Of all the head scratching theories scientists have thought up over the years, few have caused as many headaches as quantum mechanics. Its the branch of physics that focuses on the small stuff – atoms, particles, electrons – but it manages to make some pretty big claims about the nature of reality. For instance, according to quantum mechanics, particles can move in many directions at once, aims can spin clockwise and anti clockwise at the same time, and cats in boxes can be both alive and dead. Quantum mechanics is so surreal that Albert Einstein, who came up with the idea the first place, ended up arguing that it was too illogical to be true. But while humans struggle to understand its slippery logic, it turns out some far lesser brains are able to grasp quantum mechanics rather well: birdbrains, to be precise. According to recent studies, birds (all kinds) might actually be using quantum mechanics to help them navigate as they fly across the planet. Literal birdbrains doing theoretical physics might sound like a plot from an X Files episode, but the idea is gaining some serious traction in the Venn diagram where physics and ornithology overlap. For example, a ruby throated hummingbird is about as big as your thumb. It weighs two and a half grams and has a brain the size of a Tic Tac. And yet every year it makes this remarkable flight from Canada to Central America, returning each time to the same breeding ground, in the same backyard, in the same tree. In the 1970’s, the school of thought was that birds have a magnetic sense that they use to orient themselves. That there were little deposits of magnetic crystals in their brains or beaks that would act like compasses and essentially pull their noses north. On the surface, this theory isn’t so far fetched. Plenty of organisms, from bacteria to whales, have been shown to have a magnetic sense (theres even evidence human’s may have it). But even in the 70’s, some scientists noted that things didn’t really add up with this neat little explanation. The biochemistry involving magnetic force is incredibly weak. That is, unless the birds were somehow picking things up at the quantum level. To understand what might be going on in a birds brain, first you have to get your head around quantum entanglement. This is something that happens when two particles created at the same time become inextricably linked, even if they’re separated by great distances. So, say you have two electrons, and using some very precise magnets, you get one of them to start spinning clockwise. Because they are both ‘entangled’, the other electronic will instantly start to spin in the opposite direction – even if you’ve moved it all the way across the other side of the galaxy. Einstein derisively called this whole phenomenon ‘spooky’, but it actually checks out. Whats this got to do with birds? We’ll scientists now think that they might be using quantum entanglement to see the earth’s magnetic field. Its a theory thats been doing the rounds since the 70’s, but its take decades for physicists to begin to unravel how they might do this. Many now believe that when blue light enters a birds eye, an entangled electron in its retina gets dislodged, and moves a few nanometers away from its partner. These ever so slightly separated electrons then hit the magnetic field from ever so slightly different angles, resulting in different concentrations of chemicals forming in the eye. Physicists believe that these chemicals create a map like image of the magnetic field in the birds eyes, which it uses to orient itself. The idea that birds can detect something gas small as a single electron might seem hard to believe, but its these kinds of extra sensory abilities that most excites scientists. Its a reminder that the world is bigger than we know. And bigger than we can know. Birds can tap into physical spheres that humans are largely blind and deaf to. And this may be more widespread in the animal kingdom that we realise. To be continued..