Extraterrestrial, definition and study. A-Z index of Cognitio.

The term extraterrestrial (also called alien) indicates any object originating outside the planet Earth.

Earth, definition and study. A-Z index of Cognitio.

Earth

It can be referred to material such as meteorites or extraneous life forms to the Earth. In popular culture, the extraterrestrial is seen above all as a hypothetical being endowed with intelligence from another planet and is a character depicted within innumerable sci-fi works, but also in accounts of mysterious sightings – never fully tested – Part of people of all nationalities (see UFO voice).

UFO, definition and study. A-Z index of Cognitio.

UFO

The alleged horizons are divided among those who consider the extraterrestrial humanoid beings of peaceful nature and who, on the contrary, describe them as monstrous creatures and wicked. All life on Earth is based on carbon, hydrogen, nitrogen, and oxygen, and this fact could be a constant for other alien planets as well. There are, however, other chemical elements that could hypothetically form the basis for life, such as silicon. The point of view that carbon is necessarily the basis of all life on other planets since its chemical and thermodynamic properties make it far superior to all other elements, has been nicknamed carbon chauvinism. The question of the existence of other worlds as habitable places has been predominantly debated only after the invention of the telescope and its diffusion from the seventeenth century: the general idea before was that the stars and the planets – which appeared as simple Bright spots fixed in the firmament – were not real physical bodies. Despite this, already in Ancient Greece, in the 7th century BC, some philosophers realized that in the infinite extent of the universe it would be possible to come to other populated worlds.

Ancient Greece, definition and study. A-Z index of Cognitio.

Ancient Greece

 

Scientists are looking for some evidence of unicellular life on the planets of the solar system, carrying out studies on the surface of Mars, and examining the meteorites that have fallen on Earth.

Solar system, definition and study. A-Z Index of Cognitio.

Solar system

A mission for Europa, a moon of the planet Jupiter, has also been proposed, which is supposed to contain liquid reserves under its surface;

Europa, definition and study. A-Z index of Cognitio.

Europa

It remains to be verified, in addition to the actual existence of these reserves, whether they consist of water or gaseous components in the liquid state because of low temperatures (methane or ammonia); Probing expeditions are planned in the future to try to investigate the matter. It has been theorized that a highly technological society communicates through space through the transmission of information in multiple forms. Projects such as SETI currently conduct research in this regard, by looking at the information they receive from space through radio telescopes, in search of abnormal radio waves that can confirm the presence of intelligent life.

SETI, definition and study. A-Z index of Cognitio.

SETI

Both the Seti and the ARCADE system at different times recorded two different radio signals, including the Wow! The signal from the space, both of a form and nature that can not exclude, in the present state of knowledge, that they can not come from the Artificial source.

Wow, definition and study. A-Z index of Cognitio.

Wow

The appearance of hypothetical aliens has been the subject of both scientific reflections and a lot of fiction. Through mass media, such as movies and TV shows, extraterrestrials with intelligence are usually painted as humanoids, that is, human-like (four limbs, symmetry, erect station, etc.); An example of this type is made up of beings called Grays, which constitute a popular type of hypothetical alien.

Grey's, definition and study. A-Z index of Cognitio.

Grey’s

The representations of extraterrestrial characters appear in literature since ancient times, in the story A true story of Luciano of Samosata (120-190 AD), or later, in the Somnium of Kepler, in the states and empires of the moon of Cyrano de Bergerac, In the Micromégas of Voltaire.

Somnium, definition and study. A-Z index of Cognitio.

Somnium

It is mainly from the 17th century, with the invention of the telescope, which creates a widespread interest in the theme of life in other worlds. 

Extraterrestrial, definition and study. A-Z index of Cognitio.

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Extraterrestrial, definition and study. A-Z index of Cognitio.

Extraterrestrial