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have they found anything?

amb said:
Carbon and water are essential. Perhaps silicone can be substituted but water is essential, most astrobiologists agree on that point. If not so, then we would have found some kind of microbes on the moon. Carbon, hydrogen, oxygen and nitrogen are the prime elements of life. Why is that so? Why those elements and not others? Simple really: because they are four of the five most abundant elements on Earth. The fifth is helium, but it's an inert gas and takes absolutely no part in any known chemical reactions.
Water is the miracle substance that makes life and our world possible, but without carbon even that would not suffice to make life possible. So, what my point is that the first generation of stars, possibly the second as well was necessary to produce this carbon in the cores of exploding stars. Even planets would not have been possible without the elements spewed out of a supernova to create the dust to form them. All this took billions of years, hence some astronomers theories that we may be one of the first rational animals to evolve in this almost infinite universe. If the first and second generation of stars took say, 10 billion years from birth to death to create the third generation of stars which our sun seems to be if the age of the universe is correct, I see that perhaps they are correct in their estimations.
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A somewhat off topic question occurred to me as a result of amb's post: What is the minimum number of elements contained in a living organism? Does every known living organism have at least oxygen, hydrogen, nitrogen and carbon? What other elements, if any, are in the living organism with the least number of elements?
 
You'd need at least phosphorus and all known organisms also at least need sulphur, magnesium, sodium, potassium and iron off the top of my head.
The list is probably a lot longer though
 
amb said:
The elements I mentioned are essential for life, not the most abundant.
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So how should I know when you don't mean what you say?

amb said:
Carbon, hydrogen, oxygen and nitrogen are the prime elements of life. Why is that so? Why those elements and not others? Simple really: because they are four of the five most abundant elements on Earth. The fifth is helium, but it's an inert gas and takes absolutely no part in any known chemical reactions.
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davefoc said:
A somewhat off topic question occurred to me as a result of amb's post: What is the minimum number of elements contained in a living organism? Does every known living organism have at least oxygen, hydrogen, nitrogen and carbon? What other elements, if any, are in the living organism with the least number of elements?
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Good question.

IMO, the line between just chemistry and life is not so sharp. A virus has some genetic material (DNA or RNA) and a protein coat. (ETA: And a prion is just a protein.)

In the best theories of abiogenesis, you had some sort of self-replicating polymer. (I think that's where you could argue life began. You would already have a form of selection because there are bound to be more of a self-replicating polymer in any sample of water than other molecules.) Once it's enclosed in a simple membrane vessicle, you have something resembling a proto-cell. It "reproduces" when the vessicle grows into a microtubule and then breaks into two by purely chemical/mechanical means. Again, a self-replicating molecule is more likely to be present in greater abundance in the two daughter proto-cells than other molecules.

ETA: But I don't think this is a useful approach, because these elements have been abundant in the universe for billions of years. And, as mentioned above, more time has not elapsed here on Earth than anywhere else in the universe, so I can't see how this argues something special or different or unusual about the Earth.
 
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A. Zaitsev said:
I have informed about this new

Message to probable ETI

in order to note that such activity also gain ground...
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Think of a civilization just one thousand years ahead of us, with the same curiosity as man who also has sent probes into the infinite universe, or just our galaxy. My argument is that we should have received a clue of their existence by now. We haven't, that seems to prove that at best we are one of the few civilizations in existence, or at worsts, one of the few in the whole universe.
 
amb said:
The elements I mentioned are essential for life, not the most abundant.
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Yes, that's right. According to joe your quote is:

amb said:
Carbon, hydrogen, oxygen and nitrogen are the prime elements of life. Why is that so? Why those elements and not others? Simple really: because they are four of the five most abundant elements on Earth.
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They are essential to life, not because they're particularly abundant, but because they are fantastically, chemically flexible. They are capable of all sorts of neat things: carrying energy, linking into long chains, which can be folded into complex shapes whose surfaces are conducive to catalyzing reactions, creating useful structures (like membranes, cells with vacuoles, structural elements), and so on.

