Why do we see no other intelligent civilizations? (Fermi)

[Aerion]

If they are in cahoots with our governments why would the aliens see fit to put themselves into such an arrangement with us?

I find that question interesting to pose to those who believe "they are here." The answer I have just heard is perhaps they have some bad plot with the "government". Or more likely if it is the case they believe in hierarchical leadership, and only wish to communicate with the top who does not want the rest of humanity to know. I doubt in the age of Anonymous and other hacker collectives such a secret could be hidden though unless there is not a trace of evidence on any electronic files anywhere of proven extraterrestial life. Of course perhaps the government is smart enough to put THAT on separate servers not in any way connected to the 'Net.

[AiliailiA]

Perhaps there's some way Out of the universe. At some stage later than our current development, galactic civilizations get the option to leave and do so.

If you had the option of living in 4 dimensions instead of 3, for instance. Why wouldn't you?

[Aerion]

Perhaps there's some way Out of the universe. At some stage later than our current development, galactic civilizations get the option to leave and do so.

If you had the option of living in 4 dimensions instead of 3, for instance. Why wouldn't you?

One of the most intriguing answers yet! Of course it sounds like some of the spiritual people who believe we may somehow consciously/spiritually evolve into "hyper-dimensional" beings. Perhaps more practically they stumble upon some quantum technology.

Though there would be no beings left that would be like "bodhisattvas" and help light the way?

[AiliailiA]

None of the above. There are many, many reasons why we wouldn't see them. Here's a couple:
1) We have been looking for a pathetically small period of time.
2) They might have come up with a communications solution that doesn't involve horrendously wasteful outpourings of radiation in every single direction.

I like (2).

They might also have such good encryption that their communications just look like noise to us.

If you image something like the Prime Directive, encryption would be a different "bar" and perhaps more logical than "when they discover warp drives". Firstly because warp drives probably aren't possible, but that aside first contact is more likely to be by hearing aliens than meeting them.

A really quite dumb civilization could still discover radio and telescopes, just take longer about it. Requiring them to also pass some bar of encryption tests that they aren't too dumb, and also would impose delays between suspecting that a message is there, being sure a message is there, and beginning to understand the message. That delay might be a very good thing to avoid self-destructive or warlike responses from a young civilization.

[Octogots]

because space is,you know,kinda spacey

[Our Most Resplendent Goddess Sen]

It would take a single expansionist civilization perhaps a few million years to spread across the galaxy.

You may be seriously underestimating the problem. Colonizing a star a couple light-years might all by itself be a project that takes several million years to accomplish, given the need to hoard a large fraction of the energy available within one's solar system just to get enough fuel to send the ship. And then it would take millions of years to get to the next star, etc. I don't know if this is how it will turn out, but it certainly doesn't seem impossible.

You are incorrect.

[Scocialist Provinces]

So... Where is the "I believe in advanced civilizations in the universe, and the OP is making himself look like a fool by overthinking every point." Option in the poll?

[Aerion]

So... Where is the "I believe in advanced civilizations in the universe, and the OP is making himself look like a fool by overthinking every point." Option in the poll?

How am I making myself a fool? It is just a fun exercise in imagination, and theorizing.

[Scocialist Provinces]

So... Where is the "I believe in advanced civilizations in the universe, and the OP is making himself look like a fool by overthinking every point." Option in the poll?

How am I making myself a fool? It is just a fun exercise in imagination, and theorizing.

Well, someone makes a simple point, and you throw a paragraph of filler at them. I can do that too, if you'd like.

[G3N13]

I chose "Evolution to and conditions for intelligent life is rare to nonexistent", however that's not exact.

I'm more into 'space is just too darn big' -explanation.

Let's do a magnitude estimation, with optimistic numbers from the hat:
- Spacefaring species: 1000
- Ships/probes dedicated to scouting star systems: 10,000 per species
- Average probe velocity during travel: c/2
- Average stellar density: 1 per cubic parsec -> ie. closest star is roughly 1 parsec away -> ie. probe is 6 years in transit
- Average research time per system: Negligible

Average research speed of all the spacefaring species combined:
1000 * 10000/6 years = 1,67 million star systems per year

Now, size of our galaxy:
- 200 000 000 000 to 400 000 000 000 stars.
- Perhaps 1/4 is habitable

Which totals to an average research frequency of a habitable star system:
Once every 30 000 to 60 000 years.

Also, let's not forget this:
- Average time to report home: 300 years
- Average time to react back: 600 years

So, perhaps there are aliens over there but they need not have visited this place in tens of thousands of years EVEN if they were actively probing nearby stars.


