What makes the Earth habitable?

[Chris Peterson]

I decided then and there that I would never read a book by Larry Niven again!

I guess you pass on Heinlein as well. Lazarus Long makes Louis Wu look like an monk!

[Ann]

the statement that our galaxy is teeming with life and that there are millions of civilizations in the MIlky Way should be much easier to prove.

Who made that statement? Where did it come from? What is your source for that statement?

I'm sorry; I must have missed this. I don't see from where such a statement comes. I've never heard a serious assertion that our galaxy is teeming with life, nor that there are millions of civilizations in the Milky Way. Speculation, yes. Stories that are science fiction, yes. But a flat-out statement that our galaxy IS teeming with life? No. A flat-out statement that there ARE millions of civilizations in the Milky Way? Please let me know what reading material I've been missing by pointing me to a source; thanks!

Sorry, Owlice. I'm sure I exaggerated that. Those who champion the idea of a Milky Way teeming with life tend to be the most enthusiastic SETI proponents. (But I realize that you can be very interested in SETI and still not believe that our galaxy is overflowing with life. Indeed, SETI is as legitimate as a science as any other, if you do it properly.)

But I bought Astronomy Magazine a year ago or so because they had an article about the Drake Equation in it, and I was almost shocked by what author said in it. I had expected a balanced report on what we know and what we may assume. But while the article managed to sound scientific enough, it nevertheless ended up suggesting that very many of the factors of the Drake Equation are close to unity. That is, most G-type planets can be expected to have planets, and most solar systems can be expected to have at least one habitable planet, and practically every habitable planet can be expected to produce simple life form, and simple life forms can almost always be expected to evolve into complex life forms, and complex life can be expected to develop intelligence, and intelligent life can be expected to build technological civilizations.

Am I sure that the article said that? No, I'm not. It could well be that I thought that the article was way too enthusiastic about how much life we can expect to find in our galaxy, and because of my irritation I might mis-remember what the article actually said. (I don't have it any more.)

A person who was very optimistic about life on other planets in our galaxy was Carl Sagan. Surely he predicted that there was at least a million technological civilizations in our galaxy.

Another thing that irritates me, and that I have also found many times in magazines like Astronomy and Sky & Telesciope, is the assertion that astronomers used to be much more pessimistic about life on other planets in the past than they are now, because now they know so much more about the other planets that they have far more reason than before to be optimistic. I don't believe in that at all. Like I said, I vividly remember being told by a serious-sounding article from the 1960s that there was vegetation on Mars. I also vividly remember an article in my local newspaper from about 1970 where the reporter was shocked and horrified at learning that Venus was hot enough to melt lead. The reporter wrote that astronomers used to believe that Venus was clement enough to support simple life forms, and while that may well have been a misconception on his part, it was probably a misconception that was shared by many astronomically interested people at that time.

Ann

[Ann]

I decided then and there that I would never read a book by Larry Niven again!

I guess you pass on Heinlein as well. Lazarus Long makes Louis Wu look like an monk!

I haven't read much by Heinlein, but you're right, I don't much like him. But my real problem with Larry Niven's Ringworld hero was not so much his promiscuous sexual habits as the fact that he ended up killing almost all the (hundreds?) of women he had had sex with!

Ann

[Ann]

I decided then and there that I would never read a book by Larry Niven again!

I'm pretty sure I could make A Tale of Two Cities or even Little Women sound just as ridiculous if I made as much effort as you've just made to trash Niven's Ringworld. But in making that effort you failed to address the point I was making in response to your slur of all science fiction for its lack of creativity regarding planetary orbits.

Rob

I haven't read A Tale of Two Cities (and it's probably just as well that I haven't), but I have read Little Women. It was a very long time ago, so I don't remember much, but I think there were things I liked in it (or them? Were there more than one book?), and there were things I didn't like.

