Sum up the meaning of life in one sentence.

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The basic problem with the Drake equation, as you have indicated, is that no one knows what numbers to plug in. It's a lottery.

Yeah, but the Drake equation makes no accounting of weather the planet is in the galactic habitable zone (only 0.1% of stars exist in this zone, the Drake equation uses all stars) nor does it account for the need of a large moon. Both have been argued necessary for the existence of complex life.



Considering the possibility of finding that life based on the rare earth equation, it is wild optimism to suppose that complex life would exist close to us. However, if it were going to exist in our galaxy, it would have to be near us in the galactic habitable zone and in between the galactic spirals. As to the billions of stars in our galaxy; yes there are around 100 billion. The rare earth equation requires something closer to a 1 in 1000 billion chance. Even is aspects of the equation were pessimistic, you still have almost no expectation of finding life within our galaxy apart from us.

I have no problem with the possibility of advanced life on other planets; it is exceedingly slim chance its anywhere we will be able to find it any time soon.

both of those qualities can be included in n sub e of the equation (the need for a large moon, btw, is not widely accepted by the exobiology community).


couple of problems with that. First, the galactic habitable zone theory presupposes first that extraterrestrial life has the same requirements that life does, and second disregards the possibility of local conditions that create pockets of appropriate habitat even in otherwise harsh areas of the galaxy (Europa, for example, exists outside of the stellar habitable zone in our own solar system, but may have liquid oceans suitable for life akin to that of our deep sea vents). In addition, we do not actually know enough about the intrastellar space within the Milky Way to adequately deliniate which areas would be habitable even to earth-like life in unremarkable habitats (HT to Bad Astronomer). Secondly, 100bil is the lower estimate; 500bil is the upper. Thirdly, we know that the odds of finding life in this galaxy are at worst1/500bil, because life (us) is known to exist in this galaxy. Any numbers plugged into any equation that place the odds at less than one, are flawed.


Honestly, if there is intelligent life out there I hope we don't encounter it for at least another couple of centuries, at the soonest.

free to start a new sentence? or to remain shut up for eternity which would be the ultimate sentence ?

"life" is a sentence with no punctuation,
and the sentence of "life" has no full stop*.
"life's" in "forever", 'cause "life's" not in "never"
and the clever discover that life did not pop...
out of nowhere.

(* in australia we say "full stop" where you say "period", and the one word sentence "life" has no full stop)


my autistic mind is all over the place and it is 1 am so forgive my banality.

you are a good man aunt blabby. you remind me of someone but i forget who it was.

The lack of imagination in this discussion is comical. The limitation of life or even intelligence to a water-carbon base using oxygen or some similar chemical is violated even on Earth and in the huge possibilities in the universe at large there is no reason that life should even be planet based. Ionic clouds in the proximity of a black hole have all the possibilities as well as life dependent upon super-conduction near absolute zero for two examples where the Drake equations have no application. There is no way to tell about all the multitudes of possibilities and any perusal of a science fiction shelf in a decent library should reveal multitudes of ideas already explored.

I would tend to dispute that claim. Certainly the Giant Impact theory in relation to the creation of the moon is not yet accepted by the mainstream. It is hard however to dispute the fact that a moon the size of Earth's is necessary in order to regulate the flow of nutrients in the water and stabilize the rotation of the Earth. The large moon also increases the likelihood of plate tectonics; which are necessary in order to generate the planets magnetic field that protects us from solar radiation.

Also we have been very lucky in that the moon is where it is. If it were not we would not understand how the sun works though the perfect eclipses that occur.

Also the rare earth equation has only been around for a decade; its probably too short of a time to totally replace the drake equation.



I will address each of your points individually.

1) First, the galactic habitable zone theory presupposes first that extraterrestrial life has the same requirements that life does


You are correct in this, since it is almost impossible to speculate on life as we 'dont' know it. It is worth my while qualifying that both the drake and rare earth equations presuppose carbon-based life that breaths oxygen. There is also the possibility that life could exist in a way that we 'cannot' know it; it could exist in a way that is beyond our comprehension. However, though I do not always agree with him Stephen Hawking has put forward the case that it would be exceedingly unlikely for non-carbon based life to exist. The reason he has cited for this is that carbon based life has the richest chemistry.


2) disregards the possibility of local conditions that create pockets of appropriate habitat even in otherwise harsh areas of the galaxy (Europa, for example, exists outside of the stellar habitable zone in our own solar system, but may have liquid oceans suitable for life akin to that of our deep sea vents). In addition, we do not actually know enough about the intrastellar space within the Milky Way to adequately deliniate which areas would be habitable even to earth-like life in unremarkable habitats (HT to Bad Astronomer).


