why does the central part of a red blood cell appear paler than the outer part when viewed under a light microscope

The central pale area of each red blood cell is due to the concavity of the disc.

Explanation:

emerging idea only occurs as a raw idea that could appear out of nowhere. meanwhile, to reach scientific consensus , that idea must be structured and tested over and over again through various experiments. the scientific consensus transforms the raw idea into idea that is more reliable through the process of scientific elimination.