Gravitational Field vs. Spacetime Curvature: Discrepancies in GR's Lensing Model

Soumendra Nath Thakur

ORCiD: 0000-0003-1871-7803 

09-11-2024

General relativity (GR) posits that massive celestial bodies—such as galaxies or galaxy clusters—warp spacetime, causing gravitational lensing, where light’s path appears bent. In regions between massive objects, spacetime remains flat, but when a massive body is present, it curvatures spacetime, bending light as it passes.

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The photon’s path can be described in three phases:

Initial Straight-Line Trajectory: The photon starts along a straight path from the source, traveling at speed c. As it moves away from the gravitational well of the source, a slight redshift occurs, indicating a small increase in wavelength (Δλ > 0).

Interaction with External Massive Body: As the photon approaches an external massive body, it undergoes a temporary blueshift (Δλ < 0) while moving toward the body. Once the photon passes the body and begins to move away, it experiences a redshift (Δλ > 0), returning to its original wavelength. This reversible shift reflects the energy gained and lost by the photon in response to the external gravitational field. The photon’s inherent energy drives its straight-line path, but the external field temporarily adds energy, altering its trajectory in an arc-like fashion. After completing this interaction, the photon resumes its original straight path, with no net change in wavelength (Δλ = 0).

Return to Original Trajectory: After passing the gravitational influence of the external body, the photon’s trajectory returns to its original straight-line path, maintaining its inherent energy and wavelength. The photon’s wavelength remains unchanged beyond the initial shift caused by the source’s gravitational well.

However, GR asserts that light bends along the curvature of spacetime itself, where the gravitational field mirrors this curvature. In contrast, observational experiments suggest that light bending is primarily due to the curvature of the gravitational field itself, rather than spacetime. This discrepancy challenges GR's interpretation and suggests the need for a re-evaluation of theoretical models.

This study critically analyses the discrepancies between GR’s predictions and experimental observations. The findings suggest that while GR visualizes the gravitational field as mirroring spacetime curvature, this model does not fully capture the complexities of actual light-gravity interactions observed in experiments. Therefore, a re-examination of gravitational lensing and the underlying mechanisms of light propagation is necessary.

Conclusion:

GR posits that gravitational lensing occurs due to spacetime curvature, but experimental data suggest that the bending of light is primarily driven by the curvature of the gravitational field. This misalignment calls into question the validity of GR in explaining light’s interaction with gravity, suggesting that the relationship between light, gravity, and spacetime may require further exploration and modification. The study advocates for alternative models that could more accurately explain the observed phenomena, paving the way for future research into the mechanics of gravitational lensing.

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