Are We Alone?

[Berek]

I'm an astronomy buff, I learn about everything there is to know about space and what's in it. I am also a apocalypse scenario historian of sorts as well. I love to learn about what can end our days, because by learning about our weaknesses we learn about our strengths, I feel.

I would like to point out some Wikipedia and other articles I think you might enjoy about the universe, possibility (or lack thereof) of life in the universe, and ways we are reaching out to explore space. Enjoy!

Milky Way Galaxy (A big galaxy! Good article to understand what's in ours and how it compares to others):
http://en.wikipedia.org/wiki/Milky_way

Frank Drake (Creator of equation to calculate life in the universe):
http://en.wikipedia.org/wiki/Frank_Drake

Fermi Paradox (Why we may have not seen other intelligent life, yet):
http://en.wikipedia.org/wiki/Fermi_paradox

Telescope Arrays (New technologies to search for ETs):
http://en.wikipedia.org/wiki/Allen_telescope_array
http://en.wikipedia.org/wiki/Square_Kilometer_Array

Planetary Habitability (What are the chances for an "earth" like planet to exist):
http://en.wikipedia.org/wiki/Habitability

Rare Earth Hypothesis (The arguments against such a possibility. Take note, we ARE special in the universe...):
http://en.wikipedia.org/wiki/Rare_Earth_hypothesis

Planet Finders (Space telescope technologies to find earth-like planets with or with/o life):
http://en.wikipedia.org/wiki/Terrestrial_Planet_Finder
http://en.wikipedia.org/wiki/CoRoT

Space Colonization (How we may be able to get out there):
http://en.wikipedia.org/wiki/Space_colonization

 

[alexsok]

It seems weird that in such a massive universe, we reside on a single life-supporting planet from billions upon billions of galaxies (not planets mind you)... I mean, I can understand why many theoretical physicists claim that through anthropic principles, our world just happened to be the one where the conditions were favorable for the existence of human life... what I don't get is how come these favourable conditions haven't led (at least AFAIWK) to the emergence of many types of lifeforms or conscious civlications on other planets other than ours.

It is absurd.

 

[nutball]

It is absurd.

Why?

 

[The_Wolf_Who_Cried_Boy]

As a non-physicist, how is it possible to calculate, with a straight face, the likelyhood of technologically advanced alien civilisations existing? We have a proven planetary sample size of ~10 to extrapolate from.

What would be disappointing is if there actually were aliens prowling the galaxy but they really did just look like Jodie Fosters dad.

 

[Rolf N]

The problem with other life-supporting planets, which of course have a high likelihood to exist somewhere, is twofold: 1)they may not bear life now, or whenever it is we could reach them/they could reach us, 2)they are absurdly far away; unless something can travel faster than light it's completely irrelevant.

 

[Bouncing Zabaglione Bros.]

There was a very long and interesting thread on this matter a while back. Worth reading, though it has been locked after it degenerated into discussion with the hard of thinking.

 

[nutball]

As a non-physicist, how is it possible to calculate, with a straight face, the likelyhood of technologically advanced alien civilisations existing? We have a proven planetary sample size of ~10 to extrapolate from.

Well those are really two slightly separate questions. It's blatantly obvious that we can't calculate such a probability now, given the state of our knowledge of any of the influencing factors.

Taken at face value the Drake Equation is just a steaming pile of crap. It's basically just an unknown number multiplied by six more unknown numbers. If you try to use it, you'll just get out what you put in -- a complete (and useless) guess. But that's not really the point of the Drake Equation, it's point is to try to illuminate the discussion, to try to ask the question "so if we did want to calculate the final number, what would we need to know in order to do so".

My problem with it is that not all of its terms are sensibly estimable. For example, we already have a good estimate of the number of stars in the Galaxy; in another decade we'll have a good idea of the fraction of those which harbour planets; in another decade or two we'll have a good idea of the fraction of those planets which can support life(*). These are all measurables.

The remaining four terms aren't readily computable from first principles in any reliable fashion without a lot of cast iron data about the existence (or otherwise) of life in various states of evolution. (One can formulate theoretical models for sure, but without data against which to test them the models have no relevant predictive power). By the time you've got enough data to disentangle the four terms from each other and verify your models, you've probably got enough data to answer the original question directly.

