Is there life in the universe, and if so has it visited Earth?

[Schrodinger's Dog]

That's what it means to be unknown! Why does intelligent life require dry land?

You'll note I have both water and dry land, an all ocean planet I think would be less likely to develop intelligent life, considering our manual dexterity is one of the primary factors that lead to our language and intelligence, but the point is the best chance for intelligent life is on a non gaseous giant with both water in the form of seas ideally, and rock. Not that an all ocean planet couldn't develop life, just that ideally a bit of both I think would promote or increase the chances of intelligent life developing.

Well, the OP stated the assumption of life in the universe:
This was contested as a premise. I think that's how we got talking about the creation of life.

The question of intelligent life, granted, requires a lot more criteria.

I've edited my post now so as to avoid confusion, apologies.

TO CLARIFY THESE ARE PARAMETERS FOR INTELLIGENT LIFE.

OK maybe it might be better to analyse this from the point of view of what we know to start and then extrapolate, for example what do we think are the basic requirements for life, I'll start with a basic list feel free to add to it.

A planet who's gravity is not so high or two low so as to preclude the formation of life forms and which has a stable surface, ie rock.

A sun formed hopefully of a size and energy output which promotes a good amount of planetary formation and is hot enough to sustain life but not too hot.

Water at higher than freezing point, ideally at a temperature where more chemical reactions can happen more quickly.

Inorganic compounds such as Cyanide and a good supply of minerals (PolyAromatic Hydrocarbons)PAH's and so on. Perhaps a second or so generation star, so there are more basic elements.

Perhaps a good amount of Cometary material to bring more water to the planet, and or seed it with more chemicals, although not essential.

Conditions so that a stable atmosphere of some sort can form.

A distance from the sun that does not mean a runaway greenhouse effect forms and is not too cold to inhibit life forming. Ie a temperate zone.

Large gaseous giants to help soak up some of the meteors flying around amongst the suns left overs.

If you agree these are the basics, what do you think the likelihood is of finding these types of conditions?

 

[arildno]

Well, I don't see why mermaids can't weave sea-weeds together in a useful manner.

To have some appendage that is eminently suited for manipulating objects around us is certainly crucial for the evolution of intelligent life.

It doesn't follow, however, that intelligent life can only develop on dry land

 

[Schrodinger's Dog]

Well, I don't see why mermaids can't weave sea-weeds together in a useful manner.

To have some appendage that is eminently suited for manipulating objects around us is certainly crucial for the evolution of intelligent life.

It doesn't follow, however, that intelligent life can only develop on dry land

I didn't say that. I thought I'd cleared that up?

Mermaids aren't real btw just in case you didn't know

You'll note I have both water and dry land, an all ocean planet I think would be less likely to develop intelligent life, considering our manual dexterity is one of the primary factors that lead to our language and intelligence, but the point is the best chance for intelligent life is on a non gaseous giant with both water in the form of seas ideally, and rock. Not that an all ocean planet couldn't develop life, just that ideally a bit of both I think would promote or increase the chances of intelligent life developing.

 

[Newbie says Hi]

Again I disagree. I think you are being way too limiting.
It really only requires 4 ingredients:
- liquid water
- organic molecules (and inorganic material)
- energy
- time
+ sufficient quantities of the above

Are you saying that you think life doesn't even require a planet(oid) to begin?

By these simple requirements, it looks to me that we should expect to see a universe that is swarming with life as we explore further out of our solar system (it seems like liquid water may be the only "rare" requirement)?

eg. You don't even need a solid surface. Life on Earth formed in the oceans.

Note sure I entirely agree here, so, you got a reference for that? Should we effectively rule out even puddles or other "localized" scenarios? I say that because we can make the conditions for abiogenesis on Earth even less stringent, and extend that to other places in the cosmos (assuming puddles are more common than oceans). (Or maybe you meant life on Earth formed in a liquid-watery environment, possibly ocean.)

