# Does light photons have jerk

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 light which can be accelerated can also have jerk or not?

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-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 – t3st Jun 24 '12 at 11:17

## 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.

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It is not a coordinate transformation. – Ron Maimon Jun 23 '12 at 11:03
Yes, that was a clumsy answer. I've edited it to try and improve it. – John Rennie Jun 24 '12 at 7:54
+1: Thanks, John. – Ron Maimon Jun 24 '12 at 7:55
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