have they found anything?

[JoeTheJuggler]

I should add, that I agree it's true that the Earth "may be" unique, but it's much more likely not to be. Again, every time we've thought we were in a special situation, we were proven to be wrong.

The stuff in Rare Earth is just speculation. Take the example of large meteors striking the planet. Here, it seems we get one that really sort of hits the evolutionary "reset" button about every 50 million years or so. You say that if we had more frequent strikes intelligence wouldn't be able to evolve. It could well be the exact opposite. That more frequent strikes resets things more often and gives you more chances at selecting a hi-tech intelligence.

The point is we don't know.

As I've been saying, words like "rare" and "commonplace" are strictly relative terms. (Is "one in a million" or even "one in a billion" rare or commonplace?) "Unique" is a different thing. It means we're the only intelligence ever. (I do appreciate that you've scaled that back from the universe to the galaxy though.)

That seems like the same kind of extremely biased thinking that led us to think the Earth was the center of the universe. Really. . .billions of billions of stars and tens of billions of years' time is a lot of chances.

 

[davefoc]

I always thought the idea of transmitting a list of prime numbers would be an easy way of saying "We're here, and here's the way we think." It would also be different enough from any natural source of radiation to leave little doubt that it's an artificial or intentional signal.

That sounds reasonable. It is a bit of a problem because one would like to send the shortest pulses possible to maximize the distance for the power invested and not very many of them because there are a lot of stars where one might like to aim the transmissions and one might need to hit targets repetitively for years to maximize the chances of hitting a target that was capable of hitting the signal that you were transmitting.

Frank Drake, the guy of Drake's equation, where he expressed somewhat more optimism than he had previously about the number of technological civilizations in our galaxy.
http://www.wired.com/wired/archive/12.12/life.html

Of course, Drake knows massively more about this stuff than I do, but I'm in amb's camp on this. I think the number of technologically capable civilizations is probably very small and the possibility that any of them is near enough to us to communicate with is even smaller.

I will say this of all the miscellaneous subjects that I've followed and pontificated on in this forum there was never one that it was less likely to be resolved if actual facts became available. The number of planets with sentient life in the galaxy might be fairly high or extremely small. I doubt that any human being for as long as the species exists will ever know the truth about that.

 

[amb]

American cosmologist Frank Tippler believes that if extraterrestials exist, they should already be here. ''Since they are obviously not, they do not exist,'' he says. He does not deny the possibility that primitive life is widespread in the universe, but believes that the development of intelligence is vastly improbable. It has happened only once since the B/B. We are totally alone, he says.
Tippler's argument assumes that interstellar travel by self-replicating space probes is possible. If intelligent life were common, it's emergence should have had a head start on planets around stars that are billions of years older than our Sun.
At least one alien civilisation would have developed self-reproducing space probes and launched them into space.
Travelling at 90% of the speed of light an advanced technology could reach the nearest star in less than five years, depending where they are in the universe. If it takes 100 years to make a copy of itself, then the average speed at which all the probes would spread would be about 1/25 of the speed of light. At this speed, Tippler argues, the probes would spread throughout the galaxy within 10 million years.
But we have no evidence of these probes on Earth. Their absence shows the absence of aliens. That's the logic of Frank Tippler, a respected scientist, and me, a layman.

 

[RecoveringYuppy]

@amb. Two words: "Fermi Paradox"

 

[amb]

Exactly. ''If their there, why aren't they here.''

 

[JoeTheJuggler]

Of course, Drake knows massively more about this stuff than I do, but I'm in amb's camp on this. I think the number of technologically capable civilizations is probably very small and the possibility that any of them is near enough to us to communicate with is even smaller.

amb says the Earth is unique, which is very different than saying the number is relatively small.

My position is that terms like "rare" and "commonplace" are relative when you're dealing with astronomical sizes and numbers of things.

We are almost certainly not unique.

A technological civilization like ours could arise as frequently as something like 1 in every million stars, meaning our galaxy will have had tens of thousands of such civilizations, but they could still be so spread out in space and time that none of them would ever encounter another.

 

[JoeTheJuggler]

Exactly. ''If their there, why aren't they here.''

Because stuff is so spread out in space and time that it could be unlikely for any two to encounter each other.

I think people are assuming we'll find a way to travel faster than light (or even very close to it) when they're claiming that the absence of evidence is evidence of absence.

