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Ideas That Built Your Phone: the Golden Age of Science · EPISODE 2 · 2:45

Ibn al-Haytham — Light, the Eye and the Camera

For over a thousand years, great thinkers believed your eyes shoot out rays, like little torches. Then Ibn al-Haytham proved light comes INTO the eye — and explained the dark room with a tiny hole that became your phone camera. Light, the eye and the camera, in under 3 minutes. Episode 2 of Ideas That Built Your Phone: the Golden Age of Science.

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What you'll learn

  • Old idea (Euclid, Ptolemy): the eye sends out rays, like torches, and you see what they touch.
  • The puzzle: bright sunlight hurts your eyes, and you see far-away stars the moment you open them.
  • Ibn al-Haytham (about 965 – 1040, Latin name Alhazen) was born in Basra and did his greatest work in Cairo. Around 1011 he began his Book of Optics — 7 volumes: light bounces off things and travels INTO your eye.
  • He was one of the first to insist on testing ideas by experiment: change one thing at a time, check, repeat.
  • Camera obscura = "dark room": light goes in straight lines through a tiny hole, so the top of a candle lands low and the bottom lands high — the picture is upside down. Bigger hole = brighter but blurry; tiny hole = sharp but dim.
  • Your phone camera: the lens is the hole, the sensor is the wall. The picture lands upside down and the chip flips it.
  • Episode 1's challenge: binary 1101 = 8 + 4 + 1 = 13.
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Quick refreshers

EP.149 · Tech StoryTech Story #5: The blue LED that took 30 years EP.150 · Why does…?Why does…? #12: Why does your phone screen turn off at your ear? EP.200 · Explained SimplyExplained Simply #13: how does a phone camera turn light into a photo? EP.205 · Tech StoryTech Story #10 · Golden Age G3: Ibn al-Haytham — light, the eye and the camera EP.214 · Why does…?Why does…? #20: why LED lights flicker on your phone camera