If the sun turns red it could be because there was a war/battle that resulted in enough casualties that the bodies had to be burned,

…or a another plague…,

the thickness of the smoke and the shade of red the sun turns could help determine how many bodies were burned and how far away they were when they were burned, 

so how do we measure the thickness of the smoke in the air and what is the proper unit of measurement?, 

remember I’m learning with you,