(*) Meaning planets on which water can exist as a liquid.

 

[Humus]

I view the possible existance of aliens the same way as the possible existance of a god. They may or may not exist, but I remain highly sceptical until they openly present themselves to the world. Until then, their existance is only an academic question and they are insignificant for the human race.

 

[tongue_of_colicab]

I dont think we are alone. The universe is so big, why would earth be the only planet to support life? if you look at in what extreme hostile enviroments some organism can live than I think its highly unlikely that there isnt atleast something that qualifies as life on a other planet.

 

[Rolf N]

I dont think we are alone. The universe is so big, why would earth be the only planet to support life? if you look at in what extreme hostile enviroments some organism can live than I think its highly unlikely that there isnt atleast something that qualifies as life on a other planet.

Agreed.
However we will probably not have any interaction with them ("Mom, I want to be a xenobiologist!"). People who wish to use alien life as a source of warm and fuzzy feeling about not being alone and whatnot are IMO misguided. Even if we find something in our lifetime there will be nothing we can do with it. It will not change us.

 

[zed]

to all ppl saying the universe / galixes are big, read about the fermi paradox.
from memory it goes something like
basically say we devleop starflight + ppl fly to the nearest star (bernards stars or beta centura >4 lightyr) from this small step we will within ~ million years visit every single star in the galaxy,
the galaxy is ~10billion years old.
thus basically once a culture has starflight it will conquer the galaxy in a blink of the eye

so the possible choices are
A/ we are the only existing life
B/ we are the first life to evolve intelligent enuf for starflight (not happened yet, but within 100 years it will)
C/ our planet is kept quarantined
D/ some god or godlife things destroys a planet when it achieves starflight

ild say the odds are about
A/ 5% B/ 0.000001% C/ 60% D/ 35%

 

[alexsok]

However we will probably not have any interaction with them ("Mom, I want to be a xenobiologist!"). People who wish to use alien life as a source of warm and fuzzy feeling about not being alone and whatnot are IMO misguided. Even if we find something in our lifetime there will be nothing we can do with it. It will not change us

Agreed.
But what if they exist, but we will not find them during our lifetimes? In that scenario, it will not matter whether they are discovered in a million years or in 200 years or never - in either case, we're screwed unless we come up with a viable immortality mind-transfer or what have you type of mechanism which I'm highlys skeptical off.

I coudl imagine myself having a fuzzy feeling over the prospect of "third world encounters" type of confrontation beteen humans and other civilizations, but only if I could live to that moment... which i won't

 

[nutball]

thus basically once a culture has starflight it will conquer the galaxy in a blink of the eye

This is a hypothesis.

 

[Natoma]

Life can exist almost anywhere. We've found that to be the case here on earth. Whether it's recognizably intelligent life is a whole other story. The question of "does life exist elsewhere?" should really not be a question at all. We know it can.

The question really should be, "does intelligent life exist elsewhere?". That we simply cannot know. The window of technological ability to communicate vs ability to self-destruct is very small on the scale of the universe. We're still in that window today, and it's only been about 70 years since we were capable of sending out radio signals, and even less since we were capable of listening. That's a universal blip in distance to other stars that potentially bear intelligent life forms.

As others have stated, unless we find a way to travel faster than the speed of light, or unless there are other civilizations that were around tens of millions of years ago, and their signals have been sent out since then (or they travel to us), we'll never know if there is intelligent life out there.

But I think it's very safe to say that life, at least bacterial, does indeed exist out there.

 

[nutball]

Life can exist almost anywhere. We've found that to be the case here on earth.

Correct me if I'm wrong here but I think that the message we should take from Earth is that once life has evolved it can adapt to live under a wide range of conditions.

I don't think that that necessarily implies that it can evolve under a wide range of conditions. It may be the case, but I don't think that it's a given.

Again, this is the problem with having a sample of one data point, it's difficult to disentangle such things.

 

[Natoma]

Correct me if I'm wrong here but I think that the message we should take from Earth is that once life has evolved it can adapt to live under a wide range of conditions.

I don't think that that necessarily implies that it can evolve under a wide range of conditions. It may be the case, but I don't think that it's a given.

Again, this is the problem with having a sample of one data point, it's difficult to disentangle such things.

