An Analysis of the book
In The Elegant Universe, many theoretical physics topics are brought up. So far, three main topics that really interested me included How relative motion affects time, the acceleration and warping of gravity, and the general theory of relativity. First, the books topic of the relativity of motion and time is very interesting. Basically, the faster an object travels relative to another object, the clock for the first object will run slower than the object that is traveling slower than it. In the book, an example of this is shown with two people in space suits. To set the stage for this example, two people, George and Gracie are in a frictionless space, and both have clocks. To test this theory out, they both go opposite directions, starting their clocks at the same time. With no objects around them, they feel like they are at rest, though moving away from each other. If George wants to meet up again to compare clocks, he must use his jetpack to turn around and catch up with Gracie. If he does this, the perspectives of motion will be different due to the fact that George will be accelerating towards Gracie. Thus he will observe a force of acceleration and no longer be at rest. The book then states a more concrete example
“Imagine that the relative speed of George and Gracie when they pass and are moving apart is 99.5 percent of light speed. Further, let's say that George waits 3 years, according to his clock, before firing up his jet-pack for a momentary blast that sends him closing in on Gracie at the same speed that they were previously moving apart, 99.5 percent of light speed. When he reaches Gracie, 6 years will have elapsed on his clock since it will take him 3 years to catch her. However, the mathematics of special relativity show that 60 years will have elapsed on her clock” (Greene 44,45).
To explain this in a more basic manor, essentially, if you are moving faster than the object relative to you, your observable time is slowed in comparison to the other. Secondly, another of many theories in the book that interest me include the acceleration and warping of objects due to acceleration. The book, to explain a form of this, targets the tornado ride that is commonly found at amusement parks. For those who may not know, when on the tornado ride, the rider stands on the edges, with their back against the circular wall. The ride spins and the rider will feel this motion but will also be pulled away from the center of the circle. From a stationary view, one could measure the circumference and radius with ease using simple geometry. However, if the measurements were taken on the ride itself, they would come out differently. The book explains the phenomenon of contracting objects due to acceleration very well,
“... we ask Slim and Jim, who are currently enjoying a spin on the Tornado, to take a few measurements for us. We toss one of our rulers to Slim, who sets out to measure the circumference of the ride, and another to Jim, who sets out to measure the radius… As slim begins to measure the circumference, we immediately see from our bird's eye perspective that he is going to get a different answer than we did. As he lays the ruler out along the circumference, we notice that the ruler’s length is shortened. This is nothing but the Lorentz contraction discussed in chapter 2, in which the length of an object appears shortened along the direction of its motion. A shorter ruler means that he will have to lay it out, head to tail-more times to traverse the whole circumference. Since he still considers the ruler to be one foot long (since there is not relative motion between Slim and his ruler, he perceives it as having its usual length of one foot), this means that Slim will measure a longer circumference than we did. What about the radius? Well, Jim also uses the head to tail method to find the length of a radial strut, and form our bird’s eye view we see that he is going to get the same answer we did. The reason is that the ruler is not pointing along the instantaneous direction of the motion of the ride (as it is when measuring the circumference.). Instead it is pointed at a ninety- degree angle to the motion, and therefore it is not contracted along its length. Jim therefore will find exactly the same radial length as we did ( Greene 62, 63, 64).
Thirdly, another theory would be the general theory of relativity. Once again, in order to start grasping the subject, we must first understand Newton's perception of gravity. In Newtonian gravity, it is based on a flat plane and everything that has mass exerts a force of gravity. Greene helps visualize this type of gravity on a gridded plane, much like a 2d road map. With this in mind, we can start to talk about the view of Einstein's theory of gravity. Einstein essentially took Newton's view of gravity, the 2d plane, and changed it in a way. Rather than being apart of the plane, the mass, such as the sun, the mass sits on top of the plane and pushes down on it. Greene explains it as a bowling ball sitting on a sheet of rubber. The bending rubber would then act as the warping of gravity, which is truly the warping of space and time. Greene explains it further stating
“A useful, and oft-quoted, analogy is that much like a rubber membrane on which a bowling ball has been placed, the fabric of space becomes distorted due to the presence of a massive object like the sun. According to this radical proposal, space is not merely a passive forum providing the arena for the events of the universe; rather, the shape of space responds to objects in the environment. This warping in turn, affects other objects moving in the vicinity of the sun, as they now must traverse the distorted spatial fabric. Using the rubber membrane-bowling ball analogy, if we place a small ball-bearing on the membrane and set it off with some initial velocity, the path it will follow depends on whether or not the bowling ball is sitting in the center. If the bowling ball is absent, the rubber membrane will be flat and the ball bearing will travel along a straight line. If the bowling ball is present and thereby warps the membrane, the ball bearing will travel along a curved path. In fact, ignoring friction, if we set the ball bearing moving with just the right speed in just the right direction, it will continue to move in a recurring curved path around the bowling ball- in effect, it will “go into orbit.” Our language presages the application of his analogy to gravity”(Greene 68, 69 )
Through the duration of my life I always looked at the stars and pondered. Reading this book has been a really neat experience, because what I am reading is affecting and happening right then and there. Especially learning about matter that literally can pass through you like a ghost, but that is for a different day to explain.
