Extraterrestrial life

[ilikeverin]

not in this galaxy.

Scientists estimate that it would take between 5 and 50 million years for a race to colonize the entire galaxy. And we've yet to be colonized, and our sun is a relatively new star. Therefore it's highly improbable that a very advanced civilization has arisen in our galaxy, unless they're long gone.

Not nessesarily. Maybe they have a Prime Directive. Or maybe they have other reasons for not coming here. Scientists estimated that we would go to Mars by the 1980's. And, I'm still waiting for my flying car and Fusion powered cities. Maybe they have just developed differently from us. Perhaps they are more introverted and prefer to stay in their own system. Maybe some of their planets have been ripped apart by war. Maybe they are so peaceful and docile that they advance much slower than we do. Maybe other civilizations have clashed when they have met and are to preoccupied with that to visit our planet. Remember, in galactic terms, our system is fairly remote. Not only that, but a species managing to stay around and thrive for even 10 million years is a little unreasonable, let alone 50 million.

Or, maybe they visited here, once, a long time ago and saw a semi-intellegent spiecies developing, and either decided not to screw with the development of the planet, or simply weren't interested in this place, so they packed up and left.

What if we were planted here? Much like a farmer plants a seed and sits back and watches it grow.

Heh, I believe something like that, though I wonder where your seed-planting starts (the first one-celled organism or what?)

[12th Doctor]

not in this galaxy.

Scientists estimate that it would take between 5 and 50 million years for a race to colonize the entire galaxy.  And we've yet to be colonized, and our sun is a relatively new star.  Therefore it's highly improbable that a very advanced civilization has arisen in our galaxy, unless they're long gone.

I've got to disagree with the idea that an alien race would be interested in colonization.  Building out of system colonies is expensive (in terms of resources) and probably difficult to govern (or control). 

Assume that Galatic Emperor Sloob IV has an empire with 100,000,000,000 Gorfs; also assume that Gorfs are cabon based lifeforms that need air food and water.  If they are capable of interstellar flight, they are capable of doing many things.  They can build stations, settle other planets in their system, "terraforming" them.

They fill their own system up and decide to colonize.  They have a choice:  Planets in a 20 light year radius or earth 100 light years away.

There are probably a lot of planets within a 50 light year radius.  It will be expensive to colonize, because of terraforming, but its still work it.  Maybe there are one or two that are pretty much like Gorfia and don't need much work.

Sloob the Tyrant looks at the situation.  It's going to cost more to send people to Earth, 150 light years away, and ship supplies to it.  It's going to be harder to defend it, if the H'Dok'ofs start trouble (again), that it will be that nice one 5 light years away.  Further, if they revolt, it's going to be easier to supress the planet five light years away than 150 light years away.  He (or She or It) looks at the situation and decides, "Ah, we'll keep it close to Homeworld."

They may be able to keep 20 Billion in their own system, including other planets, space stations, moons, and move the rest into the ten or twelve systems closer to Gorfica.

There probably isn't anyone else within a 35 light year radius.

I agree, mostly, with what you have to say, but I have to say the number of people one could resonable expect to hold in the average inhabitable system should be more than you have supposed.  Using our technology and our system as a model (which is flawed, I know) we should be able to postulate that the average system might have 6-12 planets, of which, 2-5 are large gas giants (from what we can tell now the average system seems to have two) and 1-4 are in the habitable range (We have three, but thanks to Venus' atmoshpere, it posses a serious challenge to even the most advanced terraforming technology that we can concieve of at this point) and the others are either too close or too or too far away to be terraformed.  Also, you have moons that might be able to be terraformed, of which our solar system might have one (our own).  This is not to mention colonies that could be formed on every non-gas giant body in our system (including moons around Saturn and Jupiter.  Now, with advanced technology, in food production, sanitation, living space, matierials production, communication, transportation, environmental science and a stable social structure, I don't think it is unreasonable to think that you could fit as many as 20 billion people on an Earth sized planet alone.  In an entire system, it might not be unreasonable to think that as many as 50 billion people could live in our system alone.  Now, if you had a system with, say three Earth sized planets (Venus and Mars our both somewhat smaller than the Earth) or larger that have ecological systems or could be terraformed, and 4 or 5 smaller planets that could be terraformed and a coule of gas giants (life without larger planets in the way to keep large astroids from striking habited planets would be difficult to imagine) then you could perhaps situate as many as 100 million people in the same system.

[J. J.]

I'm trying to be conservative, and assuming that gravity will be a factor.  The moon, for example, will be hard to terraform because there is very little to hold the atmosphere.  Mars, and some of Jupiter's moons are different matters.  Even the moon could be much closer to Heinlein's vision of underground cities.

My particular point is that any civilization that has the ability to cross the distances of space has the technology to really terraform their own system.  Colonialism isn't probably going to be the goal of an alien species.

[Beefalow and the Consumer]

The Drake equation, with even somewhat conservative estimates, would yield a relatively large number of planets with intelligent life, and an even larger number of planets on which life arose. Drake himself estimates 10,000 intelligent civilizations.

Consider this very long list of criteria that have to be within very tight tolerences in order for intelligent, complex life to exist.  There are now 154 of them:

http://www.reasons.org/resources/apologetics/design_evidences/200406_fine_tuning_for_life_on_earth.shtml

[ATFFL]

The Drake equation, with even somewhat conservative estimates, would yield a relatively large number of planets with intelligent life, and an even larger number of planets on which life arose. Drake himself estimates 10,000 intelligent civilizations.

