The U.S. government released a report detailing more than a hundred instances of Unidentified Aerial Phenomena. https://www.cnn.com/2021/06/25/politics/ufo-report-pentagon-odni/index.html
Do aliens walk among us? Do they fly in our atmosphere in their space ships? The answer is ‘No’. The answer will always be ‘No’.
There is a very high probability that life exists elsewhere in the universe. In fact, that is almost certain.
There is also a very high probability that “intelligent” life exists elsewhere in the universe.
And there is a high probability that “intelligent” life with space travel exists elsewhere in the universe.
- The universe is a very big place
- Traveling faster than the speed of light is almost certainly impossible, which means it would take a creature a minimum of 25,000 light years to travel from another galaxy to our galaxy. And that is assuming light speed travel.
- It is unlikely creatures will be able to travel even half the speed of light. One tenth the speed of light may be the best we can achieve. Thus it would take 250,000 years for an intelligent creature from another galaxy to reach our galaxy.
- If a creature is intelligent enough to travel half the speed of light, or faster than the speed of light, and were able to locate life on our planet and travel here; they would also have sufficient technology to remain unnoticed if they did not want to be noticed.
- They would not be “caught” flying around in tiny ships in our atmosphere at the paltry speed our jets can fly when they can travel tens of thousands of times faster. They would not get caught because they would have plenty of technology to keep themselves totally invisible to us.
- There would be no reason for them to make such a long journey and remain hidden from us.
- Creatures within our own galaxy are the only ones we will possibly interact with. That still includes billions of stars with planets. However, even within our own galaxy the nearest star is over 4 light years away, and traveling at one-tenth the speed of light will require at least 40 years to make the trip. Most stars in our own galaxy are hundreds of light years away.
- Identifying that our solar system contains life would be very difficult, if not impossible, for a civilization that is 100 light years away from us, and do to the cost of travel it would not be likely they would chose our star and planets to visit at random; especially not if they were looking for life.
If you accept that we will never travel faster than the speed of light, as most scientists do, then they chance of directly interacting with an alien is extremely unlikely.
The best we can hope for is to communicate with another intelligent civilization. Communication can be done at light speed. This means that there is a chance, in the future, that we could exchange messages with another civilization in our galaxy; but we can also assume that it will take about one hundred years for a message to reach the other civilization, and another one hundred years to receive their reply.