What do aliens look like?

 The appearance of hypothetical aliens has been the subject of both scientific thinking and a lot of fiction.

Through the means of mass communication , such as films and television shows, with the extraterrestrial intelligence are usually depicted as humanoids , that is shaped similar to that in humans (four limbs, symmetry, standing etc..), an example of this type is constituted by beings called Greys , which are a popular type of hypothetical alien.

However, many scientists argue that there are few chances that a form of alien life might look like us at all, considering all the possible variables that could make a difference, such as environmental issues, related to the particular geological, atmospheric and weather on the planet, the physical (first of all the force of gravity different from that of Earth), the planets, such as a planet's orbit could be livable space and a more complex geography of the Earth, and those related to the biological process of evolution and natural selection. Between the Sixties and Seventies Carl Sagan and others calculated the conditions for the formation of macroscopic life, based on amino acids , relative to the atmosphere of the planet Jupiter , according to my observations of that atmosphere.

This in turn has influenced science fiction that has come to imagine non-humanoid life forms, or even quite exotic, like clouds of gas or ways of life based on the chemistry of silicon instead of carbon .