Sources:
Greene, B. The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory. New York: W.W. Norton, 1999. Print.
“Imagine that the relative speed of George and Gracie when they pass and are moving apart is 99.5 percent of light speed. Further, let's say that George waits 3 years, according to his clock, before firing up his jet-pack for a momentary blast that sends him closing in on Gracie at the same speed that they were previously moving apart, 99.5 percent of light speed. When he reaches Gracie, 6 years will have elapsed on his clock since it will take him 3 years to catch her. However, the mathematics of special relativity show that 60 years will have elapsed on her clock” (Greene 44,45).
To explain this in a more basic manor, essentially, if you are moving faster than the object relative to you, your observable time is slowed in comparison to the other. Secondly, another of many theories in the book that interest me include the acceleration and warping of objects due to acceleration. The book, to explain a form of this, targets the tornado ride that is commonly found at amusement parks. For those who may not know, when on the tornado ride, the rider stands on the edges, with their back against the circular wall. The ride spins and the rider will feel this motion but will also be pulled away from the center of the circle. From a stationary view, one could measure the circumference and radius with ease using simple geometry. However, if the measurements were taken on the ride itself, they would come out differently. The book explains the phenomenon of contracting objects due to acceleration very well,
“... we ask Slim and Jim, who are currently enjoying a spin on the Tornado, to take a few measurements for us. We toss one of our rulers to Slim, who sets out to measure the circumference of the ride, and another to Jim, who sets out to measure the radius… As slim begins to measure the circumference, we immediately see from our bird's eye perspective that he is going to get a different answer than we did. As he lays the ruler out along the circumference, we notice that the ruler’s length is shortened. This is nothing but the Lorentz contraction discussed in chapter 2, in which the length of an object appears shortened along the direction of its motion. A shorter ruler means that he will have to lay it out, head to tail-more times to traverse the whole circumference. Since he still considers the ruler to be one foot long (since there is not relative motion between Slim and his ruler, he perceives it as having its usual length of one foot), this means that Slim will measure a longer circumference than we did. What about the radius? Well, Jim also uses the head to tail method to find the length of a radial strut, and form our bird’s eye view we see that he is going to get the same answer we did. The reason is that the ruler is not pointing along the instantaneous direction of the motion of the ride (as it is when measuring the circumference.). Instead it is pointed at a ninety- degree angle to the motion, and therefore it is not contracted along its length. Jim therefore will find exactly the same radial length as we did ( Greene 62, 63, 64).
Thirdly, another theory would be the general theory of relativity. Once again, in order to start grasping the subject, we must first understand Newton's perception of gravity. In Newtonian gravity, it is based on a flat plane and everything that has mass exerts a force of gravity. Greene helps visualize this type of gravity on a gridded plane, much like a 2d road map. With this in mind, we can start to talk about the view of Einstein's theory of gravity. Einstein essentially took Newton's view of gravity, the 2d plane, and changed it in a way. Rather than being apart of the plane, the mass, such as the sun, the mass sits on top of the plane and pushes down on it. Greene explains it as a bowling ball sitting on a sheet of rubber. The bending rubber would then act as the warping of gravity, which is truly the warping of space and time. Greene explains it further stating
“A useful, and oft-quoted, analogy is that much like a rubber membrane on which a bowling ball has been placed, the fabric of space becomes distorted due to the presence of a massive object like the sun. According to this radical proposal, space is not merely a passive forum providing the arena for the events of the universe; rather, the shape of space responds to objects in the environment. This warping in turn, affects other objects moving in the vicinity of the sun, as they now must traverse the distorted spatial fabric. Using the rubber membrane-bowling ball analogy, if we place a small ball-bearing on the membrane and set it off with some initial velocity, the path it will follow depends on whether or not the bowling ball is sitting in the center. If the bowling ball is absent, the rubber membrane will be flat and the ball bearing will travel along a straight line. If the bowling ball is present and thereby warps the membrane, the ball bearing will travel along a curved path. In fact, ignoring friction, if we set the ball bearing moving with just the right speed in just the right direction, it will continue to move in a recurring curved path around the bowling ball- in effect, it will “go into orbit.” Our language presages the application of his analogy to gravity”(Greene 68, 69 )
Through the duration of my life I always looked at the stars and pondered. Reading this book has been a really neat experience, because what I am reading is affecting and happening right then and there. Especially learning about matter that literally can pass through you like a ghost, but that is for a different day to explain.
Sources:
Greene, B. The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory. New York: W.W. Norton, 1999. Print.