Have aliens visited Earth?
Elaine - YES
Just as Copernicus turned the scientific world on its geo-centric ear by declaring that the Earth is not the center of the universe , it is high time that the arrogance and short-sightedness of humans to believe that we are the only intelligent lifeforms in existence is challenged as well.
Some astronomers posit that there may be upwards of 2.5 billion different habitable planets in our galaxy, let alone countless more in other galaxies . So from a statistical standpoint, it is very likely that somewhere out there, there are beings pondering these very same issues—as well as beings poised to visit other planets.
But have any of these life forms actually ever visited Earth? Cave paintings in Spain and France depict flying objects that look very similar to what we, in modern times, equate with UFOs . And various later works show the same, the most striking of which is Flemish artist Aert De Gelder’s 1710 piece “Baptism of Christ”, which portrays a spaceship shining beams of light on the scene below . Outside of the Judeo-Christian world, antique manuscripts recount a saucer-like vessel of unknown fabrication washing ashore in Japan in 1803 .
It may be easy to dismiss these examples as artistic embellishment or even folklore; however, consistent anecdotal evidence of UFO sightings  begs the matter to be seriously entertained. In fact, the Pentagon devoted five years to investigating “unexplained aerial phenomena” that America’s servicemen had reported . And that’s not taking into account the hundreds of civilian accounts over the years, most of which point to the conclusion that earth has had some otherworldly visitors.
Michael - NO
There isn’t any objective, verifiable evidence that aliens have visited Earth . In ten thousand years of human history, we haven’t found the little green men of science fiction and folklore, and we haven’t found the microbes that we think hitch rides on comets or inhabit some of the planets and asteroids of our solar system. That’s not to say neither are out there. If you accept math, physics, and chemistry, then you must accept we’re almost certainly not alone in the universe. That’s not the same, however, as finding evidence for V, Independence Day, or Agent Mulder’s obsession. Probability doesn’t satisfy Carl Sagan’s fervent hope or validate the assumptions of astrobiology.
Since we’re almost certainly not the only life forms in all of space-time , and since we’ve got billions of years of history to look through, the odds that we’ll eventually find some of this evidence are pretty high . So are the odds that such a discovery would be, literally, the greatest story ever told. Imagine for a moment that this evidence was already on file somewhere, that some scientists knew, and had told someone. People have been betraying secrets as long as there have been people, and today, when the whiff of scandal ignites social media without even a shred of evidence, solid proof of extraterrestrial life wouldn’t make it to lunchtime in the dark. We haven’t got solid evidence aliens visited Earth.
- The United States Air Force conducted studies into UFO phenomena from 1947-1969, concluding that out of the over 12,000 unidentified flying object occurrences, over 700 could not be explained .
- A 2019 Insider poll revealed that 20% of Americans believe that aliens have visited earth .
- “Where Are the Aliens? The Search Ramps Up” — An itemized list of SETI-relevant news items from the Institute itself .
- “The implications of the discovery of extraterrestrial life for religion” — A paper from the Philosophical Transactions of the Royal Society .
- “Aliens may have already visited Earth, we just haven’t seen them recently” — A Business Insider article says the whole of human history is just a blink at the level of galactic time .