Bethany Tanner Who is the most influential physicist in history? The world around us is constantly surprising us and inviting us to explore in further depth the universe's wonderful mysteries. Throughout time there have been many great and famous physicists who have helped unravel and explain the puzzling parts of our world and who have had a big impact on our scientific knowledge and understanding. These physicists are all inspirational figures to the young aspiring physicists of today In this essay I will be discussing three physicists from different periods of time who between them have influenced many aspects of modern day physics. I will be providing the rationale to argue who in my opinion is the most influential physicist in history? Starting off with the Greeks and possibly one of the most influential physicists of his time, there is Aristotle (384 to 322 BC). Aristotle was a student of Plato and a teacher to Alexander the great. He initiated a different way of scientific thinking and his expertise stretched much further than being a physicist, with other great work in areas including music, logic, poetry, theatre, biology and most famously his philosophical writings. Aristotle’s work can be thought of as encompassing three different categories, theoretical sciences, practical sciences and scientific method. Theoretical science includes topics such as natural philosophy and metaphysics. The following is a quote from Aristotle on metaphysics, “And here we will have the science to study that which is just as that which is, both in its essence and in the properties which, just as a thing is, it has. The entire preoccupation of the physicist is with things that contain within themselves a principle of movement and rest. And to seek for this is to seek for the second kind of principle that from which comes the beginning of the change”. [1] In metaphysics the aim is to find a link, for example when you drop a ball it moves towards the earth, what is the link that causes this? In metaphysics these links are identified but not necessarily fully understood. Aristotle wanted to understand how things worked and not just that they existed. Aristotle however experienced conflict when he went against the ideas of his teacher, Plato. Plato believed that: “the material universe exists only as an inferior imitation of the forms as they exist in the immaterial world of ideas”. Plato believed that the visible world, the world which is observed by senses, is not actually real and therefore information that is sensed could not be used as a source of knowledge. Plato thought this because firstly the things in the real world are always changing and in a constant state of change (e.g. a river), secondly because any observations made would be subjective (e.g. they would by people’s prior beliefs and experiences) and thirdly because the observations would never be a perfect representation (e.g. a drawing would only represent not replicate an object). Plato believed that knowledge could be best acquired through something intelligible (something we know by thinking not by observing). He valued the exchange and analysis of opinions between intellectuals and thought that by using this approach concepts could be fully understood. Unlike Plato, Aristotle believed that what can be sensed and what is visible is the real world. Aristotle departed from Plato’s view by having a high regard for the physical world as a source of information. He was possibly the first empirical scientist as he believed that concepts could be best understood by means of experimentation. I believe that Aristotle’s most important contribution to Physics is the development of empirical scientific methods which helped improve the process of scientific understanding of many people. His scientific method known as the Organon is composed of six different writings including the Analytica Priora. The fundamentals of this method still form the basis of scientific thinking today. The Analytica Priora method examines two statements and then looks to see if a third coincides with them. When the third statement agrees, Aristotle called this the logical structure of a syllogism. This method is used today for such things Bethany Tanner as working out how much someone should be paid. Although I believe that it was good that Aristotle took the revolutionary step to explore the real world further through observation, perhaps Aristotle was not the most influential physicist in history. Many of the great discoveries have been made after learning from the mistakes of the previous generations and Aristotle had very limited work to build upon. However what he did achieve was the development of a highly organised approach to the development of scientific theories with his methods laying the foundations for future scientists. The second physicist I will discuss is Sir Isaac Newton. Newton was an English man from Kensington who lived from 1643 to 1727. As well as working in physics he was a mathematician, astronomer and similar to Aristotle, a natural philosopher. He has made many contributions to the working world of physics defining the foundations of classical mechanics as well as some of his most famous works on the three laws of motion and universal gravitation. He was even “considered to be the greatest and most influential scientist who ever lived” [2] by Burt Daniel S and has even been given the name of “father of modern society’. Newton was a student at Cambridge but after an outbreak of the plague the university was closed. It was during this time that Newton started to develop his three laws of motion. He built upon Galileo’s principle of inertia in the process of coming up with his first law, improving Galileo ideas to produce a more suitable and correct idea, Newton quotes “If I have seen further than other, it is by standing upon the shoulders of giants”. The first law states: Bodies move in a straight line with a uniform speed, or remain stationary, unless a force acts to change their speed or direction. This law provides us with a basic understanding of force and motion. His second law of motion builds a connection between the size of a force and the acceleration that force may produce. Objects with large inertia need more force to accelerate them than light objects. Expressed algebraically, Newton’s second law can be shown as F=ma so in other words, for constant acceleration, force per unit of mass is also unchanged. So the same amount of force is needed to move a kilogram whether it’s part of a big or a small object. Again Newton used the work of Galileo and proves Galileo’s imaginary experiment of what would hit the ground first if both were dropped at the same time, a cannon ball or a feather? We know that dues to air resistance the cannon ball would hit the ground first because the feather would drift slowly down. However if there was no air, they would fall at the same speed. We have even been able to see this happening when in 1971 the astronauts aboard Apollo 15, drop a feather and a hammer at the same time while on the surface on the moon and found that they did indeed fall at the same speed. Newton’s third law of motion states that every action has and equal and opposite reaction. When a marksman shoots a gun he feels the force of the gun recoiling against his shoulder, this force is equal to the original force that pushed the bullet out. I think that in addition to his work on the three laws of motion his law of gravitation have made an outstanding contribution to physics. It is said that Newton first thought of the idea of gravity after he saw an apple fall from a tree. Whether this is true or not, Newton came up with an idea that stretched his imagination beyond the earth’s boundaries to help work out the laws of gravitation. Newton developed the idea that objects that fall to the ground must have some sort of accelerating force acting upon them. Newton used his laws of motion in trying to work out what this accelerating force was that was making objects fall to the ground. He used the idea of a cannon ball being blasted, the cannon ball will travel a certain distance before it hits the ground. If the cannon ball is fired more quickly it will travel further. Newton kept questioning how the speed at which the ball is fired will affect how long it will travel for. So Bethany Tanner what would happen if the cannon ball was fired so quickly that it travelled far enough in a straight line that the Earth curved beneath it? Newton realised that it would be pulled toward s the Earth by following a circular orbit. Connecting the links even more, Newton thought about how the moon hung in the sky, and concluded that his it must be held in an orbiting position around the earth by gravity, otherwise it would just float off into space. Newton then went through a process of trying to quantify his predictions. He collaborated with other physicists and after an exchange of letters with Robert Hooke, Newton looked at the mathematical side of gravity. He noticed that gravity followed the inverse square law “Every object in the universe attracts every other object along a line of the centres of the objects, proportional to each object’s mass, and inversely proportional to the square of the distance between the objects.”[3] Newton defined the inverse square law of gravity which explains the orbits of all the planets as described in the three laws of Johannes Kepler.