Outer space, or simply space, is the void that exists between celestial bodies, including the Earth. It is not completely empty, but consists of a hard vacuum containing a low density of particles: predominantly a plasma of hydrogen and helium.
Nature, in the broadest sense, is equivalent to the natural, physical, or material world or universe. "Nature" refers to the phenomena of the physical world, and also to life in general. It ranges in scale from the subatomic to the cosmic.
History (from Greek ἱστορία, historia, meaning "inquiry, knowledge acquired by investigation") is the study of the past, specifically how it relates to humans. It is an umbrella term that relates to past events as well as the memory, discovery, collection, organization, presentation, and interpretation of information about these events.
- Demographic history
- Black history
- History of education
- Ethnic history
- Family history
- Labor history
- Rural history
- Urban history
Stories common to a particular culture, but not supported by external sources (such as the tales surrounding King Arthur) are usually classified as cultural heritage or legends, because they do not support the "disinterested investigation" required of the discipline of history. Herodotus, a 5th-century BC Greek historian is considered within the Western tradition to be the "father of history", and, along with his contemporary Thucydides, helped form the foundations for the modern study of human history.