have they found anything?

[davefoc]

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). ...

Yes, one thing that gets missed when discussions about how long it takes to get to nearby stars go on is that even without relavistic problems it may just be impossible to travel at speeds that are a significant fraction of the speed of light. It takes an enormous amount of energy to accelerate and decelerate the crafts (chemical rockets are a complete non-starter) and then once you're going that fast you better hope that you don't run into any grains of sand floating around out there, because the energy of the collision is likely to really mess up your whole craft. There also might be significantly more issues with radiation than is generally considered. Based on a Scientific American article a year or so ago it sounds like even the mission to Mars may not be possible because of the radiation.

 

[JoeTheJuggler]

Yes, one thing that gets missed when discussions about how long it takes to get to nearby stars go on is that even without relavistic problems it may just be impossible to travel at speeds that are a significant fraction of the speed of light. It takes an enormous amount of energy to accelerate and decelerate the crafts (chemical rockets are a complete non-starter) and then once you're going that fast you better hope that you don't run into any grains of sand floating around out there, because the energy of the collision is likely to really mess up your whole craft. There also might be significantly more issues with radiation than is generally considered. Based on a Scientific American article a year or so ago it sounds like even the mission to Mars may not be possible because of the radiation.

Yes.

And if we're going to ignore all the problems that seem insurmountable to us now, then why not just go whole hog and posit super-technology that allows quick and easy intergalactic transportation?

Tippler says that if at least one other ET intelligence existed, and assuming self-replicating probes are possible, then these probes would be everywhere in the galaxy within 10 million years. They're not here, so ET intelligence doesn't exist. (Ignoring that we may have just missed a probe by a mere 1 million years one way or the other.)

Since the universe is a great deal older than that, why not just assume that intergalactic transportation of self-replicating probes is possible? So since they're not here, it "proves" we're unique and alone in the entire universe.

It's the same logic and the same kind of assumptions.

 

[amb]

Still. The very beginning of life. How life started in the first place, still eludes astrophysicists. Whether it started here, or elsewhere and somehow transported here is the question that may well be answered in the near future. But for now, it's purely speculation. Does life happen often, or is this a once in a trillion chance. Even if life is found in our solar system, it will not answer this question as life could have been transported from nearby planets and moons on meteorites or comets ect.

 

[JoeTheJuggler]

Still. The very beginning of life. How life started in the first place, still eludes astrophysicists.

That sounds like a question for biologists or at least chemists rather than astrophysicists.

In fact, we're far from clueless about abiogenesis.

We've seen that conditions on a young Earth recreated in labs have resulted in the formation of amino acids. We know it's possible to make self-replicating molecules. It's not hard to come up with ways that a membrane could happen to form around such molecules. There aren't that many more intermediate steps we need to connect the dots. Once you've got something that replicates with some variation, selection starts to operate.

Whether it started here, or elsewhere and somehow transported here is the question that may well be answered in the near future. But for now, it's purely speculation. Does life happen often, or is this a once in a trillion chance. Even if life is found in our solar system, it will not answer this question as life could have been transported from nearby planets and moons on meteorites or comets ect.

I agree that it's pure speculation. I believe Occam's Razor favors the explanation of Earth life originating on EArth--at least given the current evidence.

Finding life elsewhere in the solar system also won't answer the question as to whether intelligent aliens engineered life in our solar system. The point is that these hypotheses aren't necessary (especially without evidence of extraterrestrial life in our solar system that is related to life on Earth), and there is at this point no evidence to support them.

You might be right, that life originated on Mars, for example, and spread to Earth. Right now, though, that hypothesis lacks parsimony compared to the hypothesis that abiogenesis happened on Earth.

But again, I agree, it's pure speculation. I hope to live long enough to have at least some of these questions answered.

Finding microbes on Mars that are positively related to Earth life would go a long way toward bolstering the transplanted-from-Mars notion. Finding microbes there that are clearly not related to Earth would go a long way toward falsifying that hypothesis.

