The very first thing that constitutes evidence of a UFO is the fact someone reports it. They must either tell a family member, friend or someone in authority. Reporting a UFO sighting proves that the witness saw an unidentified flying object. In other words, the witness saw something flying in the air and was unable to identify it. They were unable to tell what they saw other than to report they saw something flying.
Many are the backgrounds of the eyewitnesses to UFO sightings. Scientists, astronomers, doctors, housewives, military personnel, law enforcement and a multitude of others proves that sightings of UFO's are the real thing. No one can reasonably continue to doubt it when so many have observed and spoken about their experience.
The second line of evidence is that UFO's have been seen many times before the most recent century. In the days before telescopes were invented, hundreds of years ago, people saw heavenly objects moving about. There were comets, meteors, falling stars and closer to earth, strange birds. The simple fact that the witnesses could not identify the flying objects made them UFO's.
One easy proof that something has been seen flying and unidentified is the simple picture of the sighted object. In the recent past, many individuals have seen planes, weather balloons and other man-made objects which they called UFO's because they were unable to identify them. For some of these sightings, a camera was on hand with film and flash at the ready. Pictures prove that a UFO has been observe and recorded. A flying object seen but not identified.
Now the problem comes in when the term UFO is automatically taken to mean a space ship' of some design that is unknown to the majority of humans. And this writer says unknown to the majority because there may be some humans that have constructed a space ship' and not informed anyone as to their creation.
An unidentified flying object is not necessarily any kind of space ship. As discussed, it might be a heavenly body or even a bird unknown to the witness. However, when the term UFO is used, most people think of space ships.
And with space ships, there must of necessity be, in the minds of most people, creatures from outer space. Creatures from another planet. Strangely formed creatures with powers that humans don't possess and speaking a language no one on earth would know or would have heard before.
There is no evidence that any creature has ever come to the earth is a space ship. If there were such evidence and the government had the evidence, sooner or later someone would leak the secret. That's the way of secret information. It doesn't stay secret. As long as people have been looking for someone to come to earth, especially from the planet Mars, if a creature had visited earth, it would be known among the populace.
So we have a lot of evidence for the sighting and existence of UFO's. We have eyewitness testimony numbering in the thousands. We have all seen pictures of flying objects that the person or persons taking the picture could not identify. Some of these are of poor quality and no one can say for sure what was seen. We have read written reports of these sightings.
All of these things constitute evidence of UFO's. They are not, however, evidence of creatures that flew here from another planet in the Universe. They are also not proof that the government has anything resembling a space ship and having no part at NASA.