Fermi's paradox: where is everybody?

Today I want to talk about...

(I have always wanted to use this meme :) )

 

People believing in aliens' existence, think of them as much more technologically and maybe physically than we are... but have you ever thought about the consequences if this were the case?

The Italian Physicist Enrico Fermi (1901-1954) did and he defined what came to be known as the Fermi's paradox.

(Enrico Fermi, from wikipedia)

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 the Fermi's Paradox. [Ref. 1]

"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," the Search For Extraterrestrial Intelligence (SETI) said on its website. 

While interstellar distances are vast, perhaps too 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. Self-reproducing robots!!!!! 

From ref. 1

The idea of self-reproducing automaton was proposed by mathematician John von Neumann (1903-1957) 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. 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.

 

(From: ref. 1)

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?"

 

The Fermi's paradox is something serious and it's not something you can avoid to face. 

We have to find an answer, a solution to it.

Possible solutions to the Fermi's paradox (generously taken from ref. 1):

1) They are here:

• UFO's, Alien Artifacts, etc... Problem: evidence is not existent :(
• We are aliens! Problem: Where the hell are the original aliens?
• The Zoo theory: Aliens are here but they do not interfere with us. Problem: how can you test this scenario?

2)  They exist but have not yet communicated with 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. 
• 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. 
• The Galaxy is filled with killer robots looking for signals. Aliens are keeping low. Problem: where are the berserkers coming after us?
• ET has no interest in conversing with lesser beings. Problem: with millions of possible civilizations, someone would have some curiosity.
• 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, so they are all dead.  
• Overpopulation
• Nanobots -> Gray Goo Problem
• Dangerous Particle Physics 

3) 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

My final thought and pick(s)

Looking at how humans love money more than knowledge, how they are, still today, totally unable to solve problems like wars, pollution and religious matters, looking all of this makes me think that probably, other civilizations have/had similar troubles ending up in killing themselves :(

I know, it's very sad, but somehow sounds reasonable to me. 

However I have to admit, the Zoo theory, although untestable, is very fascinating as well! So there is still hope!

References:
http://abyss.uoregon.edu/~js/cosmo/lectures/lec28.html
http://www.space.com*/25325-fermi-paradox.html