 

[DaveC426913]

By these simple requirements, it looks to me that we should expect to see a universe that is swarming with life as we explore further out of our solar system (it seems like liquid water may be the only "rare" requirement)?

Don't discount the imporatnce of the "metarequirement" (i.e. a requirement of the requirements) : that there is suffiocient quantities of the above.

The implications here, are that your planetless, freefloating body of H2O must be both liquid and long-lasting. I'm not holding my breath on this one.

Not sure I entirely agree here, so, you got a reference for that? Should we effectively rule out even puddles or other "localized" scenarios? I say that because we can make the conditions for abiogenesis on Earth even less stringent, and extend that to other places in the cosmos (assuming puddles are more common than oceans). (Or maybe you meant life on Earth formed in a liquid-watery environment, possibly ocean.)

Whatever bodies of water you want to consider of suffiicient size and longevity and contain the appropriate organic compounds. It doesn't matter.

All I'm saying is a solid surface is not a requirement for life (though it might be a large part of the requirement for long-standing liquid water.)

The point is, it would be folly to look at a planet, see it has no rocky surface, and summarily disqualify it on that basis as a candidate for life.

 

[fournier17]

TOO CLARIFY THESE ARE PARAMETERS FOR INTELLIGENT LIFE.

OK maybe it might be better to analyse this from the point of view of what we know to start and then extrapolate, for example what do we think are the basic requirements for life, I'll start with a basic list feel free to add to it.

A planet who's gravity is not so high or two low so as to preclude the formation of life forms and which has a stable surface, ie rock.

A sun formed hopefully of a size and energy output which promotes a good amount of planetary formation and is hot enough to sustain life but not too hot.

Water at higher than freezing point, ideally at a temperature where more chemical reactions can happen more quickly.

Inorganic compounds such as Cyanide and a good supply of minerals (PolyAromatic Hydrocarbons)PAH's and so on. Perhaps a second or so generation star, so there are more basic elements.

Perhaps a good amount of Cometary material to bring more water to the planet, and or seed it with more chemicals, although not essential.

Conditions so that a stable atmosphere of some sort can form.

A distance from the sun that does not mean a runaway greenhouse effect forms and is not too cold to inhibit life forming. Ie a temperate zone.

Large gaseous giants to help soak up some of the meteors flying around amongst the suns left overs.

If you agree these are the basics, what do you think the likelihood is of finding these types of conditions?

I know that planets like Jupiter are being found in solar systems, astrobiologist are optimistic that there will be Earth like planets around the planets that are similar to jupiter. These Earth like planets could possibly meet the criteria above.

Another basic ingredient that i just read about is that the atmosphere in which chemical evolution is occurring must be reducing and not oxidizing. An oxidizing atmosphere is believed to inhibit the formation of macromolecules.

 

[Schrodinger's Dog]

I know that planets like Jupiter are being found in solar systems, astrobiologist are optimistic that there will be Earth like planets around the planets that are similar to jupiter. These Earth like planets could possibly meet the criteria above.

Another basic ingredient that i just read about is that the atmosphere in which chemical evolution is occurring must be reducing and not oxidizing. An oxidizing atmosphere is believed to inhibit the formation of macromolecules.

Not so much of an issue if life first formed under the sea, which of course it did at least from our perspective. Another reason I suppose why water is very important.

 

[SGT]

I know that planets like Jupiter are being found in solar systems, astrobiologist are optimistic that there will be Earth like planets around the planets that are similar to jupiter. These Earth like planets could possibly meet the criteria above.

Another basic ingredient that i just read about is that the atmosphere in which chemical evolution is occurring must be reducing and not oxidizing. An oxidizing atmosphere is believed to inhibit the formation of macromolecules.

