How long is the universe capable of supporting intelligent life

Great Debates
1

In my view, you need at minimum a second generation star (and possibly a 3rd generation) in order to have the chemistry necessary to create intelligent life because fusion reactions would create the elements necessary for organic molecules. So intelligent life could not exist for the first 5+ billion years of the universe because solar systems would not have any elements bigger than helium in any meaningful amount. On another thread someone claimed that intelligent life could arise out of plasma on or in stars, but I honestly do not know enough about that to know if it is true or not.

Supposedly stars will run out of gas and stop forming in 100 trillion years. So w/o stars there really cannot be life, unless it can somehow arise out of geothermal energy. But I doubt life would advance to the point where it became intelligent in that situation.

However would the concentration of metals and elements larger than helium make it too poisonous for life to exist long before that point? If stars arise out of molecular clouds created by the death of previous stars, and since stars are constantly adding to the supply of metals heavier than helium wouldn’t that soon cause a point where these would poison whatever life existed? Here on earth we are poisoned by lead, mercury, arsenic, uranium, chromium, as well as tons of other elements. If concentration in the environment were 100x higher, then I don’t know if life could survive or really evolve beyond simple celled organism. Prokaryotes seem capable of survival almost anywhere, but I do not think multicellular eukaryotes are capable of that. Unless they could evolve advanced purification systems, who knows.

So if the beginning of a universe capable of supporting life (that requires a minimum of metals) is a 2nd or 3rd generation star, is there a point in the future where metals are so concentrated that organic life cannot arise without poisoning itself? Or would life in that scenario find ways to evolve that incorporated those metals?

Also, it is my view that as a society advances in technology, they can transcend certain limitations that a non-technological intelligent society could not.

As an example, if there are no suns then an advanced society might be able to use nuclear and geothermal energy to power hydroponic farms and underground civilizations. However a non-technological civilization could not do that and would die w/o a sun. So I’d assume at most intelligent life can’t exist for more than 100 trillion years because of the death of suns.

2

Until 2012. Next question? :wink:

3

There are also tidal energy and chemical energy at the very least. IN your universe filled with heavy elements why wouldn’t lithotrophs thrive?

You do realise this is just the anthropic argument with a broader spin, right? The universe has just the right amounts of these heavy elements, ergo those levels must be a necessity for our existence.

The fact is that life is poisoned by those things because it evolved without them, and it evolved without them because they are so very, very rare. There is no physical reason why the horribly reactive elements like aluminium, sodium and copper are essential for life, whereas unreactive elements like arsenic are toxic. It’s simply that the elements that life evolved with were incorporated into the system, and the others that were never encountered never were, and so are toxic.

If you do a Google search I’m sure you will find several versions of an article published decades ago that shows the correlation between the abundance of an element in seawater and its abundance in the mammalian body. Quite impressive, and not coincidental.

IOW an organism that evolves on a world with high arsenic and chromium levels will have arsenic based respiratory pigments and cadmium based photopigments. And they will be constructing arguments that intelligent life was impossible for the first trillion years of the universe because the levels of essential elements like arsenic and cadmium were too low in planetary crusts, and that intelligent life could never evolve using such reactive, light species as iron and manganese.

You only need to look at the response of life to oxygen to prove this point. Oxygen is hideously reactive and was lethal to early life. Once it became ubiquitous life exploited it and it is now vital for much life. Saying that life can cope with oxygen but it can’t cope arsenic doesn’t make much sense.

No, as I noted, the abundance of elements n the mammalian body closely correlates to their abundance in the ocean. If the ocean had more metals our bodies would also have more metals. If the ocean had more metals than carbon life would probably be metals based with a carbon framework.

Again, this is the anthropic principle at work. We fit this hole so well, the shape of the hole must be necessary.

If a planet has an abundance of metals it will have an abundance of lithotrophs. Lithotrophs can exist independently of suns provided that tidal or geothermal heat can keep the water liquid. Intelligent organisms dependent on a lithotrophic food chain could develop exactly as humans developed based on a phototrophic food chain.

IOW if intelligent can evolve at all without a sun there is no reason why they would have to remain technologically stagnant.

4

Stars are always being created, though some from the crap left behind by dead stars. Still, I have to go with the answer of my Astronomy prof, years before the modern hypotheses and geometry, "Longer than will matter for you.’

5

I didn’t consider lithotrophs, which is why I’m asking for other people’s opinion since they will have novel feedback.

