아리스토텔레스와 갈릴레오의 운동론 비교

Abstract

The dynamics of Galileo and Aristotle were compared and analyzed in terms of (1) falling motion, (2) motion of projectiles and (3) concepts of inertia to investigate the historical meaning of Galilean dynamics. (1)Falling motion : The falling motion of Aristotle was related not only to his view of nature but his view of materials. He classified motion into natural motion, which began from the nature of the object, and forced motion, which was forced to move due to external power. On the other hand, the dynamics of Galileo started from observations and measurements. Aristotle considered that the speed of a falling object was in proportion to the weight of the object but in inverse proportion to the resistance of the medium. In contrast to the dynamics of Aristotle, Galileo explicated that the falling speed had in no relation to the weight, but was related to the medium with the speculative experiment under an idealized condition of a vacuum. Therefore, Galileo made a basis for early modern science by explicating the relationship among variables with idealized conditions and experiments. (2)Motion of the projectile : Aristotle was not able to explain the trajectory of the projectile motion such as a parabola motion since he explained that the forced and natural motions were independent and could not work on an object at the same time. In projectile motion, an object fell down to earth as the natural motion when the forced motion quit. On the other hand, Galileo was able to deconstruct the complicated motion into simple elements. The projectile motion consisted of the mixture of horizontal motions and uniformly accelerated diagonal motions, which described the trajectory of a projected object mathematically. (3)Concept of inertia : About the rotation of the earth, Aristotelians raised the question why an object dropped from the top of a tower falls down on the same point on the earth although it should fall down in the different direction based on the rotation of the earth. In order to solve this problem, Galileo introduced a new concept of inertia. He explained that the motion of a dropped object has the same form as the motion after the object passed the highest point in the projectile motion since the tower and the object rotate along as the earth rotates. As we have seen so far, whereas Aristotle, seeing motion as having a cause-effect relationship, started from commonsense and empirical observation, and then reached a generalization through rational speculation, Galileo, seeing motion as a state, idealized conditions, and generalized using mathematical and experimental methods. This can be said to be a paradigm shift as it shows that Aristotle’s and Galileo’s viewpoints and methods of motion are completely different from each other. Therefore, Galileo is often called the father of early modern science.