section_path: History/Medieval European and Islamic
section_name: Medieval European and Islamic
paragraph_text: Medieval European and Islamic
  
  The Western Roman Empire fell in the fifth century, and this resulted in a decline in intellectual pursuits in the western part of Europe. By contrast, the Eastern Roman Empire (usually known as the Byzantine Empire) resisted the attacks from the barbarians, and continued to advance various fields of learning, including physics.
  
  In the sixth century, Isidore of Miletus created an important compilation of Archimedes ' works that are copied in the Archimedes Palimpsest.
  
  In sixth-century Europe John Philoponus, a Byzantine scholar, questioned Aristotle 's teaching of physics and noted its flaws. He introduced the theory of impetus. Aristotle's physics was not scrutinized until Philoponus appeared; unlike Aristotle, who based his physics on verbal argument, Philoponus relied on observation. On Aristotle's physics Philoponus wrote:
  
  But this is completely erroneous, and our view may be corroborated by actual observation more effectively than by any sort of verbal argument. For if you let fall from the same height two weights of which one is many times as heavy as the other, you will see that the ratio of the times required for the motion does not depend on the ratio of the weights, but that the difference in time is a very small one. And so, if the difference in the weights is not considerable, that is, of one is, let us say, double the other, there will be no difference, or else an imperceptible difference, in time, though the difference in weight is by no means negligible, with one body weighing twice as much as the other
  
  Philoponus' criticism of Aristotelian principles of physics served as an inspiration for Galileo Galilei ten centuries later, during the Scientific Revolution. Galileo cited Philoponus substantially in his works when arguing that Aristotelian physics was flawed. In the 1300s Jean Buridan, a teacher in the faculty of arts at the University of Paris, developed the concept of impetus. It was a step toward the modern ideas of inertia and momentum.
  
  Islamic scholarship inherited Aristotelian physics from the Greeks and during the Islamic Golden Age developed it further, especially placing emphasis on observation and a priori reasoning, developing early forms of the scientific method.
  
  Although Aristotle's principles of physics was criticized, it is important to identify the evidence upon which he based his views. Aristotle's science was the backbone of the science taught in schools today. Aristotle published many biological works including The Parts of Animals, in which he discusses both biological science and natural science. Aristotle played an important role in the progression of physics and metaphysics, and his beliefs and findings are still taught in science classes today. The explanations that Aristotle gives for his findings are also simple.
  
  When thinking of the elements, Aristotle believed that each of the four classical elements (earth, fire, water, air) had its own natural place. Because of their differing densities, each element will revert to its own specific place in the atmosphere. So, because of their weights, fire would be at the top, air underneath fire, then water, then lastly earth. He also stated that when a small amount of one element enters the natural place of another, the less abundant element will automatically go towards its own natural place. For example, if there is a fire on the ground, the flames go up into the air as an attempt to go back into its natural place where it belongs. Aristotle called his metaphysics "first philosophy" and characterized it as the study of "being as being". Aristotle defined the paradigm of motion as a being or entity encompassing different areas in the same body. Thus, a person who is at a location (A) can move to a new location (B) and still take up the same amount of space. This is involved with Aristotle's belief that motion is a continuum. In terms of matter, Aristotle believed that the change in category (e.g. place) and quality (e.g. color) of an object is defined as "alteration". But, a change in substance is a change in matter. This is also similar to the idea of matter today.
  
  He also devised his own laws of motion that include 1) heavier objects will fall faster, the speed being proportional to the weight and 2) the speed of the object that is falling depends inversely on the density object it is falling through (e.g. density of air). He also stated that, when it comes to violent motion (motion of an object when a force is applied to it by a second object) that the speed that object moves, will only be as fast or strong as the measure of force applied to it. This is also seen in the rules of velocity and force that is taught in physics classes today. These rules are not necessarily what is described in physics today but, they are mostly similar. It is evident that these rules were the backbone for other scientists to revise and edit his beliefs.
  
  The most notable innovations under Islamic scholarship were in the field of optics and vision, which came from the works of many scientists like Ibn Sahl, Al-Kindi, Ibn al-Haytham, Al-Farisi and Avicenna. The most notable work was The Book of Optics (also known as Kitāb al-Manāẓir), written by Ibn al-Haytham, in which he presented the alternative to the ancient Greek idea about vision. In his Treatise on Light as well as in his Kitāb al-Manāẓir, he presented a study of the phenomenon of the camera obscura (his thousand-year-old version of the pinhole camera) and delved further into the way the eye itself works. Using the knowledge of previous scholars, he began to explain how light enters the eye. He asserted that the light ray is focused, but the actual explanation of how light projected to the back of the eye had to wait until 1604. His Treatise on Light explained the camera obscura, hundreds of years before the modern development of photography.
  
  The seven-volume Book of Optics (Kitab al-Manathir) influenced thinking across disciplines from the theory of visual perception to the nature of perspective in medieval art, in both the East and the West, for more than 600 years. This included later European scholars and fellow polymaths, from Robert Grosseteste and Leonardo da Vinci to Johannes Kepler.
  
  The translation of The Book of Optics had an impact on Europe. From it, later European scholars were able to build devices that replicated those Ibn al-Haytham had built and understand the way vision works.