A former NASA research scientist has made some unexpected comments on aliens and their visit to earth. He claimed that humans are not alone in this universe and many governments know about the existence of these extraterrestrial entities but they have kept it as a top secret.

The shocking revelation has come from the retired scientist Kevin Knuth, who is now a professor of physics at the University of Albany. As per his statement, there are shreds of evidence available in the universe that supports the existence of alien spacecraft, commonly known as UFO.

There are some people who actually believe in such entities and their frequent visit to earth but Knuth says that those, who still haven't accepted the facts related to aliens, the time has come for them to face the possibility that aliens do come to this blue planet and that's the reason behind UFO sightings. The ex-scientist also stressed on a point that rather than neglecting this possibility, people should conduct research on the topic, as the entire study will be helpful for the mankind.

The New York professor recently revealed these unbelievable facts on The Conversation, where he clearly stated, "With July 2 being World UFO Day, it is a good time for society to address the unsettling and refreshing fact we may not be alone. I believe we need to face the possibility that some of the strange flying objects that outperform the best aircraft in our inventory and defy explanation may indeed be visitors from afar – and there's plenty of evidence to support UFO sightings."

On the other hand, as per the Fermi paradox, which was proposed by the nuclear physicist Enrico Fermi has claimed that even though the galaxy has almost about 300 billion stars, many of them are older than sun, but as of now, there is no concrete evidence on alien life or any positive contact has been made. As per researcher Carl Sagan's summarized version of this matter, "extraordinary claims require extraordinary evidence," and since there is no well-documented evidence of UFO or aliens, it is hard to make people believe in extraterrestrials, Knuth said.

Later, he added that during his career as a scientist he was told to ignore the topic, as it is nothing but a nonsense subject and it requires scientific study as well as rational discussion, "which unfortunately leaves the topic in the domain of fringe and pseudoscientists, many of whom litter the field with conspiracy theories and wild speculation."

He mentioned that all over the world especially Canada, New Zealand, Russia, Brazil, Denmark, France, Swede and UK have declassified UFO-related files for many years. He also shared some pictures of top secret government documents that showed the higher authority knows about the sighting incidents but still try to cover up all UFO encounters.

"The situation is exacerbated by the fact that many governments around the world have covered up and classified information about such encounters," he said.

"If there are indeed extraterrestrial craft visiting Earth, it would greatly benefit us to know about them, their nature and their intent. Moreover, this would present a great opportunity for mankind, promising to expand and advance our knowledge and technology, as well as reshaping our understanding of our place in the universe," he further added.