One of his main claims is that darkness is necessary for the human body to function properly. He goes on to say “ Our bodies need darkness to produce the hormone melatonin, which keeps certain cancers from developing, and our bodies need darkness for sleep. Sleep disorders have been linked to diabetes, obesity, cardiovascular disease and depression, and recent research suggests one main cause of “short sleep” is “long light.”” (Bogard). Although the reader may not have a complete understanding of these foundations these improve the credibility of the author which is the use of ethos. These credible sources and their research work allows us as readers to dive deeper and acknowledge the publishing for its