SETI has only ruled out the nearest stars in about a 30 year period. We could have "just missed" a relatively nearby civilization whose demise happened a mere 10 million years ago.

 

[JoeTheJuggler]

Tippler's argument assumes that interstellar travel by self-replicating space probes is possible. If intelligent life were common, it's emergence should have had a head start on planets around stars that are billions of years older than our Sun.
At least one alien civilisation would have developed self-reproducing space probes and launched them into space.
Travelling at 90% of the speed of light an advanced technology could reach the nearest star in less than five years, depending where they are in the universe. If it takes 100 years to make a copy of itself, then the average speed at which all the probes would spread would be about 1/25 of the speed of light. At this speed, Tippler argues, the probes would spread throughout the galaxy within 10 million years.

And there's still billions and billions of stars to aim at, and really really vast distances.

As I mentioned, this assumed technology that doesn't exist and may not be possible. (We simply don't know.)

You're also assuming that such an advanced technological civilization will be motivated to send out these things. (Why would they? They'd all be one-way machines. Or are these civilizations naturally extremely long-term thinkers--unlike us?)

These calculations assume none of these machines would ever fail. (There's nothing in space that could harm a probe, right?)

And you're still leaving time out of considerations. What if one such probe passed through or near our solar system 1 million years ago.

But we have no evidence of these probes on Earth. Their absence shows the absence of aliens. That's the logic of Frank Tippler, a respected scientist, and me, a layman.

Absence of evidence is not evidence of absence.

Or rather, in this case, the absence of self-replicating alien probes is not evidence of the absence of ET intelligence.

There's no reason to suppose conditions on Earth are unique in the universe or even in the galaxy. How rare is, as davefoc says, a question that will probably never be answered.

 

[davefoc]

amb says the Earth is unique, which is very different than saying the number is relatively small.

My position is that terms like "rare" and "commonplace" are relative when you're dealing with astronomical sizes and numbers of things.

We are almost certainly not unique.

A technological civilization like ours could arise as frequently as something like 1 in every million stars, meaning our galaxy will have had tens of thousands of such civilizations, but they could still be so spread out in space and time that none of them would ever encounter another.

Drake's original parameters for his equation put the number of technological civilizations at 10 in our galaxy at the current time, I believe. If it's as few as ten it is wildly unlikely that we are near enough to any of them to detect them. Wikipedia puts the number at 2.3 based on current estimates for the parameters. I would call 10 rare and 2.3 more rare.

If Amb is saying that a technological civilization at about our level of technology or higher is unique in the galaxy I think it's more likely than not he's wrong.

 

[JoeTheJuggler]

Drake's original parameters for his equation put the number of technological civilizations at 10 in our galaxy at the current time, I believe. If it's as few as ten it is wildly unlikely that we are near enough to any of them to detect them. Wikipedia puts the number at 2.3 based on current estimates for the parameters. I would call 10 rare and 2.3 more rare.

My point is that even if the number is much higher than those, it would still be unlikely for any two such civilizations ever to encounter one another.
ETA: I note that this figure is for those existing right now. If we take into account the life span of stars or the life span of the galaxy/universe then the numbers would be MUCH higher.

I think what Drake said in the article you linked above is more on target. We really shouldn't think so narrowly that life requires a near-duplicate of the Earth. There are many other scenarios that might give rise to conditions conducive to life.

Since we don't know, we should be careful not to put on the blinders.

 

[davefoc]

All reasonable JTJ,
As to the reason for the Fermi paradox and tipplers ideas don't rule out other civilizations: I suspect that civilizations blow themselves up before the appropriate technology for any kind of galaxy seeding/visiting goes on either because the technology is not possible or because civilizations just don't develop an inclination to invest the resources in that stuff before they blow themselves up.

My guess is that part of the nature of the development of all sentient entities is some penchant for violence and eventually this potential for violence is unleashed in such a way that the civilization is destroyed.

When I had that thought I was a little depressed about it for a day or so. Now, I just throw it on the stack heap of other troubling notions that I don't worry about.

At one point I thought that there might be some intergalactic civilizations around the center of our galaxy because the stars are so much closer. But now it looks like that idea has been shot down because as you get closer to the galaxy center the radiation levels go way up and sentient life seems unlikely at the elevated levels.