Well the answer to this point is both you are right and that you are wrong. Complex life is considered to require two habitable zones; both galactic and local. At the galactic level the stars are far too close together, there are a great deal of supernova that can harass life (this is also combined with a large amount of variable radiation). Also if a plant forms near the galactic center its local conditions would be too variable to create a stable platform upon which any complex life could evolve. If it is too far away from the galactic core then the metallicity of the stars declines cause it to be far less likely that planets of a decent size would form. Also these planets being the larger ones in those systems would attract the most impacts.

In the circumstellar habitable zone the planet must be in a specific spot in relation to the size of the star in order for liquid water to exist at or below the surface. The size of the star is therefor very important. For example our star was less massive (like 90% of the stars in our galaxy) then the gravity effect on the planet in the circumstellar habitable zone would be such that the orbit would be locked in without rotation. It is very unlikely that any complex life could tolerate the vast planetary extremes in temperature. The planet would also experience much larger amounts of solar flare activity.

It is also worth indicating that we are talking about complex life. It is likely that forms of life exist in the more inhospitable locations. However it is less likely that these environments are stable enough to support the large timelines we are talking about to create complex life.


3) we know that the odds of finding life in this galaxy are at worst1/500bil, because life (us) is known to exist in this galaxy. Any numbers plugged into any equation that place the odds at less than one, are flawed.


Well no actually. We know the odds are at least 1/universe. There is no reason so suppose that the odds MUST be more than this. The odds may be so low that only one in ever x number of galaxies produce life.

What I was taking a shot at was the invocation of the principle of mediocrity. It is clear from the rare earth hypothesis that we are not just some random common planet that is unexceptional in the universe. The rare Earth equation comes out (when calculated with just 10% variance in each factor, this is in most quite conservative in favor of the probability) comes out to about one in every trillion stars evolving complex life.



I hope this too. It is unlikely however that if life exists out there, that it is anywhere near us.

more a hopeful conceptual tool for those folk bereft of ET.

i don't understand how that would be a "free to go" situation. be patient with my brain, por favor.



charlie brown was said to be a good man also, so maybe i remind you of him. i often remind myself of charlie brown. i've never managed to catch the blessed ball.

Yah, Sand is kind of a dick. If atheism was such a good alternative to the evils of religious ideology, why did the holocaust happen? Yah, atheists insist Hitler was a Christian, but you can find quotes where he called religious people morons and referred to Communism as being the bastard child of Christianity when he wasn't speaking before crowds of people. It was based in the idea of Eugenics, the idea that you could find societal harmony by ending the lineages of racially, non-hygienic people. This was based in a very deterministic and materialistic worldview that juxtaposed that criminality was a genetic trait and that free will had little or nothing to do with how an individual behaved.

Of course, inferiority is subjective, and being a bunch of egotistic nationalists, they assumed anyone who wasn't racially similar to them was inferior and threw them into concentration camps where they were systematically murdered with the intent of cleansing the population to catalyze the next stage in human evolution. These very deterministic notions of behavior and genetics and the idea you could socially engineer criminals out of existence go back to British naturalist and cousin of Charles Darwin, John Galton, who was also a staunch atheist.

There's also Stalinism, which was also a very deterministic view of things. They felt that the end of history, where no hierarchy existed, needed to be fulfilled and that a very strong police state was a good way of catalyzing it. The result of early experiments with centrally planned economies was mass starvation in the Ukraine, but they felt millions of people dying was justifiable in the long run because of the ideal ends that they felt would be achieved. If mind is preceded by matter and no free will exists, then whats so bad about insignificant bits of protoplasm dying off on the road to the end of history?


...and I'm not going to excuse the crusades or the inquisition. Those were driven by ideology as well, which saw the will as god as being the over riding factor over human free will, and if some heathens had to die to fulfill God's divine plan, then it didn't matter if a few of his little play things were broken.

The truth is that any ideology, divorced of any basic human intuition for compassion, is bound to end this way if put into full force. It doesn't really matter if its atheistic or religious. Now Jesus would have said to love your enemies as you love yourself, and I don't think the inquisitors were following his teachings by torturing people. Karl Marx condemned capital punishment and personality cults, but the Soviets seemed to overlook this. Eugenics is a good idea as far as eliminating really bad, fatal genetic illnesses that cause a lot of pain before a premature death, but when you apply prejudiced, racial theories to it, as the Nazis did, you've definitely lost all connection with any sense of morality.

good point.


You have it exactly backwards; the giant impact theory is the dominant paradigm for Lunar formation; the necessity of a moon for life is not. Certainly the planet would be vastly different if there was no moon, but that does not mean that its intrinsic properties would be so different that it would never have fostered life.


