Extraterrestrial life, alien life, or colloquially simply aliens is life which does not originate from Earth. No extraterrestrial life has yet been conclusively detected. Such life might range from simple forms such as prokaryotes to intelligent beings, possibly bringing forth civilizations that might be far more advanced than humanity. The Drake equation speculates about the existence of sapient life elsewhere in the universe. The science of extraterrestrial life is known as astrobiology.
The Fermi paradox is the discrepancy between the lack of conclusive evidence of advanced extraterrestrial life and the apparently high likelihood of its existence. As a 2015 article put it, "If life is so easy, someone from somewhere must have come calling by now."
The Omphalos hypothesis is one attempt to reconcile the scientific evidence that the Earth is billions of years old with a literal interpretation of the Genesis creation narrative, which implies that the Earth is only a few thousand years old. It is based on the religious belief that the universe was created by a divine being, within the past six to ten thousand years, and that the presence of objective, verifiable evidence that the universe is older than approximately ten millennia is due to the creator introducing false evidence that makes the universe appear significantly older.
Alien invasion or space invasion is a common feature in science fiction stories and film, in which extraterrestrial lifeforms invade the Earth to exterminate and supplant human life, enslave it, harvest people for food, steal the planet's resources, or destroy the planet altogether. It can be considered as a science-fiction subgenre of the invasion literature, expanded by H. G. Wells's seminal alien invasion novel The War of the Worlds.
Robert James Sawyer is a Canadian and American science fiction writer. He has had 24 novels published and his short fiction has appeared in Analog Science Fiction and Fact, Amazing Stories, On Spec, Nature, and numerous anthologies. He has won many writing awards, including the best-novel Nebula Award (1995), the best-novel Hugo Award (2003), the John W. Campbell Memorial Award (2006), the Robert A. Heinlein Award (2017), and more Aurora Awards than anyone else in history.
Ancient astronauts refer to a pseudoscientific set of beliefs which holds that intelligent extraterrestrial beings visited Earth and made contact with humans in antiquity and prehistoric times. Proponents suggest that this contact influenced the development of modern cultures, technologies, religions, and human biology. A common position is that deities from most, if not all, religions are extraterrestrial in origin, and that advanced technologies brought to Earth by ancient astronauts were interpreted as evidence of divine status by early humans.
Young Earth creationism (YEC) is a form of creationism which holds as a central tenet that the Earth and its lifeforms were created by supernatural acts of the Abrahamic God between about 6,000 and 10,000 years ago. In its most widespread version, YEC is based on the religious belief in the inerrancy of certain literal interpretations of the Book of Genesis. Its primary adherents are Christians and Jews who believe that God created the Earth in six literal days. This is in contrast with old Earth creationism (OEC), which holds literal interpretations of Genesis that are compatible with the scientifically determined ages of the Earth and universe. It is also in contrast to theistic evolution, which posits that the scientific principles of evolution, the Big Bang, abiogenesis, solar nebular theory, age of the universe, and age of Earth are compatible with a metaphorical interpretation of the Genesis creation account.
Xenoarchaeology, a branch of xenology dealing with extraterrestrial cultures, is a hypothetical form of archaeology that exists mainly in works of science fiction. The field is concerned with the study of the material remains to reconstruct and interpret past life-ways of alien civilizations. Xenoarchaeology is not currently practiced by mainstream archaeologists due to the current lack of any material for the discipline to study.
The zoo hypothesis speculates on the assumed behavior and existence of technologically advanced extraterrestrial life and the reasons they refrain from contacting Earth. It is one of many theoretical explanations for the Fermi paradox. The hypothesis states that alien life intentionally avoids communication with Earth to allow for natural evolution and sociocultural development, and avoiding interplanetary contamination, similar to people observing animals at a zoo. The hypothesis seeks to explain the apparent absence of extraterrestrial life despite its generally accepted plausibility and hence the reasonable expectation of its existence. A variant on the zoo hypothesis suggested by the former MIT Haystack Observatory scientist John Allen Ball is the "laboratory" hypothesis, in which humanity is being subjected to experiments, with Earth serving as a giant laboratory.
