Why We Haven't Met Aliens Yet

[Corsair 115]

The assumption is that a civilization would spread throughout the galaxy.

The underlying assumption is that each galaxy is like that portrayed in Star Trek or Star Wars, where it contains dozens, if not hundreds or even thousands, of intelligent species. But what is the hard evidence that says each galaxy must contain many multiples of advanced civilizations? That is a galaxy-centric focus it seems to me.

Consider: even if on average there was only one advanced civilization per galaxy, since there are roughly 100 billion galaxies in the universe, that'd mean there are 100 billion other advanced civilizations out there. That sounds like a hell of a lot of other advanced species to me, a universe teeming with it in fact. (But due to the vast intergalactic distances we'll never get to know about them.)

 

[Dcdrac]

There is the possibility that all races are still in the early stages of technical development, also it could be that they come and go all the time and only exist for brief moments then wink out.

13.9 Billion years was the last estimate I saw for the age of the Universe, the Earth is 4.5 billion years old and we have only been around for something like 250,000 or 400,000 depending on who you read, so we have only just arrived it could be the same elsewhere.

 

[El Greco]

It could also be that we have already met aliens without knowing it, like bacteria in a culture are not aware that they are being monitored.

 

[mikeyx]

http://seedmagazine.com/content/article/why_we_havent_met_any_aliens/

This was an interesting article. I've never heard of this before. He's written a book on the subject that sounds like a good read. Not sure I go along with the implications yet though.

They may well have passed by taken a look and felt it better to keep on going.

 

[Skeptic Ginger]

http://seedmagazine.com/content/article/why_we_havent_met_any_aliens/

This was an interesting article. I've never heard of this before. He's written a book on the subject that sounds like a good read. Not sure I go along with the implications yet though.

That's a funny piece.

 

[dlorde]

The scale of the universe means that even if each galaxy has plenty of life at various stages of development, the chances of physical contact are probably remote, as are the chances of radio contact, because they're likely to be so far separated in space (& time) - or so it seems to me.

 

[3point14]

It's the combination of vast amounts of time and vast amounts of space that would make me believe that even if life is not uncommon in the universe, incidents of any species of one planet meeting any species of another planet are exceedingly rare across the whole of the universe.

The odds of the two species intersecting on the 'space axis' are probably fairly slim, the odds of them intersecting on the 'time axis' are also pretty slim. Multiplied together, that's fairly anorexic.

I think we'd need to be fairly lucky (or unlucky, depending on circumstances) to be one of the very few intelligent species that gets to meet with other non-terrestrial intelligent species.

 

[godless dave]

It's the combination of vast amounts of time and vast amounts of space that would make me believe that even if life is not uncommon in the universe, incidents of any species of one planet meeting any species of another planet are exceedingly rare across the whole of the universe.

The odds of the two species intersecting on the 'space axis' are probably fairly slim, the odds of them intersecting on the 'time axis' are also pretty slim. Multiplied together, that's fairly anorexic.

Yeah that's what I was trying to say above.

As to aliens visiting earth - that's like finding a needle in a Texas-sized field of haystacks.

 

[gnome]

I think the assumption that intelligent aliens would inevitably colonize the entirety of the galaxy they were in is unjustified. They might have no urge to colonize outside their solar system; they might find it cost-prohibitive; they might die out before they develop the technology to do so.

I agree in part--they might choose not to do so, or die out before they begin. But once it starts I think the genie is out of the bottle since the eggs aren't in "one basket" so to speak.

Unless interstellar travel at sublight is so impractical it isn't done even on scales of millions of years, in which case we'd never meet aliens that way either.

But once it starts... the galaxy is say 100,000 light years across. If we were able to expand at .01c (is that perhaps plausible, if we really applied ourselves?), that means about 10,000,000 years for our influence to encompass the entire galaxy. That's not really enough time for a competing planet to evolve sentient life--the only possibility of competition would be if by some amazing coincidence they were already at advanced stages of evolution around the same time that we were.

On the other hand, if it takes us say 10 times that long, and we expand at .001c, there would seem to be enough time for another planet to evolve life and intelligence and get out into space with us. So it really does depend on that expansion rate.

 

[Gawdzilla Sama]

I find it funny that those theories about aliens speak about them as if they were merely a different race of humans or something. We have absolutely no idea how an alien life form would be and whether they would reproduce like earth life forms or whether their evolution would have anything to do with our evolution.

"Those theories" being ones in this thread?

 

[godless dave]

I agree in part--they might choose not to do so, or die out before they begin. But once it starts I think the genie is out of the bottle since the eggs aren't in "one basket" so to speak.

Unless interstellar travel at sublight is so impractical it isn't done even on scales of millions of years, in which case we'd never meet aliens that way either.

That's what I'm thinking.

 

[Dinwar]

that means about 10,000,000 years for our influence to encompass the entire galaxy. That's not really enough time for a competing planet to evolve sentient life--the only possibility of competition would be if by some amazing coincidence they were already at advanced stages of evolution around the same time that we were.

