In Chapter 3 of the Fabric of the Cosmos, the differences between Newton’s and Einstein’s theories are compared. The difference between the two theories lies in the constants each of them have. Newton says that time must be the constant in the universe while Einstein says that the speed of light is the constant in the universe. In the first section of the reading, Newton’s theory is discussed. I can understand how he would think that time is constant simply because time travel seems so unrealistic. Einstein’s theory is based of the idea that light moves constantly regardless of the frame of reference it is in. Because of the simple equation speed = distance x time, assuming Einstein is right and the speed of light always moves constantly, time can be distorted and changed. This concept is not easy for me to understand, but Einstein’s logic behind this makes sense and also makes this theory/accepted idea very intriguing.