Dr. Peter Ward says that the growing consensus among biologists and chemists is that there probably are not any other chemistries upon which life can be built besides ours; other life may incorporate other elements, but they probably won't be life if they aren't centered around those four elements.
 
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amb said:
Think of a civilization just one thousand years ahead of us, with the same curiosity as man who also has sent probes into the infinite universe, or just our galaxy. My argument is that we should have received a clue of their existence by now. We haven't, that seems to prove that at best we are one of the few civilizations in existence, or at worsts, one of the few in the whole universe.
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A big hole in your logic is the two parts I highlighted. We are an intelligent civilization that has NOT sent out probes that are now ubiquitous in the galaxy.

This flaw was part of the numbered rejection of your argument for the non-existence of ETIs based on Fermi's Paradox. There are many ways to explain Fermi's Paradox other than the conclusion that they don't exist.

I wish you'd quit repeating this mistake.
 
JoeTheJuggler said:
A big hole in your logic is the two parts I highlighted. We are an intelligent civilization that has NOT sent out probes that are now ubiquitous in the galaxy.
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There might be holes in his logic, but our civilization don't serve as a counter example to what you qoted him saying because we aren't a thousand years more advanced than we are. And a thousand years isn't a big amount of time in regard to the Fermi Paradox.
 
RecoveringYuppy said:
There might be holes in his logic, but our civilization don't serve as a counter example to what you qoted him saying because we aren't a thousand years more advanced than we are. And a thousand years isn't a big amount of time in regard to the Fermi Paradox.
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No. He meant that this civilization a thousand years ahead of us sent out probes a thousand years ago. We've been going over and over this for about year on this thread.

He's arguing that the only explanation for Fermi's Paradox is that ETIs do not exist. I've pointed out several times there are a number of other explanations. (I even numbered them.) That any one of them is possible refutes the argument amb has been making, and at this point all of them are possible.

Just off the top of my head, the points I made are that the technology to make evidence of a civilization ubiquitous in the galaxy might not be possible.

If possible, it might be that no civilization lasts long enough to discover it.

If discovered, it might be that the technology isn't feasible (economically, perhaps).

If feasible, it might be that such civilizations have no motivation to fill the galaxy with evidence of their existence (that is, they might choose not to use the technology).

It could also be that evidence of their existence is *almost* ubiquitous in the galaxy, and just missed us by a mere light year's distance or a mere thousand years' (or million years') time.

It could also be that such advanced ETIs are so advanced they could make themselves undetectable to us by intention.

Finally, it could be that no ETIs exist.

The lack of evidence does not point to this last explanation as the only possibility.

So my position is, we don't know whether or not ETIs exist.
 
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We don't know yes, but my point been is that the universe is not a friendly place for life as we know it. I have put up the fact that more than 70% of the stars in our galaxy are not like our sun. A few a are twenty times bigger than good old sol. The majority though are much smaller than sol and that most of these are binary, therefore not suitable for any animal life. Radiation in space will kill any life form within minutes without protective life support systems as it would on all planets without a protective atmosphere which is only possible on rocky planets around the the same size and distance from their mother star as Earth is. And the most important thing that life needs to flourish, liquid water. I don't believe any kind of animal life is possible without this essential ingredient. It may be in abundance in space as hydrogen, but liquid water? It may prove to be rare.
 
amb said:
We don't know yes, but my point been is that the universe is not a friendly place for life as we know it.
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And it's been pointed out to you that thinking in terms of whether certain conditions are "friendly" to life is a backward approach, and also that evolution seems to be driven by trauma rather than friendliness in the environment.

But, in fact, you don't know that there aren't a great many places in the galaxy as "friendly" as the Earth. You also don't know that the Earth is the most "friendly" place for life in the galaxy, but you reason as if it were.

