Who believes in Aliens and UFOS , I don’t, with all the technology we have and a billion camera phones now, we still have no clear evidence at all of them, I think sadly we are all alone.

Or it proves that FTL travel is not possible/ /no one has found our insignificant speck of dirt we live on.
ETA: I do beleive there’s plenty of life out there.

The basic building blocks of life were created in a lab so it’s not that hard when repeated across untold billions of planets.

Moved from General Questions to IMHO.

samclem, moderator

if i were an ant, how far away would another ant/alien be if it were 1) in the nearest star system; 2) in the nearest galaxy?

Do coral polyps know about radio? Do we even have the conceptual framework to rule *everything *out?

I believe we have been visited by other species in the past.

They put up warning signs around the galaxy, telling everyone else to steer clear of the nutjobs on the third planet.

When you say you don’t believe in aliens, do you mean that you don’t believe there is any life anywhere in the universe besides us, or that no alien life has yet come to earth and is hiding among us? If the former, I think your data set is way to small to reach a definite conclusion. If the latter, well, I’d probably agree in the absence of any compelling evidence.

“Two possibilities exist. Either we are alone in the universe, or we are not. Both are equally terrifying.” - Arthur C. Clarke.

I don’t believe the circumstances that lead to intelligent life evolving on Earth are likely to be unique among the hundreds of billions of stars in our own galaxy, let alone the universe as a whole. However physics rests on the understanding that FTL travel is impossible, so UFOs visiting our pale blue dot? Unlikely.

A friend of mine had a medallion with a crop circle pattern on it; she’d ask people if they knew what it meant and if they did, it meant they were aliens. I recognized it before she asked me, so I said “No services this exit. Why?”

We really have no clue what the realistic tenure of any “intelligent” life might be. At this point in our existence, language and abstract reasoning, to the point that we can devise and build stuff, is something less than 10 millennia old, and when you look at the state of global civilization, optimistically, 5 or 6 more millennia looks like the very most we are likely to get. Assuming that the theory of the development of life on earth is correct (that the Earth is effectively our sole progenitor), intelligent aliens would probably have to in a time frame of less than one thousandth of one percent of a given star’s main sequence lifespan (the dynamics of other types of stars could possibly yield slightly different results).

Hence, a star would have to be large enough and stable enough to support suitable conditions long enough for life to evolve on a suitable planet, then that alien race would have to exist in a time frame fairly current to our own. In other words, our twenty thousand year tenure would have to overlap with theirs, in a vast range of billions of years. We might not be the only life in the universe, but it is entirely likely that we are the only life in this galaxy right now.

Or life is really rare, or intelligent life is really rare, or we’re under some kind of quarantine, or they don’t like to travel, or civilizations destroy themselves first, or we’re the first ones, or… or… etc.

Fermi’s Paradox does a pretty good job of limiting the possible cases, at least concerning our galaxy.


  1. We are alone in our galaxy
  2. Aliens are already here, but concealed (including the “zoo” special case)
  3. Intelligent life cannot / will not spread to other stars (self destruction, loss of will, lack of technology)

Interestingly, the whole idea of SETI is only interesting for case 3.

I personally believe that case 3 is way too pessimistic, and hard to believe to boot. I suppose self destruction is possible, but the very fact that we are able to consider that possiblility leads me to believe that at least some intelligent life is capable of avoiding that trap. Loss of will and lack of technology seems to me to be clearly implausible.

I could buy into case 2. Any civilization capable of colonizing the galaxy would be equally able to conceal themselves from us. I could even be convinced that if such a benevolent alien presence can hide itself from us, then maybe there are other intelligent species out there a little closer to our level of development, and perhaps SETI might have a purpose; assuming of course, that our theoretically benevolent alien observers would allow it.

However, I believe that case 1 is the most likely situation. It’s the simplest answer, holds out some degree of optimism for the future, and makes our future solely our own responsibility. This only holds for our own galaxy. Things may get quite dicey when our galaxy merges with Andromeda…I wonder what happens when two galaxy-class civilizations collide?

Actually, I think the most likely scenario is

  1. Intelligent civilizations are plentiful, but too far apart to ever contact one another
    We could colonize every star we see in the night sky from Earth, and our interstellar civilization would still be barely a blip on the total span of the Milky Way galaxy. There could right now be literally hundreds of interstellar civilizations just in the Milky Way, and they’d all have no idea of the others’ existence.

Space is BIG. And that’s not even getting into the great span of time that could separate civilizations.

The Fermi Paradox clearly shows that once a civilization gets rolling, it takes a comparative small amount of time to colonize the entire galaxy. I suppose you could make a special case of 3: civilizations do spread a little bit and then stop for some reason. However, it’s hard for me to come up with any compelling reasons why this should be.

“Separated by time” is not really that interesting. Unless the times separating galaxy-class civilizations go into the billions of years, you would expect to see evidence of the previous civilization around our own system. We’ve had a bunch of threads on here about how hard it is to completely remove all evidence of a technological civilization, so I would expect that if any aliens had been to any of the planets in our little ole system, we would see evidence of this. Unless of course, you would like to plead the “Zoo” scenario, but that would mean we were not separated by time at all.

I agree with many here: There is a probability for life on other planets, but it is beyond remote that we will ever encounter it.

I think there is life outside of Earth, but I don’t believe it has visited us. Yet?