Exploring Alternative Mechanisms for Gravitational Wave Detection: Field Coupling and Matter Response in Flat Spacetime

Exploring Alternative Mechanisms for Gravitational Wave Detection: Field Coupling and Matter Response in Flat Spacetime

Abstract

We propose a framework for interpreting gravitational wave (GW) phenomena without assuming metric strain in spacetime. In this model, gravitational waves interact directly with physical fields and matter: (1) coupling with the electromagnetic (EM) field to produce measurable phase shifts, and (2) coupling with atomic and subatomic forces, leading to mechanical stretching of matter. We discuss the implications of these couplings for terrestrial versus space-based detectors, and outline experimental signatures that could distinguish between spacetime-metric effects and alternative coupling mechanisms.

1. Introduction

Gravitational waves have been detected by terrestrial interferometers such as LIGO and Virgo, and upcoming space-based detectors like LISA aim to extend observational capabilities. The prevailing interpretation within general relativity is that GWs manifest as ripples in the spacetime metric, producing differential displacements of freely suspended test masses.

We propose exploring an alternative hypothesis: GWs may interact directly with physical fields and matter without requiring spacetime itself to stretch. This model has two principal components:

  • Electromagnetic field coupling: GWs directly modulate the phase of EM fields used in detection, producing signals interpreted as distance changes.
  • Material response via atomic-force coupling: GWs interact with the forces binding matter (electromagnetic and strong nuclear interactions), producing minuscule mechanical deformations of matter, including detector mirrors.

These mechanisms produce relational measurements of distance changes without invoking metric strain.

2. Coupling of Gravitational Waves with the Electromagnetic Field

2.1 Conceptual Framework

In a flat-spacetime paradigm, gravitational waves propagate as perturbations in the gravitational field. The EM field, which serves as the measuring instrument in interferometric detectors, couples directly to these perturbations. The apparent motion of test masses is therefore an emergent effect, inferred from phase shifts in the light field.

2.2 Predicted Observational Signatures

  • Phase shifts in interferometers arise without requiring the mirrors to move.
  • Time-of-arrival delays across multiple detectors arise naturally from the finite propagation speed of gravitational field perturbations.
  • Quadrupolar patterns of differential arm signals can be produced if EM–GW coupling depends on relative orientation.

3. Material Response via Coupling to Atomic and Nuclear Forces

3.1 Conceptual Framework

Gravitational waves may couple directly to the internal forces that hold matter together. In particular, the strong force and electromagnetic interactions within atoms and molecules can mediate mechanical responses to passing GWs. This produces measurable differential displacements in detectors as actual physical deformations of mirror substrates or other material components.

3.2 Predicted Observational Signatures

  • Differential arm lengths of interferometers appear due to mechanical stretching, not spacetime distortion.
  • Resonant frequency response depends on material properties, potentially creating frequency-dependent amplification or suppression.
  • Detectors in low-gravity environments (e.g., in space) may experience enhanced sensitivity because terrestrial detectors are coupled to the bulk motion of Earth, which cannot mechanically respond at high GW frequencies.

4. Comparative Analysis: Terrestrial vs. Space-Based Detectors

Feature Terrestrial Detectors Space-Based Detectors
Gravitational coupling to EM field Detectable via laser phase shifts; unaffected by Earth anchoring Detectable via laser phase shifts; free-floating mirrors may enhance sensitivity
Material (atomic-force) response Mirrors anchored to Earth experience partial mechanical deformation; Earth’s bulk rigidity partially transmits or suppresses response If GWs couple primarily to material forces, free-floating mirrors may not experience deformation, so signals could be absent or greatly reduced
Environmental noise Seismic, thermal, atmospheric noise may obscure subtle EM-field or matter coupling effects Reduced noise; better isolation allows detection of weaker EM-field coupling signals
Signal interpretation Apparent strain arises from combination of EM-field modulation and mechanical deformation filtered through Earth If only EM-field coupling exists, clear differential phase shifts; if only matter coupling exists, signals may vanish in space-based detectors

Key Implication: This emphasizes a diagnostic test: If a space-based interferometer like LISA detects gravitational waves that terrestrial detectors also see, it suggests EM-field coupling is present. If a space-based interferometer fails to detect signals while terrestrial detectors do, it implies a mechanical/matter-coupling–dominant mechanism, reliant on Earth-bound material to produce measurable effects.

5. Proposed Experimental Tests

  • Phase-only interferometers in space: Compare signals from free-floating mirrors in vacuum with terrestrial detectors to isolate EM-field coupling effects.
  • Material-specific resonators: Construct detectors using materials with differing atomic-force constants to test for mechanical response to GWs.
  • Polarization and orientation studies: Measure how differential arm signals vary with orientation relative to the incoming wave to differentiate EM-field vs. mechanical coupling contributions.
  • Cross-field correlation: Compare interferometer signals with non-EM mechanical detectors and pulsar timing arrays to constrain or confirm coupling mechanisms.

6. Discussion

This framework suggests that the apparent stretching of spacetime may be an emergent phenomenon, interpreted through our EM-based measurement systems and material response. While it does not yet provide a complete predictive theory, it offers a logically consistent alternative to the metric-strain interpretation, one that could be tested with a combination of space-based interferometry, material-dependent resonators, and multi-detector correlation studies.

7. Conclusion

We postulate that gravitational waves may interact with both electromagnetic fields and matter itself, producing observable signals that do not require spacetime to change its metric. Future experiments, particularly in space, could distinguish between these coupling-based mechanisms and the traditional GR-based metric strain interpretation. This alternative perspective opens a pathway to exploring the fundamental nature of gravity and its interactions with matter and fields.

References (Conceptual / Motivational)

  • LIGO Scientific Collaboration, et al., Observation of Gravitational Waves from a Binary Black Hole Merger, 2016.
  • Maggiore, M., Gravitational Waves: Volume 1, 2007.
  • Alternative gravity and flat-spacetime models (various speculative papers in preprints and journals).