I tend toward
Rare Earth Hypothesis territory. So #1, #2, and #5 would usually be my automatic defaults. But accordingly I can mindfully specify something else on occasion. It's just that by being a contrarian about it, things can potentially get more interesting. You may witness passionate reactions oozing out of our secular orientations that could resemble the confidence or haughty anger traditionally attributed to religious-like beliefs defending themselves.[*]
The
principle of mediocrity isn't really panning out in terms of exoplanet research. Our solar system actually does place on a spectrum from "kind of weird" to "very weird", with the Earth slotting similarly. In sloppy metaphor context, perhaps a crude astronomical equivalent of how westerners are
WEIRD.
For almost 4 billion years there was no complex life on Earth. IOW, it's apparently not easy to arise even on a favorable world also blessed with the long-running luck of dodging various major cosmic catastrophes (a few intermittent small asteroid impacts during later eras, volcanic disturbances, climate changes, and so-forth don't count as those in magnitude). After complex life finally did enter the scene circa 600 million years ago, it wasn't until the last million that anything resembling open-ended, self-programming technological species arose.
It's truly remarkable how scientists fall over themselves to assert that evolution isn't teleological, that results like complex life and especially intelligent life aren't inevitable or predetermined after _X_ span of time. Yet they then seem to toss that out the window and hand over the reins to calculating folks using probabilities derived from just-so-story expectations. (Since there is no set of examples to abstract from in terms of worlds with life; just Earth alone to draw a quantified likelihood. Along with dogmatically clinging to the mediocrity principle despite evidence otherwise, such resting in the background as a biased influence.)
- - - footnote - - -
[*] I recall that once happening in Sciforums. It's ironic that MR gets into trouble if he comes across as too "pro" about space aliens, but there's trouble with SF orthodoxy if one goes too far the other way, too.
Until shown any evidence to the contrary, #1.
1. There aren't any aliens to find.
I'll assume that "aliens" here means "extraterrestrial life" of any form. My own view is that given the incredible and almost surreal complexity of Earth life, that life of whatever sort (that calls for a functional definition of life) is a very rare and fortuitous thing. Given the incredible and almost surreal scale of the universe, I'd guess that there are indeed things functionally like Earth life out there. They are probably spread very thinly though. The closest examples might be very far away. Needle in a haystack.
2. There is no intelligent life besides us
If Earth life is about 3 1/2 billion years old, and human-like hominins only a few million (and the earliest ones were pretty crude), the vast majority of "life-forms" (or their functional equivalents) may not be intelligent. I do expect that there are intelligent space aliens, but they will be spread even more thinly than life.
3. Intelligent species lack advanced technology
The Scientific Revolution was only a few hundred years ago. Hunters/gatherers or simple agricultural cultures might be more prevalent than scientifically advanced civilizations.
4. Intelligent life self-destructs
That's too pessimistic, but even if it doesn't it probably only has a limited lifespan.
5. The universe is a deadly place
Could be. Apart from plagues, asteroid impacts, gamma ray bursts and supernovas, alien life might not all be friendly.
6. Space is big
Interstellar travel will be exceedingly difficult. If intelligent life is distributed very thinly, then the distances to be crossed will likely be even more daunting and vast. Even if aliens have beaten Einstein and developed super-luminal vehicles, they would still have to find us (billions of stars in each of billions of galaxies).
7. We haven't been looking long enough
If we are listening for transmissions, our hypothetical aliens would have to have been making suitable broadcasts at precisely the point in time when their broadcasts would be arriving here now.
8. We aren't looking in the right place.
If they are in another galaxy or somewhere like that, would a transmission, even a highly directional beam, even find its way to us? Or just get lost in the cosmic background noise? Why would their directional beam be directed towards us?
9. Alien technology may be too advanced.
Use of radio waves might be replaced by something else. Aliens might assume that a suitably advanced civilization would be using it too. (Just like we expect them to be broadcasting radio waves.)
