IBN AL-HAYTHAM (ALHAZEN) AND OPTICS

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Ibn al-Haytham (Alhazen) corrected an error made by Ptolemy concerning the index of refraction. [A Jew who converted to Islam made this correction before Alhazen did.]
Alhazen calculated reflection off a sphere.
Alhazen invented correct explanations of why stars seemed to slow down a few minutes before they set, and why the moon appears to be larger when it is on the horizon.
The camera obscura (pinhole camera) had originally been invented in 5th century BC China, and had been used by Greeks.
Alhazen’s theory of light was identical to that of Euclid.
Alhazen’s incorrect explanation of how the eye worked was copied from Galen of Pergamon.
Alhazen’s incorrect explanation of rainbows was copied from Seneca the Younger.
Alhazen gave incorrect explanations of why sunset is red and why the sky is blue.
Alhazen copied other teachings about optics (some correct and some wrong) from the Greeks and Romans.
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RAINBOWS

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Alhazen’s theory of rainbows (clouds were huge concave reflecting mirrors) was copied from Roman philosopher Seneca the Younger’s first choice explanation.
Either Avicenna (Ibn Sīnā) or al-Qarafi copied the incorrect second choice explanation of Seneca the Younger that reflection but not refraction caused rainbows.
The correct theory that rainbows were caused by refraction of light by droplets of water in the air was proposed by the Qutb al-Din al-Shirazi.
Kamāl al-Dīn al-Fārisī was the first to give a correct mathematical explanation of the details.
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GRAVITY AND MOTION

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Ibn Bâjja (Avempace) fudged his measurements of motion on an inclined plane, because his belief in Allah creating a perfect universe convinced him that speed is proportional to the height from which an object was dropped. Actually, speed is proportional to the square root.
Although Christian theologian John Philoponus correctly wrote that an object would continue moving through a vacuum, all Islamic Golden Age scientists agreed with Aristotle that objects would stop moving in a vacuum.
Most Islamic Golden Age scientists (except for a Greek slave owned by a Muslim) rejected the theory of Aristotle that the force of gravity got weaker as you got further away from the Earth.
Al-Biruni did not know the moon had gravity until a Hindu told him about tides.
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