...
solar eclipses are not necessary to study the sun. They're not even necessary to study the corona; modern telescopes, for example, can artificially eclipse the sun with disks that block the central body. While observing total eclipses is interesting and probably did inspire questions in some of our enlightenment ancestors, it is extremely doubtful that they were dependent on the natural blockage of the disk by that time if they wanted to examine solar phenomena.


Possibly; if it were 'better enough,' though, it could have replaced it within a few years.


I agree with this; however, 'carbon-based' is not the same as 'having the same requirements as terrestrial life.' Just as a speculative example, life evolved in colder environments than earth might have genetic material much less stable than DNA but tolerate colder temperatures; the reciprocal could be true of life evolved in hotter areas (both cold and hot referring to all types of electromagnetic radiation in this example, not just IR). Those organisms would still be carbon-based, though.


Even within the arms and closer to the galactic center, stars are not spaced evenly; within relatively dense areas of stars, there can be lacunae of relative safety. As for metallicity, that implies a gradient inner border, not a hard-and-fast one.


Again, refer to Europa. It is outside of what would be considered the 'habitable zone' for our star. Even Earth is somewhat outside of the 'sweet spot,' but is kept warm by the greenhouse effect of our atmosphere. The sun is actually a rather average star.


This is a good point; there are probably a lot of areas that would support life at the archean level, but not at a multicellular level.

{snip discussion of odds}
After the fact, the odds of 'what happened' actually happening is one. In this case, the odds of civilized life happening in Sol system is one; the odds of civilized life happening in the Milky Way is at least one; the odds of civilized life happening in the known Universe is at least one.


10% variance from what? How are the values for this equation any less speculative than those of the Drake equation?

Don't run around this world
looking for a hole to hide in.

There are wild beasts in every cave!
If you live with mice,
the cat claws will find you.

The only real rest comes
when you're alone with God.

Live in the nowhere that you came from,
Even though you have an address here.

Rumi

Very fundamentally, life is an information process. DNA is one way of storing, processing and utilizing information. That this is the only way, or even a necessary way for life to exist is a massive delusion.

is to experience love & death and after we live through it we either become a strong/ wiser person or we take a longer path in life with more distractions that either make us or break us.

either way we get scarred and we need to be able to pick up and move the F on ..cause we can't change the past the future we have in our hands if you chose to .

hello saint_jane and welcome to WP

"When I have sacrificed my angel soul,
I shall become what no mind ever conceived." [Rumi]

The meaning of life is something which I believe is inherently impossible to articulate in words for communication from person to person. I think it's an incredibly personal question, and as such, no answer I could give would really be adequate, because it wouldn't fit anyone else but me. But, I suppose I can at least give some sort of version of my own personal philosophy:

To me, the meaning of life is to acknowledge the indifference of the cosmos and hostility of our world, and to yet still resolve one's self to the proposition that, regardless of what anyone else has to say about the matter, some things are worth the fight.

Unfortunately this is not true. Evidence from our exploration of the moon has moved against Giant Impact Theory. As I stated previously; a moon the size of Earth's is necessary in order to regulate the flow of nutrients in the water and stabilize the rotation of the Earth. The large moon also increases the likelihood of plate tectonics; which are necessary in order to generate the planets magnetic field that protects us from solar radiation.’

You are correct that Earth probably would still have life on it without the moon. Considering the vastness of the Earth's oceans it is statistically very improbable that these early proteins would ever link up. “The solution is that the huge tides from the Moon produced inland tidal pools, which would fill and evaporate on a regular basis to produce high concentrations of amino acids". (Schombert, James. "Origin of Life". University of Oregon.)



The problem here is one of timelines. One needs a great deal of time in order for life to become complex. The safe areas near the galactic centre are unlikely to provide proper galactic orbits that provide long periods of time for the development of complex life. If one argues, is it possible, the answer is yes, statistically but one could make the same argument about complex life evolving on an Earth like planet. Even if one has a terrestrial planet, then it is still a statistical long shot for life to develop to a complex form and survive for length of time.



Europa almost certainly cannot produce complex life of the sort described in either the drake or rare earth equations. Also our star is not average. 90% of the stars in our galaxy are less massive than ours.



Well the difference is in the factors not just the variance. Obviously the variance can only be estimated but the factors can be identified. For example the Drake equation uses every star in the galaxy for establishing its calculation. We know with a good deal of certainty that most of the outer and inner stars cannot produce the kind of planets that can survive long enough to produce the kind of life the equations describe. When one takes a more accurate account of the factors, then the equation beings to account for the Fermi paradox.