Creationist cosmologies are explanations of the origins and form of the universe in terms of the Genesis creation narrative (Genesis 1), according to which God created the cosmos in eight creative acts over the Hexameron, six days of the "creation week":
Young Earth creationists interpret the six days as six 24-hour periods; old Earth creationists allow for millions or even billions of years within the "creation week". Both regard the Genesis story as history, and both conflate the creation of the Earth and the universe, (i.e. they hold that the two are equally old and were created together).
Cosmology is the study of the origin, evolution and ultimate fate of the universe. Scientific cosmology uses the scientific method, which means forming theories or hypotheses which make specific predictions that can be tested with observations; depending on the outcome of the observations, the theories will be abandoned, revised or extended to accommodate the data. The scientific model of the origin and evolution of our universe is the Big Bang. The Bang was not like a conventional explosion, in which fragments of a bomb are thrown outwards, but rather was an explosion of space within itself; all the matter and energy of the universe had been contained in a single point, and at the Bang all of the particles of the embryonic universe began rushing away from each other. The "bang" occurred approximately 13.8 billion years ago, which is thus the age of the universe.
Creationism is premised on belief in the inerrancy of the bible. According to prominent young Earth advocate Ken Ham, president of creationary ministry Answers in Genesis, the Book of Genesis cannot be questioned, lest the entire bible be compromised: "Refute or undermine in any way the biblical doctrine of origins, and the rest of the bible is compromised." Ham continues: "Genesis is the only book that provides an account of the origins of all the basic entities of life and the universe: the origin of life, of man, of government, of marriage, of culture, of nations, of death, of the chosen people, of sin, of diet and clothes, of the solar system..." The first chapter of Genesis describes God creating the world through divine command over six days: