6th
“A curious thing about the ontological problem is its simplicity. It can be put in three Anglo-Saxon monosyllables: ‘What is there?’ It can be answered, moreover, in a word – ‘Everything’ – and everyone will accept this answer as true. However, this is merely to say that there is what there is. There remains room for disagreement over cases; and so the issue has stayed alive down the centuries.”
— Willard Van Orman Quine: ‘On What There Is’
Comparison of a Lévy flight with a Brownian random walk. Lévy flights are a theoretical construct that has attracted wide interdisciplinary interest. Empirical evidence shows that the principle applies to the foraging of marine predators. nature
Developing pig eye, light micrograph. From right the structures seen are: the cornea (purple), the lens (yellow green), the retina (dark green), the choroid (dark purple line) and the sclera (white of the eye, purple). The optic nerve is at centre left.