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Greeks measuring angles during different phases of the moon attempted to measure the ratio of the distance to the sun and the distance to the moon. Their calculation, which was copied by Muslims, was off by a factor of ten.
Because al-Battani assumed that heavenly bodies traveled at constant, his calculated percentage variation in the distance between the Earth and the sun was about double the variation.he observed.
Al-Battani accurately wrote down the difference in time between 2 consecutive eclipses of the sun. Edmond Halley around the year 1693 did the same, discovering the moon was taking a longer time to go once around the Earth than it had around the year 1100.
Al-Biruni had read works of the 5th century Hindu astronomer Aryabhata who claimed the planets and the moon do not have their own light.
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astronomers of the Islamic Golden Age thought that heavenly bodies were intelligent beings capable of thinking.
GREEKS CALCULATED DIAMETER OF MOON FROM ECLIPSE DATA
The solar eclipse of 129 BC had been a total eclipse in Syene but only 4/5 of the sun had been covered in Alexandria. By measuring angles and applying distances between the 2 cities, Hipparchus in the 2nd century BC calculated the distance from the Earth to the moon. From this, he calculated the actual diameter of the moon.
DIAMETER OF THE MOON
Aristarchus of Samos, in the 3rd century BC, had made measurements of what the angles were between the sun, moon, and Earth when the moon became exactly half lit. Using geometry, he calculated an estimate of how many times further away the sun was than the moon, but this estimate gave a value of 1/15 (later revised to 1/10) of what we now know the distance is.
Due to the angles being very small, he was actually calculating the minimum of how far away the sun was, and his personal beliefs prevented him from even considering that the sun could be further away than that.
MUSLIMS COPYING HINDU NONSENSE ABOUT DIAMETER
The astronomers Yaʿqūb ibn Ṭāriq (in the 8th century) and Sind ibn Ali (in the 9th century) copied from Hindu astronomers complete nonsense that the moon’s diameter was 5 times the diameter of the Earth.
Because al-Battani assumed in his model that the sun traveled in a perfectly circular path at constant speed around a point not exactly at the Earth, his calculated percentage variation in the distance between the Earth and the sun was about double the actual variation.
As a result, he incorrectly predicted the variation in how much of the sun is hidden by the moon during an eclipse.
Al-Mahani in the 9th century wrote down the time and date of eclipses.
Al-Zarqālī published tables that could be used to predict solar and lunar eclipses.
Around the year 1100,
Al-Battani accurately wrote down the difference in time between 2 consecutive eclipses of the sun. Edmond Halley around the year 1693 did the same, discovering the moon was taking a longer time to go once around the Earth than it had around the year 1100. Eventually, scientists determined that this was caused by the gravitational attraction of high tide in the Earth’s oceans causing the moon to accelerate (in kilometers per hour), putting the moon into a higher orbit, slowing down how long it takes the moon to go once around the Earth.
ARISTOTLE ON PATH OF MOON
Aristotle wrote that the path of the moon around the Earth was a perfect circle with the moon moving at a constant speed. Later astronomers made the center of the circle not exactly the Earth.
EPICYCLES IN PATH OF THE MOON
The equant was used to explain the elliptical orbit of the Moon, moving faster at perigee and slower at apogee than circular orbits would,
PATH OF THE MOON
Al-Tusi sought to confirm that Allah had created a perfect universe with only circles but no ovals. This is why he had difficulties explaining why the observed motion of the moon did not match his theory of perfect circles, refusing to accept that the path of the moon around the Earth was an oval.
In the late 14th century, Ibn al-Shatir made improvements to the calculation of the path of the moon.
Ibn al-Shatir’s theory agreed better with observations, by rejecting the concept that the moon was moving around the Earth in a perfectly circular path at constant speed around a point that was not the center of the Earth.
Evection (formerly called the moon’s second anomaly) was written about by Indian astronomers and by Ptolemy, but they and the Muslim astronomers did not know it was caused by the gravity of the sun.
Abū al-Wafā’ Būzjānī did not discover the 3td inequality in the moon’s motion later called variation.
Al-Biruni had read works of the 5th century Hindu astronomer Aryabhata. (Aryabhata claimed the planets and the moon do not have their own light.)
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