10Ma puts us back in the Tortonian, the early Late Miocene. It's about 2x to 3x times how long it took for our own taxa to evolve us. Multiple species of humans arise and went extinct in that time, though that may be because it's in the diversification phase of Punctuated Equilibrium. I'd say that 10Ma is more than enough time for a sentient species to arise and develop an advanced civilization. That's assuming one CAN arise, and it's entirely based on chance whether one will.

I'd say that colonization of multiple star systems is required for long-term survival of any civilization. Our own has a maximum of 4 to 5 billion years left--once the Sun becomes a red giant, we're an inclined plane wrapped helically around an axis. Plant colonies around multiple suns, and you're safe from that.

 

[casebro]

Nearest habitable planet is umm 400 light years away. That means it will take anothe 30 years for our first radio signals to get there.

On the other hand, if some other civilization can make it here at all, they would need some advanced tech just to go FTL. Perhaps they are here, and using other advanced tech to hide- cloaking devices on their ships in orbit, or hypnosis fields around the lizard men so they look like Belorussians to us?

 

[Gawdzilla Sama]

Nearest habitable planet is umm 400 light years away. That means it will take anothe 30 years for our first radio signals to get there.

Damn, your math is worse than mine.

 

[Dinwar]

Nearest currently known habitable planet is umm 400 light years away.

Fixed that for you.

On the other hand, if some other civilization can make it here at all, they would need some advanced tech just to go FTL.

Nah. I've given this some thought. I have a ship that can go to other stars. I arive at one with a number of potentially inhabitable bodies (remember, I'm living in a self-sustaining metal box--ANY planet is potentially colonizable). Obviously, the gas giants are out, at least at first. I'd say Mercury and Venus are out as well--too hot on Mercury and I don't want to deal with sulfuric acid rain. One planet has hostile natives, so let's avoid that one and the ones nearest it. That leaves me with the Asteroid Belt, the Ort Cloud, and the moons of the gas giants--enough that if we keep inter-body transports to a minimum, we're effectively invisible by accident. The hostile natives of the third planet send the occasional probe, but we can see that coming and hide ourselves (remember, they're potentially hostile--best to not provoke them). Or, we use technology or biology they can't recognize so we're entirely unconcerned--a silica-based organism, or one that lived on a planet where methane served as the main fluid, would be undetected, particularly if we haven't even found the object they're on yet.

It's related to my problem with Sci-Fi robots: why fight humans? They're ROBOTS--they don't need atmospher, or protection from radiation, or the like, so they could operate on airless asteroids, moons, and the like and never come into conflict with us. There's no reason to assume they'll want to kill us. There's no profit margine in it for them.

 

[kedo1981]

I think it could be an issue of underestimation.
Underestimating how vast the galaxy and the rest of the universe really is.
And underestimating how long it would be before a civilization needs to leave it’s home solar system.

 

[Gawdzilla Sama]

It's related to my problem with Sci-Fi robots: why fight humans? They're ROBOTS--they don't need atmospher, or protection from radiation, or the like, so they could operate on airless asteroids, moons, and the like and never come into conflict with us. There's no reason to assume they'll want to kill us. There's no profit margine in it for them.

"Carbon based lifeforms must be eliminated."

 

[Roboramma]

It's related to my problem with Sci-Fi robots: why fight humans? They're ROBOTS--they don't need atmospher, or protection from radiation, or the like, so they could operate on airless asteroids, moons, and the like and never come into conflict with us. There's no reason to assume they'll want to kill us. There's no profit margine in it for them.

I pretty much agree, but they may see the potential for conflict for resources. If they are using the asteroids in the asteroid belt, they may see that at some point in the future we may want to do the same, for whatever purposes. There are plenty of resources there. We may see that as well, and find that it's better to destroy these invading robot asteroid colonizers before they've built their infrastructure to the point that we no longer have the capacity to destroy them.

But I pretty much agree with your assessment: if aliens arrive, it will likely be their machines that arrive. And they are far more likely to make use of the asteroids and comets in our solar system (why go down a deep gravity well when you don't need to?) than come to the earth. But if they change the orbits of those asteroids, and bring resources that are scarce on one to another (both of these things are likely and not dependent on the biology of the builders or the design of the robots), then we'll likely notice at some point, though not necessarily early on.

 

[Gawdzilla Sama]

We're assuming robots will be rational? In that case they would eliminate humans without warning.

 

[Roboramma]

We're assuming robots will be rational? In that case they would eliminate humans without warning.

Not necessarily entirely rational, but capable of solving complex problems to further whatever their goals happen to be.

They may not even notice us. It's entirely possible that their builders may assume that other intelligent life simply doesn't exist and not program them with the capacity to look for life. Their "ability to solve complex problems" may be directed explicitly to a specific goal (developing specific infrastructure based on available materials, perhaps), in which case they might not be capable of developing a plan to deal with us if we begin to make ourselves known. The level of AI in such robots, and the variety of situations its capable of dealing with, is not something I pretend to have any insight into, except that it will have to be of a certain minimal level to deal with whatever it is that they were sent here to do.