It is not enough to have an Earth like planet. It must orbit a Sol like star.
Huge, very bright stars (A,B,O in the main sequence) are too short lived to allow complex life to evolve in their planets.
Small, dim stars don´t output enough energy for life. So, we are probably limited to class G stars (about 1/1000 of all starts)

 

[Ivan Seeking]

It is not enough to have an Earth like planet. It must orbit a Sol like star.
Huge, very bright stars (A,B,O in the main sequence) are too short lived to allow complex life to evolve in their planets.
Small, dim stars don´t output enough energy for life. So, we are probably limited to class G stars (about 1/1000 of all starts)

How do you arrive at that number?

Class G stars are probably the best known, if only for the reason that our Sun is of this class. They have even weaker hydrogen lines than F, but along with the ionized metals, they have neutral metals. G is host to the "Yellow Evolutionary Void". [1] Supergiant stars often swing between O or B (blue) and K or M (red). While they do this, they do not stay for long in the G classification as this is an extremely unstable place for a supergiant to be. These are about 8% of all main sequence stars.

http://en.wikipedia.org/wiki/Spectral_class

 

[SGT]

How do you arrive at that number?


http://en.wikipedia.org/wiki/Spectral_class

I stand corrected. I wanted to write 1/10 and not 1/1000. Thanks for pointing my mistake.

 

[hayshed]

my idea of life is that life really just huge complex numbers of reactions that form into 1 aparnet entity. a lot of the stuff up there is about "is this planet fit for life?", but wat is life? people can't even decide if viruses are living. so basically "life" is things that react in a human like way...we think of it as animals and plants, but because the universe is basically infinatly, there is a 100% chance on my book that life exists out there. if we ever met it? probably 100% didnt we find some bacteria on mars? please correct me on any of this if I am wrong

 

[SGT]

my idea of life is that life really just huge complex numbers of reactions that form into 1 aparnet entity. a lot of the stuff up there is about "is this planet fit for life?", but wat is life? people can't even decide if viruses are living. so basically "life" is things that react in a human like way...we think of it as animals and plants, but because the universe is basically infinatly, there is a 100% chance on my book that life exists out there. if we ever met it? probably 100% didnt we find some bacteria on mars? please correct me on any of this if I am wrong

Let´s answer your questions one by one:

lifeThe property or quality that distinguishes living organisms from dead organisms and inanimate matter, manifested in functions such as metabolism, growth, reproduction, and response to stimuli or adaptation to the environment originating from within the organism.

Any complex system that fits all those properties is a living being. Viruses don´t, so they are not alive.


As far as we know, the Universe is finite.

The probability of life existing in the Universe is very high, but we are discussing the existence of intelligent life and technological civilization. Even if it is very likely that other technological civilizations exist in the Universe, we don´t know if they are concomitant and, if they are, are they near enough to communicate?

No bacterium was found on Mars. Meteorites found on Earth, that for their characteristics seem to come from Mars, show patterns that are similar to what paleontologists believe are fossils of bacteria on Earth.

 

[Newbie says Hi]

didnt we find some bacteria on mars? please correct me on any of this if I am wrong

Well, if you are referring to the "positive results" of '76 NASA Viking missions to Mars, the scientific consensus now is that the "positive results" were due to chemical reactions with the Martian soil and, therefore, of a non-biological origin.

 

[DaveC426913]

We need to define our goals. I was talking about life of any sort, complex or not. In terms of what we as a people are searching for, I can't see us canceling a mission to a planet teeming with life simply because they're simple.

So, it is not necessary to have a long-lived sun for OUR interest to be piqued in the planet's life.

To state it explicitly: I am arguing what conditions are necessary for life to form (and thus pique our interest), regardless of how complex it may or may not get.

 

[SGT]

We need to define our goals. I was talking about life of any sort, complex or not. In terms of what we as a people are searching for, I can't see us canceling a mission to a planet teeming with life simply because they're simple.

So, it is not necessary to have a long-lived sun for OUR interest to be piqued in the planet's life.

To state it explicitly: I am arguing what conditions are necessary for life to form (and thus pique our interest), regardless of how complex it may or may not get.

I agree with you that the existence of life, regardless of its complexity is of interest to us. But the original question is about intelligent life and the possibility of technological aliens being visiting or at least trying to communicate with us.