 

[arthwollipot]

Wait - Tipler's a respected scientist now? I was under the impression that he was generally regarded as a bit of a kook.

 

[amb]

So was Andrew Gold of whom renowned physicist Freeman Dyson said. ''Gold's theories are always original, always brilliant, usually controversial-and usually right.''
He was commenting on Gold's theory that contradicts the conventional wisdom that petroleum and natural gas are fossil fuels. On the contrary, says Gold, these resources are constantly being manufactured deep in the Earth by natural processes from the initial materials that formed the Earth. No one has as yet proved Gold was wrong.
The same with this discussion.
The likelihood of the universe been full of life in most galaxies is not in dispute. What is in dispute is animal and intelligent life.

I said before, extremophiles life has been found in the most extreme places on Earth including Antarctica, in volcanos and deep sea vents.
Our own solar system may be brimming with such microbes.
It remains to be seen if there are other Earths out there. I think intelligence is not a given in the scheme of things.
Imagine a planet that has a few of the attributes of the Earth, but has scorching temperature like in the Gobi or Sahara desert. Would intelligence still evolve on such a place? Or the extremes of Antarctica?
Unless a rocky planet is positioned just at the right distance from a similar star as Sol, then it needs a large moon, a giant gas world like we have to act as a magnet for straying giant asteroids, life, animal life that is, is likely to be very rare.
We may well be unique in this part of the galaxy. After all, how many times can you throw a set of sixes in a game of chess?

 

[JoeTheJuggler]

Unless a rocky planet is positioned just at the right distance from a similar star as Sol, then it needs a large moon, a giant gas world like we have to act as a magnet for straying giant asteroids, life, animal life that is, is likely to be very rare.

And all of this is just pure speculation.

I already showed that your requirement for no more frequent big meteor strikes than the Earth has had (roughly every 50 million years) could work out to be just the opposite. If you reset the ecosystem more frequently, you might get more chances of a intelligent life form. (Do you suppose if the one that ended the reign of the dinos hadn't happened, that dinos would have become a radio-technology using civilization? If not, it seems that hitting the old "reset" button for a planet's ecosystems might be a good thing.)

You just don't know which of those things are absolute requirements and which aren't.

We may well be unique in this part of the galaxy. After all, how many times can you throw a set of sixes in a game of chess?

None. But if you roll a pair of dice billions and billions of times, you're guaranteed a great many "boxcars".

Again: 100 billion stars in our galaxy and 100s of billions of galaxies in the universe, and some 14 billion years so far since the Big Bang.

 

[JoeTheJuggler]

As to the reason for the Fermi paradox and tipplers ideas don't rule out other civilizations: I suspect that civilizations blow themselves up before the appropriate technology for any kind of galaxy seeding/visiting goes on either because the technology is not possible or because civilizations just don't develop an inclination to invest the resources in that stuff before they blow themselves up.

My guess is that part of the nature of the development of all sentient entities is some penchant for violence and eventually this potential for violence is unleashed in such a way that the civilization is destroyed.

If you want to get more optimistic, it could just be that the self-replicating, near-lightspeed probes have problems that makes them not feasible (aside from a civilization having no good reason to make them). Presumably, they're AIs. So if they're programmed to reproduce and to travel elsewhere, it could be that they decide reproduce is the more important goal, and end up fighting amongst themselves over resources near their "creator" and end up evolving into their own sentient "life" form or destroying each other.

Or it could be that near-lightspeed isn't practically possible, or that self-replicating machines tend to break down and stop replicating (and "die" off) within a few thousand years.

But you're right. We have no reason to assume that intelligent civilizations last particularly long---since the only one we know about has only been around so far for a geological eyeblink (which is less than an astronomical eyeblink). There's no reason to assume that any technical feat that is even possible will necessarily be possible to attain.

 

[JoeTheJuggler]

Our own solar system may be brimming with such microbes.
It remains to be seen if there are other Earths out there. I think intelligence is not a given in the scheme of things.

I'm certainly not claiming intelligence is a given. I just think it's presumptuous to claim that we're unique. (And it's presumptuous to claim that a large moon is prerequisite and all the rest.)

So far, in our only sample we're one for one on microbial life evolving into animals (or higher forms, or whatever). As Stephen Jay Gould points, while there's no directionality in evolution, there is a "left wall". You can't get any simpler than the simplest archaebacteria. As diversity increases, you get complexity (even though the mode stays at the simplest forms).

