Birds like the European robin pack a $10,000 lock-in amplifier into a 2 micron cell:
Earlier this year, the night-migratory European robin (Erithacus rubecola) made the headlines. Evidence has emerged that it may be using quantum mechanical effects to sense Earth’s magnetic field in order to migrate. Few expected to find quantum mechanical manipulation in the eye of a bird. Zoologist Eric Warrant, who was not involved in the research, says, that magnetic direction sensing is “the last sense we know, effectually, nothing about.” But this mysterious intelligence appears essential to migration, and hence, to the survival of many birds. So how, exactly, do they do it?News, “Physicist: Migrating birds’ mysterious quantum sense is “spooky”” at Mind Matters News
Experimental physicist Rob Sheldon notes,
Magnetic effects are so small, the molecule needs to be in a very fragile “excited” state to sense the magnetic field. It is thought that the “cytochrome” molecule gets excited by blue light, and in the excited state, magnetic fields preferentially cause it to de-excite in a certain direction.
They tested this in the lab, by coupling the cytochrome to a fluorescing or glowing molecule, shining a dim blue light on the cell, and watch it glow. Then when they passed a magnetic field over the cell, the glow was dimmed, proving that the cytochrome molecule was doing something in response to magnetic field.
Since this sensing is happening at the level of electron spins and excitation, it is an inherently QM [quantum mechanical] effect, hence the title of the article.
This isn’t spooky, and isn’t unusual. Lots of molecules have QM effects. Most of the odor receptors in your nose employ QM effects to identify odorants. Chlorophyll that makes leaves green absorbs light through a QM cascade of electrons. And of course, when the rods & cones in your retina sense photons, it is a QM effect.
What makes the magnetic QM effect so unusual, is that magnetic fields are perhaps 1000 times smaller than the other QM effects I mentioned. So the system has to detect a very weak signal-to-noise-ratio (SNR).
In the lab, we often use difference circuits that are modulated by a frequency and the result is integrated. The difference knocks out the common signal, so its called common mode rejection. The modulation averages over the noise, where real noise always has a zero sum. Then SNR can be boosted by factors of 1000 to 1,000,000, and somehow that is happening in a single cell. That’s the part that is spooky. Packing a $10,000 lock-in amplifier into a 2 micron cell.News, “Physicist: Migrating birds’ mysterious quantum sense is “spooky”” at Mind Matters News
Takehome: This mysterious intelligence, magnetoreception, seems essential to migration, hence, to the survival of many birds. They may even “see” Earth’s magnetic field.
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