 

[Schrodinger's Dog]

Yeah if possible I'd prefer to stick to the original topic, otherwise it might get a little confusing with some talking about x and the others about y; you can always start another thread about the likelihood of any type of life I suppose.

 

[DaveC426913]

Yes but the OP specifically offers the Drake equation as the basis.

The variables in the Drake equestion need to be determined one at a time without consdieration for subsequent variables. So we have to determine the value for #3 and #4 before we proceed to #5, else we'll skew the results.

 

[SGT]

Yes but the OP specifically offers the Drake equation as the basis.

The variables in the Drake equestion need to be determined one at a time without consdieration for subsequent variables. So we have to determine the value for #3 and #4 before we proceed to #5, else we'll skew the results.

You´re right. Even so, we must consider only reasonably long lasting suns.
Life on Earth began about 1 billion years after the birth of the solar system. Most huge stars don´t live that long.
Dim stars, that constitute about 78% of all suns, don´t output enough energy to allow the complex chemical reactions necessary to life.

 

[Schrodinger's Dog]

Yes but the OP specifically offers the Drake equation as the basis.

The variables in the Drake equestion need to be determined one at a time without consdieration for subsequent variables. So we have to determine the value for #3 and #4 before we proceed to #5, else we'll skew the results.

Fair enough.

 

[SGT]

I just learned about chemical evolution in my cell and molecular biology class. Basically it is believed that Earth's ancient atmosphere, contained inorganic compounds such as nitrogen gas, carbon dioxide, water, hydrogen gas, ammonia, and methane. When you apply electricity to these inorganic compounds in a container, you spontaneously get organic compounds, even amino acids. When you add clay into the picture, which there was a lot of in early earth, scientist have seen the spontaneous synthesis of larger molecules like protiens, and small strands of RNA and DNA. The fact that you can get RNA from having the conditions that were believed to be present in early Earth, is AMAZING because it is believed that RNA was the first self replicating molecule, which gave rise to biological evolution. Now if scientist can create organic molecules from inorganic compounds during an experiment, its going to happen in other parts of the universe that has the right conditions

What I believe is needed for life to evolve is:
1.) Inorganic compounds listed above
2.) A source of energy
3.) Water is essential
4.) And a surface
5.) The planet that has potential for evolution, has to be within a certain range of a star.
6.) A large amount of time in between catastrophic events like asteriod strikes. This is were huge planets like Jupiter come into play. It is believed that Jupiter deflected a lot of asteriod strikes which gave life on Earth time to evolve. I think if the Asteriod that took out the dinosaurs didnt strike earth, this planet would have evolved a reptellian intelligent species, or maybe even a bird like intelligent species. If it wasnt for that perticular asteriod strike that took out the dinosaurs, we would not be here today.

We all agree that there must be abundance of organic compounds in the primeval soup, so oceans are needed.
Clay is only available to the mixture in shallow waters. But those waters must be sporadically in contact with the ocean, which probably means tides.
For large tides to be possible, we need a large satellite, relatively near the planet. From all the planets in the solar system, only Earth and Pluto have such a satellite, but the distance of Pluto to the Sun cancel the other requirements for life.
So, maybe even a planet with abundance of liquid water and enough energy, will not develop life, or develop it very slowly, for lack of a moon like satellite.

I don´t think that a fierce predator, like a dinosaur, would develop intelligence. They don´t need it. For instance, sharks did not evolve substantially in the last 300 million years. There is no evolutionary pressure.
In the other extreme, an herbivore does not have a fast enough metabolism to develop a big brain.
So, I think intelligence is important to a middle sized predator, like primates, dogs or birds as you suggested. But intelligence without manipulative appendages, cannot lead to a technological civilization.
Anyway, without the extinction of dinosaurs, the smaller predators should be hiding and it would be very hard to build a civilization.
But before the extinction of the large reptiles, a more important one happened at the end of the Cambrian, when a large number of marine life disappeared.
It was at the Cambrian that appeared the Pikaia, the first chordate and possible ancestor of all vertebrates. The Pikaia was a small animal (4 cm), surrounded by invertebrate predators, some of them more than a meter long. If those invertebrates had not be extinct, maybe fishes, amphibians, reptiles and mammals would never appear.

