The BBC has a fun piece on the fellow most English speakers might not recognize, even though he’s the guy who invented the scientific method:
For, without doubt, another great physicist, who is worthy of ranking up alongside Newton, is a scientist born in AD 965 in what is now Iraq who went by the name of al-Hassan Ibn al-Haytham.
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He proved experimentally, for instance, that the so-called emission theory (which stated that light from our eyes shines upon the objects we see), which was believed by great thinkers such as Plato, Euclid and Ptolemy, was wrong and established the modern idea that we see because light enters our eyes.
What he also did that no other scientist had tried before was to use mathematics to describe and prove this process.
So he can be regarded as the very first theoretical physicist, too.
He is perhaps best known for his invention of the pinhole camera and should be credited with the discovery of the laws of refraction.
He also carried out the first experiments on the dispersion of light into its constituent colours and studied shadows, rainbows and eclipses; and by observing the way sunlight diffracted through the atmosphere, he was able to work out a rather good estimate for the height of the atmosphere, which he found to be around 100km.
He also laid the groundwork for Kepler and Galileo’s work with planetary motion.
All while pretending to be crazy.