Speed of light measured in/by a parallel frame moving at c

San K
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Scenario:

Alice is "sitting" on photon A
Bob is "sitting" on photon B

both are moving in same direction, their paths are parallel to each other.

Per relativity the speed of light is constant

So Alice will measure Bob's speed to be c
and Bob will measure Alice's speed to be c

yet they are both moving at constant velocity c

how is this (paradox?) resolved?
 
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If Alice accelerates, trying to catch up with photon A, she finds that it still eludes her, traveling at c.
 

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