At all times and always had about aliens reverie, but now mankind has not actually detect any aliens exist, but we can roughly describe Ten Characteristics aliens.
Aliens will not eat humans
Sci-fi horror movie aliens will swallow humans, but from scientific point of view it is impossible to achieve space travel biological intelligent civilizations have gone beyond the stage of prey live animals, in addition, the alien has the digestive system may not be able to digest the Earth biological proteins.
Aliens not strong
Aliens are not strong, once they reach space exploration science and technology range, thousands of years will no longer need to brute force, they should be thin groups, with the lowest energy consumption to maintain the body.
Has spoken and written language
An extension and development of civilization must require communication and written records, for the alien, for their civilization to achieve a similar degree of mankind on the planet, the inevitable need language and culture, and the corresponding text, the different periods of cultural heritage down.
Non-human physical characteristics
In some sci-fi movie, the mysterious aliens possess characteristics similar to human faces, the fact that they and the Earth in a completely different environment conditions, human evolution has been adapted in arboreal apes, primitive apes limbs for climbing trees climb trees if the ball is not a star, and the corresponding evolution of intelligent life on imaging without the structure of human limbs.
In some sci-fi movie, an alien civilization has been described as the feudal system of society, they compete for territory disputes occur. This is not a put-on, they are able to achieve interstellar travel, you need to have a very high IQ ability, they will war arrows pointing interstellar space.
Not a huge alien insects
Science fiction movies appear mysterious giant alien insects can not be explained from a scientific point of view, the concept derived from human fear of losing dominance of the planet, as well as insect disgust, based on the current content of oxygen in Earth’s atmosphere, insect bio- can not grow into behemoths.
Not like some science fiction movie alien described so friendly, in most cases, they come from a distant planet, the other planet’s main purpose is the development of colonization, the goal is to eliminate all the creatures on this planet.
With viral and bacterial immunity
Exploration program extraterrestrial intelligence (SETI) Senior Seth – Shostak pointed out that the bacteria survive in the relevant biochemical properties only life forms evolved bacteria survive in the human body’s unique DNA, so living in a completely different environment alien creatures, they do not infect Earth viruses and bacteria.
Aliens are explorers
Any reach Earth from alien life forms a certain sense, they are explorers.
University of Missouri research report pointed out that the aliens might very aggressive if they are more intelligent than humans, they will be considered as a very good earth resources and the environment, will clear all the farm animals killed.