Finding fossilized bacteria in the meteorites of Martian origin would've bolstered the theory. That they weren't there sure doesn't help it. (In a similar way, if we didn't find planets when we had the technology to detect them of a given mass, it wouldn't help the idea that planet formation is relatively commonplace.)

 

[amb]

I believe planet formation is quite common. But do they get all the conditions that encourages animal life to evolve? Like the right star, the right distance from their star, [too close and the same face would face the sun as does our moon] tectonic plates, an abundance of liquid water, a large moon to stabilize it's orbit and tilt to give a change of temperatures, [ no moon, no seasons] I don't believe animal life would survive long in extreme conditions such as Mars, Venus.
We have an example right here on Earth. There's very little life in the Sahara desert, Gobi desert, Antartica. What life there is there evolved elsewhere and then adapted to the conditions.

 

[JoeTheJuggler]

I believe planet formation is quite common. But do they get all the conditions that encourages animal life to evolve?

No they don't.

Again I'm objecting to the claim that Earth is unique in the galaxy. I'm not claiming that life is ubiquitous. Has anyone claimed that all planets get "all the conditions that encourages animal life to evolve?"

Also, I don't think we know what all those conditions might be. The flaw in the rare Earth argument is claiming that we do.

 

[JoeTheJuggler]

Like the right star, the right distance from their star, [too close and the same face would face the sun as does our moon] tectonic plates, an abundance of liquid water, a large moon to stabilize it's orbit and tilt to give a change of temperatures, [ no moon, no seasons]

This is the stuff I'm talking about. We don't know that these things are all required.

Seasons? I can tell you from where I sit, seasons aren't friendly to animal life!

As for tidally locked planets, the Drake article that Davefoc linked to earlier in this thread pointed out that the twilight zone on these planets might be just the place to look for life.

The point is that we just don't know. IN the absence of this knowledge, it is premature to think the Earth is unique.

 

[JoeTheJuggler]

a large moon to stabilize it's [sic] orbit

Is there any evidence whatsoever that planets without large moons can have stable orbits?

It might be true that a large moon is necessary, but it also might not be. That's why this is mere speculation.

Even if they're necessary, is there any evidence that large moons are extremely rare (or, more to the point, that ours is unique in the galaxy)?

Here's a nifty image from NASA (posted by Woollery on another thread):

Even within that tiny area where we've detected planets, we're very limited on what kinds of planets we can detect. If you tried to draw it such that the size was limited to the area where we can detect 100% of the planets down to Earth-mass planets, then we're limited to our own solar system, which is too small to show as an area on this image.

So, just on the issue of the existence of large moons around earth-mass planets, it is presumptuous to think that ours is unique in the galaxy.

 

[amb]

Our star is around 30.000 light years from the center of the galaxy, which according to some astronomers is the Goldilocks area of any other Earth like planet. Any closer and the ultraviolet light would sterilize any planet. Any further out the elements is probably to low to form rocky planets as large as Earth with a solid/liquid core. Both attributes seem to be necessary to the development of animal life.

It is often said that the sun is a typical star, but this is not true.
95% of all stars are less massive than the sun.
Smaller stars habitual zone is located farther inward, meaning that any rocky planets would have to orbit much closer to get any warmth and allow the retention of liquid water, and locking the planet into a moon like orbit around it's star would cause one side to be forever dark while the other side forever day just like our moon and Mercury.
Imagine the temperatures of such a planet. Too severe for the evolution of animal life i suggest.

 

[JoeTheJuggler]

Our star is around 30.000 light years from the center of the galaxy, which according to some astronomers is the Goldilocks area of any other Earth like planet. Any closer and the ultraviolet light would sterilize any planet. Any further out the elements is probably to low to form rocky planets as large as Earth with a solid/liquid core. Both attributes seem to be necessary to the development of animal life.

