The fact that we are alone in this universe seems hard to believe because there are more than 100 billion galaxies in the cosmos and each galaxy has hundreds of billions of stars and countless earth-like planets. Alan Boss, astronomer at the Carnegie Institution and author of The Crowded Universe: The Search for Living Planets says:
“Our Milky Way galaxy, one of the billions of galaxies, has more than 100 billion Earth-like planets or one Earth-like planet for every sun-type star."
With the possibility of so many earth-like planets in our own galaxy, the possibility of an intelligent civilization outside our planet cannot be ignored. That’s why research institutes such as SETI (Search for Extra-Terrestrial Intelligence) was established to detect any existence of alien civilizations on other planets. The Center for SETI research develops various signal processing technologies and uses these technologies to search for signals from advanced civilizations in our galaxy. From the first modern SETI experiment “project Ozma" in 1960 (by Frank Drake) to the famous Ohio State University SETI Program, SETI’s contribution in the field of extraterrestrial research is immense.
SETI follows a more viable approach in its attempts to prove the existence of an alien civilization, compared to the baseless assertions about the links between ancient civilization and extraterrestrials and the findings.
There might be some strange claims about extraterrestrial visitations in the remote past, even stranger ancient relics to prove their existence, but unless an extraordinary solid proof is provided, these claims will always remain science fiction to the scientific world.
[Image, Top Left: Are we alone? An image of the universe with innumerable galaxies, Photo courtesy: NASA and the European Space Agency, http://en.wikipedia.org/wiki/File:Hubble_ultra_deep_field_high_rez_edit1.jpg]