Who Proposed the Planetary model | History of Planetary model

Al-Urdi, was a 13th-century Arab astronomer and mathematician who is credited with inventing a mechanical planetary model that was later used as the basis for similar models built by European astronomers like Tycho Brahe and Nicolaus Copernicus.

Al-Urdi's planetary model was based on the geocentric cosmology of Ptolemy, which held that the Earth was at the center of the universe and that the planets and stars moved in circles around it. However, unlike Ptolemy's model, which relied on a complex system of epicycles and deferents to explain the irregular motion of the planets, Al-Urdi's model used a series of nested spheres to represent the movements of the celestial bodies.

The core of Al-Urdi's planetary model consisted of a set of nine spheres, each representing one of the known celestial bodies at the time: the Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn, and the fixed stars. The spheres were arranged in a specific order, with the Moon closest to the Earth and the fixed stars furthest away.

Each sphere was mounted on a series of concentric rings that were connected by a system of gears and cogs. The outermost ring was driven by a crank, which caused all of the spheres to rotate at different speeds and in different directions, simulating the complex motion of the planets as seen from Earth.

Al-Urdi's planetary model was a remarkable achievement for its time, and it demonstrated a deep understanding of the principles of mechanics and astronomy. It also paved the way for future generations of astronomers to refine and improve upon his design, eventually leading to the development of the heliocentric model of the solar system 

Al-Urdi's mechanical planetary model was a complex system of nested spheres that represented the movements of the celestial bodies in the geocentric cosmology of Ptolemy. The model was designed to simulate the motion of the planets as seen from Earth, using a series of gears and cogs to drive the rotation of the spheres.

The core of Al-Urdi's model consisted of a set of nine spheres, each representing one of the known celestial bodies at the time: the Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn, and the fixed stars. The spheres were arranged in a specific order, with the Moon closest to the Earth and the fixed stars furthest away.