The discussion centers around the concept of light acceleration, particularly in the context of general relativity and the bending of light near massive objects. Participants explore the implications of light's path following a null geodesic and whether this indicates acceleration.
The discussion remains unresolved, with multiple competing views on whether light can be said to accelerate and how to interpret its path in the context of general relativity.
Participants express differing interpretations of light's behavior in curved spacetime, highlighting the complexities of defining acceleration in this context. The discussion also touches on the mathematical framework used to describe these phenomena, which may lead to varying conclusions based on definitions and assumptions.
Coordinate acceleration.petrushkagoogol said:
It can have coordinate acceleration. Geodesic world-line corresponds to zero proper acceleration.petrushkagoogol said:
No it is not correct. A geodesic is followed BECAUSE there is no force being applied to the light. The geodesic is "bent" if looked at via Euclidean geometry, which would imply a force on the light, but space-time does not follow Euclidean geometry, It follows Riemann geometry and the geodesic is a straight line implying no force.petrushkagoogol said:A beam of light bends when near a star. Since velocity is a vector, although the path still follows a null geodesic, a change in direction implies that acceleration is present. Light does then, in fact, accelerate. Is this correct ?
Just to be specific:phinds said:
OK. ThanksOrodruin said:
The spatial path of light is curved and the propagation direction does change. Only its world-line is a geodesic (locally straight).phinds said: