sample size of zero.

Fermi was right.

As long as we're just creatively speculating... Panspermia

But one of my fav toons...

[IMG][/IMG]

part of a symbiotic relationship with something that disguises itself as an extra-terrestrial invasion so as not to alarm us.
-Terence McKenna (from a lecture)

I like that quote.

Because there is no solid evidence that we've been visited by ETs, I don't think we have been.

but wouldn't even hazard a guess as to the probability of it. It might not have even been something we'd be able to detect. It might be something that couldn't detect us, for that matter. They might not even *be* matter, or even a they.

Last edited Wed Apr 9, 2014, 02:15 PM - Edit history (4)

There is no place nearby to us where any aliens could be living. The nearest star is four light-years away. Even if the extremely unlikely event came true and there were intelligent life forms on one of the closer stars, that's still an unrealistic distance for any conscious critter to likely ever travel.

Any life form would have evolved to the conditions of its own planet. The chances for anyone of finding an adequately similar planet anywhere close to their neighborhood is small. The incentive to search for any such planet is low, compared to the disincentive due to the extreme costs and probable insurmountable challenges.

One would have to make the trip in one lifetime since it would be extreme child abuse to give birth in space, whether human or space critter.

The fact that we live on an habitable planet is no clue to the likelihood of there being life on an individual planet around another star. All we know is that life is possible. Any intelligent life will automatically live on one of those habitable planets, and this fact may unrealistically bias it (including us) to the likeliness of there being life on other planets.

I think there are likely a huge number of planets beyond earth with intelligent life, but the odds for an individual planet are extremely low. But since the visible Universe is probably a tiny speck of the totality of our Universe. There are a lot of planets out there with potential life

In Big Bang inflation theory, our Universe drastically expanded in an unimaginably very short period of time well before the first second of its existence was over. This caused our original lumpy Universe to spread far apart, the great majority well beyond the horizon of any future conscious creature that may inhabit a future planet. So that tiny speck of our Universe that we see has almost no lumps in its Cosmic Background Radiation, and now our visible Universe is mostly uniform.

This means there are an unimaginably huge number of planets in our Universe alone (and probably many universes beyond our own), and a lot of life beyond our horizon. Reality plays a lot of lottery tickets to create life, but you'd have to win the lottery to find life on an individual planet.

if they exist at all. Finding planets that could likely support some kind of life is probably hard. Finding planets with intelligent life is probably very, very hard to find. In the 4 billion years of Earth's history, intelligent human life has been here on the planet (that we know) only for the tiniest fraction of time. Finding planets with intelligent life that have managed to become space-faring cultures on a grand galaxy wide scale is probably quite rare.

But there only has to be one. The Milky Way has existed for over 13 billion years. There are more than 300 billion stars in the Milky Way. I'm not a mathematician but I would guess that there would be at least a very, very likely chance of at least one very advanced, very old civilization among the billions of possibilities. One intelligent civilization more than a billion years old might have had time to evolve into that Type III civilization according to the Kardashev scale, the one that Michio Kaku and many other scientists describe as one that has harnessed extreme types of energy such as a Dyson sphere (harnessing the energy of a star) and even of a supermassive black hole. That level of energy would probably allow for space travel approaching the speed of light and many other things we haven't dreamed of. Members of such a civilization probably would have long shed their organic bodies and done away with such things as lungs, a heart, and a circulatory system as it allows only life in a very narrow zone and is too prone to dangers and inefficiencies. Those beings probably long-ago melded with and evolved into machines and the machines themselves resemble organic structures, not rigid and heavy metallic structures, but flexible, lightweight, and adaptable and self-regenerating (like organic skin, muscle, and bone) bodies. The members of such a society may have become virtually immortal and may have evolved into a group mind, no longer existing as independent thinking entities. Space-faring cultures of a billion years of age and more would probably have long left their original planet and found themselves at home in deep space. Such old cultures would long ago have set about to exploring all parts of the galaxy and, given the exponential spread of their kind over a very long period of time, eventually made their way to all 300 billion stars of the Milky Way.

I think it's very likely that at least one such old and very advanced civilization exists and that it have spread throughout the galaxy just as humankind has spread throughout planet Earth. My doubt however is that they have actually come to Earth, although they would surely be aware of it. That's why I marked "not sure".

Personally, I'd like a definition of "species" before answering the question.

Species of what?

"Visiting" Earth sounds like a purposeful, intentional, and temporary act. If they are some kind of space-dwelling bacteria that floated to Earth by accident (in which case some scientists think they've already come) I don't think the word "visiting" would apply. Considering this question is posed in the "offbeat" section of DU and follows several posts discussing aliens, ufos, and the like, I think it's reasonable to assume that its subject is ET without having to define each and every word.

I guess I can't interpret it for anyone else but I think the others in the thread also read it that way. I don't know the answer to your interesting question but I think it deserves a thread of its own.

Are we talking multicellular organisms? Viruses?

Please narrow down what you mean by "species".

Many alien species of rock have certainly visited earth.

Because I am a doubting Thomas I guess. I don't know. I don't if there is a "God" or not either.

That said, I certainly think that we can think outside the box about UFOs and mankind. My own pet theory is that we are a genetic experiment conducted by an advanced race, UFOs, half them, half hominid earth creature.

Then I ran into people like Stitchen and Pye and they seem to have came to the same conclusion.

I don't know, but it is interesting to speculate about.

If multicellular life arrived in a comet then we are all aliens, well adapted ones at that. All those rocks in space came from dead planets. It is possible that the star that preceded ours had a planet with life. That star exploded and get some yummy left overs. When our sun goes the only that may survive is the rock eating bacteria miles down.

I would have to say yes

And accomplishing that feat, remain healthy enough once they arrive . . . to do their infamous probing.