Compare those numbers to the age of human civilization:
- Homo Sapiens: Several hundred thousand years
- Culture & Irrigation: 7-8000 years
- Road networks: 2000 years
- Radio: 100 years
- Space age: 50 years

Humans haven't been obviously visible for much longer than 1000-2000 years and beyond 8000 years you would need a much longer than cursory glance to tell that one of the species is intelligent, so I'd think it would be pretty unlikely that an alien species would be aware of us.

I would also guess that the signal trace of an advanced species would probably be less than the omnidirectional beacon we're exhibiting or expecting, because that's just wasteful.


Also, one interesting consideration is that science will have great difficulty detecting alien signals. I don't mean that the intended signal itself would necessarily be hard to detect, but verifying it's source and that it's artificial will be nigh impossible because sending a continuous signal from an orbiting system to another orbiting system is hard and probably 'not worth the effort'.

Consider the Wow!-signal: It might have been a burst from a sentient species not dissimilar to the signals we've been sending out...but as it cannot be detected again it cannot be accepted as evidence.

[Scocialist Provinces]

*snip*

/Thread.

[Araraukar]

Earth is intentionally isolated either as some kind of "wilderness reserve" or because of a "Prime Directive" policy.

This so much.

[Samuraikoku]

I wish this were the case. Filthy xenos.

[Khadgar]

I chose "Evolution to and conditions for intelligent life is rare to nonexistent", however that's not exact.

I'm more into 'space is just too darn big' -explanation.

Let's do a magnitude estimation, with optimistic numbers from the hat:
- Spacefaring species: 1000
- Ships/probes dedicated to scouting star systems: 10,000 per species
- Average probe velocity during travel: c/2
- Average stellar density: 1 per cubic parsec -> ie. closest star is roughly 1 parsec away -> ie. probe is 6 years in transit
- Average research time per system: Negligible

Average research speed of all the spacefaring species combined:
1000 * 10000/6 years = 1,67 million star systems per year

Now, size of our galaxy:
- 200 000 000 000 to 400 000 000 000 stars.
- Perhaps 1/4 is habitable

Which totals to an average research frequency of a habitable star system:
Once every 30 000 to 60 000 years.

Also, let's not forget this:
- Average time to report home: 300 years
- Average time to react back: 600 years

So, perhaps there are aliens over there but they need not have visited this place in tens of thousands of years EVEN if they were actively probing nearby stars.


Compare those numbers to the age of human civilization:
- Homo Sapiens: Several hundred thousand years
- Culture & Irrigation: 7-8000 years
- Road networks: 2000 years
- Radio: 100 years
- Space age: 50 years

Humans haven't been obviously visible for much longer than 1000-2000 years and beyond 8000 years you would need a much longer than cursory glance to tell that one of the species is intelligent, so I'd think it would be pretty unlikely that an alien species would be aware of us.

I would also guess that the signal trace of an advanced species would probably be less than the omnidirectional beacon we're exhibiting or expecting, because that's just wasteful.


Also, one interesting consideration is that science will have great difficulty detecting alien signals. I don't mean that the intended signal itself would necessarily be hard to detect, but verifying it's source and that it's artificial will be nigh impossible because sending a continuous signal from an orbiting system to another orbiting system is hard and probably 'not worth the effort'.

Consider the Wow!-signal: It might have been a burst from a sentient species not dissimilar to the signals we've been sending out...but as it cannot be detected again it cannot be accepted as evidence.

The prudent question is, how old are these aliens? All a civilization has to do is make some Von Neumann probes and they'd have the entire galaxy scouted out in about a half million years. Remember, the Milky Way is 13 billion years old, intelligent life on Earth is only at best, a million years old. Alien civilizations could be (and very probably would be) vastly older than us, and they should know about us. All you need is to spread probes throughout the galaxy, when one receives a radio signal it initiates contact.

[Pinkie D Pie]

My option isn't on the list so here goes:
Because we don't have the technology to find other civilisations yet. We have barely even begun to find our first earth sized planet, let alone, a sufficiently large sample to have a fair chance of finding one conducive to life, let alone having the technology to do simple analyses to determine if those planets are actually hospitable to life, such as spectrographically determining the composition of its atmosphere. If you are referring to communication, reasons of a similar nature.

The only thing that might be implied by our current level of obliviousness regarding the possibility of the existence of other civilisations in our universe is that faster than light travel may be actually impossible, or at the very least terribly impractical. Not even that is necessarily implied, though.

[G3N13]

The prudent question is, how old are these aliens? All a civilization has to do is make some Von Neumann probes and they'd have the entire galaxy scouted out in about a half million years.
...
All you need is to spread probes throughout the galaxy, when one receives a radio signal it initiates contact.

What would be the motivation behind the self-replicating probes? How intelligent would they be? How long-lived? What would be their energy source? Why would they make the first contact and not just report home?

