One of the challenges that historians face is the issue of time. When an event, for example Dred Scott v. Sanford takes place in 1857, it is very hard to study, because people that witnessed Dred Scott decision may not be alive centuries after the case and it makes it very hard to write about the event. Historians gather up evidences and write upon them. Historians are also interested in people’s perceptions and memories, in other words, they use human-created evidences, while scientists use physical evidences. Paul Finkelman, a historian and author of Milestone Documents in African American History, cannot return to past in order to have a better understanding of the Dred Scott case, while scientists can recreate experiments to repeat observations.
