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February 13, 2005


Anonymous Coward

> The estimation of the number of worlds
> harboring intelligent life would increase
> due to an increase in the number of planets
> capable of supporting biological systems

It's tough to beat our current odds, though. 100% of the planets we know that has life also has intelligent life. Hopefully, those odds would decrease some in the future.



Titan may very well decrease these odds to 50%. It is an artificial restriction to couple the existence of biologic systems with the presesnce of intelligent life. Consider the early Earth, for example. Of course, most of this thinking will continue to be conjecture until we have more data to work with, but it's just so fun to speculate. In fact, speculation is one of the coolest side effects of being intelligent and creative systems.

Anonymous Coward

> If we define life as a pattern of physical
> behavior that is independent of its specific
> physical and chemical ingredients

I have some problem with this definition of life. Take one of our virus for example. Its behavior is dictate entirely based on its chemical make-up. Yet, it's managed to even reproduce. If we found a virus on Titan, surely, we'd declare that as the greatest discovery ever. With the lack of a satisfactory definition, perhaps life should be treated the same as porn -- "I'll know it when I see it."


The problem with the porn analogy is that the life signatures we will be looking for around our galaxy, for example, will be contained in points of light on which spectral analyses will be performed. This means that we have to have some preconceived ideas of what we're looking for. This is why the notion of a life pattern (extended to atmospheric chemical state, for example) is so compelling. Of course, this still falls in the life-like-ours category since, theoretically, life doesn't require the existence of an atmosphere (consider Europa and the interesting possibilities there).

Re virus: a virus by definition can not "live" without the aid of a host which makes copies of the virus as a result of dna hijacking. If we were to detect viruses on Titan, you are correct that this would be the greatest discovery of all time as it would mean that there are cellular genetic systems present on a world besides our own. The things that these Titan viruses infect would be what we classified as life, however.

Anonymous Coward

> are points of light on which spectral analyses are performed.
> This means we have to have some preconceived idea of what
> we're looking for. This is why the notion of a life pattern
> is so compelling.

Well, yeah. Spectral analyses can only give us so much. Now, if a planet shows up w/ 80% nitrogen & 20% oxygen, that would be exciting news. Better yet, an "I Love Lucy" episode from a far-off star would be nice. Is it me, but space has became very exciting all of a sudden? Mars Rover & Cassini came out of nowhere.

> Re virus: a virus by definition can not "live" without the aid
> of a host which makes copies of the virus as a result of dna
> hijacking

I used that because it's not clear even here whether that's life. That's definitely more life than not. Plus, I'm not even sure that all us homosapiens are "independent of our specific
physical and chemical ingredients."


As far as I know, there is no *definition* of life yet. We can't be even sure if we want to find a planet with simmilar conditions to Earth's - even on Earth we've found bacterias able to live in extremely high temperatures and feed or breathe with sulfur. Why then do we want to find conditions for *humankind*? There are so many possibilities... They don't have to have cells, DNA, anagolic life-cycles... Everything may be different. The truth is that we know ONLY ONE planet and ONE possibility of life developement. Can we describe the climate knowing only one day weather? No, that's not enough.
All we want from the life we seek for is to exist - we can't define what else would it do, because it doesn't have to correspond with life on Earth.
Well, then.... we don't know what we are looking for?

Tom Servo

The search for life in the universe is a nice thing, but we should get FTL travel working first, or at least FTL communications.


ikari, you are right: there is no completely satisfactory definition of life at this point in time. However, if you look at one form of life as a planetary surface property (like what we have here on Earth, cumulatively) then you have something to work with and you have something to look for that you understand. This is why the atmospheric observation of distant worlds via spectral analysis (to see if the atmosphere is in a state of chemical disequilibrium) is a good idea. In fact, this is exactly what ESA and NASA will be doing over the next 10 years. James Lovelock, though he won't be credited by ESA and NASA, really deserves a lot of kudos for both his definition of life as a planetary property that is tightly bound to the planet upon which it goes about living and devising a means to remotely detect the existence of this type of geobiologic system.

The search for life can be thought of as the search for geobiologic life signatures (atmospheric entropy gradients). Yes, life like ours in the sense that, if it exists on a broad enough scale on the surface of a rocky planet with an atmosphere and interacts with surface geology and atmospheric processes in a cybernetic way (adaptive feedback), then we can find it.


Tom, faster than light technology will probably be achieved sometime after we detect other worlds bearing life. We already have most of the technology to look for life around our galaxy. In 10 years, we will definitely be able to find life similar to what we have here (if only similar in how the cumulative effect of the extra-solar life perturbs planetary surface properties like atmosphere and geology). And, as I've mentioned in an earlier post, there is still the possibility that living systems are present on Titan. And, we can get there without the need for FTL technology.

Paul Golovin

"Big Numbers aren't so Big"
I am Amazon-reviewer "pg--az", who synchronicity-wise just endorsed David Swift's "Evolution Under the Microscope". A pointed quote from page 243:
"the frequency of individual (DNA) mutations( about one in a billion ) is comparable numerically with the years of geological time( a few billion )...if the large size of bacterial populations and their short generation time means they can find three simultaneous mutations in one year( due to about 10**27 search attempts ), then comparable populations would have a good chance of finding four simultaneous mutations in the whole of geological time, but probably not five."

Pgolovin believes everyone who chats about astronomical numbers should read this book - Swift tries to point out the implications, if you really believe that mutations are random-independent, how awesomely hopeless the statistics of dead-dumb-trial-and-error actually is. This book is perhaps four times as detailed and throrough as "Darwin's Black Box", which itself is a great read, sez me.

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