The Science Book

28

LIGHT TRAVELS

IN STRAIGHT LINES

INTO OUR EYES

ALHAZEN (c.965–1040)

T

he Arab astronomer and

mathematician Alhazen,

who lived in Baghdad,

in present-day Iraq, during the

Golden Age of Islamic civilization,

was arguably the world’s first

experimental scientist. While

earlier Greek and Persian thinkers

had explained the natural world in

various ways, they had arrived at

their conclusions through abstract

reasoning, not through physical

experiments. Alhazen, working in a

thriving Islamic culture of curiosity

and inquiry, was the first to use

what we now call the scientific

method: setting up hypotheses and

IN CONTEXT

BRANCH

Physics

BEFORE

350 BCE Aristotle argues that

vision derives from physical

forms entering the eye from

an object.

300 BCE Euclid argues that the

eye sends out beams that are

bounced back to the eye.

980s Ibn Sahl investigates

refraction of light and deduces

the laws of refraction.

AFTER

1240 English bishop Robert

Grosseteste uses geometry in

his experiments with optics

and accurately describes the

nature of color.

1604 Johannes Kepler’s theory

of the retinal image is based

directly on Alhazen’s work.

1620s Alhazen’s ideas

influence Francis Bacon, who

advocates a scientific method

based on experiment.

The light of the Sun

bounces off objects.

To see, we need to do nothing

but open our eyes.

The light bounces off

in straight lines.

Light travels in

straight lines into

our eyes.

methodically testing them with

experiments. As he observed:

“The seeker after truth is not one

who studies the writings of the

ancients and...puts his trust in

them, but rather the one who

suspects his faith in them and

questions what he gathers from

them, the one who submits to

argument and demonstration.”

Understanding vision

Alhazen is remembered today as

a founder of the science of optics.

His most important works were

studies of the structure of the eye

and the process of vision. The