Aliens have not visited.

If aliens existed, they must be so different that earthly resources are of no value to them. Or they have plenty of resources of their own and don't need to invade.

Both possibilities are unlikely, so I don't think they've visited despite all the science fiction and imaginative fantasy over the years. The reason: There's only one type of DNA code. If aliens ever arrived I would expect them to have brought in their own biological language. And then we'd have two or more genetic-models in competition on earth. But there's only one code. There's also no sharp point where evolution jumps to something completely new and different.. So evidence shows that there's only one evolutionary story on earth these last 2+ billion years.
If they came, they would have stayed.

So aliens I guess the unspoken premise of the UFO meme out there is that the Greys or whoever are treating the earth like a zoo.. This seems unlikely and in any case, in the long run it's unsustainable. Assuming the same rules of life out there as exist right here - i.e. - constant searching for growth, Darwinian competition, destruction and absorption of the weak by the strong, etc. Columbus and the Americans did not go to the new world to have a look around and sight-see. After discovery pressure for invasion came from every direction in European society, just as it would in an 'Alien society' counterpart.


Given physical law and the natural order of things, which are universal, there is no other scenario I can comprehend in which they would exist, but choose to stay away.

Life doesn't work that way. It seems more likely that nobody has visited at all. Logic points against any contact. Maybe interstellar flight truly is beyond the sumit of evolutionary biology, here and elsewhere. We might indeed just be too small to ever make the jump.

Of course aliens are usually a tool in cinema and fiction for different psychological facets of human experience.

These include:
1) A stand-in for God / Higher Power among scientific/secular types like myself.

2) A way to give a three-steps-removed perspective on human events and foibles from an outsider's point of view.

3) A way to explore monsters/demons, politics & social situations in our imagination which do not correspond to earthly Nature. - I.E. - to wipe the earthly slate clean and allow the writer and reader to fiddle with parameters of a story which would be inflexible in more down-to-earth fiction.

4) As a way to speculate about the future of science and it's impact on humanity, a field which the Aliens will developed in some curious and unexpected direction.

Our curiousity is endless. What we're interested are basically a group of questions about convergent evolution, both biological and technological. I.E. - How are we the same, how do we differ, and why?

Most of science believes that, like Dolphins and sharks and long-extinct ichtheosaurs, or wolves vs. Tasmanian Tigers, or Birds vs. Pterosaurs, or modern trees vs. prehistoric fern-trees, we may be substantially similar in many details, a subject of endless sci-fi speculation. There is only one way to build a car - with four wheels. Five is too many, three is not enough.

Similarly there may be only one way for intelligence to evolve - through a quadruped, standing upright and developing brainpower to add functionality to it's freed for-limbs.. There are embryonic developmental-reasons why all advanced earthly lifeorms all are designed through bilateral mirror-symnetry, that is, two eyes, opposing arms, legs, ears, etc.

And then a vast variety of other questions come to mind. Do they sleep? Do they have religion? Do they have crime/war/poverty/ morality/ mortality/gender & individuality & politics? What does their music sound like? How do their social structures work? Are they hive-minds? Do they have castes? What do they look like? Do they want our women? - (probably not).

Although an alien planet would is almost infinitely distant, the physical rules should still apply. And of course, our brain and psyche has evolved in certain ways to meet our needs. Are they down the same path, or not? Have they taken control of their own evolution, as humanity is likely to do in the next 200+ years? How's that worked out?

They don't really answer spiritual questions, though. If they created us, the next question is .. who created them? And then who created the creators, etc. It's the standard infinite-regression problem, which religious folks refuse to recognize, but which Darwinism has proven to be the only logical answer.