Extraterrestrial life in the context of "Voyager Golden Record"

Life is matter that has biological processes, such as signaling and the ability to sustain itself. It is defined descriptively by the capacity for homeostasis, organisation, metabolism, growth, adaptation, response to stimuli, and reproduction. All life over time eventually reaches a state of death, and none is immortal. Many philosophical definitions of living systems have been proposed, such as self-organizing systems. Defining life is further complicated by viruses, which replicate only in host cells, and the possibility of extraterrestrial life, which is likely to be very different from terrestrial life. Life exists all over the Earth in air, water, and soil, with many ecosystems forming the biosphere. Some of these are harsh environments occupied only by extremophiles. The life in a particular ecosystem is called its biota.

Life has been studied since ancient times, with theories such as Empedocles's materialism asserting that it was composed of four eternal elements, and Aristotle's hylomorphism asserting that living things have souls and embody both form and matter. Life originated at least 3.5 billion years ago, resulting in a universal common ancestor. This evolved into all the species that exist now, by way of many extinct species, some of which have left traces as fossils. Attempts to classify living things, too, began with Aristotle. Modern classification began with Carl Linnaeus's system of binomial nomenclature in the 1740s.

The damsel in distress is a narrative device in which one or more men must rescue a woman who has been kidnapped or placed in other peril. The "damsel" is often portrayed as beautiful, popular, and of high social status; she is usually depicted as a princess in works with fantasy or fairy tale settings. Kinship, love, lust or a combination of those motivate the male protagonist to initiate the narrative, and potentially become a hero of valour.

Critics have linked the helplessness of these women to societal views that women as a group need to be taken care of by men and treated nicely. Throughout the history of the trope, the role of the woman as the victim in need of a male savior has remained constant, but her attackers have changed to suit the tastes and collective fears of the period: "monsters, mad scientists, Nazis, hippies, bikers, aliens..."

A creepypasta is a horror-related legend which has been shared around the Internet. The term creepypasta has since become a catch-all term for any horror content posted onto the Internet. These entries are often brief, user-generated, paranormal stories that are intended to frighten readers. The subjects of creepypasta vary widely and can include topics such as ghosts, cryptids, murder, suicide, zombies, aliens, rituals to summon supernatural entities, haunted television shows, and video games. Creepypastas range in length from a single paragraph to extended multi-part series that can span multiple media types, some lasting for years.

In the mainstream media, creepypastas relating to the fictitious Slender Man character came to public attention after the 2014 "Slender Man stabbing", in which a 12-year-old girl was stabbed by two of her friends; the perpetrators claimed they "wanted to prove the Slender Man skeptics wrong". After the murder attempt, some creepypasta website administrators made statements reminding readers of the "line between fiction and reality". This case is part of a pattern of people, especially children, developing misconceptions around the reality of creepypastas.

An extremophile (from Latin extremus 'extreme' and Ancient Greek φιλία (philía) 'love') is an organism that is able to live (or in some cases thrive) in extreme environments, i.e., environments with conditions approaching or stretching the limits of what known life can adapt to, such as extreme temperature, pressure, radiation, salinity, or pH level.

Since the definition of an extreme environment is relative to an arbitrarily defined standard, often an anthropocentric one, these organisms can be considered ecologically dominant in the evolutionary history of the planet. Extremophiles have continued to thrive in the most extreme conditions, making them one of the most abundant lifeforms. The study of extremophiles has expanded human knowledge of the limits of life, and informs speculation about extraterrestrial life. Extremophiles are also of interest because of their potential for bioremediation of environments made hazardous to humans due to pollution or contamination.

In astronomy and astrobiology, the habitable zone (HZ), the circumstellar habitable zone (CHZ), the Goldilocks zone, is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure. The bounds of the HZ are based on Earth's position in the Solar System and the amount of radiant energy it receives from the Sun. Due to the importance of liquid water to Earth's biosphere, the nature of the HZ and the objects within it may be instrumental in determining the scope and distribution of planets capable of supporting Earth-like extraterrestrial life and intelligence. As such, it is considered by many to be a major factor of planetary habitability, and the most likely place to find extraterrestrial liquid water and biosignatures elsewhere in the universe.

The habitable zone is also called the Goldilocks zone, a metaphor, allusion and antonomasia of the children's fairy tale of "Goldilocks and the Three Bears", in which a little girl chooses from sets of three items, rejecting the ones that are too extreme (large or small, hot or cold, etc.), and settling on the one in the middle, which is "just right".

Ancient astronauts (or ancient aliens) refers to a pseudoscientific set of beliefs, also called paleocontact, that hold that intelligent extraterrestrial beings (alien astronauts) visited Earth and made contact with humans in antiquity and prehistoric times. Proponents of the theory 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.

The idea that ancient astronauts existed and visited Earth is not taken seriously by academics and archaeologists, who identify such claims as pseudoarchaeological or unscientific. It has received no credible attention in peer-reviewed studies. When proponents of the idea present evidence in favor of their beliefs, it is often distorted or fabricated. Some authors and scholars also argue that ancient astronaut theories have racist undertones or implications, diminishing the accomplishments and capabilities of indigenous cultures.

In astronomy, a thalassogen denotes a substance capable of forming a planetary ocean. Thalassogens are not necessarily life sustaining, although most interest has been in the context of extraterrestrial life.

The term was coined by Isaac Asimov in his essay "The Thalassogens", later published in his 1972 collection The Left Hand of the Electron. Said term was coined via the Ancient Greek prefix thalasso- ("sea") and the suffix -gen ("producer").