Seeing our world through the eyes of a migratory bird would be a rather spooky experience. Something about their visual system allows them to ‘see’ our planet’s magnetic field, a clever trick of quantum physics and biochemistry that helps them navigate vast distances.
Now, for the first time ever, scientists from the University of Tokyo have directly observed a key reaction hypothesised to be behind birds’, and many other creatures’, talents for sensing the direction of the planet’s poles.
Importantly, this is evidence of quantum physics directly affecting a biochemical reaction in a cell – something we’ve long hypothesised but haven’t seen in action before.
Using a tailor-made microscope sensitive to faint flashes of light, the team watched a culture of human cells containing a special light-sensitive material respond dynamically to changes in a magnetic field.
The change the researchers observed in the lab match just what would be expected if a quirky quantum effect was responsible for the illuminating reaction.
“We’ve not modified or added anything to these cells,” says biophysicist Jonathan Woodward.
“We think we have extremely strong evidence that we’ve observed a purely quantum mechanical process affecting chemical activity at the cellular level.”
So how are cells, particularly human cells, capable of responding to magnetic fields?
While there are several hypotheses out there, many researchers think the ability is due to a unique quantum reaction involving photoreceptors called cryptochromes.
Cyrptochromes are found in the cells of many species and are involved in regulating circadian rhythms. In species of migratory birds, dogs, and other species, they’re linked to the mysterious ability to sense magnetic fields.
In fact, while most of us can’t see magnetic fields, our own cells definitely contain cryptochromes. And there’s evidence that even though it’s not conscious, humans are actually still capable of detecting Earth’s magnetism.
To see the reaction within cyrptochromes in action, the researchers bathed a culture of human cells containing cryptochromes in blue light caused them to fluoresce weakly. As they glowed, the team swept magnetic fields of various frequencies repeatedly over the cells.
They found that, each time the magnetic filed passed over the cells, their fluorescent dipped around 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 – a innate property of electrons.
We already know that spin is significantly affected by magnetic fields. Arrange electrons in the right way around an atom, and collect enough of them together in one place, and the resulting mass of material can be made to move using nothing more than a weak magnetic field like the one that surrounds our planet.
This is all well and good if you want to make a needle for a navigational compass. But with no obvious signs of magnetically-sensitive chunks of material inside pigeon skulls, physicists have had to think smaller.
In 1975, a Max Planck Institute researcher named Klaus…