 

[DaveC426913]

I don´t think that a fierce predator, like a dinosaur, would develop intelligence. They don´t need it. For instance, sharks did not evolve substantially in the last 300 million years. There is no evolutionary pressure.
In the other extreme, an herbivore does not have a fast enough metabolism to develop a big brain.

1]
There is a continual struggle between predator and prey, a perpetual game of one-upmanship. The prey gets faster or jump higher and the predators have to as well or perish.

Either one will develop intelligence if it gives them an advantage over their counterpart. The prey might get more adaptable to hiding or escaping the predators, or the predators might get more sophisticated and subverting the prey's attempts to remain unseen.

2]
There are two major survival strategies in prehistory: specialization and adaptability.

Animals such as giraffes with their long necks, and koalas, who eat only one food are specialists. They do well when their environement is stable over long periods. They find a niche that works and stick to it. This is a very successful strategy. The problem is, if their environment changes too much, they are doomed.

Dinosaurs and sharks did not develop intelligence because their environments were stable - their hunting techniques continue to work.


Other animals such as humans and rats are opportunists, able to adapt to a changing environment. They are the types that carry on after great upheaval (such as a meteor strike). Soime species do this by being omnivores, or other generalized adaptations, some do it by evolving intelligence that allows their behaviour to adapt to changing circumstances.

Humans were predators just like dinosaurs and sharks, but they lived in a time of great change (eg. the ice age). Being adaptable helped them survive.

 

[SGT]

1]

Humans were predators just like dinosaurs and sharks, but they lived in a time of great change (eg. the ice age). Being adaptable helped them survive.

So did the wolves and the cats, who did not develop intelligence.
My point is that very strong predators don´t need intelligence. Smaller ones do! Wolves are not intelligent, but they have developed group behavior, that makes them more effective in hunting and in protecting themselves.
Lions and tigers, that are more strong predators did not develop group behavior. They are lone hunters, even when living in family, like lions do. A lioness hunts alone and shares the kill with the members of the family, but they don´t have group hunting strategies like wolves.

 

[DaveC426913]

So did the wolves and the cats, who did not develop intelligence.

What on Earth makes you think these animals aren't intelligent?? Cats and dogs are a mere eyeblink behind us in evolutionary terms. In terms of evolutionary traits, I think the degree of intelligence is a matter of splitting hairs.

Are you talking human-level intelligence? Well, if you want to know what happens when there are two competing intelligent species on one planet - ask Neandertal...

 

[Schrodinger's Dog]

What on Earth makes you think these animals aren't intelligent?? Cats and dogs are a mere eyeblink behind us in evolutionary terms. In terms of evolutionary traits, I think the degree of intelligence is a matter of splitting hairs.

Are you talking human-level intelligence? Well, if you want to know what happens when there are two competing intelligent species on one planet - ask Neandertal...

No one really knows why the Neanderthal died out, there has been no evidence of aggressive competition between the Cro-magnon and the Neanderthall, and in fact populations were so small that it would of probably been fairly rare that they even met. The reason they became extinct is hypothesised, some suggest they lacked an ability to adapt to the changing climate post ice age, but no one really knows, suffice to say though, aggresive dispute between two species is not supported by any evidence, and it's hard to see why they would need to fight for land or food anyway.

Well I don't know about him but by intelligent I meant sentient, self aware, capable of sophisticated conscious thought and communication .

 

[DaveC426913]

Well I don't know about him but by intelligent I meant sentient, self aware, capable of sophisticated conscious thought and communication .

All of which apply to higher mammals.

 

[radou]

Lions and tigers, that are more strong predators did not develop group behavior. They are lone hunters, even when living in family, like lions do. A lioness hunts alone and shares the kill with the members of the family, but they don´t have group hunting strategies like wolves.

