# Does light photons have jerk? [duplicate]

This question already has an answer here:

While searching in web regarding whether rate of change of acceleration is possible or not; I came across the concept of jerk. I want to know whether photons which can be accelerated can also have jerk or not?

-

## marked as duplicate by Qmechanic♦Oct 5 '13 at 16:51

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

-1: This is not a good question. The answer is "sort of". – Ron Maimon Jun 23 '12 at 11:06
hey ron, i am not a physicist just out of curiosity i have asked this question and i believe that no questions are stupid and every question has an answer – Eka Jun 24 '12 at 11:17
Possible duplicates: physics.stackexchange.com/q/20289/2451 and links therein. – Qmechanic Aug 4 '13 at 14:59

## 1 Answer

Strictly speaking light can't be accelerated. Viewed from a local frame it always travels at a speed of $c$ and in a straight line. Since the acceleration is always zero the jerk is also always zero.

Light can be bent by gravitational fields, i.e. in curved space-time, and therefore it is accelerated in the sense that it's velocity changes direction so I suppose the jerk is non-zero. However the bending of light we see is just the result of the curvature of spacetime. Viewed locally the light travels in a straight line at constant velocity, so it's not clear to me that jerk is an especially useful concept in calculating the trajectory of a light beam.

-