I don't mean to slur all science fiction for its lack of creativity regarding planetary orbits. I'm sure you are right that if I had kept reading science fiction for longer than I did, and if I had put up with writers like Larry Niven, I might indeed have come across some very interesting creativity regarding planetary orbits. I ended up strongly disliking Ringworld because I was shocked that the hero would kill all his former lovers, but I really did think, all the same, that the Ringworld itself was a very creative and fascinating idea.

Ann

[Chris Peterson]

I haven't read much by Heinlein, but you are right, I don't much like him. But my real problem with Larry Niven's Ringworld hero was not so much his promiscuous sexual habits as the fact that he ended up killing almost all the (hundreds?) of women he had had sex with!

Well, technically, they weren't women, but females of a different hominin species. And technically, it wasn't sex but rishathra, a ritualized, interspecies sexual practice (often used to seal contracts). And the decision to kill millions of "people" is part of a series of ethical dilemmas Wu faces in trying to save a world that contains hundreds of billions of sentient beings.

BTW, if you continue with the Ringworld series, you'll discover that not many were actually killed by the restabilization jets.

[Henning Makholm]

I'm sorry; I must have missed this. I don't see from where such a statement comes. I've never heard a serious assertion that our galaxy is teeming with life, nor that there are millions of civilizations in the Milky Way. Speculation, yes.

I've heard pretty serious claims that the galaxy might be teeming with life.

Note, however, the difference between "might be" and "is". Claiming that the galaxy might be teeming with life is a lot more reasonable than claiming that, based on what we know now, it does teem with life.

Ann appears to contend that a significant number of scientists claim galactic life-teeming as fact rather than possibility. That is what I think is a strawman construction.

[owlice]

Chris, speculation is one thing, and I agree that speculating there are other planets which host life is reasonable. It's the claim that there is an assertion that this is so that I question. Of course there will be those who claim all kinds of fantastic things, but a credible, serious assertion, one that is accepted by many (or even some critical number)... that, I question.

This whole thread, and the earlier one on the color of the sun, makes me think of Santa Claus. Not everything kids believe when they are little, regardless of whether the belief was planted or grew out of children's limited experience with the world, is true.

Re: Heinlein, I read him until I got to a certain Lazarus Long story; I had thought before that that Heinlein had some serious issues of his own to work out, and after that, I was certain of it! I still reread the Heinlein I've already read, but haven't sought out anything of his I don't already know since.

Ann, you're taking an article here, a journalistic exaggeration there, as evidence of a wide-spread belief, and then getting irritated about it. Instead of looking at the oddball articles, maybe concentrating on the larger share of writings would be a better idea? So long as there are more than two people on the planet, there will not be perfect agreement about everything, or possibly anything!! <g>

Henning, yes, exactly my point: this strikes me as a strawman argument, too.

[Chris Peterson]

Chris, speculation is one thing, and I agree that speculating there are other planets which host life is reasonable. It's the claim that there is an assertion that this is so that I question. Of course there will be those who claim all kinds of fantastic things, but a credible, serious assertion, one that is accepted by many (or even some critical number)... that, I question.

Sure. Of course, one person's speculation may be another's assertion. We certainly see that occasionally in this forum, where a few of our more credulous members are quick to repost any number of extremely speculative ideas as strong assertions!

[Ann]

I'm sorry; I must have missed this. I don't see from where such a statement comes. I've never heard a serious assertion that our galaxy is teeming with life, nor that there are millions of civilizations in the Milky Way. Speculation, yes.

I've heard pretty serious claims that the galaxy might be teeming with life.

Note, however, the difference between "might be" and "is". Claiming that the galaxy might be teeming with life is a lot more reasonable than claiming that, based on what we know now, it does teem with life.

Ann appears to contend that a significant number of scientists claim galactic life-teeming as fact rather than possibility. That is what I think is a strawman construction.

