Why can't Einstein's law of gravity predict gravitational lensing?

Soumendra Nath Thakur

08-11-2024

To clarify, there are three main considerations in the photon’s path:

Consideration 1: The Photon’s Initial Straight-Line Trajectory

The photon begins its journey from the source along a straight-line trajectory with velocity c. Here, an initial redshift occurs as the photon loses a slight amount of energy due to gravitational interaction with the source’s gravitational well, resulting in a corresponding increase in wavelength (Δλ>0). This change follows the relationship E = hf = hc/λ, where the energy E and frequency f are inherent to the photon and directly proportional to the wavelength.

Consideration 2: Arc Path and Energy Exchange During Gravitational Bypassing

As the photon approaches and passes an external massive body, it undergoes a temporary arc-shaped deviation in its trajectory due to the external gravitational influence. 

This interaction involves two phases:

First Half-Arc: A blueshift occurs, corresponding to a wavelength decrease (Δλ<0) as the photon gains energy due to gravitational influence while approaching the massive body.

Second Half-Arc: As the photon moves away, a redshift (Δλ>0) occurs, returning the photon’s wavelength to its original state as it completes the arc and leaves the gravitational field. This reversible shift is due to energy exchange within the field, summarized by E + Eg= E + 0, where Eg represents the energy gained and then lost by the photon within the gravitational arc path.

Consideration 3: Return to Original Straight-Line Trajectory

After exiting the gravitational field, the photon resumes its original straight-line path. At this point, it retains its inherent energy, with any additional energy or momentum imparted by the gravitational field removed. Its wavelength also remains as it was upon entry into the gravitational encounter, indicating no net change in wavelength (Δλ=0) beyond that caused by its initial emission.

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.

#GravitationalLensing