Seeing our world through the eyes of a migratory bird would be a pretty spooky experience. Something in their visual system allows them to “see” the magnetic field of our planet, a clever trick of quantum physics and biochemistry that helps them navigate great distances.
Now, for the first time, scientists at the University of Tokyo have directly observed a key reaction based on the dowries of birds and many other creatures, to detect the direction of the planet’s poles.
It is important to note that this is evidence that quantum physics directly affects a biochemical reaction in a cell, which we have long hypothesized but have not seen in action before.
Using a custom-made microscope that was sensitive to faint flashes of light, the team saw how a culture of human cells containing a special light-sensitive material responded dynamically to changes in a magnetic field.
The fluorescence of a cell darkens as a magnetic field passes. (Ikeya and Woodward, CC BY)
The change that the researchers observed in the laboratory coincides with what was expected if a peculiar quantum effect were responsible for the illuminating reaction.
“We haven’t modified or added anything to these cells,” says biophysicist Jonathan Woodward.
“We believe we have very strong evidence that they have observed a purely quantum mechanical process that affects chemical activity at the cellular level.”
So how are cells, especially human cells, able to respond to magnetic fields?
Although there are several hypotheses, many researchers think that the ability is due to a unique quantum reaction involving photoreceptors called cryptochromes.
Cirptochromes are found in the cells of many species and are involved in the regulation of circadian rhythms. In migratory bird species, dogs and other species, they are related to the mysterious ability to detect magnetic fields.
In fact, even though most of us don’t see magnetic fields, our own cells definitely contain cryptochromes. And there is evidence that, while not conscious, humans are still able to detect the Earth’s magnetism.
To see the reaction of cryptochromes in action, the researchers bathed a culture of human cells containing cryptochromes in blue light and caused them to flow weakly. As they shone, the computer repeatedly swept magnetic fields of various frequencies over the cells.
They found that each time the magnetic file passed over the cells, their fluorescents dropped by about 3.5 percent, enough to show a direct reaction.
So how can a magnetic field affect a photoreceptor?
It all comes down to something called spin: an innate property of electrons.
We already know that spin is significantly affected by magnetic fields. Arrange the electrons correctly around an atom and collect enough of them in one place and the resulting material mass can be moved using nothing more than a faint magnetic field like the one surrounding our planet.
Everything is fine if you want to make a needle for a navigation compass. But with no obvious signs of magnetically sensitive pieces of material inside the pigeon skulls, physicists have had to think smaller.
In 1975, a researcher at the Max Planck Institute named Klaus Schulten developed a theory about how magnetic fields could influence chemical reactions.
It was something called a radical couple.
A garden variety radical is an electron in the outer layer of an atom that is not associated with a second electron.
Sometimes these single electrons can adopt a wing man into another atom to form a radical pair. The two are not paired, but thanks to a shared story they are considered tangled, which, in quantum terms, means that their turns will correspond strangely, regardless of how far apart they are.
Since this correlation cannot be explained by ongoing physical connections, it is purely a quantum activity, which even Albert Einstein considered “spooky.”
In the hustle and bustle of a living cell, its mess will be ephemeral. But even these briefly correlated twists should last long enough to make a subtle difference in the behavior of their respective parent atoms.
In this experiment, as the magnetic field passed over the cells, the corresponding drop in fluorescence suggests that the generation of radical pairs had been affected.
An interesting consequence of the research could be how even weak magnetic fields could indirectly affect other biological processes. While the evidence for magnetism affecting human health is weak, similar experiments may lead to another avenue of research.
“The joy of this research is to see that the relationship between the rotations of two individual electrons can have a significant effect on biology,” says Woodward
Of course, birds are not the only animal that trusts our magnetosphere to go. Species of fish, worms, insects and even some mammals have their talent. Humans could even be cognitively affected by the Earth’s weak magnetic field.
The evolution of this ability could have produced a series of very different actions based on different physics.
Having evidence that at least one of them connects the strangeness of the quantum world with the behavior of a living being is enough to force us to ask what other pieces of biology arise from the spooky depths of fundamental physics.
This research was published in PNAS.