The Cosmic Story of the Middle Ages

Through the development of rationalism since the days of Ancient Greek philosophers, gradually the mythological cosmic story was replaced by a more rational cosmic story, although still colored by philosophical speculation. The philosophers who play here, for example, are Thales of Miletus who argues that the earth lies floating on the water. Based on data he obtained from Babylonian observers also succeeded in predicting a solar eclipse event. Another character, for example, is Anaxagoras who thinks that the Sun is a burning iron ball. In addition, there is also a character named Empedocles who believe that the universe shaped like an egg and dominated by love and hate in turn).

After these figures came to Pythagoras who lived around the sixth century BC. According to Diogenes who lived in the second century AD, he was the first to declare that the earth was a sphere, and the sky was the cosmos.

He describes the universe as having geometric order and governed by mathematical laws. He believes that the universe is geometrical, all of its spherical members move around a "Central Fire" in a circular trajectory. He goes on to say that in the movement of heavenly bodies it produces certain notes that can not be heard by ordinary people.

Another very influential figure is Plato. He can be regarded as a figure that bridges mythological thinking with a scientific thought in understanding the universe that reached its peak through the thinking of Copernicus and Kepler two thousand years later.

Plato has the idea that the world (the universe) is divided into two, namely the real world and the world of ideas. The real world is a world that we perceive through sensual observation, and there we can see all the chaos, disorder, and dissonance. Instead, the world of ideas is the underlying world of the real world, where in this world everything is perfect, orderly and harmonious. This world of ideas can never be absorbed by sensual experience but through philosophical deepening.

Further, Plato argues that the sky and all its contents are the manifestations of the world of ideas closest to the observation of human senses. Therefore, he strongly recommends that humans learn astronomy in order to better understand what it is actually the world of ideas. For the philosophy of the Platonic school, the ultimate goal to do is to find the afterlife behind the mortal and discover the laws that govern everything that goes on in the universe. This spirit is in existence today, especially in the quest for human beings to discover the basic laws governing the dynamics of all elements of the inhabitants of the universe.

Plato's view of heavenly bodies and their movements follows his philosophy. Because he argues that the most perfect geometric shape is a circle and a sphere, then he thinks that all the celestial bodies are spherical and orbit the Earth in a circular trajectory.

After Plato, an important figure is Aristarchus of Samos. Using certain geometric arguments he estimates the size of the sun and he concludes that the sun's size is much larger than Earth's. From here he then thinks that an object is not possible around other objects that are much smaller in size. He then concludes that the Earth must be turning on its axis to explain the motion (pseudo) of the stars. Aristarchus has put forward the points of Copernicus theory
17 centuries before the birth of Copernicus. This view was rejected by Aristotle, because if the earth spins how can an object be thrown up will fall again in its original place? Also, why does this Earth's rotation not produce very strong winds? It is these things that made the heliocentric theory (the Sun that became the center of the universe) Aristarchus was not accepted until the time of Copernicus. Aristotle was a philosopher who could be paralleled with Plato in terms of the effects it caused. His view of the universe is a synthesis of the views of his predecessor.

According to Aristotle, the Earth is the center of the universe and is in a state of silence, which becomes the center of the rotation of all heavenly bodies. The whole universe is surrounded by a ball that places the stars. Aristotle's cosmology is based on his view of the movement of elements in nature. Heavy elements (water and soil) tend to move toward the center of the universe (in this case Earth), whereas lighter elements, namely air and fire tend to move away from the center of the universe. The lighter element in Aristotle's view is the ether that forms the foundation of the heavens. In an attempt to apply his thoughts to the movement of heavenly bodies, Aristotle constructed a geometric system made up of 55 Earth-centered balls capable of explaining and predicting the movement of stars and planets.

In this age of Aristotle lived also a philosopher named Eudoxus. He began to observe that the planets move irregularly. To clarify this he argues that each planet lies in a concentric sphere (centered on Earth), and moves at a speed and has a different axis of rotation. Here the stars are in a silent outer circle. This is the first scientific attempt to explain the irregular movement of the planet. Some time after Aristotle lived a man named Claudius Ptolomeus who lived around the year 140. This figure is trying to refine Aristotelian thinking which then poured in his work entitled Almagest (Big System). In this book Ptolomeus's writings are written about his epicycle theory (epicycle). It is depicted that all celestial bodies move around a point, and the trajectory of this thing is called an episode. The episode moves in a larger circle and is called deferent. The earth is not located in the center of the deferent; it lies not too far from the deferent center at the point called equant. This model was made by Ptolemy among others to explain the motion of retrograde Mars. Though very complicated, this epicycle system proved to last very long (14th century) until the heliocentric system by Nicolaus Copernicus in his book De Revolutionibus Orbium Coelestium in the year 1543.

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