Oh come on people. We are not being visited by aliens who hate media exposure and keep their thousands of visitations secret except to a select few people who think they saw some weird lights in the sky. People see things they can't explain, sure. It would be a remarkable thing if everybody could identify every single object they ever saw in the sky. But there is a huge difference between seeing an unidentified flying object and seeing definite proof of an extraterrestrial spacecraft. If you're so sure it's an extraterrestrial spacecraft, call it an IFO.

If these stories are real, first of all, life has to evolve somewhere else in the universe. That doesn't seem particularly unlikely; I'm willing to bet there are lots and lots of different places where life has arisen. However, life is a very improbable thing that requires a lot of rare specific circumstances, so these islands of life are probably very very very far away from each other.

Consciousness and sophisticated intelligence then need to evolve. I think this is probably one of those things that doesn't happen very often. In four billion years of evolution on Earth, we are the only animals that have acquired enough intelligence to design machines that can go to outer space. Considering that this type of intelligence has arisen only once in all the bajillions of species there have ever been on Earth, it is probably a rare feature of life throughout the universe. I suspect the vast majority of these islands of life consist of animals no smarter than dolphins and Neanderthals and therefore cannot get to outer space.

Not only would life have to evolve and become spacefaring, it would have to decide for some reason that it wants to explore the universe (hey, maybe they wouldn't), and then for some reason come visit Earth. From a distance, there is nothing particularly interesting about our solar system. We have a typical star with a typical arrangement of planets that looks very typically like all the billions of other solar systems in the galaxy. Beyond the few dozen light years that our radio transmissions have so far traveled, there is no sign of life or intelligence on Earth. Aliens would have to randomly stumble upon our solar system and inspect our planet very closely to figure out we are here in the first place. Unless they live in one of the closest star systems, they would not have been able to detect our radio waves and reply by coming to check up on us.

And UFO believers want me to swallow even more than that! I'm also expected to believe that after the extraterrestrials located intelligent life on Earth, they decided to come back thousands and thousands of times with all sorts of different funky spaceships with no consistent design features, avoiding all media exposure. They don't want to talk to our political leaders, announce their existence to humanity, help us out with our society's flaws, or share anything with us. They want to not be known to anybody, so they have this super-secret super-successful cover-up operation going on, but...they suck at hiding! Millions of people report being abducted by aliens, and millions more report seeing alien spacecraft anyways. However, nobody has any real credible hard evidence of it. If all this were really going on, either (a) we would have more than just anecdotal evidence and fuzzy pictures or (b) the aliens would be so stealthy that nobody would ever see them.

It just doesn't make any sense. And by the way, when you're making up stories about aliens you saw, please don't make them look like gray humans with big black eyes and maybe antennae...real alien life forms would look nothing like anything we've ever seen, and they would have all sorts of interesting biological features that would just blow our minds if we saw them.