The Fermi Paradox - Are We Alone in the Universe

[Conservomax]

Fermi's Paradox

Fermi's Paradox (i.e. Where are They?):

The story goes that, one day back on the 1940's, a group of atomic scientists, including the famous Enrico Fermi, were sitting around talking, when the subject turned to extraterrestrial life. Fermi is supposed to have then asked, "So? Where is everybody?" What he meant was: If there are all these billions of planets in the universe that are capable of supporting life, and millions of intelligent species out there, then how come none has visited earth? This has come to be known as The Fermi Paradox.

Fermi realized that any civilization with a modest amount of rocket technology and an immodest amount of imperial incentive could rapidly colonize the entire Galaxy. Within a few million years, every star system could be brought under the wing of empire. A few million years may sound long, but in fact it's quite short compared with the age of the Galaxy, which is roughly ten thousand million years. Colonization of the Milky Way should be a quick exercise.

So what Fermi immediately realized was that the aliens have had more than enough time to pepper the Galaxy with their presence. But looking around, he didn't see any clear indication that they're out and about. This prompted Fermi to ask what was (to him) an obvious question: "where is everybody?"

Also, if one considers the amount of time the Galaxy has been around (over 10 billion years) and the speed of technological advancement in our own culture, then a more relevant point is where are all the super-advanced alien civilizations. Russian astrophysicist Nikolai Kardashev proposed a useful scheme to classify advanced civilizations, he argues that ET would posses one of three levels of technology. A Type I civilization is similar to our own, one that uses the energy resources of a planet. A Type II civilization would use the energy resources of a star, such as a Dyson sphere. A Type III civilization would employ the energy resources of an entire galaxy. A Type III civilization would be easy to detect, even at vast distances.

This sounds a bit silly at first. The fact that aliens don't seem to be walking our planet apparently implies that there are no extraterrestrial anywhere among the vast tracts of the Galaxy. Many researchers consider this to be a radical conclusion to draw from such a simple observation. Surely there is a straightforward explanation for what has become known as the Fermi Paradox. There must be some way to account for our apparent loneliness in a galaxy that we assume is filled with other clever beings.

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Bracewell-Von Neumann Probes:

While interstellar distances are vast, perhaps to vast to be conquered by living creatures with finite lifetimes, it should be possible for an advanced civilization to construct self-reproducing, autonomous robots to colonize the Galaxy. The idea of self-reproducing automaton was proposed by mathematician John von Neumann in the 1950's. The idea is that a device could 1) perform tasks in the real world and 2) make copies of itself (like bacteria). The fastest, and cheapest, way to explore and learn about the Galaxy is to construct Bracewell-von Neumann probes. A Bracewell-von Neumann probe is simply a payload that is a self-reproducing automaton with an intelligent program (AI) and plans to build more of itself.

Attached to a basic propulsion system, such as a Bussard RamJet (shown above), such a probe could travel between the stars at a very slow pace. When it reaches a target system, it finds suitable material (like asteroids) and makes copies of itself. Growth of the number of probes would occur exponentially and the Galaxy could be explored in 4 million years. While this time span seems long compared to the age of human civilization, remember the Galaxy is over 10 billion years old and any past extraterrestrial civilization could have explored the Galaxy 250 times over.

Thus, the question arises, if it so easy to build Bracewell-Von Neumann probes, and they has been so much time in the past, where are the aliens or at least evidence of their past explorations (old probes). So Fermi Paradox becomes not only where are They, but why can we not hear Them and where are their Bracewell-von Neumann probes?

Possible solutions to Fermi's Paradox fall in the following categories:

• They Are Here
  • They Were Here and They Left Evidence
    • UFO's, Ancient Astronauts, Alien Artifacts: all fall under the heading of proposals that aliens are here now (and they call themselves Republicans) or have been here in the recent past. Problem: evidence for aliens is non-existent.
  • They Are Us
    • Humans are the descendents of ancient alien civilizations. Problem: where are the original aliens? Where are all the other alien civilizations
  • Zoo/Interdict Scenario
    • The aliens are here, and they are keeping us in a well designed zoo (cut off from all contact) or there is an interdiction treaty to prevent contact with young races (us). Problem: scenario lacks the ability to be tested. Takes only one ET to break embargo.

