title: Why are living things sensitive to weak magnetic fields?
abstract: There is evidence for robust interactions of weak ELF magnetic fields with biological systems. Quite apart from the difficulties attending a proper physical basis for such interactions, an equally daunting question asks why these should even occur, given the apparent lack of comparable signals in the long-term electromagnetic environment. We suggest that the biological basis is likely to be found in the weak (∼50 nT) daily swing in the geomagnetic field that results from the solar tidal force on free electrons in the upper atmosphere, a remarkably constant effect exactly in phase with the solar diurnal change. Because this magnetic change is locked into the solar-derived everyday diurnal response in living things, one can argue that it acts as a surrogate for the solar variation, and therefore plays a role in chronobiological processes. This implies that weak magnetic field interactions may have a chronodisruptive basis, homologous to the more familiar effects on the biological clock arising from sleep deprivation, phase-shift employment and light at night. It is conceivable that the widespread sensitivity of biological systems to weak ELF magnetic fields is vestigially derived from this diurnal geomagnetic effect.
authors.affiliation: Department of Physics, Oakland University , Rochester Hills, MI , USA.
authors.forename: Abraham R
authors.initials: AR
authors.lastname: Liboff
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D002940:Circadian Rhythm; D004781:Environmental Exposure; D019143:Evolution, Molecular; D060526:Magnetic Fields; D016082:Solar System
keywords: Biological clock; chronodisruption; cryptochrome; magnetic diurnal change; melatonin; weak-field interactions