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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[RadioAstronomer]

I take it then that you don't believe humankind can ever explore another solar system.

I did not say that. What I said was that the Fermi Paradox does not correlate to the possibility of life out there. It only addresses that they are not here. So when I hear that we are alone in the universe because the Fermi Paradox says so, my reply is codswallop.

[edsheppa]

Because of the distances and energies involved...

They aren't as great as they seem, in cosmic terms of course. It's entirely reasonable with realistic improvements in current technology to cross the galaxy in a million years or so. Basically you'd need a 100 fold increase in rocket exhaust velocities. I think that'd be easily achieved with nuclear based propulsion.

[RadioAstronomer]

How do you stay alive, where are you headed, and would your spacecraft last that long? Also the faster you go, your radiation exposure will increase.

[chickens]

The argument that, if intelligent life did exist in the universe, it would already be here -- is akin to the time travel argument, that if time travel did indeed exist, time travelers would also be among us. This takes us back to the space time continuum, and tends to make the case that time and distance, although relative, have irrefutable laws that cannot be bent or breached to cause Earthlings to venture into the void, and conversely keeps venturers from the void from Earth.

Time-line studies show that every time a level I civilization perfects a device that scientists agree may be capable of going where no man has gone before, someone starts a war. The price of gasoline goes up, and the costs associated with the program skyrocket. Congress cuts the funding and the project languishes on the drawing board -- until the cycle is repeated. This process goes on for billions of years.

[AndrewC]

What I said was that the Fermi Paradox does not correlate to the possibility of life out there.

But it does, in a roomful of air, what is the probability of encountering a neon atom in a cubic inch of that room? An atom of nitrogen?

[Yeti]

The Krell Theory (from "Forbidden Planet"). Technology evolves to the point where any insane individual can wipe out civilization on a whim.

That is actually a serious problem we all face. Anything that can travel at anything near light-speed could be a problem if it were pointed at Earth.

It creates a bit of a dilemma, if you consider the good for humanity. Technology builds on other technology, and for us to advance optimally, we need everything out there, freely avalable for for all six billion of our minds minds to mull.

On the one hand, we have this death-decay culture evolving toward dominance, when it needn't even exist. The widespread prosperity that could develop from colonizing the solar system is almost incomprehensible, but here we live in this unecessarily competitive, factionalized society. The guys who discover nifty intertia extraction drives to take us to the stars(first, the planets and the asteroid belt!) want to run out into the street shouting "Eureka, I've found it! We're free!"

But then there's that recent suicide bombing.

But, then again, we might be better able to protect ourselves from suicide-bomber types if the technology were more widespread, and humans would also be more widely distributed, geographically.

Yeti's Dilemma: If you love Humanity and The Good, what is the best thing to do, all-in-all?

I'm inclined to put it out there.

[Phsstpok]

Are you arguing with the article's worth or that of the paradox which many of the world's top physicists have wrestled with for over 50 years?

Article

I don't believe that Fermi was arguing against the existence of other life, or intelligent life. He was saying, like any good proponent of the scientific method, that he didn't understand it, given the notions laid out in the paradox. This was what Einstein would have called a “gedanken experiment” or “thought experiment.” When you can't measure something directly because of lack of instruments you have to lay out reasonable models in your head (or across a lunch table) and then try to deduce what it was you couldn't see.

Are they not there? Problem with that is that it assumes that we're it, or we're the first (what are the odds of that?)

Are they there but we can't detect them? I think this is the most likely, but what's wrong with that premise? He argues that odds are better than not that if they are there then we should see evidence that we can detect. So what are we missing?

The author lays out those arguments like a dead fish on the table but then locks himself in to the MUST NOT BE SINCE WE CAN'T SEE THEM ALREADY (absence of evidence IS evidence of absence) side of the equation, without asking the "what are we missing" part of the “gedanken experiment.”

Bad science. Fermi was not a bad scientist. He would not have said that they were there (on faith) if he hadn't found evidence. He wanted evidence, one way or the other.

[samtheman]

God created atomic numbers over 90 to limit intelligent life forms to one planet.

Very clever.

[wbill]

I'll throw one other idea out here.....

All of the discussion on this thread assumes that if a) There are aliens and b)They are here and c) They want to contact someone that ..... they'd contact us. They might not even look at us as life forms.

[Doctor Stochastic]

There's a percolation theory approach to the Fermi paradox. One looks at the probability of colonizing the "next" region of space. If this is below a critical value, there will be no universal saturation of colonies. If it is above that, colonies spread everywhere.

[Just another Joe]

I understand that, Doc, but we also must have the mind open enough to allow that an extraterrestrial species may be unlike us enough that we wouldn't even recognize it as being alive. Even an intelligent species.
What if they would have life spans in the tens of thousands of years instead of in the hundreds of years? Would they really be moving as fast as we do? What if they don't even move physically at all but only in some sidereal fashion.
The possibilities are endless in an infinite universe.

[zeugma]

God created atomic numbers over 90 to limit intelligent life forms to one planet.

I like that. Really funny! I believe it is Administratium though, that is the real civilization killer.

[Pharmboy]

I thought this settled all the questions:

[zeugma]

Actually, I believe two did. Cro-magnon(sp?) didn't survive the experience though.

[ZULU]

I', impressed. As a layman, I have always been interested in cosmology, deep space astromony and astrophysics and read the popular books on the subject. I haven't got the math background to get into the technical material - just had one semester of Calculus in undergradute school.

[zeugma]

Crapweasles. I just knew I shouldn't post before I'd had two cups of coffee this morning. The neanderthals where the folks I was thinking about in my previous post.

[Phsstpok]

They might not even look at us as life forms.

Sagan's ants on an anthill analogy from Contact comes close to this as well. A life form, but worth communicating with?

There are lots of other possibilities as well. They're out there, but they've all discovered just how dangerous the universe is and have shut themselves up inside their own Dyson spheres and are intentionally hiding, lest some other beastie finds THEM. The ones who survived, that is. The ones (like us) who sit there, radiating out a "we're here" message get to do that for around 100 years. By that time the Vogon's see us and come read us some poetry. Fini.

[AFreeBird]

B4L8r

[longshadow]

(And I even worked on the Space Station)

You meant to say "Mir II," right?

;-)

[OregonRancher]

"It has often been said that, if the human species fails to make a go of it here on Earth, some other species will take over the running. In the sense of developing high intelligence this is not correct. We have, or soon will have, exhausted the necessary physical prerequisites so far as this planet is concerned. With coal gone, oil gone, high-grade metallic ores gone, no species however competent can make the long climb from primitive conditions to high-level technology. THIS IS A ONE SHOT AFFAIR. IF WE FAIL, THIS PLANETARY SYSTEM FAILS SO FAR AS INTELLIGENCE IS CONCERNED. The same will be true of other planetary systems. On each of them there will be one chance, and one chance only." (Hoyle, 1964)