Chapter four of the Fabric of the Cosmos introduces quantum mechanics. Quantum mechanics is a very interesting topic because according to it, we can not predict the exact location and exact velocity of even a single particle in the universe. I find this concept difficult to understand. One of the most interesting concepts in the chapter was the nonlocality described by the red and blue boxes. It is intriguing to think that even though two separate things can randomly occur in space yet have a similar affect between them. After reading about quantum mechanics, I have realized that even today, there are still many things to learn in the world of physics. For example, in space it is unknown why the two boxes would randomly appear the same color. This reading also went on to explain that light is a wave. It was previously thought that light was not a wave, but due to the finding of Davisson and Germer, interference patterns can be found when beaming particles through two slits. Rather than appearing at two expected locations behind the slits, an interference pattern was formed, proving that light was a wave.