In fact, everything you raise here has already been raised and refuted months ago:

I have put up the fact that more than 70% of the stars in our galaxy are not like our sun. A few a are twenty times bigger than good old sol. The majority though are much smaller than sol and that most of these are binary, therefore not suitable for any animal life.
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First, you don't know that life is impossible around larger stars (in the twilight zones on a tidally locked planet orbiting a red giant, for example). Second, even if it is, how many stars does that leave that are prime candidates? It's still a huge number. And we still don't know how common Earth-like planets are, but the trend seems to be that whenever we have employed a method to detect planets of given characteristics, we have found them in abundance.

Radiation in space will kill any life form within minutes without protective life support systems as it would on all planets without a protective atmosphere which is only possible on rocky planets around the the same size and distance from their mother star as Earth is.
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Also asked and answered. We're not talking about life in space, but on planets or large moons. There are plenty of ways the environment can protect life from damaging radiation. There are also ways that life could evolve its own protection. It may also be that more radiation would be a less friendly environment and spur more rapid evolution giving the odds for complex and intelligent life an advantage rather than a disadvantage.

And the most important thing that life needs to flourish, liquid water. I don't believe any kind of animal life is possible without this essential ingredient. It may be in abundance in space as hydrogen, but liquid water? It may prove to be rare.
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But it may not prove to be rare. Since you have no evidence that liquid water is rare, you can't assume it is.
 
When we look up at the night sky under ideal conditions away from the city glare, with the naked eye we see around 3000 stars out of the myriads that are out there, the common gut feeling is that surely out there are millions of civilizations in the vastness of space. It is difficult to believe we may well be alone. But appearances can be deceptive. Out of that roughly 3000 stars we can see with the naked eye, how many of those observed stars do you think would be hospitable to our form of life. Very few is my guess.
The gut reaction we perhaps all feel when we look at the night sky-there must be intelligent life somewhere in the vastness of space is not a good guide. We have to be guided by reason, not gut reaction, when discussing this matter.
The Drake equation is a product of several terms. If one of those terms is zero, then the product of the Drake equation will be zero; if several of the terms are small, then the product of the D equation will be very small. We will be alone.
If one factor in the D equation is close to zero, then we can reasonably identify that factor as being the solution to Fermi's paradox.
There are still many scientists who argue that the emergence of life was almost miraculous fluke, a one time event a 1 in 10 with 100 zeros event, a number that dwarfs the number of planets in the universe, and when expressed as a probability becomes, for practical purposes, indistinguishable from zero.
The improbability of the prokaryote-eukaryote transition could be another reason for Fermi's paradox.
There may be a number of reasons or one single reason/solution to the paradox. but it all boils down to that we are one of a few, or we could very well be alone. We could be unique. Excuse me if I wondered around a little on this post, I'm on my fourth stubby of beer. :p
 
amb said:
When we look up at the night sky under ideal conditions away from the city glare, with the naked eye we see around 3000 stars out of the myriads that are out there, the common gut feeling is that surely out there are millions of civilizations in the vastness of space. It is difficult to believe we may well be alone. But appearances can be deceptive. Out of that roughly 3000 stars we can see with the naked eye, how many of those observed stars do you think would be hospitable to our form of life. Very few is my guess.
The gut reaction we perhaps all feel when we look at the night sky-there must be intelligent life somewhere in the vastness of space is not a good guide. We have to be guided by reason, not gut reaction, when discussing this matter.
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See the Sagan quote I offered. Many of us don't like to think with our gut.


There may be a number of reasons or one single reason/solution to the paradox. but it all boils down to that we are one of a few, or we could very well be alone. We could be unique. Excuse me if I wondered [sic] around a little on this post, I'm on my fourth stubby of beer. :p
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No. You're wrong. There is also the possibility that there could be hundreds or even thousands of ETIs similar to us in the galaxy.

All your speculation on the probabilities with insufficient information to calculate them doesn't eliminate this possibility.
 
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