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After acknowledging that the Universe is extremely enormous, an intuition had already built up in the scientific commubity that life might exist on other planets just like our earth. It was concluded logically without any probe or observation that since there are billions of stars there could thousands of life forms out in the space. By simple definition an extraterrestrial life is the one that does not originate or exist on earth. The extraterrestrial life ranges from bacteria-like organisms to complex organisms like humans or even more complex. Many astrophysicists such as Carl Sagan and Stephen Hawkings argue that life must exist in other parts of as well bringing forth the Copernican theory and Mediocrity principle, which tells that there is nothing special about life on earth, to support their argument.
Officially no government has recognised the existence of alien life yet but findings still continue. Though there are many controversial claims of unidentified flying objects that are of extraterrestrial origin and many alien abduction cases.