Yeah, if you add in lithotrophic reactions then life should be able to exist without suns. However wouldn’t the temperatures make it impossible for the molecular reactions necessary to sustain life in multicellular organisms to survive? I’m more looking for info on intelligent life, not just single celled life. Would a world full of lithotrophs be capable of evolving into intelligent life or would it stop at single celled life? I know bacteria can survive almost anywhere, but I do not believe multicellular life with various organ systems (circulatory, nervous, endocrine, etc) can do that.

My concern is that intelligent life seems to require advanced biology since intelligence is theorized to be a side effect of social organizations made up of multicellular organisms. So if there was a world full of various metals, these could damage the chemical reactions going on inside their bodies. I’m sure they’d likely evolve purification methods to deal with them the same way we evolved various defenses and purification methods to combat environmental stresses.

6

Why? What are these reactions? I don’t know what reactions you are talking about here, but since liquid water only exists at >0oC I can’t think of any reactions that won;t proceed just fine.

Once again, be wary of the anthropic principle. Life reactions on Earth are optimised for 15-25oC because that is the temperature of most of the oceans. If the oceans were colder the reactions would be optimised for those temperatures.

Given that we have plenty of multicellular animals thriving in the lithotrophic system around the deep sea vents it seems there is no inherent barrier to multicellular life surviving under those conditions.

You didn’t understand what I posted above.

Some metals are toxic because we rarely encountered them in our evolutionary history. That’s it. Entirely. As far as we can tell there is no reason of reactivity or atomic mass that makes lead toxic and calcium an essential micronutrient. Or that makes cadmium toxic and copper an essential micronutrient. It’s entirely, completely down to which elements were encountered in the environments in which we evolved. Those elements that were common were incorporated into our systems. Those that were rare never got incorporated, and so they become toxic when we encounter them, largely because they displace other metals.

If the world were full of arsenic and selenium then arsenic and selenium would have been incorporated into our systems. We would have arsenic respiratory pigments rather than iron and we would have selenium side chains on our amino acids rather than sulphur.

These organisms would not have evolved purification mechanisms. They would have evolved mechanisms to scavenge maximum amounts of these elements out of the environment. They would be heavy metal accumulators. Just as we have mechanism to allow us to scavenge maximum amounts of sodium and calcium out of the environment, and just as we are sodium and calcium hoarders.

I really don’t think you are getting this point. Metals are a very valuable resource for life. If metal is reliably available enough it will inevitably be incorporated into the biological system and become an essential component and, by definition, non-toxic. In Earth’s oceans the metals that were reliably available were sodium, calcium, iron and so forth. And all these reliably available metals have become essential parts of biological systems. If cadmium and uranium were reliably available you can bet your bottom dollar that life would have incorporated them too.

Don’t fall into over-applying the anthropic principle. Just because and absence of heavy metals is beneficial to you, that doesn’t mean that it is beneficial to all life. For life that evolved in an arsenic rich ocean, the Earth would be terminally nutrient deficient. It just couldn’t get enough arsenic to stay alive. It would die as surely as a terrestrial organism dies if it can’t get enough calcium.

7

I agree with Blake, and this is why I think it’s nonsensical to be only looking for water and carbon based e.t. life. Yes that’s how life *on Earth *evolved, but it’s not like there was an intergalactic committee setting rules for these things. It just happened that way here, and it’s hilariously misguided to set Earth centric limits for what can and can’t exist in the universe.

8

There are lots of good reasons to believe that life must be carbon based and utilise water as a solvent. It’s not just about availability, though that is part of it. Water and carbon have lots of other properties that other materials just don’t have.

It’s tough to imagine a lifeform that isn’t carbon based with a water solvent system, and impossible to imagine how it could arise naturally.

9

My ignorance clearly needs to be fought on this issue then…could you explain some of the special properties of carbon and water that you have in mind? Although if it requires a degree in chemistry I’ll take your word for it.

10

Well, maybe not.

An argument can be made that life may virtually require a system at least quite similar to our own terrestrial environment. “Carbon-based” life is dependent on its particular valence arrangement and unique bonding qualities that allow it to develop into the complex structures needed for life - and there is no other atom so versatile. They just don’t have the chemistry. Maybe you could make a case for silicon life, but even then that’s only because it can (kinda, sorta, probably not) mimic those same carbon-based molecules. So there’s really no way to get around this particular part.