It is often said that the sun is a typical star, but this is not true.
95% of all stars are less massive than the sun.
Smaller stars habitual zone is located farther inward, meaning that any rocky planets would have to orbit much closer to get any warmth and allow the retention of liquid water, and locking the planet into a moon like orbit around it's star would cause one side to be forever dark while the other side forever day just like our moon and Mercury.
Imagine the temperatures of such a planet. Too severe for the evolution of animal life i suggest.

First, most of this is conjecture. It assumes that the only way to get higher life forms is an exact duplication of the conditions of the Earth. That's very limited thinking (and presumes that we know a helluva lot more than we actually do).

Second, even if more or less Earth conditions are required, there's no reason to think we are unique in the galaxy. The physical processes that resulted in the Earth are not forbidden elsewhere.

I'd like to quote Nobby Nobb's post from the other thread on this subject in its entirety because he said this very well:

Rare doesnt mean unique, but as time progresses, every day, Life becomes less likely.

Um...no. Quite the opposite in fact.

Listen, there was a time when Europeans thought that there couldn't possibly exist any other place other than Europe. Then the Far East and the New World were discovered.

There was a time when it was thought that Earth was the only planet in existence. Then it was discovered that some of the other lights out there are planets too.

As little as 20 years ago, it was thought that our solar system was the only one with planets. Then they discovered extrasolar planets.

As little as 5 years ago, it was thought that the rocky planets in our solar system were the only rocky planets there were. Then extrasolar rocky planets were discovered.

We have found water on Europa. Evidence of water on Mars. The chemical signature of water vapor on at least one extrasolar planet.

In direct opposition to your baseless claim, everyday we learn more about the universe, it seems to become more likely that there is life out there.

 

[JoeTheJuggler]

I suppose I should respond to some of the specific speculations here. They're just speculation (and not knowledge), so the fact that I can speculate the opposite case is as meaningful.

Our star is around 30.000 light years from the center of the galaxy, which according to some astronomers is the Goldilocks area of any other Earth like planet. Any closer and the ultraviolet light would sterilize any planet.

Thicker atmosphere, stronger magnetic field or a form of life that tolerates (or even thrives on) UV.

Any further out the elements is probably to low to form rocky planets as large as Earth with a solid/liquid core.

There are plenty of stars farther our than we are. How much matter do you think it takes to make a rocky planet? (Far less than it takes to make a star.) There's plenty of matter.

Or do you mean something else by "the elements is probably to low"?

 

[amb]

I meant elements heavier than helium. Outside of the habitual orbits of stars too far from the center, the relative abundance of heavy elements is probably too low to form terrestrial planets as large as the Earth.
In real estate jargon, the Earth has location location location. [for Earth like animal life]

 

[JoeTheJuggler]

I meant elements heavier than helium. Outside of the habitual orbits of stars too far from the center, the relative abundance of heavy elements is probably too low to form terrestrial planets as large as the Earth.

I thought that's what you meant. You're wrong, though. There's plenty of matter (including more than enough elements heavier than helium to make planets). A planet like the Earth represents only a relatively tiny amount of matter at the scale of the outer portion of the galaxy. Your claim is that there's not even enough matter to make one such planet. That's just over-the-top.

And again, even if your baseless assumption were true (that stars farther from the galactic center than Sol don't have any Earth-like planets), there are plenty of stars that aren't that far out, and you don't know for sure that earth-like planets are requisite for higher forms of life.

The problem with the claim that the Earth is unique in the galaxy is that it would require knowledge we don't have.

 

[shadron]

I thought that's what you meant. You're wrong, though. There's plenty of matter (including more than enough elements heavier than helium to make planets). A planet like the Earth represents only a relatively tiny amount of matter at the scale of the outer portion of the galaxy. Your claim is that there's not even enough matter to make one such planet. That's just over-the-top.

