Illusion?

I needed to type part of the title above in all caps.   It seems that upper case 'I' (matey) looks the same as lower case 'L'.

How do we know if what we believe we see as obvious truth, is true?  The circle on the left and right above are the same.  One seems clearer, more 'obvious' based on the contrast.  Hmmm.

Here is more.

A and B above are the same color.
Here.

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Avalanche of mustard seeds

Granular materials react to shear stresses differently than do ordinary fluids. Rather than deforming uniformly, materials such as dry sand or cohesionless powders develop shear bands: narrow zones containing large relative particle motion leaving adjacent regions essentially rigid. Since shear bands mark areas of flow, material failure and energy dissipation, they play a crucial role for many industrial, civil engineering and geophysical processes. (More).

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