Who or what created the universe? How did it start? Humans have always wondered: has the universe always existed as we see it now, or did it somehow suddenly begin? In the last century it was discovered that the universe was expanding and people wondered why. These are the questions that the Big Bang theory tries to answer. Although no one is completely sure of all the details, the big bang is the most widely accepted theory about the beginning of our universe. The big bang theory states that the universe began by expanding from an infinitesimal volume with extremely high density and temperature. Initially it was smaller than the head of a pin. The theory states that space was created at the same time as the Big Bang and expanded, taking matter with it. Many physicists believe that time began with the big bang. The evidence for the big bang was so great that in 1951 the Catholic Church declared that the big bang model conformed to the Bible. One of the first discoveries made in support of the big bang model was the discovery that the universe was expanding. An astronomer named Vesto Slipher observed that there are more galaxies receding from the earth than are approaching it. Physicists know that a galaxy is approaching or receding by looking at the spectrum of its light. If its spectrum is towards the shorter wavelength, called blueshift, then the galaxy is moving closer and if its spectrum is towards the longer wavelength, called redshift, then the galaxy is moving away. The amount of displacement depends on the speed with which the object is approaching or receding. Slipher observed more galaxies whose spectra were red-shifted than those whose spectra were blue-shifted. Further support emerged in the late 1920s, when Ed...... middle of paper... big bang provides a clear picture of how the universe began. Looking back at the expanding universe, scientists can imagine a hot and violent start to the universe. Furthermore, the high temperatures from the beginning give an explanation for the high quantity of helium and even the existence of deuterium. Additionally, scientists were able to detect faint radiation from the big bang. The theory that the universe began with a big bang is essentially conclusive and could prove to be one of humanity's greatest astronomical discoveries. Works Cited Big Bang: How Did the Universe Begin?" Ugcs.caltech.edu. Web. April 27, 2014. · THE BIG BANG:" Umich.edu. Network. 20 Apr. 2014· "Philosophy of science". http://www.csus.edu/. Network. April 21, 2014. · "Technology sees the birth of the universe." NASA Jet Propulsion Laboratory. Network. April 27. 2014.