduced a number of vastly different actions based on different physics.

Evidence that at least one of them links the weirdness of the quantum world to the behavior of an organism is enough to force us to question the other parts of biology that arise from the frightening depths of fundamental physics.

This research was published in PNAS.