The discussion centers around the examination of the spectrum of gravitationally lensed light, specifically whether variations in red or blue shifts have been observed in the light from different parts of an Einstein ring. Participants explore the implications of gravitational lensing and potential effects of frame dragging around rotating massive objects.
Participants generally agree that light bending does not depend on frequency according to general relativity, but there is no consensus on the potential effects of frame dragging or whether such effects could lead to observable frequency shifts in lensed light.
The discussion highlights the complexity of gravitational lensing and the potential influence of additional factors like frame dragging, which may not be fully resolved within the current conversation.
notknowing said:I was wondering whether one has examined the spectrum of gravitational lensed light (nice description on wikipedia : http://en.wikipedia.org/wiki/Gravitational_lensing ). Have there been indications on some red or blue shifts in the light from different parts of the observed ring? Does anyone know?
Rudi Van Nieuwenhove
Chris Hillman said:Well, in gtr, light bending certainly does not depend on frequency (in the geometrical optics approximation), but it's not clear to me what he has in mind.
Chris Hillman said:Rudi, sorry, but I don't yet understand your question. Did you take the point (already mentioned by meopemuk) that according to gtr, "light bending" (e.g. in "gravitational lensing") does not depend on the frequency of the light being bent?