Let's look at this galaxy: http://antwrp.gsfc.nasa.gov/apod/ap051022.html . It is the Ring Galaxy (AM 0644-741) as visualized by HST. The ring is a series of very bright, young stars and star birthing areas (nebulae) which were ignited by a collision with another galaxy, as the shock wave passed from the point of pass-through outwards.

The ability of these areas to light up upon the passing of a pressure wave indicates how plentiful star-producing gas is in the outer arms of a normal spiral galaxy. All the galaxies that we can see within a half billion light years seem to have the same sort of cold gas - estimated to be about 3% heavy elements. If anything, the gas is more plentiful in the outer edges rather than at the central regions, where it has been depeleted by much star generation in the past (the same is true for whole elliptical galaxies).

 

[JoeTheJuggler]

This is a total derail, but while we're on the subject of galaxies, there's a great distributed project to classifies tons of photos of galaxies at:
http://www.galaxyzoo.org/

ETA: Maybe not so far off topic. You sit and classify galaxies for a good half hour, and you get a much more gut-level sense of how many there are in the universe. Each one with tens of billions (or more) stars.

 

[amb]

I thought that's what you meant. You're wrong, though. There's plenty of matter (including more than enough elements heavier than helium to make planets). A planet like the Earth represents only a relatively tiny amount of matter at the scale of the outer portion of the galaxy. Your claim is that there's not even enough matter to make one such planet. That's just over-the-top.

And again, even if your baseless assumption were true (that stars farther from the galactic center than Sol don't have any Earth-like planets), there are plenty of stars that aren't that far out, and you don't know for sure that earth-like planets are requisite for higher forms of life.

The problem with the claim that the Earth is unique in the galaxy is that it would require knowledge we don't have.

Don't forget, they need to be as close as possible to Earth size. Too small, and they will have not enough gravity to hold on to liquid water. Too large, and the greater gravity would make any animal life impossible unless it's gigantic creatures able to withstand the enormous pull of gravity.

Naturally we are just speculating as we only have this planet as a model.
But when we look at the enormous number of coincidences that enabled life to evolve on this ''just right'' planet in a ''just right'' part of the galaxy, there can't be too many Earths out there with animal life. Let alone an intelligent species.
Why is it that out of the billion or so species of life here on Earth, only one has developed intelligence enough to construct a technological civilasation?
Does that not give the odds of around a billion to one that intelligence can evolve elsewhere?

 

[JoeTheJuggler]

Don't forget, they need to be as close as possible to Earth size. Too small, and they will have not enough gravity to hold on to liquid water. Too large, and the greater gravity would make any animal life impossible unless it's gigantic creatures able to withstand the enormous pull of gravity.

That's a mighty big "unless" there. The fact is, to claim that the Earth is unique, you would have to know for sure that higher life forms can't evolve on a smaller or larger planet, and that no other earth-size planets exist.

Why is it that out of the billion or so species of life here on Earth, only one has developed intelligence enough to construct a technological civilasation?
Does that not give the odds of around a billion to one that intelligence can evolve elsewhere?

Well that's just not true either. There are certainly other species with intelligence. Even other primates have tool use and some of the other things that we used to claim made humans unique. There's no reason to think that if we weren't here another species wouldn't have filled our niche. (I'm not claiming I know that for sure, but claiming that humans are sui generis is akin to claiming special creation when we know full well we're related to the rest of life on Earth.)

And I do think the kind of thinking behind the claim that humans are unique in the galaxy is the same kind of thinking that humans are fundamentally not animals, or that Europe was the only civilization, or that the Earth was the center of the universe.

Besides, what would that one to a billion (I think you said it backwards of what you intended) ratio mean? Another planet with complex life forms might have a billion or so species as well. In terms of the planet (over 4 billion years' time), using the only sample we have (the Earth) the ratio is one in one. If you want to keep the 1:1 billion figure, then you're talking about the sum total of species in the galaxy (rather than stars or planets). It doesn't help your case to look at it that way.

We still just don't know. There is no evidence of ET intelligence, but there is also no evidence to support the claim that we are unique in the galaxy.

