Russell Foster

“What makes a good scientist is the speed at which preconceptions are abandoned in the face of new knowledge”
― Russell Foster, Life Time

“In the 4th century BC, Plato argued that we are able to see because light emitted from the eye and that this light seizes objects with it's rays. This was the "extramission" theory of vision, and as bizarrely as it seems to us today, until the 1500s this was the widely held view in Europe of how the eye worked. To his credit Aristotle (384-322BC) was one of the first to reject the extramission theory of vision, arguing in favour of the "intromission" theory, whereby the eye receives light rays rather than projecting light into the world. Sadly, this eminently sensible theory from the ancient world was not embraced. Even Leonardo da Vinci in the 1480s first supported the extramission theory, but after dissecting the eye in the 1490s, he switched to the intromission theory. early observations by Islamic physicians, notably Hasan Ibn al-Haytham, who lived from 965 to 1040 AD and is known in the West as Alhazen, documented that the pupil dilates and contracts in response to different levels of light and that the eye is damaged by strong light. He used these observations to argue correctly that light enters the eye and that light is not emitted from the eye.”
― Russell Foster, Life Time