Consider this very long list of criteria that have to be within very tight tolerences in order for intelligent, complex life to exist.  There are now 154 of them:

http://www.reasons.org/resources/apologetics/design_evidences/200406_fine_tuning_for_life_on_earth.shtml

That list is not what is needed for compex life to exist, but for complex life to exist in precisely earthlike conditions.  If we do find solid evidence of life elsewhere in the solar system, even simple life, we can safely assume that the universe is not so precise that only Earth and Earth clones can support life.

[J. J.]

The Drake equation, with even somewhat conservative estimates, would yield a relatively large number of planets with intelligent life, and an even larger number of planets on which life arose. Drake himself estimates 10,000 intelligent civilizations.

Consider this very long list of criteria that have to be within very tight tolerences in order for intelligent, complex life to exist.  There are now 154 of them:

http://www.reasons.org/resources/apologetics/design_evidences/200406_fine_tuning_for_life_on_earth.shtml

That list is not what is needed for compex life to exist, but for complex life to exist in precisely earthlike conditions.  If we do find solid evidence of life elsewhere in the solar system, even simple life, we can safely assume that the universe is not so precise that only Earth and Earth clones can support life.

Note that in my example, I've assumed carbon based life similar to humans.  We might be talking about a species that breaths nitrogen, for example, or something based on silicon (with carbon based computers).

[Beefalow and the Consumer]

We might be talking about a species that breaths nitrogen, for example

Nitrogen gas (N2) would have zero value for respiration.  The Nitrogen triple bond takes enormous amounts of energy to break.

[Emsworth]

We might be talking about a species that breaths nitrogen, for example

Nitrogen gas (N2) would have zero value for respiration.  The Nitrogen triple bond takes enormous amounts of energy to break.

But why should our experience as to the capabilities of beings on the Earth constrain the capabilities of hypothetical creatures from other planets?

[J. J.]

We might be talking about a species that breaths nitrogen, for example

Nitrogen gas (N2) would have zero value for respiration.  The Nitrogen triple bond takes enormous amounts of energy to break.

You are assuming respiration in a carbon based life sense, as seen on earth; the migh have evolved another method.

[Beefalow and the Consumer]

We might be talking about a species that breaths nitrogen, for example

Nitrogen gas (N2) would have zero value for respiration.  The Nitrogen triple bond takes enormous amounts of energy to break.

You are assuming respiration in a carbon based life sense, as seen on earth; the migh have evolved another method.

Nitrogen takes huge amounts of energy to break, whether you are Carbon, Silicon, or Marshmellow-based life.  The laws of chemistry don't change just because you're on another planet.

[Emsworth]

Nitrogen takes huge amounts of energy to break, whether you are Carbon, Silicon, or Marshmellow-based life.  The laws of chemistry don't change just because you're on another planet.

The laws of chemistry, yes: but such is not necessarily the case with the principles of biology. We cannot assume that our observations of the abilities of living beings on the Earth will apply throughout the universe.

[12th Doctor]

The Drake equation, with even somewhat conservative estimates, would yield a relatively large number of planets with intelligent life, and an even larger number of planets on which life arose. Drake himself estimates 10,000 intelligent civilizations.

Consider this very long list of criteria that have to be within very tight tolerences in order for intelligent, complex life to exist.  There are now 154 of them:

http://www.reasons.org/resources/apologetics/design_evidences/200406_fine_tuning_for_life_on_earth.shtml

Almost everything on that list is too elementary to warrent discussion, already assumed, not nessesarily so, irrelevant, taken care of by nature and chance (or a Higher Power) or simply too narrow minded a very of how life and advanced civilizations could blosom and flurish.

[12th Doctor]

This chart seems to assume that conditions that exist now in our galaxy, system and planet have always been as they are now.  the fact is, life forms have thrived on this planet when the continental shift was greater, when sunspot patterns were more frequent and more intense, when there was more iron in the oceans, when there was less oxygen in the atmosphere, when there was more nitrogen in the atmosphere, when gravitational poles were different in our solar system.  When certain stars and nebuli(sp) were closer or farther away, when there was less sediment, when the planet was colder, hotter and everywhere in between, when astroids strikes were more frequent, when the environment was more or less acidic... I can do this pretty much all day.  And obviously, other planets and, presumablly, star systems exist inspite of the sometimes hostile conditions of the Universe.

[??????????]

And all of this speculation assumes they are carbon based lifeforms. It's possible life forms exist in merely energy form, etc.

[Gabu]

And all of this speculation assumes they are carbon based lifeforms. It's possible life forms exist in merely energy form, etc.

Well, assuming that they're made of matter, carbon is the most likely base for any living thing, purely because of how many bonds it can make to other elements.  The other items below it in the periodic table, like silicon, are also possibilities, depending on the gravitational properties of the planet (it would have to have a lesser gravitational pull for organisms based on heavier elements to be able to live).  I suppose that you could also make an argument that, say, a nitrogen-based life form would be possible, but it would be very likely to not be capable of being nearly as complicated.  Anything further to the right of that is simply not at all likely.  I once heard a person speculate that an iodine-based life form was a possibility - no, I would say that it is not, given that iodine can only bond with one single other element and is therefore known as a terminal element.