How about Gloop, who considers the possibility that the fact that the sky is blue now has no actual bearing on what the color of the sky might have been when the scraps of paper were written? He can entertain the possibility that the composition of the atmosphere might have changed during all the time people spent underground, so he establishes a laboratory to investigate if A) what particles were present in the air at the time the paper was written and B) if they were able to scatter blue or green light more efficiently?