No, my point isn't that a significant number of scientists claim galactic life-teeming as fact rather than possibility. I don't think that is the case at all. My point is, rather, that there is a lot of speculation as well as discussion that life is common in the universe, but a lot less discussion about the possible uncommon-ness of the Earth. I googled "life is common in the universe" and got 12,600 hits. I googled "life is rare in the universe" and got 1,410 hits.

I can't help noting that no one here has so far commented on my claim that we have reason to think that the Earth is rare. Personally I believe that the Earth is like a lottery winner, which, just out of pure coincidence, happened to win all the necessary characteristics that work together to make a planet very suitable for life. I also think that this "habitable planet lottery" is a very big lottery, and that there are few winners.

Any comments on my list of factors that help make the Earth habitable, a list I made in an earlier post?

Ann

[Henning Makholm]

No, my point isn't that a significant number of scientists claim galactic life-teeming as fact rather than possibility. I don't think that is the case at all. My point is, rather, that there is a lot of speculation as well as discussion that life is common in the universe, but a lot less discussion about the possible uncommon-ness of the Earth. I googled "life is common in the universe" and got 12,600 hits. I googled "life is rare in the universe" and got 1,410 hits.

How it is even logically possible for there to be a lot of discussion of A without there being the same abount of discussion of not-A? You cannot discuss one possibility without at the same time discussing the other; otherwise it would not be a discussion of the question at all.

[owlice]

How it is even logically possible for there to be a lot of discussion of A without there being the same abount of discussion of not-A? You cannot discuss one possibility without at the same time discussing the other; otherwise it would not be a discussion of the question at all.

:: hopes someone brings her an unbirthday cupcake this afternoon ::

[Ann]

Any comments on my list of factors that help make the Earth habitable, a list I made in an earlier post?

Naaaah. Didn't think so.

Ann

P.S. You're right, Owlice, it isn't my birthday. So I don't mind that unbirthday cake.

P.P.S. What do you people think of the mediocrity principle? Do you agree that the Earth can't be very special because the mediocrity principle says that we can't, amen?

[owlice]

Ann, I have Zingers; they're not cupcakes, but I'm happy to share them with you!

zingers4.jpg (7.88 KiB) Viewed 883 times

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[Henning Makholm]

Any comments on my list of factors that help make the Earth habitable, a list I made in an earlier post?

Naaaah. Didn't think so.

It seems quite apparent that nobody feels any particular need to champion the position you want to oppose.

How is that our fault, again?

P.P.S. What do you people think of the mediocrity principle? Do you agree that the Earth can't be very special because the mediocrity principle says that we can't, amen?

And there's another strawman.

[Ann]

Ann, I have Zingers; they're not cupcakes, but I'm happy to share them with you!

zingers4.jpg

[/i]

Mmmmmmmmmmmmmmmmmm!!!!

Ann

[>>--Swainy-->]

Ann, I have Zingers; they're not cupcakes, but I'm happy to share them with you!

zingers4.jpg

[/i]

Life is like a box of chocolates, you never know what your going to get.

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I can't help noting that no one here has so far commented on my claim that we have reason to think that the Earth is rare. Personally I believe that the Earth is like a lottery winner, which, just out of pure coincidence, happened to win all the necessary characteristics that work together to make a planet very suitable for life. I also think that this "habitable planet lottery" is a very big lottery, and that there are few winners.

We are all winners. I personally beat 2.5 million to the Egg. How Many did you Beat?

tc

[neufer]

I can't help noting that no one here has so far commented on my claim that we have reason to think that the Earth is rare. Personally I believe that the Earth is like a lottery winner, which, just out of pure coincidence, happened to win all the necessary characteristics that work together to make a planet very suitable for life. I also think that this "habitable planet lottery" is a very big lottery, and that there are few winners.