Additionally, life can obviously not exist in equilibrium with its surroundings. You (hypothetical alien primordial lifeform you) need a way to exclude certain things from “you” while also selectively uptaking other compounds. Since solids don’t diffuse nearly fast enough and complicated structures in atmosphere don’t really work, we’re also going to require some sort of liquid medium. Even if we hypothesize wildly about liquid ammonia or methane or something a this selective up/downtaking of nutrients and waste will build concentration gradient that will need some barrier to diffusion in order to prevent it. Lipid bi(and sometimes mono)layers work fantastically for us and somewhere, somehow you (hypothetical alien you remember) are going to need SOMETHING similar. Some kind of planar solubility difference that prevents your liquid medium from spreading out into the environment. With everything we know about biochemistry right now we’ll need a cell of some sort. Of course we might consider self-replication RNA molecule-style things life, but there’s no way that’s going to become intelligent. So (IMHO) we can’t get around this particular part either.

Both of these things require (by cosmic standards) complicated, elaborate structures and these things simply cannot exist in the very early universe, where things are too hot and elements too scarce, or in the late universe (I’m talking heat-death kind of late.) I’m not a cosmologist so I can’t speculate on the figures, but I suspect this is a valid question with a factual answer.

11

Oh, and I should also mention (accursed edit timer!) that you WILL need a sun, and of a particular intensity (as to not boil off your liquid medium, but also not freeze it too often) and output (to not blow apart your complicated molecules). Tidal forces might generate enough heat to sustain a primitive ecosystem of lithotropic (as has been discussed) but that won’t develop into intelligent life, and you’ll also need the output of the sun to enable these first primordial structures to gradually form. Maybe it’s a rhythmic drying and evaporation. Maybe it’s some soggy mud puddle that’s been hit with lightning. Maybe (probably not) it originated in the deep sea vent (which may bypass the sun but still needs your liquid medium and complicated structures.

12

Why do you think that?

Why?

13

It’s my understanding that the universe will either continue expanding, eventually freezing all life out, or stop expanding and contract again, eventually crushing all life in the next big bang. I haven’t heard how long ether of those things will take.

14

The question “How long will conditions exist that allow intelligent life to arise from scratch?” is different from “How long will existing intelligent life be able to survive?”. Existing intelligent life can adapt as long as some energy can be scraped up somewhere, even if it’s not suitable for supporting natural biospheres.

15

Are you sure about that? Massive stars have very short lives, going bang in under a billion years.

16

Well before Multivax comes up with an answer.

17

Pfft… quitters.

18

Well, because bacteria have been found ~3km deep within the earth’s crust. Some of these species are thermophilic, thriving in the heat generated by geological activity. As I understand it, planets are molten balls with crusts because of the immense heat generated by tidal forces. These bacterium are, from a nutrition and habitat standpoint, isolated from the phototropic sphere entirely exist in conditions that would work perfectly well if your planet were orbiting a dead neutron star of equivalent mass. I realize we’re talking about bacteria and not intelligent life, but it’d be neat to get a factual answer on this and setting a limit for life, period frames the limits of the question nicely. So, at least conceptually, geological (and thus tidal) action in and of itself can sustain life.

This is less definite, but I’m of the personal opinion that the RNA-world hypothesis, or something very similar, is the correct explanation for biogenesis. This posits that over time and natural processes, such as a cyclic drying-evaporating or concentrating-diluting actions progressively more complicated structures of self-catalytic nucleotides (polymerizing through ultraviolet radiation, virtually all of which we get from the sun, became the common ancestor for all life. Obviously this is something that’s only now becoming intensely researched and , regardless, the question of biogenesis is going to be contentious.

Really? You think we’re going to outlive the microbes?

But in any case, the two questions really aren’t different at all. From a cosmic standpoint, life is an insignificant blip on a radar filled with ever-increasing entropy and devastating impact events. When you pull your frame back to a question that contains “how long is the universe…” you see that pretty much as soon as our planet was capable of support life, it did. And it’s been marching relentlessly towards intelligence (or at least, more complex life depending on your definition of “intelligence”) ever since. Sure, it takes a while before we have internet forums that ask us that sort of question. But again, I’m hoping to see at least a wide, actual timeframe where the universe’s environment is even capable of sustaining life at all

19

uh… progressively MORE that is. :smack:

20

But you haven’t actually answered the question. Why do you believe that a lithotrophic ecosystem can never produce intelligent life?

It’s not just less definite, it’s all pure speculation. We have absolutely no idea how and under what conditions life arose on Earth, much less whether or how it might arise elsewhere.

Given those facts, you declaring it a factual absolute that solar energy is needed for life to arise might be considered… premature.