At 12:39 AM 01/04/2003 -0800, Sarad AV wrote:
There has been much speculation around Fermi's famous question: "Where are they? Why haven't we seen any traces of intelligent extraterrestrial life?". One way in which this question has been answered (Brin 1983) is that we have not seen any traces of intelligent extraterrestrial life because there is no extraterrestrial life because intelligent extraterrestrial life tend to self-destruct soon after it reaches the stage where it can engage in cosmic colonization and communication.
I prefer the argument (I think from Calvin & Hobbes) that any aliens smart enough to do space travel are smart enough not to waste their time on this messed-up planet with loser species like Homo sapiens.
I'd argue that this is different.So does the fermi paradox mean that there are no extra terrestrials. Can't we throw away this paradox like every other paradox?
Most interesting paradoxes are interesting because they're caused by the
weaknesses in our tools (e.g. Xeno not being very good at continuous math),
and become more interesting if they encourage us to build better tools,
or because they question or expose edges in the applicability
of language as a tool for analyzing reality, or because they help us
to question our assumptions about fundamental issues like
the nature of ourselves and other things (e.g. Zen koans),
or because they expose the differences between a surface understanding
of an issue and the deeper aspects that take more work to understand.
In the case of the "Fermi Paradox", the weaker form (why aren't they here)
is easier to counter than the stronger form (why don't we at least see
signals from their radio communications), but it's a probabilistic argument
bases on a large number of assumptions, and unless the probabilities are
large enough, it doesn't catalyze into an expanding system that we'd see,
as opposed to at most a bunch of little blips that we'd miss.
Some of the assumptions for the stronger form
- what life is
- how prevalent are the conditions that life needs to form,
- what's the probability that it will form if it can,
- how long that will take,
- how old the Universe is and how fast it's expanding,
- how long it will take for conditions in which life can evolve to obtain,
- how likely that life will evolve beings that use radio or other noisy
long-distance communication tools or signal byproducts
- how long the beings stay in that phase
- how strong the signals will be at the source
- how far away they'll be from us at the time,
- thus how weak the signals will be
- whether we have the capability to detect those signals,
- how likely it is that we'll actually detect them if we can,
- how likely it is that we'll recognize them as signals if we detect them,
- how likely that a group of aliens that have technology
would be *interested* in contact unknown distant life forms
- whether aliens who were interested would think it was worthwhile,
given that the response time for such a project would be very long,
unless they thought there were lots of aliens nearby,
- whether they'd try doing it using signals of types we'd listen for,
- how loud their signals would be at the source if they do
- whether they succeed in reaching other aliens if they try
(similar arguments about whether those aliens could detect it,
scaled up by the number of listening aliens within range)
- whether those other aliens decide it's worth replying,
as opposed to deciding that the senders are long-dead
- whether the original senders would be around to have a slow conversation
- whether the second group of aliens would decide to start a SETI program
whether or not they replied
- whether we'd detect the reply or any followon SETI program
- whether the density of aliens with SETI programs is sufficient to
evolve into conversations
- whether any group of intercommunicating aliens can find anything
interesting to say to each other, given the time delays
- whether the conversations evolve into The Net Of A Million Lies
- whether the conversations merely evolve into a scaled Usenet,
which has been described as a slowly-moving parody of itself
- whether some of the potential participants decide not to bother,
because the other aliens appear to be made out of meat :-)
http://www.terrybisson.com/meat.html
The weaker form involves aliens actually doing interstellar space travel.
It gets into additional assumptions about
- how closely spaced together are star systems capable of supporting alien life?
Such systems are more common that planets that can evolve sentient life,
because the aliens would be technologically advanced and able
to tolerate a wider range of conditions, at least for a while,
and the alien life might end up staying in space rather than
colonizing planets, depending on conditions
- how long can those systems support technologically advanced civilizations?
- Interstellar space is amazingly, mind-bogglingly big.
How much does it cost to cross it, in terms of the resources available
to a species in a given solar system?
- How long does it take for a sentient species to advance to a point that
it can design and afford interstellar travel?
- Given the cost, how often would they try? Just once, before their star blows up?
Zero times, because they didn't have time or resources?
Many times, as insurance?
- How often would interstellar travel succeed as opposed to dying somewhere?
- How fast would a starship be? Near-light-speed may be impossible,
and I'm assuming that above-light-speed tricks aren't feasible.
Slightly above escape velocity would be easier -
but would they do colony ships or frozen bodies or just AIs?
How well do aliens freeze? Would AIs be interested?
- How long does it take to get to nearby habitable star systems,
compared to the lifetime of habitable star systems?
This also gets back to the "what's the probability of success?"
- What's the probability of successful colonization once you arrive?
- How many groups of aliens in the Milky Way galaxy are capable of this?
How many are doing it? How many hops away are they?
How many consider this neighborhood to be interesting?
How long have they been traveling, and when did they start?
- Intergalactic space is much bigger than travel within galaxies -
Is it even feasible, whether you do or don't have a Galactic Empire?
How long does it take for a species to acquire the resources to do it?
Have any? When did they start, and are they headed to the Milky Way,
and if so will they stop by Earth? Do they write cookbooks?
