Gravitational Lensing and Frequency-Dependent Light Travel Time

AI Thread Summary
Gravitational lensing causes light to bend around massive bodies, but this bending is independent of light's frequency, meaning it does not split like a prism. The discussion highlights that in General Relativity, the path-bending of null geodesics does not depend on color, as color is a relative property. There is mention of recent observations suggesting that high-energy photons may travel at slightly different speeds due to effects akin to a "vacuum" refractive index. The concept of vacuum refractive index is acknowledged as complex, and the original poster expresses a desire to understand it better. Overall, the interaction of gravitational lensing with frequency-dependent light travel time remains a nuanced topic in astrophysics.
wolram
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Light that has traveled millions of years is gravitationaly (lensed) around a body,
if there is any frequency dependant light travel time ,would it not show up as if it
had been split by a prism when it was lensed around said body, or would the various frequencies recombine?
 
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Basically no, the path-bending of null geodesics in GR is independent of colour (indeed, colour is relative).

There are other arguments to consider, the most significant being the recent possible observation that high energy photons move at slightly different speeds (think "vacuum" refractive-index).
 
cesiumfrog said:
Basically no, the path-bending of null geodesics in GR is independent of colour (indeed, colour is relative).

There are other arguments to consider, the most significant being the recent possible observation that high energy photons move at slightly different speeds (think "vacuum" refractive-index).

Thanks cf, i do not know what , "vacuum" refractive-index is, i will look it up, i have an idea but could be way out.
 
The only papers i can find with (vacuum refractive index ) are sub only.
 
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