• They Exist But Have Not Yet Communicated
  • They Have Not Had Time To Reach Us
    • Speed of light slows communication levels, relativity makes space travel long. ET's message may not have reached us yet. Problem: Galaxy has been around for billions of years, even if one ET civilization formed a few million years before us, the Galaxy would be filled with Bracewell-von Neumann probes.
  • They Are Signaling, But We Do Not Know How To Listen
    • EM radiation, gravity waves, exotic particles are all examples of methods to signal. Problem: they may use methods we have not learned yet, but if there are many civilizations someone would use EM methods.
  • Berserkers
    • The Galaxy is filled with killer robots looking for signals. ET is keeping low. Problem: where are the berserkers coming after us?
  • They Have No Desire To Communicate
    • ET has no interest in conversing with lesser beings. Problem: with millions of possible civilizations, someone would have some curiosity.
  • They Develop Different Mathematics
    • Mathematics is the universal language. But humankind may have a unique system of mathematics that ET cannot understand. Problem: then where are their incomprehensible signals?
  • Catastrophes
    • Civilizations only have a limited lifetime, They are all dead.
      • Overpopulation
      • Nanobots -> Gray Goo Problem
      • Dangerous Particle Physics

• They Do Not Exist
  • We are the First, Life is New to the Galaxy
    • Life is new to the Galaxy, evolution takes time, we are the first civilization. Problem: Sun is average star, if other stars formed a million years ahead of us, then They would be a million years ahead of us in technology.
    

  • Planets With the Right Conditions are Rare
    • Planetary systems are rare
    • Habitable zones, proper distance from star for liquid water, are narrow
    • Galaxy is a dangerous place (gamma-ray bursters, asteroid impacts, etc)
    • Earth/Moon system is unique (large tides needed for molecular evolution)
  • Life Is Rare
    • Life's Genesis is rare
    • Intelligence/Tool-Making is rare
    • Language is unique to humans
    • Technology/Science is not inevitable

In general, solutions to Fermi's paradox come down to either 1) life is difficult to start and evolve (either hard for the process or hard to find the right conditions) or 2) advanced civilizations destroy themselves on short timescales. In other words, this is an important problem to solve in the hope that it is 1 and not 2.

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[Fitzcarraldo]

Aliens have go one to other dimensions, or have transfered themselves to a computer simulated universe ("Matrix").

[RightWhale]

The Cone of Light would function between galactic clusters, but not within the local galactic cluster. Within the local galactic cluster there would be no way to travel intergalactically since no power source, including nuclear, would last the several million years needed to make the trip. We might populate the Milky Way were it not for Congress, but we wouldn't ever go beyond the Milky Way.

[Fitzcarraldo]

correction: Aliens have gone on to...

[Fitzcarraldo]

This would be the "we are the last ones to leave the party" scenerio.

[Physicist]

Nanobots -> Gray Goo Problem

This is sort of the correct answer, I believe, although I think of it as the Gray Goo Solution. There's much more room at the bottom than there is at the top. As civilizations progress, the timescale that is relevant to the society gets ever shorter. Because of the speed of light limitation, this means that the relevant distance scale gets ever shorter. There's nothing to do but shrink.

Dangerous Particle Physics

LOL, someone should ban this before it's too late!

[brbethke]

That's the Borg - they aren't here yet.

Nope. Berserkers were Fred Saberhagen's idea.

[Still Thinking]

Scenario IV: They exist but are all Democrats, and thus cannot get anything done on their own planet, let alone communicate with us.

[xrp]

Not to mention that, assuming what we regard as a path of evolution, intelligent species at some point use radio waves to communicate with each other, if any other intelligent species developed in the last 80,000 years in the Milky Way (since no point in the Milky Way is more than 80,000 light years from Earth), we would have detected them because of their radio waves.

So, from an arrogant, Earth/human-centric point of view of the Milky Way Galaxy, there has been no other development of intelligence in the Milky Way Galaxy at least as of 80,000 years ago.

[talleyman]

Lack of "money". It's expensive to travel throughout the Galaxy.

Which is Bush's fault. But the aliens do manage to show up in droves every election to vote Demorat.

