Immanuel Velikovsky was a Russian-American psychoanalyst, writer, and catastrophist. He is the author of several books offering pseudohistorical interpretations of ancient history, including the U.S. bestseller Worlds in Collision published in 1950. Velikovsky's work is frequently cited as a canonical example of pseudoscience and has been used as an example of the demarcation problem.

In geology, catastrophism is the theory that the Earth has largely been shaped by sudden, short-lived, violent events, possibly worldwide in scope. This contrasts with uniformitarianism, according to which slow incremental changes, such as erosion, brought about all the Earth's geological features. The proponents of uniformitarianism held that the present was "the key to the past", and that all geological processes throughout the past resembled those that can be observed today. Since the 19th-century disputes between catastrophists and uniformitarians, a more inclusive and integrated view of geologic events has developed, in which the scientific consensus accepts that some catastrophic events occurred in the geologic past, but regards these as explicable as extreme examples of natural processes which can occur.