The Great Filter is the idea that, in the development of life from the earliest stages of abiogenesis to reaching the highest levels of development on the Kardashev scale, there is a barrier to development that makes detectable extraterrestrial life exceedingly rare. The Great Filter is one possible resolution of the Fermi paradox.
Russell's teapot is an analogy, formulated by the philosopher Bertrand Russell (1872–1970), to illustrate that the philosophic burden of proof lies upon a person making empirically unfalsifiable claims, as opposed to shifting the burden of disproof to others.
"The Star" is a science fiction short story by English writer Arthur C. Clarke. It appeared in the science fiction magazine Infinity Science Fiction in 1955 and won the Hugo Award in 1956. It is collected in Clarke's 1958 book of short stories The Other Side of the Sky, and it was reprinted in the January 1965 issue of Short Story International as the lead-off story.
The planetary systems of stars other than the Sun and the Solar System are a staple element in many works of the science fiction genre.
Fossil Hunter is a novel written by Canadian science fiction author Robert J. Sawyer. The sequel to Far-Seer, it is the second book of the Quintaglio Ascension Trilogy. The book depicts an Earth-like world on a moon which orbits a gas giant, inhabited by a species of highly evolved, sentient Tyrannosaurs called Quintaglios, among various other creatures from the late cretaceous period, imported to this moon by aliens 65 million years prior to the story. Originally published in 1993 by Ace Science Fiction, it won the Homer award for "Best Novel" during its initial release date. It was reissued in 2005 by Tor Books.
Supernovae have been featured in works of fiction. While a nova is strictly speaking a different type of astronomical event, science fiction writers often use the terms interchangeably and refer to stars "going nova" without further clarification; this can at least partially be explained by the earliest science fiction works featuring these phenomena predating the introduction of the term "supernova" as a separate class of event in 1934. Since these stellar explosions release enormous amounts of energy, some stories propose using them as a power source for extremely energy-intense processes, such as time travel in the Doctor Who serial The Three Doctors from 1972. For the same reason, inducing them is occasionally portrayed as a potential weapon, for instance in the 1966 novel The Solarians by Norman Spinrad.
Robert J. (Bob) Schadewald was an author, researcher, and former president of the National Center for Science Education (NCSE). An internationally recognized expert on pseudoscience, Schadewald penned numerous articles on creationism, perpetual motion, flat earthism, and other pseudoscience for such magazines as Science 80, Technology Illustrated, Smithsonian, and Science Digest.
Donald Ross Prothero is an American geologist, paleontologist, and author who specializes in mammalian paleontology and magnetostratigraphy, a technique to date rock layers of the Cenozoic era and its use to date the climate changes which occurred 30–40 million years ago. He is the author or editor of more than 30 books and over 300 scientific papers, including at least 5 geology textbooks.
The dark forest hypothesis is the conjecture that many alien civilizations exist throughout the universe, but they are both silent and hostile, maintaining their undetectability for fear of being destroyed by another hostile and undetected civilization. It is one of many possible explanations of the Fermi paradox, which contrasts the lack of contact with alien life with the potential for such contact. The hypothesis derives its name from Liu Cixin's 2008 novel The Dark Forest, although the concept predates the novel.
The Hart–Tipler conjecture is the idea that an absence of detectable Von Neumann probes is contrapositive evidence that no intelligent life exists outside of the Solar System. This idea was first proposed in opposition to the Drake equation in a 1975 paper by Michael H. Hart titled "Explanation for the Absence of Extraterrestrials on Earth". Assuming that the probes traveled at 1/10 the speed of light and that no time was lost in building new ships upon arriving at the destination, Hart surmised that a wave of Von Neumann probes could cross the galaxy in approximately 650,000 years, a comparatively minimal span of time relative to the estimated age of the universe at 13.7 billion years. Hart’s argument was extended by cosmologist Frank Tipler in his 1981 paper entitled ‘Extraterrestrial intelligent beings do not exist’.
