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

[Maurepas]

We likely lack the technology and/or perspective to notice it, I'd wager.

[G3N13]

With more plausible technology, you're looking at several million years to spread across the galaxy. But his assumptions are pretty hilarious.

Of course they're hilarious, that's the whole point!

It's a calculation of magnitudes involved, not a realistic scenario.

But for your argument, just for arguments sake, a civilization could easily create 10,000 probes traveling at half a c without ever having capability of true interstellar travel.

All it needs to do is give a 1 tonne probe kinetic energy equivalent of a year's production of electrical energy in USA (ca. 10^19 J).*

On the other hand sending a small colony ship, several times larger than biggest modern ships, would require tens of millions of years of equivalent energy production for the simple reason that the colony ship would be millions of times more massive (and would also need to brake and need life support and more maintenance and food and...).


* If the method of propulsion was moving with the ship, the ship would require ca. 500 tonnes of fusion fuel (30% efficiency, assuming non-relativistic speed and optimistic v_e) in order to accelerate to c/2.

[SanctusEmpire]

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.

I think you are being naive in assuming you understand their train of thought. I am assuming they are here but the flipside of that is they are not here however my logic prohibits that assumption. Our greatest misgiving is the huge importance we make of ourselves whether its in regard to other races or species. We are constantly finding new lifeforms here on Earth and to imply that there is no life beyond our planet in this context is simply dumb in my mind.

We may as well go back to assuming the world flat again

[Svalbar]

they think on us the way they think on ants how many are trying to talk to ants?

[SanctusEmpire]

they think on us the way they think on ants how many are trying to talk to ants?

How do you know?

[Great Nepal]

they think on us the way they think on ants how many are trying to talk to ants?

How do you know?

Because for any civilization that is able to contact us, we are at similar technological level to that of ants... and if pressed I give an edge to the ants.
Why will they bother.

[SanctusEmpire]

How do you know?

Because for any civilization that is able to contact us, we are at similar technological level to that of ants... and if pressed I give an edge to the ants.
Why will they bother.

I agree. To what benefit except for scientific curiosity would we want to communicate with ants? Let alone keep it on the down low

[Risottia]

Basically discussing the Fermi Paradox

Much simpler. The distance between stars is fucking huge, and electromagnetic signals lose coherence quite quickly.

[AiliailiA]

Basically discussing the Fermi Paradox

Much simpler. The distance between stars is fucking huge, and electromagnetic signals lose coherence quite quickly.

Square of the distance, right?

[Risottia]

Much simpler. The distance between stars is fucking huge, and electromagnetic signals lose coherence quite quickly.

Square of the distance, right?

More or less. To be accurate, "square of the distance" would be the field magnitude. The decoherence (hence, loss of ability to carry information) depends from other quantum stuff which is ultimately related to the uncertainity principle.

http://en.wikipedia.org/wiki/Quantum_decoherence

[AiliailiA]

Square of the distance, right?

More or less. To be accurate, "square of the distance" would be the field magnitude. The decoherence (hence, loss of ability to carry information) depends from other quantum stuff which is ultimately related to the uncertainity principle.

http://en.wikipedia.org/wiki/Quantum_decoherence

I should have learned this by now: ask a silly question, get an incomprehensible answer.

EDIT: OK, I read the

In quantum mechanics, quantum decoherence is the loss of coherence or ordering of the phase angles between the components of a system in a quantum superposition. One consequence of this dephasing is classical or probabilistically additive behavior. Quantum decoherence gives the appearance of wave function collapse (the reduction of the physical possibilities into a single possibility as seen by an observer) and justifies the framework and intuition of classical physics as an acceptable approximation: decoherence is the mechanism by which the classical limit emerges out of a quantum starting point and it determines the location of the quantum-classical boundary. Decoherence occurs when a system interacts with its environment in a thermodynamically irreversible way. This prevents different elements in the quantum superposition of the system+environment's wavefunction from interfering with each other. Decoherence has been a subject of active research since the 1980s.[1]

Decoherence can be viewed as the loss of information from a system into the environment (often modeled as a heat bath),[2] since every system is loosely coupled with the energetic state of its surroundings. Viewed in isolation, the system's dynamics are non-unitary (although the combined system plus environment evolves in a unitary fashion).[3] Thus the dynamics of the system alone are irreversible. As with any coupling, entanglements are generated between the system and environment. These have the effect of sharing quantum information with—or transferring it to—the surroundings.

Decoherence does not generate actual wave function collapse. It only provides an explanation for the appearance of the wavefunction collapse, as the quantum nature of the system "leaks" into the environment. That is, components of the wavefunction are decoupled from a coherent system, and acquire phases from their immediate surroundings. A total superposition of the global or universal wavefunction still exists (and remains coherent at the global level), but its ultimate fate remains an interpretational issue. Specifically, decoherence does not attempt to explain the measurement problem. Rather, decoherence provides an explanation for the transition of the system to a mixture of states that seem to correspond to those states observers perceive. Moreover, our observation tells us that this mixture looks like a proper quantum ensemble in a measurement situation, as we observe that measurements lead to the "realization" of precisely one state in the "ensemble".

