Ibn al-Haytham established light travels from object to eye

Evidence

Ibn al-Haytham demonstrated that light travels from the object to the eye, whereas previously Ptolemy and Euclid had argued that the eye perceived things by sending rays out to the objects. — Robert Irwin, For Lust of Knowing, 62

Categorization

• CANDY: A fun reversal: for over a millennium the best Greeks thought the eye emitted rays; Ibn al-Haytham got it backwards-to-us but right.