10. Nobody is transmitting
Possible. Or not transmitting in a form that we would recognize as being a transmission.
I've long suspected that we might detect noise aliens make rather than transmissions. I can imagine the business-end of a super-powerful star-drive being fleetingly and entirely accidently pointed in our direction for a short time. Or electromagnetic crashing and banging from cosmic-scale industrial processes like cutting up planets to make Dyson-spheres. Would we be able to recognize it for what it was?
11. Earth is deliberately not being contacted
I'm skeptical about that one, it sounds like a Cold War conceit. Unless superluminal transport is easier than we think. Otherwise they would have no reason to fear our arriving wherever they are, for many thousands of years at least.
12. Aliens are already here and we just don't realize it.
That's another possibility, but I'd give it a low probability for the reasons above.
If life begins in a watery environment then it may be that this is where it stays. Transitioning to land may be a very rare occurrence for life containing planets. Thus it might be highly unlikely technology advances underwater and if it does then it would be so vastly different from ours that we may never detect it. It could be that most of the life in the universe is contained in oceans beneath a shell of ice, with little need to contact us or anyone else.
That’s why I loved the movie The Abyss. A super intelligent underwater civilization, complete with a technology so vastly different from ours that we never even suspected they were there.
For those who need ''evidence''...what would suffice in order for you to believe in the possibility of alien life? (extraterrestrial)
(Feb 7, 2020 06:06 AM)Leigha Wrote: [ -> ]For those who need ''evidence''...what would suffice in order for you to believe in the possibility of alien life? (extraterrestrial)
I have more evidence for life in the universe than I do for God(s). I don’t even have to leave the planet.
Quote:6. Space is big
That's probably the main reason imo for no contact with ET's. 100 billion stars in our galaxy. 100 billion galaxies. Ofcourse that ups the odds of there being intelligent life out there. But the odds that we'd be contacted out of all those other places seems very low to me.
(Feb 6, 2020 03:43 AM)Zinjanthropos Wrote: [ -> ]If life begins in a watery environment then it may be that this is where it stays. Transitioning to land may be a very rare occurrence for life containing planets. Thus it might be highly unlikely technology advances underwater and if it does then it would be so vastly different from ours that we may never detect it. It could be that most of the life in the universe is contained in oceans beneath a shell of ice, with little need to contact us or anyone else.
That’s why I loved the movie The Abyss. A super intelligent underwater civilization, complete with a technology so vastly different from ours that we never even suspected they were there.
Yes, I agree. At least here in our Solar System, water oceans under shells of ice might be more common than Earth like conditions. If that's true in the rest of the universe, it's conceivable that most life lives in conditions more like a moon of Jupiter or Saturn.
They may have no idea that the rest of the universe is even out there.
(Feb 7, 2020 06:06 AM)Leigha Wrote: [ -> ]For those who need ''evidence''...what would suffice in order for you to believe in the possibility of alien life? (extraterrestrial)
As far as simple life goes, I wouldn't be surprised if some other body in the solar system harbored it. But I'd be initially skeptical that biogenesis occurred in its immediate surroundings rather than its ancestors distantly originating on Earth or primeval Mars billions or millions of years ago, or via even a "recent" space probe. In the same vein but minus dependence on this planetary system, I wouldn't be that surprised if simple life arose on some exoplanet (but if nearby in terms of not too many light-years, I guess Earth or Mars still couldn't be ruled out as provenance prior to microscopic analysis).
But for extraterrestrial, complex, intelligent life in this galaxy: Well, as one theory for the state nickname of Missouri goes: "
I come from a state that raises corn and cotton and cockleburs and Democrats, and frothy eloquence neither convinces nor satisfies me. I am from Missouri. You have got to show me."
Show me an actual instance of it that reliably hangs around or persists for inspection, or artificial, historic remains of engineering -- or a surviving legacy of self-replicating spacecraft or artificial space wildlife hibernating in nomadic excursions between stars.