In any case, it would be prudent that there would be a limitation, and some sort of self-destruct mechanism, to the amount of probes that will be created and considering the vastness of space, each succeeding generation would breed more slowly than the previous one because of the signal delay and would progress relatively slower each cycle:
- Each generation would advance roughly one parsec in every direction.
- Diameter of our galaxy: 30,000 parsecs
- Average time between generations would be in order of 12 times the advanced parsecs in years (2 x from to and fro signals, 2 x from omnidirectional progresss, 3x from parsec->lightyear conversion)
- Average time to study the galaxy...well, simple integration gives 5,4 billion years...

But that's with zero travel time, zero failure rate and no fail safes in case of sudden problems, like supernovae frying circuits, so actual time would be somewhat larger.

The point of above calculation is that, sure, you could explore the galaxy much faster with free replication, but in case of trillions of probes and a single malfunction capable of eating up a solar system's solid bodies in a time span of millions of years, it's also a terrible risk that no rational species would ever take because it could also doom themselves.

Remember, the Milky Way is 13 billion years old, intelligent life on Earth is only at best, a million years old. Alien civilizations could be (and very probably would be) vastly older than us, and they should know about us.

However intelligent life couldn't appear that early.

You need several star generations before metallicity of the Universe reached a value that's high enough to create complex star-faring life. Basically you need a population I star and I'd say the oldest ones out there are ca. 7 billion years old.

Add 3-4 billion years for cooling and evolution to get an estimate of oldest star-faring civilization appearing at earliest 3-4 billion years ago.

The actual appearance could be much younger as younger Milky Way probably had more violent star deaths and therefore mass extinctions — ...and we still have no idea about the probability of life let alone intelligence! — but not really older.


For that matter, why wouldn't a civilization be comfortable with immortality, population control and a star or two that last 5 billion years – A Dyson ring would easily support 100s of billions of beings with a freedom to do anything. There's simply no need to colonize huge parts of space, even 2-3 stars is enough to escape most extinction scenarios, let alone have active surveillance when all you're interested in is science.

A system of telescopes would do the trick of observing space. Of course there would still be the delays involved and the vastness of the galaxy to contend with: Always remember that a million star systems searched per year isn't really enough to contact & communicate with a species that's younger that 50,000 years in our galaxy.

[Capitolinium]

I notice that one of the choices in the poll isn't something along the lines of "Space is mind-bogglingly big and traversing the universe at light speed has some staggeringly formidable obstacles".

[Azelkaeth]

Because any other intelligent civilization is really really really really really really really really really really really really far away.

[Tmutarakhan]

I notice that one of the choices in the poll isn't something along the lines of "Space is mind-bogglingly big and traversing the universe at light speed has some staggeringly formidable obstacles".

So much this ^

[Formisia]

I can't seem to find the "they're too bloody far for us to see them yet" option.

[Cameroi]

while i believe in a reasonable probability of interdiction for safety and well being of the civilized universe, as to why evidence of such civilization is not yet clearly visible to the people of earth, the answer is simply that earth does not yet possess a technology of sufficient capability, as to enable such an observation.

or, as more simply and succinctly expressed by Formisia, above.

[Big Jim P]

You are aware we dont send out a signal saying we are here right?
Because it's expensive.
We just listen for other signals.
The implications of this logical step we took should make everyone facepalm.

We've been sending out those signals (inadvertently of course) for what, 100 years or so now?

[Tmutarakhan]

You are aware we dont send out a signal saying we are here right?
Because it's expensive.
We just listen for other signals.
The implications of this logical step we took should make everyone facepalm.

We've been sending out those signals (inadvertently of course) for what, 100 years or so now?

Not in any focussed direction. Our radio emissions are such a pathetically small fraction of the radio emission of Jupiter, let alone the sun, that at distances of light-year they could not possibly be picked out.

[Big Jim P]

Considering that 5,000 years ago humans could only move as fast as their feet could carry them, I think it is safe to say that me haven't even scratched what is out there in the Universe. Especially since the vast majority of cosmologists and astronomers believe that we can't even see the whole universe itself. Let alone speaking to other intelligent civilizations and/or species.

Our space faring technology is incredibly primitive. Fifty years ago the first human was in space. Just forty years ago, humans were able, for the first time, to land on the moon. We have no extraterrestrial settlements on the moon. The ISS is the biggest human-made object in space. It's only a research station. Humanity is more likely to colonize our solar system first before we actually speak with other intelligent civilizations.

An important question puts this whole discussion into perspective. -------> Have the Voyager spacecraft even breached the edge of our solar system?

Not quite, but soon I think.

[Big Jim P]

We've been sending out those signals (inadvertently of course) for what, 100 years or so now?

Not in any focussed direction. Our radio emissions are such a pathetically small fraction of the radio emission of Jupiter, let alone the sun, that at distances of light-year they could not possibly be picked out.

Wouldn't hat depend on how sensitive the detection equipment used is? (And of course how powerful the computers used to sift out our radio signals)