Do you believe aliens exist on another world?
Mathematically speaking it's almost impossible for there not to be alien life. The only thing we lack is actual evidence.
However, I also believe that whatever alien life is out there is no more advanced than we are. Which is why we have no evidence.
It is my personal belief that it took some 10 billion years, at least, for this solar system to form. And it took another 4 billion years for intelligent life like us to finally walk onto the scene.
It seems to me that the universe is only old enough for this set of circumstance to have occurred right now, in the time frame that we live in. So if there ARE other life forms out there, they would have evolved at the same time, and they wouldn't have gotten any further than us.
The only problem with this theory - and I acknowledge it - is that intelligent life could have formed earlier in other places. It could have gotten a toe-hold 2 million years ago instead of only 250,000 years ago. And as such, they could have evolved technology that far surpasses ours.
Except for one thing. There doesn't appear to be any evidence of it.
I'm interpreting ‘believe' in this case, to be analogous to ‘suspect'. I have a hunch aliens exist. It's not a hill I plan to die on.
It's a big galaxy out there, and many more beyond that. We've explored only the tiniest fragment of a sliver of one corner of it. and even at that, ‘explored' is absurdly generous. We've watched nearby stars for shadows of planets. Beyond the fact that potentially habitable planets seem to be more common than originally expected, we know precisely bupkiss about any of them.
Given that, from a few light-years, our system would appear to have 3 habitable planets, we can expect to be disappointed in a fair swath of the hundreds of rocky, Goldilocks-zoned planets we've found so far. It's reasonably likely that, on closer inspection, none of those hundreds are actually habitable.
But, as noted above, this is still a fragment of a sliver of a lonely corner. There's way, way more out there.
With over 100 billion glalxies out there, in a universe that's existed for over 10 billion years, I find it absolutely absurd to believe we are the only intelligent life forms that ever existed. Even if intelligent life only shows up once in every 100,000 galaxies, that's still a huge number of intelligent civilizations.
I want to doubt that an alien civilization has ever made it to our planet, but with all the depictions of spaceships in ancient artworks... anything is possible.
I think probably yes, since there are literally billions of other worlds, but I don't think that we can have any interaction with them, because of the huge distances involved.
However, we cannot at the present time, prove that life exists on other planets, so we might have the only such planet.
Present day physics tells us that we cannot interact with those billions of worlds, however, it is conceivable that some future discover might allow it.
This is a very common question on Quora. Given the vastness of this universe, I would say yes, I do believe that our planet is not the only one that harbors life. Any extraterrestrial life is considered alien life. But I do tend to believe, on faith mind you, but based on some logic, that there are other sentient lifeforms out there as well.
Simply because the universe is so inconceivably big and there are so many planets out there that have the conditions for life as we recognise it, not to mention potential other lifeforms.
I think there is a good chance that we may never encounter another sentient race because the universe is functionally infinite as far as we can tell. But because of that, I personally have no doubt that aliens are out there.