Decoherence represents a challenge for the practical realization of quantum computers, since such machines are expected to rely heavily on the undisturbed evolution of quantum coherences. Simply put, they require that coherent states be preserved and that decoherence is managed, in order to actually perform quantum computation.

I feel smarter now. Not because I understood it (I didn't) but just because I read it.

So what's the "environment" that radio signals in space "share information with"? Is it the tenuous matter there, or fields (gravitational mostly I guessing), or something else which is there?

Also, how come decoherence doesn't kill the information from distant sources before it gets to our telescopes?

[Aerion]

Modern humans have been around for roughly fifty thousand years (citing from Wikipedia). So let's assume we'll be around another 50k years, and that we'll be sending out radio signals for all of that time. But we won't make any significant expansion out of the solar system, although we will colonise other planets and moons within it. And, because otherwise we can just give our aliens any characteristics we want, let's assume they're fundamentally similar to humans in this way. So there's only a fifty thousand year window you can detect an arbitrary intelligent species in. Take 2000 such species, and then that's a total of 100 million years. Or about the duration of the dinosaurs. Entire civilisations can trivially have risen and fallen throughout the entire history of the galaxy without one ever being within the same time as us. In the time it takes for their first radio emissions to reach us, a civilisation on the far side of the galaxy (100 thousand light years) can rise and fall again. Meanwhile, we've only been listening well for perhaps 50 years at the outside, now. In that time, even if 2k other alien species reached technological maturity at the same time we have, the chance of any of them being within the very close neighbourhood of earth they would need to be is minute.

Unfortunate way to look at it, but what makes you think that an intelligent species would only survive 100,000 years at the max? If they reach the level of technology to travel through, and colonize space (which we should easily have within the next 1,000 years or sooner at the rate of technological development if we survive climate change) then they should survive longer thus spreading out as life seems to have an inherent movement toward growth.

[AiliailiA]

Modern humans have been around for roughly fifty thousand years (citing from Wikipedia). So let's assume we'll be around another 50k years, and that we'll be sending out radio signals for all of that time. But we won't make any significant expansion out of the solar system, although we will colonise other planets and moons within it. And, because otherwise we can just give our aliens any characteristics we want, let's assume they're fundamentally similar to humans in this way. So there's only a fifty thousand year window you can detect an arbitrary intelligent species in. Take 2000 such species, and then that's a total of 100 million years. Or about the duration of the dinosaurs. Entire civilisations can trivially have risen and fallen throughout the entire history of the galaxy without one ever being within the same time as us. In the time it takes for their first radio emissions to reach us, a civilisation on the far side of the galaxy (100 thousand light years) can rise and fall again. Meanwhile, we've only been listening well for perhaps 50 years at the outside, now. In that time, even if 2k other alien species reached technological maturity at the same time we have, the chance of any of them being within the very close neighbourhood of earth they would need to be is minute.

Unfortunate way to look at it, but what makes you think that an intelligent species would only survive 100,000 years at the max? If they reach the level of technology to travel through, and colonize space (which we should easily have within the next 1,000 years or sooner at the rate of technological development if we survive climate change) then they should survive longer thus spreading out as life seems to have an inherent movement toward growth.

They might be Post Evolution, and have contained that "inherent movement towards growth".

About time we did, btw.

[Sobaeg]

what do you mean, we are constantly not nuking other nations like usa china etc.

We almost did it. And apart from war there is: Global warming, Pandemics, Asteroids, Hungers, Financial Crisis... And that to mention the ''not sci-fi'' forms of dissapearing as a race.

we are going to be fine… unless the mayans do return as zombies to start the apocalypse

[Xsyne]

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.

Problem: with the stated level of propulsion technology it is completely trivial for said civilization to colonize the entire galaxy.

All of it.

Probably inside of half a million years.

Let's say they start at the exact center of the galaxy. That means they have around 50,000 light years to travel. So they're moving at 0.1c. Do you know how much energy it takes to accelerate something to .1c?

[Sidhae]

I remember reading an article a long time ago which stated that the reason no alien transmissions have ever been picked up is because of the signal strength loss as distance increases. It is a misconception that the first human radio transmissions should by now be audible 80 light-years away - the average radio signal from Earth isn't likely to make it further than 2 light-years before dissipating into unrecognizable static. It requires a powerful transmitter with a focused beam to project a signal further than that, and that in turn reduces the chance of the signal being intercepted by an alien civilization even further. So what chance there is that a concentrated beam of radio transmission will hit Earth at the exact moment the SETI Project receivers are active and on the right side of the world? Consider that aiming a radio beam at a planet in a star system several light-years away is a feat comparable to shooting a bullet through a ring that's located on the Moon...

[Chinese Regions]

Space is big.

[Zweite Alaje]

How do you know?