Interesting, what I heard in a few animal documentaries differs from this pretty much.

 

[Tony11235]

Lions and tigers, that are more strong predators did not develop group behavior. They are lone hunters, even when living in family, like lions do. A lioness hunts alone and shares the kill with the members of the family, but they don´t have group hunting strategies like wolves.

I know this is very off topic, but lions, that is the female groups, DO have hunting strategies. You're right about tigers though. Anyway, back to the topic.

 

[Schrodinger's Dog]

All of which apply to higher mammals.

True but then by sophisticated thought I meant, philosophy and science, and by communication I meant verbal linguistic skills, but seeing as we're talking about animal life atm, it wasn't really relevant.

AFAIK only chimps and dolphins have shown evidence of self awareness, and even then the evidence is disputed.

Predators are smarter than prey, they also usual have sophisticated social structures and highly competative infrastructures, which many herd animals lack, I think it's safe to say that predatory animals would be more likely to develop intelligence, although I'm of course only basing that on Earth life, hunting takes some real co-operative skills also.

 

[DaveC426913]

I think you're splitting evolutionary-scale hairs here. Suggesting mammals aren't quite intelligent is a highly humanocentric bias. Compared to the other 99.9999999% of the biomass on the planet, mammals are rocket surgeons.

 

[Ivan Seeking]

Rocket surgeons?

 

[SGT]

I think you're splitting evolutionary-scale hairs here. Suggesting mammals aren't quite intelligent is a highly humanocentric bias. Compared to the other 99.9999999% of the biomass on the planet, mammals are rocket surgeons.

Octopi can open a closed jar to pick a crab that is inside. Not many mammals can do that.

 

[DaveC426913]

Octopi can open a closed jar to pick a crab that is inside. Not many mammals can do that.

Certainly. Which is why octopi are so fascinating for their oddball convergent trait of intelligence.

 

[Schrodinger's Dog]

Octopi can open a closed jar to pick a crab that is inside. Not many mammals can do that.

I think generally sea life has a much better chance at achieving technology if it migrates to land, again this is obviously a humanocentric idea, but I can see where it might be generally applicable, due to the nature of the environment over waters environment.

Intelligence can form in the sea and indeed life is most likely to form there, but the chances of octopuses building an advanced technology? Is it as good as say Chimps assuming man disappears off the scene? Who's the most likely species to form an intelligent, sapient, verbally communicating, scientific society?

Water is vital, but In my mind planets with both water and land, not only have an abundance of water for basic life forming, but have land to provide a more conducive environment for intelligent life formation. Thus I personally think the best chance of speciation comes from a land, water planet.

 

[SGT]

I think generally sea life has a much better chance at achieving technology if it migrates to land, again this is obviously a humanocentric idea, but I can see where it might be generally applicable, due to the nature of the environment over waters environment.

Intelligence can form in the sea and indeed life is most likely to form there, but the chances of octopuses building an advanced technology? Is it as good as say Chimps assuming man disappears off the scene? Who's the most likely species to form an intelligent, sapient, verbally communicating, scientific society?

Water is vital, but In my mind planets with both water and land, not only have an abundance of water for basic life forming, but have land to provide a more conducive environment for intelligent life formation. Thus I personally think the best chance of speciation comes from a land, water planet.

I agree with you, simply by the fact that the development of metallurgy is impossible in an aquatic environment and without metallurgy a technological civilization is impossible.
I only mentioned octopuses because of Dave´s affirmation that mammals are smarter than all other life forms.
It seems that dolphins are as intelligent as chimps, but in the absence of mankind, chimps are more likely to rule the planet than dolphins. Chimps have prehensile limbs and live on firm ground, where in a few million years they could perhaps develop a civilization.

 

[DaveC426913]

I only mentioned octopuses because of Dave´s affirmation that mammals are smarter than all other life forms.

Not quite what I said but who's counting...