Historical research involves carefully studying and analyzing past events and data to better understand how the past impacts the present. It relies on primary sources like documents, artifacts, and oral histories, as well as secondary sources. The research process involves collecting data, critically analyzing its authenticity and reliability, and then synthesizing the validated information to establish facts and test hypotheses. Some areas of historical study include specific time periods, geographical locations, and topics like military history. A variety of methods and tools are used, such as corroborating evidence, photography, revisionism, change logs, and examining human and social evolution.