“Why are Living Things Sensitive to Weak Magnetic Fields?” Electromagnetic Biology and Medicine, by Abe Liboff, posted online August 5, 2013.
“[W]e speculate that the widely observed weak-field [~50 nT] biomagnetic responses typified … stem from early evolutionary recognition of the diurnal change in the [geomagnetic field] as a precise zeitgeber; indeed one that outperforms the sun itself, in that it happens independently of cloudy skies.”
