Seeing our world through the eyes of a migratory bird would be a rather frightening 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 travel long distances.
Now, for the first time, scientists at the University of Tokyo have directly observed a key reaction hypothesized to be behind the talents of birds and many other creatures to feel the direction of the planet’s poles.
Importantly, this is proof that quantum physics directly affects a biochemical reaction in a cell – something I have long hypothesized, but have never seen in action.
Using a custom microscope, sensitive to faint flashes of light, the team tracked a culture of human cells containing a special light-sensitive material that responds dynamically to changes in a magnetic field.
The fluorescence of a cell fades as a magnetic field passes over it. (Ikeya and Woodward, CC BY)
The change that the researchers observed in the laboratory match exactly what one would expect if a strange 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 extremely strong evidence that we 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 there, many researchers believe 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 regulating circadian rhythms. In migratory bird species, dogs and other species, they are related to the mysterious ability to feel magnetic fields.
In fact, although most of us cannot see magnetic fields, our own cells certainly contain cryptochromes. And there is evidence that, although it is not conscious, humans are actually still able to detect the Earth’s magnetism.
To see the reaction inside the cryptochromes in action, the researchers bathed a culture of human cells containing cryptochromes in blue light, causing them to fluoridate poorly. As they shone, the team swept magnetic fields of different frequencies repeatedly over the cells.
They found that each time the magnetic material passed over the cells, their fluorescence dropped by about 3.5% – 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 rotation is significantly affected by magnetic fields. Arrange the electrons correctly around an atom and gather them enough from one place, and the mass of the resulting material can be made to move using nothing more than a weak magnetic field like the one that surrounds our planet.
Everything is fine and if you want to make a needle for a navigation compass. But without obvious signs of magnetically sensitive pieces of material inside the pigeon skulls, physicists had to think less.
In 1975, a researcher at the Max Planck Institute named Klaus Schulten developed a theory about how magnetic fields could influence chemical reactions.
It involved something called a radical pair.
A garden variety radical is an electron in the outer shell of an atom that is not associated with a second electron.
Sometimes these bachelor electrons can adopt a wing in another atom to form a radical pair. The two remain unmatched, but due to a shared history they are considered confused, which means that, in quantum terms, their rotations will correspond strangely, no matter how far they are.
Since this correlation cannot be explained by ongoing physical connections, it is simply a quantum activity, something that even Albert Einstein considered “scary.”
In the agitation of a living cell, their entanglement will be transient. But even these briefly correlated rotations should last long enough to make a subtle difference in how their parent atoms behave.
In this experiment, as the magnetic field passed over the cells, the corresponding decrease in fluorescence suggests that the generation of radical pairs was affected.
An interesting consequence of the research could be how even weak magnetic fields could indirectly affect other biological processes. While evidence of magnetism affecting human health is weak, similar experiments like this could prove to be another way of investigating.
“The happy thing about this research is that the relationship between the rotations of two individual electrons can have a major effect on biology,” says Woodward.
Of course, birds are not the only animal that relies on our magnetosphere for direction. Species of fish, worms, insects and even some mammals have a talent for this. We humans could even be cognitively affected by the Earth’s weak magnetic field.
The evolution of this ability could have performed 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 organism is enough to force us to ask what other bits of biology arise from the frightening depths of fundamental physics.
This research was published in PNAS.