Because for any civilization that is able to contact us, we are at similar technological level to that of ants... and if pressed I give an edge to the ants.
Why will they bother.

One critical difference between us and ants, we can learn how to use whatever tech any extraterrestrial race has to offer. Ants are incapable of higher order thought.

[Nordic Saxony]

We've been observing space and attempting to communicate with other species for, what, 100 years at most?


We've barely touched the surface of the universe.

This.

I'm so certain there is other life (intelligent or not) that I'd bet my own life on it.

[Great Nepal]

Because for any civilization that is able to contact us, we are at similar technological level to that of ants... and if pressed I give an edge to the ants.
Why will they bother.

One critical difference between us and ants, we can learn how to use whatever tech any extraterrestrial race has to offer. Ants are incapable of higher order thought.

1. If a advanced dark matter powered slipstream drive which works by penetrating fabric of space-time going into another dimension utilizing incredibly complex equation without time and thereby enabling faster than light transport appeared in front of you at this very time: would you (or any human) be able to wake it work?
2. Why will extraterrestrial race want to offer us any technology; especially when they would have to waste time teaching us how to use it as well.

[Xsyne]

One critical difference between us and ants, we can learn how to use whatever tech any extraterrestrial race has to offer. Ants are incapable of higher order thought.

1. If a advanced dark matter powered slipstream drive which works by penetrating fabric of space-time going into another dimension utilizing incredibly complex equation without time and thereby enabling faster than light transport appeared in front of you at this very time: would you (or any human) be able to wake it work?

Easily. We wrote the book on running stuff that uses sci-fi gobbledegook.

Next time just say "something that allows for faster than light travel" and don't try to make up something you don't understand to explain it. Because someone else will understand it.

Edit: I am impressed that you somehow managed to get a goddamn genre of fiction in there, though.

[Zweite Alaje]

One critical difference between us and ants, we can learn how to use whatever tech any extraterrestrial race has to offer. Ants are incapable of higher order thought.

1. If a advanced dark matter powered slipstream drive which works by penetrating fabric of space-time going into another dimension utilizing incredibly complex equation without time and thereby enabling faster than light transport appeared in front of you at this very time: would you (or any human) be able to wake it work?
2. Why will extraterrestrial race want to offer us any technology; especially when they would have to waste time teaching us how to use it as well.

Given enough time, yes we'd eventually learn how it operates. The same reason anyone "wastes" time teaching, to share knowledge.

[Salandriagado]

Leaving aside the fact that infinitesimal is the exact opposite of the word you're looking for, neither of these is correct.

I kinda derped up. I could've sworn "infinitesemally large" was a thing people said but whatever.

Also, how else would you describe the scale of the universe from the perspective of a single species if not as unimaginably huge and and how do you propose interstellar travel can be made likely or at least realistically plausible?

"Big" would do it. And it isn't realistically plausible in the sense that most people are thinking about. Any kind of interstellar travel including actual people is going to be very much of the one-way, very rare, very slow, very long term, generation ship variety, but the vast, vast majority of such travel will be of the (still very long-term) probe variety.

[Ifreann]

They're smart enough not to come.

^this. The reason intelligent life hasn't contacted us is because they are intelligent.

Maybe this kind of misanthropy(or a term more fitting to a non-human species that thinks itself evil) gets boring after meeting a civilisation or two so they've given up.

---

How do you know?

Because for any civilization that is able to contact us, we are at similar technological level to that of ants... and if pressed I give an edge to the ants.
Why will they bother.

You're aware that we study ants, right? Including how they communicate with each other?

[UNIverseVERSE]

Unfortunate way to look at it, but what makes you think that an intelligent species would only survive 100,000 years at the max? If they reach the level of technology to travel through, and colonize space (which we should easily have within the next 1,000 years or sooner at the rate of technological development if we survive climate change) then they should survive longer thus spreading out as life seems to have an inherent movement toward growth.

We've spent the last fifty thousand years of being a species inventing new and better ways to kill each other, and then employing them with deadly efficiency. Frankly, giving a civilisation which has achieved atomic technology fifty thousand years sounds incredibly optimistic to me. But we've made fifty so far, so we might make 500.

There are a whole bunch of potential ways to wipe out a solar system's worth of life forms in one go (the one which occurs offhand would be a large gamma ray burst from a nearby supernova, that happens to be aimed in the right direction). More probable, combine a planetary extinction event, whether an asteroid or atomic holocaust, with no viable off-world colonies for long term preservation of the species. That could trivially happen within our lifetimes.

Note I explicitly discounted interstellar colonisation. For a number of reasons, I think that is essentially impossible, although I suppose a type II Kardashev civilisation could do it. But then the time it takes to get to that point, I feel confident in predicting that a highly advanced technological species will manage to wipe itself out first.

Easily. We wrote the book on running stuff that uses sci-fi gobbledegook.

Next time just say "something that allows for faster than light travel" and don't try to make up something you don't understand to explain it. Because someone else will understand it.

Can I have your babies?