We've found life at the bottom of the ocean, for example, that receives no sunlight and thrives without the presence of oxygen or carbon dioxide. They live on the minerals and chemicals and heat coming from fissures in the earth's crust, at significantly higher temperatures and crushing pressures than we ever thought possible, for example. That doesn't smack of evolution-then-adaptation. That smacks of evolution in that environment.

Also consider that we've found bacterial fossils in fragments of comets, for example.

 

[nutball]

We've found life at the bottom of the ocean, for example, that receives no sunlight and thrives without the presence of oxygen or carbon dioxide. They live on the minerals and chemicals and heat coming from fissures in the earth's crust, at significantly higher temperatures and crushing pressures than we ever thought possible, for example. That doesn't smack of evolution-then-adaptation. That smacks of evolution in that environment.

So you are suggesting that life evolved on multiple independent occasions on Earth?

Also consider that we've found bacterial fossils in fragments of comets, for example.

This is news to me, got a link for that? There's a (rather controversial) claim of the detection of fossilised bacterial life in meteorites from Mars. It's not even clear that Mars and the Earth are truly independent, there remains the (very remote) possibility of the exchange of viable living organisms between the two planets.

 

[Natoma]

So you are suggesting that life evolved on multiple independent occasions on Earth?

Yes. The environments are too dissimilar. Where you get cross pollination are areas where they mix. For example, animals that lived in the shallows becoming amphibious and eventually evolving to be permanent land dwellers.

Besides, going from photosynthesis to chemical synthesis (not to mention the temperature and pressure differences) requires a significant change in the basic biology of the baseline bacteria. Occam's razor would dictate that chemical-synthesizing bacteria evolved there, and communities of life sprung up from those bacteria, not adapted to that region of the ocean from life that is built around photosynthesis.

This is news to me, got a link for that? There's a (rather controversial) claim of the detection of fossilised bacterial life in meteorites from Mars. It's not even clear that Mars and the Earth are truly independent, there remains the (very remote) possibility of the exchange of viable living organisms between the two planets.

google bacteria fossil meteor comet. There are mentions of Mars finds, but there are also tons of mentions of meteorite and comet fragments that fell to earth.

 

[Bouncing Zabaglione Bros.]

We've found life at the bottom of the ocean, for example, that receives no sunlight and thrives without the presence of oxygen or carbon dioxide. They live on the minerals and chemicals and heat coming from fissures in the earth's crust, at significantly higher temperatures and crushing pressures than we ever thought possible, for example. That doesn't smack of evolution-then-adaptation. That smacks of evolution in that environment.

Also consider that we've found bacterial fossils in fragments of comets, for example.

It certainly doesn't make for intelligent life. If anything, life's evolution could be extremely restricted by a harsh environment itself. If nothing but dormant bacteria can live on the surface of an asteroid or a planet like Mars, then that maybe all there is to find in those environments.

On top of that, there is the biological maxim that specialization is preferable to generalization. An example is when dinosaurs filled every ecological niche for tens of millions of years more than us apes have done, and yet failed to develop into an intelligent, tool using civilization. They had some society, and maybe even some basic communication (such as pack hunting or warning off competitors from food or mates), but never developed into space-faring lizard men. They had no need to, because they adapted to their environment, and things like tool using, language, and the big brains to go along with that were simply not needed to fulfil those roles in the ecology.

Insects have been around even longer, but their basic construction limits the size they can grow to, and so how big their brains and intelligence can get. You'd have to adjust them away from insect norms and towards mammals and lizards (such as giving them a mammalian pulmonary and respiration system).

In short, there could be a lot of life sustaining worlds out there, and some of them could have life seeded from meteor strikes just as we could have been. That life could have adapted and grown to fill all ecological niches over a long period of time. That doesn't mean they will be anything we could have a conversation with, or anything that we would consider to be intelligent in a human sense. At best, we might consider them to be alien animals.

Intelligent life like us could be very, very rare indeed. We've certainly got no evidence that it's common or nearby, and if evolution works in a similar fashion on other planets (and there no reason why it wouldn't be the same), then intelligent beings like ourselves are simply not the preferred format for evolution to fill those ecosystems.

 

[Natoma]

I agree. http://www.beyond3d.com/forum/showthread.php?p=909519#post909519