Personally, I think it entirely likely. I am not going to point to UFO sightings or any such thing but rather just a little bit of logic. But first we need to establish our place in the universe. By that I mean, exactly where are we in this great big universe?
It is believed that we sit on one of the spiral arms of the Milky Way Galaxy. It is only a belief because, of course, we simply do not have a good vantage point to see our entire galaxy. In reality, the shape of our galaxy is mostly an educated guess, but probably a pretty good one. Our galaxy is between 100 and 120,000 light years across. Light travels 5.87849981 × 1012 miles in one year, or about 6,000 trillion miles. And it gets better. Within our galaxy there exist a least 1 billion stars. Now if you consider the chance of life just within our galaxy to be a million to one against that any single star has life in its proximity, that means life is almost a sure thing within our galaxy alone.
Astronomers know that there are at least a billion galaxies each with a billion stars in our universe. With such numbers the chance of life is not only a sure thing, but is more a case of how many instances does it exist.
The Andromeda Galaxy is our closest galactic neighbor. It sits a mere 200 million light years away. That means that any life form that set out from Andromeda at a speed just slightly less than the speed of light had to have left long before dinosaurs existed on Earth just to arrive here in present day. I think it reasonable to conclude that travel from there is unlikely using all light speed based scenarios.
The closest star to us in Proxima Centauri which is a mere 4.2 light years away, or 20,000 trillion miles away. Right now about the only theories of how to travel such distances exist mainly in science fiction. While physicists speculate how we might build a space ship to accommodate such speed, the energy required is greater than all known sources. And yet I say other beings have likely resolved such problems. How?
Astro-phycisists speculate that the way to traverse such a distance is through the distortion of space-time. Scientists have been able to minutely affect the shape of space-time which allows for far greater distortions even though we do not have the means at present.
Our solar system has existed for the last third of the time the universe has existed. That means another “solar system” could have been in existence during the 4 billion years prior to ours, have given rise to intelligent life forms who in turn have resolved many of the problems of long distance travel. It is possible they have existed for billions of years where mankind has existed for only 1 to 2 million years. That would give them a pretty good leg up on us in all respects. So much so that they could have foreseen the demise of the star where they originally existed and have moved on to another. That being the case, their traveling to our solar system would be old hat.
How does this bending of space work? Let’s consider we decide we want to travel from New York City to Sydney Australia. We get on an airplane and travel over 10,000 miles to get there. At 500 MPH that would take about 20 hours of flying time. But, if we could go straight through the earth to Sydney the distance is reduced to a little over 3000 miles, or 6 hours of time at 500 MPH. That is the “bending” that physicists suggest we do with space-time to reduce travel time.
We earthlings are right now devising theories to tackle to problems of traveling great distances. It is not unreasonable to expect that a society a mere 1,000 years advanced from us may well have such problems at least partially resolved. And when you allow for an alien society to have existed even more than that you by extension increase the probability that they have also done interstellar travel and possibly intergalactic travel.
All things considered, I think it most likely that we have been visited and studied by E.T. I suspect that contact has not been made simply because we are viewed as far too primitive, and also probable communications problems. How do you tell a primitive society, us, that you come in peace? Considering how warlike humans are that is no easy task.