Aliens - where are they?

[CORed]

When dealing with questions of extraterrestrial life and intelligent extraterrestrial life, we are handicapped by an insufficient sample size. One is a pretty small sample, so any hypotheses we come up with are going to be highly speculative. However, I'll give it a go.

I suspect that life is pretty common in the universe, but that life capable of interstellar travel is extremely rare. Actually, we have a sample size of zero with respect to life capable of interstellar travel. We humans would like to think that we are smart enough to pull this off, but whether we will remains to be seen.

Earth is approximately half way through its habitable life span. It formed about 5 billion years ago, and about 5 billion years in the future, the sun will exhaust it's hydrogen, expand into a red giant, and incinerate the Earth. So, based on our sample size of one, we would have to say that life capable of producing complex technology takes a long time to evolve and may well be pretty rare in the universe.

The second factor is interstellar travel. It is a tough nut to crack. Assuming that there are none of the loopholes in Relativity that are so popular in science fiction, such as warp drives, hyperspace, wormholes (that one can actually travel through without being broken down into ones component elementary particles), traveling to another star system will take an incredible amount of time, an incredible amount of energy and other resources, or both, and even if we accomplish this, there is no guarantee that we we will find habitable planets or other intelligent life at the other end.

So, even if we manage to advance our technology to the necessary degree before nuclear war, exhaustion of resources, asteroid impact, global warming, or some other man-made or natural disaster leads to our extinction or the collapse of industrial civilization, it is not inconceivable that we (or hypothetical intelligent E.T.'s) will decide that it just ain't worth it. So we really don't have any idea how common actual or potential star-faring species are. 1000 per galaxy? 10 per galaxy? 1 per galaxy? 1 for every 100 galaxies? If the frequency is on the low end of that range, we may never find any of the others.

[m_the0ry]

All of the things you list are both probable and possible. You're describing Fermi's Paradox almost exactly.

There are about 10^18 stars in the average galaxy, and about 10^10 observable galaxies. That's a crapload of stars. Fermi's Paradox poses the question of why life can't be detected elsewhere.

I personally think intelligent life has existed many times in the universe and will continue to.

[Piers]

The obviouls reason that we dont see any alians is that there really is no way around the speed of light.

So sad for Sci Fi fans [img]/images/graemlins/frown.gif[/img]

Come on is any other explanation really needed.

[Metric]

I subscribe to the "technological life is too rare" approach. Basically, once you have a technological species, it's a matter of a very short time until 1) it dies out or 2) goes through a technological singularity which results in its effective emergence as a new unimaginably advanced species, easily capable of spreading throughout the universe (galactic colonization would take place extremely quickly for such a species, compared to the timescale for evolution).

So the fact that our solar system isn't inhabited by intelligence spreading throughout the galaxy tells me that the evolution of intelligent life itself must be rare. This can be supported by the following chain from the book "Where is Everybody? -- fifty solutions to the Fermi paradox"

80% of the stars in our galaxy are outside of the galactic habitable zone, where gravitational perturbations prevent the existence of sufficiently stable planets, lasting long enough to devolop life.

Of those, only 5% of the stars are in the right spectral class to support life.

Of those that remain, we need a terrestrial planet to remain in the extremely narrow continuously habitable zone for billions of years. That 1% of the stars that remain have planets that meet this requirement is a very generous estimate.

On what fraction of these will primitive cellular life actually emerge? The answer ranges from none to "very few" to "lots" -- given the absence of intelligent life permiating the galaxy, I opt for "very few" but many will take "lots" for the sake of a more interesting argument.

On what fraction of these will life be snuffed out at an early stage due to planetary disasters? Not sure, but it's probably a significant fraction.

How many of these life forms ever make the critical prokaryote-eukaryote transition? It apparently took an extremely long time on earth. This may mean that it's far from inevitable on any given life-inhabited planet.

Of these, how inevitable is abstract, high-level intelligence to evolution? Of those, how inevitable are the use of tools and advanced language? Of those, how many survive technological adolecence without destroying themselves?

Being a little conservative, it's not hard to put the estimate at one human-like intelligence per galactic supercluster, which is of the size scale of hundreds of millions of light years. This, I think, might be sufficient to make reasonable the observed fact that some post-singularity species has not yet saturated the resources of our solar system along with the rest of the galaxy.

[MaxWeiss]

Also, I thought we were sending out very strong busts of prime number sequences that they could pick up with technology comparable to our own. But again, even at light speed, it might take a while for them to get it.

[Double Down]

The problem with all of these speculations is that they are all based on a very Earth centric idea of what life is.

We are making assumptions such as that is has to be a carbon based life form, that it would use similar technologies to what we use (metal, electricity, etc) and that they would be limited in other similar ways, such as resources, life expectancy, and similar mentalities.

Yes, it is probably unlikely that a species similar to us will make contact, because we are well aware of our technological limitations. But truly, if there is a lifeform that is so advanced so as to be able to reach us, it is entirely possible that they are also so far advanced in other ways, such as mentally, or spiritually (don't flame) that their reasons for wanting to visit us might be very different than what we would speculate, such as to colonize.

Survival of the fittest may not be an issue in other areas of the universe, e.g. the Borg from Star Trek, a species that revered itself as one entity.

It is entirely possible that there exist lifeforms in different dimensions of reality, and that have made contact with us in any number of ways, such as taking 3rd dimensional forms and making contact, or influencing our thought patterns. There is some speculation that crop circles are messages from higher dimensional entities that pass through our three dimensions.

We need to open our minds a little here. Similarly to another bothersome thing about the SMP forum, which is that every other thread is arguing Christianity. There are hundreds of philosophies and religions, and to continue to banter back and forth about this single one is like having a poker forum where every thread is about Sit N Goes.


And no, I'm not a crackpot with a tinfoil helmet. I'm sure I come across as one by now [img]/images/graemlins/tongue.gif[/img]

[CORed]

[ QUOTE ]
Also, I thought we were sending out very strong busts of prime number sequences that they could pick up with technology comparable to our own. But again, even at light speed, it might take a while for them to get it.

[/ QUOTE ]

The real danger is that some truly advanced civilization will see an episode of "Fear Factor" and decide that the Earth has an infection that demands complete sterilization of the planet.

[tisthefire]

didn't you see men in black?

[yukoncpa]

Hi Metric,

When I read your post, it reminded me of a book I read long ago. One of the other things that the book mentioned was that most likely for terrestrial life to evolve, ( along with every other thing that you mentioned ) a planet would need to have a moon roughly the size of ours, thus making the search for an appropriate planet even more rare.

[ QUOTE ]
The regular rise and fall of sea level creates an unique environment in the Solar System, where life is exposed to both immersion in water and exposure to air in the space of a few hours. This interface between two distinct ecological niches is thought by many to be crucial in evolutionary terms.


[/ QUOTE ]

From a web page that I googled the key words, Moon, evolution, life

[TimWillTell]

This universe is infested with aliens; and there all hundreds of millions of light-years away.
They are trying to communicate with us with the help of "parallel-particles", but we still haven't been able to read those particles.

BTW these aliens are of-course AI.