The beginning of our universe has sparked much speculation over the many years of human existence. Many theories have been proclaimed over the centuries, although one of them is the most popular in the scientific world. The Big Bang theory is best known when it comes to the creation of the existing cosmos. The Big Bang theory is based on the idea that the entire universe was compressed into an extremely dense and hot state. It is believed that this state was only a few millimeters wide. It existed for about a fraction of a second before its expansion began. A giant explosion occurred ten to twenty billion years ago, creating the expanding universe. This explosion was caused by an unknown form of ancient energy. A trillion billion seconds after this explosion, the universe began to expand at an enormous speed. The universe continues to expand today, but at a much slower rate. At the time of the big bang, the temperature was around ten billion degrees Fahrenheit. After the big bang, various different particles began to form. At the very beginning, there were no particles; there was only an equal amount of antimatter and matter. As the cosmos continued to expand, new particles began to materialize. These new atoms were called baryons. . These new atoms were called baryons. Baryons were made up of photons, neutrinos, electrons and quarks. These particles became the foundations of all the diverse particles in our universe. Baryons paved the way for the most common particles we know today, like protons and neutrons. When the universe cooled a bit, protons and neutrons began to form. Protons and neutrons have been classified as hadrons. Protons and middle of paper ...... help prove the Big Bang theory, like Arno Penzias and Robert Wilson. Arno Penzias and Robert Wilson had discovered the existence of the cosmic microwave background, which is essentially a remnant of early light in our universe from the Big Bang. The Big Bang theory has a long history and its discovery can be attributed to two scientists and/or cosmologists. The Big Bang theory has significantly changed the course of the scientific world over the past century. Before the Big Bang was theorized, many scientists believed that the universe was unchanging and static. The Big Bang Theory not only taught us how the universe began, but also its age and the fact that our universe continues to expand after 13.8 billion years of its existence. The Big Bang theory has played a major role in the exploration and study of our universe.