hi,
I guess inspite of all these questions-I will wait till I get to see a real one.But how will I know if it was a real alien? what if we are being tricked-If I could go back in time along with a projector that projects a holographic image of an alien and trick our ancestors to beleive that they had seen an alien,how less probable are we being tricked of the same.I think thats one more question you can add to that list. the argument is fine but there are as you say too many unknowns and there is no meaning on operating on them as if they were constant,we want models for things we observe and not what we speculate-so may be there is no point in speculating since we only end up with same questions and our understanding gets no better than it was. Regards Sarath. --- Bill Stewart <[EMAIL PROTECTED]> wrote: > 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. > > >So does the fermi paradox mean that there are no > extra > >terrestrials. Can't we throw away this paradox > like > >every other paradox? > > I'd argue that this is different. > 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 === message truncated === __________________________________________________ Do you Yahoo!? Yahoo! Mail Plus - Powerful. Affordable. Sign up now. http://mailplus.yahoo.com
