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.

---

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.

---

[VeritatisSplendor]

Nice post. I've always thought the solution was simply that Earth is such a remote backwater that they only check us out every millennium or two, which they can do without leaving the kind of evidence that would survive for centuries -- next time they come back we'll know it.

[parsifal]

The Parsy Principle: The universe is much older and much larger than we think. Our 12-20 billion year sphere of observation is only .000000000000000000001 to the nth power (or however you phrase it) of the actual size of the universe.

Like babies, we think that what we see is what there is.

Therefore, the probes started out way over yonder on the other side and haven't has time to reach us yet.

parsy, the pseudo-astrophysicistical cosmologist.

[brbethke]

How about: they've been here. And we didn't taste good.

[wbill]

I would argue that we're not alone, but the fact remains that the Earth is several billion years old. If it has taken us this long to evolve to a point where we can travel to the closest celestial body (the moon) then would it not stand to reason that other lifeforms would take as long to evolve, assuming that they are able to evolve at all?

I think that it's entirely possible that alien species are at more-or-less the same point that we're at. Furthermore, If Einstein was correct, and light-speed travel is not possible, then we may never see any other alien races, just due to the vast distances in Outer space. For instance, the Voyager (I think) space probe just exited the solar system. That's not even a short rock throw on a cosmic scale, but it still took 30+ years to accomplish.

[RadioAstronomer]

I like the "gray Goo" visualization. :-)

[cookcounty]

These arguments about the probability of life on other planets assume that we have a grip on the odds of life developing on earth. That it may have happened does not mean it was a certainty, or that it was likely or probable. Since we don't know (assuming a set of natural causes), exactly how life got here, there is no way to calculate, then extrapolate out to the probablilities of life arising anywhere else in the universe. Assertions that life "must be" on other planets are based not on logic but religious necessity. People that say life "must be" out there are making statements of blind faith.

[dangus]

The reason that I used the Smithsonian exhibit to do the calculation was (besides the fact I happenned to be there) that the exhibit provides all the numbers for you. (Such as, how many stars in a galaxy, how many galaxies in a universe, etc.) You get a very large number if you presume that life isn't so hard to come by.

General rule of thumb: Physicists tend to get enormous numbers. We biology types get much lower numbers. The amazing thing to me was that I could never have deliberately calculated how to get a number so close to 1. I mean think of all the numbers like 5x10^60 that go into such an equation!

[RightWhale]

The moon provides the earth with

variations in tides.

[RadioAstronomer]

We do know that there is at least one planet with life....us.

[RadioAstronomer]

And the stability of our axial tilt.

[ZULU]

True, but it does something else - I can't remember - perhaps it blocks asteroids or affects the magnetic fields which protect us from radiation. Its something like that.

[PatrickHenry]

PING. [This list is for the evolution side of evolution threads, and some other science topics like cosmology. FReepmail me to be added or dropped. Long-time list members get all pings, but can request evo-only status. New additions will be evo-only, but can request all pings. Specify all pings or you'll get evo-pings only.]

[Major_Risktaker]

[cookcounty]

" 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 -.........

I think you're wrong. Are you sure you have all the variables accounted for? How about you list them, just to be sure?

[zeugma]

I hope I remember to read this when I have more time bump.

[xrp]

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.

Wouldn't there be radio wave evidence of such?

In addition, going on how sloppy humans are, I refuse to believe that this planet has been visited by any ETs, whether it be 1947 in Roswell, NM or ancient times. There would have to be some solid and obvious evidence left behind, such as a cigarette butt (poor example, sorry, but it is America's favorite litter, followed by the aluminum soda can). If there was evidence, or a visit, such as Roswell, NM in 1947, I also refuse to believe that the US government is efficient enough to 100% cover it up with NO piece of evidence left untouched and unavailable for the public. The only thing government does efficiently is inefficiency.

[RightWhale]

The variations of tides would be very important. If tides alone were significant, then Venus would have done better. Complex variation of the environment would force complex adaptation, which would imply complex varities of lifeforms. Alternatively, this could be viewed as an additional source of subtle energy requiring subtle responses. Venus would lack the subtle energy source.

[Alamo-Girl]

Thanks for the ping!

[jennyp]

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.

Unless we learn how to tap into dark energy! (Assuming the density of dark energy is high enough in between galaxies.)

[dangus]

You presume a Type II Dyson sphere. Dyson said what he foreaw was a loose collection of over 100,000 objects traveling on independent orbits. Dyson also predicted a Type III sphere called a ringworld, which would require only the amount of matter of a large asteroid, and yet would capture a significant portion of a star's energy.