The burden of proof is on the people who say they've been in contact with aliens and I've never read of any account that is actually plausible.

However, its not a question of belief with me. I think that by nature of probability its very likely that aliens exist considering how large the universe is. We have mechanisms that explain pretty much everything needed for life. And in such a large universe I highly doubt that Earth is the only example of of these things happening in one place.

Do I think aliens have visited earth? Im a skeptic in that regard. But do I think life is likely to exist somewhere else in the universe? Yes.

i personally believe that is absolutely foolish to believe that earth is the only planet capable of having life in a universe over 72 light years in size (this is the last guesstimation i heard, its probably bigger now).  but the question if there beings from another planet here on earth, im not too sure if thats likely because odds are that beings from another planet need a different gas or liquid to live other than our oxygen and water.  even the aircrafts dont seem accurate because when they came into earths gravity they would be brought down like our spaceships do at speeds that break the sound barrier.  the only way their aircrafts could enter our atmosphere without damage is if they had some type of technology that allowed the craft to ignore air resistance and gravitational pull.  but who knows, aliens could possess powers beyond all our reasoning.

The splitting of the atom is an amazing feat. And it would be very noticeable. it would draw the attention of aliens if they were already observing Earth.

I dont think intelligent life is common in the universe. So the planets that do have it would be of particular interest to those capable of interstellar travel. Think of it like interstellar anthropology.

If they were anything like us they would be intensely interested in us purely out of curiousity. However them actually getting here is unlikely due to the distance and the idea that they keep themselves hidden from everyone except the occasional hillbilly also stretches credibility.

Currently reported UFO sightings do not have the consistency or repeatability to be taken seriously.

@Kichiverde, I don't even know where to start. You make so many assumptions that it is hard for me to take you seriously. I'll try again tomorrow morning.

i believe in aliens but not in big head, big eyes, green or gray aliens. I believe in  micro-organism or bacteria aliens but when i see a REAL photo or video of a big head alien in a spaceship then i will believe.