It would be quite spooky to see the world through the eyes migratory birds. Their visual system is able to "see" the planet's magnetic fields, which is a clever trick of quantum Physics and biochemistry that allows them to navigate long distances.
Scientists from the University of Tokyo reported that they had observed for the first-ever time a key reaction. This reaction is believed to be responsible for birds' (and other animals') ability to sense the direction of Earth's poles.
This is a clear example of quantum physics directly impacting a biochemical reaction within a cell. This is something we have long suspected but never seen in practice.
The team used a microscope that was sensitive to faint flashes light to observe a culture of human cells with a light-sensitive material react dynamically to magnetic field changes.
As a magnetic field passes through a cell, its fluorescence dims. (Ikeya & Woodward, CC BY 4.0
Researchers observed a similar change in the laboratory to what might be expected if a bizarre quantum effect was behind the illuminating reaction.
Jonathan Woodward, a biophysicist, stated that "we have not modified or added anything" to these cells.
"We believe we have strong evidence that we have observed a quantum mechanical process affecting chemical activities at the cellular level."
How are cells, especially human cells, capable to respond to magnetic fields?
There are many theories, but most researchers believe that the unique quantum reaction of photoreceptors and cryptochromes is responsible for the ability.
Many species have cryptochromes in their cells. They regulate circadian rhythms and can be found in many cell types. They are linked to the ability to sense magnetic field in migratory birds, dogs and other animals.
Despite the fact that most people can't see magnet fields, cryptochromes are found in human cells. There is evidence that humans can still detect Earth's magnetism, even though they aren't conscious of it.
The researchers exposed a culture of cells containing cryptochromes to blue light and observed how they fluoresced. The team applied magnetic fields at different frequencies to the cells, causing them to glow.
The researchers found that the magnetic field was able to pass over cells and cause fluorescence to drop by 3.5 percent. This allowed them to demonstrate a direct reaction.
How does a magnetic field influence a photoreceptor's ability to read? It all boils down to spin, an intrinsic property of electrons.
Magnetic fields have a significant impact on spin, as we know. If you arrange electrons around an atom in the correct way, and gather enough of them in one place, the resultant mass of material can be made moveable by a weak magnetic field such as the one surrounding our planet.
If you are making a navigational compass needle, this is all fine and dandy. But with no obvious signs of magnetically-sensitive chunks of material inside pigeon skulls, physicists have had to think smaller.
Klaus Schulten, a Max Planck Institute researcher, developed a theory about how magnetic fields might influence chemical reactions in 1975.
It was a radical pair. An electron that isn’t paired with another electron is a garden-variety radical.
These bachelor electrons may adopt an atom's wingman to form a radical couple. They remain unpaired but due to their shared history, they are considered entangled. This means that their spins will coincide eerily no matter how far apart.
This correlation cannot be explained by continuing physical connections. It's therefore purely a quantum activity. Albert Einstein even considered it'spooky.
Their entanglement is fleeting in the bustle of a living cell. Even these brief correlating spins will only last for a short time enough to make a subtle change in the behavior of their parent atoms.
This experiment shows that when the magnetic field passes over cells, the fluorescence dips in the same direction. This suggests that the generation radical pairs has been affected.
One interesting result of this research is how weak magnetic fields can indirectly affect biological processes. Although there is no evidence that magnetism affects human health, similar experiments could be used to investigate.
Woodward said, "The joyous part about this research was to see that spins of two individual electrons could have a major impact on biology."
Our magnetosphere isn't just for birds. It is possible for many species of fish, worms and insects to do this. The Earth's magnetic field might have cognitive effects on humans.
This ability could have evolved to allow for a variety of actions that are based on different physical laws.
Evidence that at least one link the strangeness of quantum world behavior with that of a living being is enough to make us wonder what other bits biology might emerge from the dark depths of fundamental Physics.
This research was published by PNAS.
A previous version of this article appeared in January 2021.
