세상에, 사막에, 그 마른 땅에 어떻게 벼락이 치는가에 대해 배웠고, 그걸 되새기고 있던 [[참이었다]]. I looked in the dictionary and none of them make sense to me.
역+참 is mean of 'road' or 'station'
역 = korean word, 참 = chinese word
In history, there is a limit to running away from the horse, so made '역참' (inn) made the horse rest in the middle.
But as time passed, the words changed 역참 -> 참 -> 역.
Being in (역)참 means somewhere on the way, so
~하던 참이었다 = i was doing something
※(reference) Distance between 참 and 참 was 12~40Km. So 한참을 가다 means go for a long time
Sorry about bad english :(
From Naver dictionary:
(의존명사) 무엇을 하는 경우나 때.