Magneto-Optical Influence of Earth's Geomagnetic Field on LIGO Interference PatternsAbstract: LIGO has revolutionized astrophysics by detecting gravitational waves via laser interferometry, primarily through minute fringe deviations. Conventionally, these fringe shifts are attributed to spacetime distortions from astrophysical gravitational wave sources. In this paper, we propose an alternative hypothesis: that some LIGO fringe deviations may arise due to Faraday-type polarization rotations induced by natural fluctuations in Earth's geomagnetic field. These magnetic variations, caused by Earth's rotation, thermal convection in its molten core, and solar interactions, could produce µT-level field changes sufficient to affect the optical path within the interferometer, thus altering interference patterns. This hypothesis is grounded in magneto-optical physics and supported by empirical sensitivity of LIGO to picometer-level displacements. We present a theoretical model, derive the expected order of rotation, and recommend correlating geomagnetic field data with LIGO fringe events to test the validity of this alternative mechanism. 1. Introduction The Laser Interferometer Gravitational-Wave Observatory (LIGO) identifies gravitational waves by detecting incredibly small changes in the relative lengths of its perpendicular arms. These changes are typically of the order of 10^-18 meters, detected via destructive or constructive interference of laser beams. A landmark example is the GW150914 event, the first confirmed gravitational wave detection. While multiple fringe deviations have been interpreted as signatures of gravitational waves, a large number of similar fringe shifts are classified as background noise without known cause.  This paper suggests that Earth's dynamic geomagnetic field may be responsible for some of these unexplained fringe deviations through a Faraday-type optical polarization rotation.

Abstract:  LIGO has revolutionized astrophysics by detecting gravitational waves via laser interferometry, primarily through minute fringe deviations. Conventionally, these fringe shifts are attributed to spacetime distortions from astrophysical gravitational wave sources. In this paper, we propose an alternative hypothesis: that some LIGO fringe deviations may arise due to Faraday-type polarization rotations induced by natural fluctuations in Earth’s geomagnetic field. These magnetic variations, caused by Earth's rotation, thermal convection in its molten core, and solar interactions, could produce µT-level field changes sufficient to affect the optical path within the interferometer, thus altering interference patterns. This hypothesis is grounded in magneto-optical physics and supported by empirical sensitivity of LIGO to picometer-level displacements. We present a theoretical model, derive the expected order of rotation, and recommend correlating geomagnetic field data with LIGO fringe events to test the validity of this alternative mechanism.  1. Introduction  The Laser Interferometer Gravitational-Wave Observatory (LIGO) identifies gravitational waves by detecting incredibly small changes in the relative lengths of its perpendicular arms. These changes are typically of the order of 10^-18 meters, detected via destructive or constructive interference of laser beams. A landmark example is the GW150914 event, the first confirmed gravitational wave detection. While multiple fringe deviations have been interpreted as signatures of gravitational waves, a large number of similar fringe shifts are classified as background noise without known cause.  This paper suggests that Earth’s dynamic geomagnetic field may be responsible for some of these unexplained fringe deviations through a Faraday-type optical polarization rotation.