I just don't buy arguments that say if ET intelligence exists in our galaxy, we'd have known about it by now. We've only searched an infinitesimally small part (in time and space) of the cosmic haystack for that needle (or those needles).

I really agree with the Sagan quote I offered earlier.

 

[amb]

DNA is an extremely complex molecule with a very small chance of occurring on it's own.
That it has accrued at least once because we are here discussing it doesn't mean it happens willy nilly. But because of the trillions of stars in the universe, it's bound to have happened at some point elsewhere.
Thus, the theory of a 'Rare Earth.'
I love Sagan's work, and have read a few of his books. But I believe he was a little too optimistic in his belief that intelligent life is flourishing in the universe.

 

[JoeTheJuggler]

DNA is an extremely complex molecule with a very small chance of occurring on it's own.

How do you know the chances of DNA occurring on its own? (By the way, how else does it occur?)

So I guess you've changed your mind about microbial life being very common even in our own solar system then.

That it has accrued at least once because we are here discussing it doesn't mean it happens willy nilly.

I'm not sure what you mean by that, but I think you're again saying that the opposite of "we are unique" is "intelligent life is ubiquitous". I don't believe either one of those is true.

But because of the trillions of stars in the universe, it's bound to have happened at some point elsewhere.

Yes. Or perhaps another replicating molecule capable of playing the same role as DNA in our life. Or. . maybe something completely different that we haven't yet even imagined.

Thus, the theory of a 'Rare Earth.'

No. The theory of "Rare Earth" as you've described it (with the list of requirements) assumes we have a lot more certain knowledge than we actually have. The business about a large moon or a Mars-like planet or some of these other conditions being necessary for life and even animal life is pure conjecture.

I love Sagan's work, and have read a few of his books. But I believe he was a little too optimistic in his belief that intelligent life is flourishing in the universe.

He was very clear that belief is irrelevant. He said, we simply don't know. He did say it would be surprising if, in the vastness of space and time, the Earth is unique. But to date, we have no evidence of any ET intelligence or life.

About all we can say is that we're reasonably certain that no radio-using ET intelligence exists in our near neighborhood in recent years. Beyond that, it's all speculation.

It sounds like you're backing off of the "unique" claim to a claim that life and intelligence may be "rare".

I would agree, but with the caveat that "rare" is a relative term.

Something that is "rare" in the universe might still occur tens, hundreds or thousands of times in our galaxy alone. Even so, something as "commonplace" as occurring thousands of times over the expanse in time and space of our galaxy could still be spread out enough as to never encounter another.

 

[amb]

I have always stated that life, animal life that is, is extremely rare. I have said that perhaps we could well be unique in our galaxy, not the whole cosmos.
That would be a foolish statement as there are bound to be other Earths in this almost infinite universe that is still expanding at the speed of light.
Are we an accident, or are we part of an ordered universe that's life friendly, with all it's implications. Either a 'designer,' or a multiverse of universes, and with this one out of billions been just right for the evolution of animal life.
You only have one choice.

 

[JoeTheJuggler]

I have always stated that life, animal life that is, is extremely rare. I have said that perhaps we could well be unique in our galaxy, not the whole cosmos.

Fair enough.

That would be a foolish statement as there are bound to be other Earths in this almost infinite universe that is still expanding at the speed of light.

I agree, but I'd go further and say it's also a foolish statement to make even limited to a galaxy of 100 billion stars and a billions of years' time span.

Are we an accident, or are we part of an ordered universe that's life friendly, with all it's implications. Either a 'designer,' or a multiverse of universes, and with this one out of billions been just right for the evolution of animal life.
You only have one choice.

I don't understand what you're saying. It sounds again like you're using that odd backward "fine-tuner" thinking. Life evolved to fit conditions that exist. We know with 100% certainty that conditions that are "friendly" to life (and animal life) exist in our universe (and indeed, in our galaxy).

I see no compelling reason to think such conditions could only occur once (or even once in this galaxy).

The stuff about "accident" and "designer" and "multiverse of universes" sounds more like a theological or philosophical discussion. Neither a designer nor a multiverse is necessary to explain life in our universe or galaxy. Neither adds anything to the discussion of ET intelligence.