 

[amb]

Apart from homo sapiens, I have yet to see any other species on this planet with anything like a child of two or three years of age's intelligence.
Our closet's relative the Chimps, show an intelligence of a two or three year old homo sapien. Give them another million years to evolve, I still doubt they will ever reach our dumbest of people's brain power.
What if we are one the first of civilisations to emerge in the universe? And it will be homo sapiens that will colonise the cosmos in the next million years or so?
The universe has evolved to a point where it's become self-aware, can look back at itself, work out how it came about through us. We are the next step in the universe's evolution: consciousness.
Intriguing speculation you must admit. I love it. My one regret, I may not live long enough to see mankind take that extra step into the cosmos.

 

[JoeTheJuggler]

Apart from homo sapiens, I have yet to see any other species on this planet with anything like a child of two or three years of age's intelligence.

So? Your contention that humans are the ONLY species out of a billion on Earth to evolve intelligence is just wrong.

As I said already, if you're merely saying we're the only species to devlop radio technology out of a billion, that's fine. But that 1:1 billion then is a ratio of radio-tech-civilizations to ALL SPECIES in the galaxy (rather than to stars or planets). We don't know that figure, but based on the only sample we know of a planet with life (and assuming the one billion figure is right), the ratio of planet to species is 1:1 billion. So using this number doesn't help your argument in the least.

Our closet's relative the Chimps, show an intelligence of a two or three year old homo sapien. Give them another million years to evolve, I still doubt they will ever reach our dumbest of people's brain power.

You don't know that. Even so, it still doesn't mean that humans are the ONLY intelligent species on Earth. Yes, we're the most intelligent, but that's not the same as only.

What if we are one the first of civilisations to emerge in the universe? And it will be homo sapiens that will colonise the cosmos in the next million years or so?

I doubt that anyone will ever colonise the cosmos (or even a significantly large portion of a galaxy)--just because of the incredible distances involved. (Even at the speed of light, and not counting acceleration and deceleration time, it would take 100 years--more than an average human lifespan--to reach a star 100 light years away. Realistically, that trip would be many times longer than that. And, galactically speaking, that's just in our near neighborhood!)

Are you saying that IF humans radiated to fill up the universe (something I think is impossible), that we'd have the same effect on ET intelligence species as we've had on chimpanzees on Earth?

OK--even if that were possible, it still wouldn't mean that those other intelligences don't exist.

The universe has evolved to a point where it's become self-aware, can look back at itself, work out how it came about through us. We are the next step in the universe's evolution: consciousness.

And there's plenty of experimental evidence that shows that humans are not unique in that regard. (The spot-on-the-face/looking-in-a-mirror tests come to mind immediately.) There are a number of other species on Earth that are demonstrably self-aware. (There may be more than that, but we don't know.)

It sounds like now you're arguing that humans aren't animals--that we're fundamentally different than other life on Earth.

Intriguing speculation you must admit. I love it. My one regret, I may not live long enough to see mankind take that extra step into the cosmos.

I'm not talking about going out there--I'm just talking about evidence of ET life. We might get pretty strong evidence of microbial life on Mars in my life time. That in itself would be awesome!

 

[LarianLeQuella]

Another factopr to consider with the "Fermi 'Paradox'" is that we are refining our "broadcast technology so NOW we "leak" LESS. We're using fiber optics, have more finely focused signals, etc. So, given a theoretical lifespan of a civilization, how long are they really, really noisy? And as has already been shown, even that noise isn't that easy to detect beyond a few lightyears (relative to the size of the galaxy) really.

Now, some other things to consider:
- Who says that an alien civilization must develop radio technology in order to be civlized? We have no idea how a civlization would develop in a totally different environment, let alone on a different biology.
- Who says that an alien civlization would even be concerened about anyone else "out there" to them? Maybe they don't care, or just accept some default position.

Again, I find the human/earth centric thinking displayed in this thread very discouraging.