[adx]

Lack of "money". It's expensive to travel throughout the Galaxy.

Exactly. Nobody would go for economic reasons, unless something is out there that's so unique that a) it couldn't be replicated at home and b) that it's worth making a trip to go get it.

No, nobody is going for economic reasons. If there's any reason to go, it'll be for political and/or religious reasons. And people that are comfortable with where they are won't leave, so that leaves the dissidents/persecuted. And it's a lot cheaper to simply kill them all instead of paying out lots of money to ship them off somewhere else if they're proving to be too much of a problem.

The only plausible way anybody's going is if there's absolutely no other choice, say like living conditions on the homeworld becoming untenable.

[Still Thinking]

Dangerous Particle Physics. LOL, someone should ban this before it's too late!

When Dangerous Particle Physics are outlawed, only Dangerous Particle Physicians will have... Oh, never mind!

[Little Ray]

How 'bout they all "trancended."
That's another way of saying that they uploaded themselves and are are busy playing Quake X^nth and other advanced VR games. They have no incentive to go out and be imperialists - real life isn't as much fun as VR and they don't need much in the way of resources.

[RightWhale]

The other point is that galactic civilizations may arise, but they may also burn out. There may have been dozens of civilizations pass through the Solar System in the past millions of years, but none are here now. It is possible we are the remnant of one of the latest ones to pass through.

[Little Ray]

Transcended. Sheesh. Need to learn the to use the spell checker.

[Little Ray]

Transcended. Sheesh. Need to learn the to use the spell checker.

[Little Ray]

Transcended. Sheesh. Need to learn the to use the spell checker.

[xrp]

We should build a Dyson Sphere.

Where do you plan to get the materials for the Dyson Sphere? :-)

There isn't enough matter in the solar system, outside of mining the sun, to construct one.

[ZULU]

One more possible solution.

They have seen the earth and how we behave and have no desire to visit here.

I think the vast distances involved would preclude travel even by robots.

The closest star is several light-years away, and not every star has planets. Of those stars which DO have a planet system, very few of them may possess a system capable of sustaining earth. Not only would a life-sustaining planet have to be the proper distance from its star, it would also have to have a moon like ours. The moon provides the earth with some kind of astrophysically essential ingredient for the existence of life which I can't recall.

Also, we are not sure that evolution on those few planets that may be capable of sustaining life progressed to the level of intellignet life. Intelligent life as we define it, may be a rare or non-existant trait in other worlds.

[Constitution Day]

BTTT, read later.

[Gorjus]

This is essentially a mathematics problem, with a lot of estimated values. However, even if you use very low probabilities for the various factors (probability of a planet in the liquid-water zone, etc.) you still get a very large number of should-be-inhabited planets when you multiply it by the total number of stars - very likely enough that we should see evidence of them. So another way to formulate the question is: What forces the various factors low enough that we don't see any evidence of extra-terrestrial life?

There was a science-fact article on that several years ago in Analog. They said the formulation is missing a key factor - what is the probability that a 'stubborn' species would develop?

The article examined the physical characteristics of man, and what that meant for an evolutionary niche. I won't go into all the evidence, but the result of being two-legged, with disproportionately large lungs, and better heat rejection (sweat) than other animals is that man is adapted to be a 'cursorial hunter.' That is a hunter who runs doggedly (a descriptor derived from the other known cursorial hunter) after a prey until the prey is worn down and can be killed.

To succees at that, the cursorial hunter has to be stubborn - unwilling to give up until the prey is worn out. The expression, "If at first you don't succeed, try, try again" is uniquely applicable to stubborn hunters. In contrast, Tony the Tiger's attitude is, "If at first you don't succeed, to hell with it."

Building a technical civilization takes heaps of stubborn. As Edison said, "Genius is 1% inspiration and 99% perspiration."

So, if you take the calculation of likely civilizations and add another factor that requires the sort of environment - wide, flat, reasonably dry plains with good lines of sight to keep an eye on the prey - you can drop the likelihood of another technological civilization down low enough that it's unlikely we'd see evidence of them, even if all the other factors are reasonable.

I'm not trying to 'prove' that analysis of Fermi's paradox, though the logic of man as a cursorial hunter was compelling.