The momentum of discoveries is ALL going in the direction of life being abundant in the universe:

• 1) the radio telescope discovery of complex hydrocarbons in space
  2) the Miller–Urey creation of 22 amino acids "in a test tube"
  3) the discovery of the simplicity of DNA replication
  4) the discovery of prokaryotes 700 million years after the formation of the Earth
  5) the discovery of prokaryotes both deep below the ocean & under the earth
  6) the discovery of more than 100 billion galaxies in the observable universe
  7) the discovery of earth-like planets around other suns

We also have clear evidence that parasites, disease & catastrophes ALL help to speed up the evolution of any life once formed. In fact the development of eukaryotes 2 to 3 billion years ago was probably a direct result of prokaryotes and their parasites benefiting from mutual symbiosis.

Can Ann give even ONE example of any discovery that suggests that life might somehow be rare in the universe?

[rstevenson]

I can't help noting that no one here has so far commented on my claim that we have reason to think that the Earth is rare.

I did, but you ignored it. Here it is again...

"As for your initial question, and the title of this thread, I can only reply, "Who knows?" A data set containing only one point makes a poor chart." In case I was being too cryptic, let me explain. While we now have quite a few hints that there are at least the conditions that might lead to life on other panets and moons in our own system, and while we have lots of "candidates" for Earth-like planets elsewhere, we have so far only one planet with verifiable life -- some might even say intelligent life -- on it. Earth. One data point. Ergo, not enough data. Any discussion about how rare that is reduces to a discussion of belief. We simply don't know.

Rob

[neufer]

I can't help noting that no one here has so far commented on my claim that we have reason to think that the Earth is rare.

As for your initial question, and the title of this thread, I can only reply, "Who knows?" A data set containing only one point makes a poor chart." In case I was being too cryptic, let me explain. While we now have quite a few hints that there are at least the conditions that might lead to life on other planets and moons in our own system, and while we have lots of "candidates" for Earth-like planets elsewhere, we have so far only one planet with verifiable life -- some might even say intelligent life -- on it. Earth. One data point. Ergo, not enough data. Any discussion about how rare that is reduces to a discussion of belief. We simply don't know.

You are talking about the expectation that life exists elsewhere
simply based upon the ONE fact that life exists on Earth.

Based upon the sum total of ALL the discoveries which I have stated above I believe
that we can confidently conclude beyond a reasonable doubt that life is abundant in the universe.

[swainy]

Neufer, You really are growing on me. Your not a Barnacle are you?



Tc

[rstevenson]

Based upon the sum total of ALL the discoveries which I have stated above I believe that we can confidently conclude beyond a reasonable doubt that life is abundant in the universe.

I believe you are right Art. I even hope you are right. But I don't think you are right -- or wrong.

Rob

[Henning Makholm]

Earth. One data point. Ergo, not enough data. Any discussion about how rare that is reduces to a discussion of belief.

Belief. That is quite possibly the elephant in the room.

Someone seems to have decided that if intelligent life is abundant in the universe, that would be an argument that God does not exist. And, conversely, if life on Earth is truly unique, then it must be due to divine intervention. I don't find either inference to be particularly persuasive, but the idea makes some of us wary of approaching a debate that could turn out to be a preamble for a pointless and unproductive atheist/theist shouting match.

[swainy]

Someone seems to have decided that if intelligent life is abundant in the universe, that would be an argument that God does not exist. And, conversely, if life on Earth is truly unique, then it must be due to divine intervention. I don't find either inference to be particularly persuasive, but the idea makes some of us wary of approaching a debate that could turn out to be a preamble for a pointless and unproductive atheist/theist shouting match.

Did not the great man input this info, into to his equations? Or was it the other way round? (You work out who).

tc

[bystander]

When did Devine enter the conversation? Let's leave divinity out of the thread, unless you are talking divinity, then make sure you bring enough for everybody.

[rstevenson]

It might be interesting to see what values each of us who are interested in this discussion get when they run the Drake Equation interactive. Mine works out to 798,400 -- a bit on the high side compared to most of you, I imagine. That's mainly because I'm optimistic about the life span of an intelligent species.

For some, this version of the equation might be more suitable.

Rob