Aliens probably long dead, say scientists

[littlebabyjesus]

I'm not saying that time is the (only) limiting factor. I'm saying (well, actually totally speculating) that it's a really long shot even over a typical 5 billion year life span of a planet of a planet that can support life.

Think we need to be really specific about what it is that we think is the long shot here. Is it life with minds, which create representations of themselves in the world that we call conscious awareness? Or is it life that has developed ways of thinking that allow it to, for instance, ask the kinds of questions we are asking here?

Once evolution has produced multi-cellular life and that multi-cellular life has started developing nervous systems, certain kinds of thing seem to be selected again and again - the 'good tricks' of evolution. Eyes, for instance, but also smartness - such as the entirely separate evolution of tool-making mammals and birds. I would suggest that, once a certain threshold of complexity has been reached, it is highly likely, given enough time, that things such as a problem-solving intelligence would appear.

 

[littlebabyjesus]

If there's other life out there, I would imagine it's mostly unicellular, although that assumption is merely based on what happened on Earth. Although to take the speculation one step further - whatever form any potential alien life takes, it's possibly likely that its evolution would be significantly limited by its environment. If you consider all the types of planetary bodies that may be hospitable to life, most of them are probably ocean worlds with thick global ice coverage - much like Europa. The conditions required for a world with both water & land under a thick, but not too thick, atmosphere are quite specific. Whereas a small ice covered world doesn't need a strong magnetic field, doesn't need to worry about an atmosphere & has excellent protection from impacts, super nova, etc. And given that small, long lived stars such as red dwarfs are far more numerous than Sun types stars, the combination of small, ice covered ocean worlds, orbiting close in to red dwarfs, potentially offers far greater prospects for the emergence of life than terrestrial type bodies. But it would also, most likely, provide quite a dull environment, without many of the dramatic effects that influenced evolution on earth.

I do think discovering any kind of life whatever on Europa would be a massive piece of information. If life has appeared twice in one apparently rather typical solar system, that gives us data to work on in calculating odds. It suggests that life is common.

It is my hunch that life is common. The history of humans and our consideration of our place in the universe has been a history of realising step by step that we're not special - indeed, the so-called 'Copernican principle' states that we should be using as our heuristic the assumption that we are not special. Our discoveries so far regarding exoplanets certainly fit in with this direction of thought.

 

[EastEnder]

I'm not saying that time is the (only) limiting factor. I'm saying (well, actually totally speculating) that it's a really long shot even over a typical 5 billion year life span of a planet of a planet that can support life.

Assuming you imagine evolution on Earth was a typical case, which it may or may not be, there's no way at the present time we can know.

I would also add that, if Earth is typical, it might be even harder than might be imagined. We are, relatively speaking, at the tail end of the epoch of habitability for our planet. In another billion years time, the expanding sun will have cooked the earth, making life as we know it Jim, impossible. So if the pace of evolution on Earth had been out by only a billion, or maybe just a few hundred million, years, life may have been extinguished before it ever had a chance to worry about it.

 

[littlebabyjesus]

We've got around 5 billion years left, no?

 

[EastEnder]

We've got around 5 billion years left, no?

The planet does, we don't. In a billion years time the sun will have increased in luminosity by about 10% - doesn't sound like much, but it's enough to shift the habitable zone beyond our current orbit. The Earth will slowly heat up, the oceans will evaporate, the atmosphere will become a choking mix of steam & CO2. Way, way before the sun consumes the Earth, the planet will be turned into a Venus like environment.

And interestingly, our once benevolent magnetic shield will become our enemy. As Venus heated up, the solar wind blasted most of its water vapour out into space. On earth, the magnetosphere will prevent that from happening, which means our atmosphere will become much hotter & denser even than Venus' is today. The jury's out on exactly how long it'll take to play out, but life on Earth probably doesn't have more than 1 or 2 billion years left.

 

[weltweit]

The planet does, we don't. In a billion years time the sun will have increased in luminosity by about 10% - doesn't sound like much, but it's enough to shift the habitable zone beyond our current orbit. The Earth will slowly heat up, the oceans will evaporate, the atmosphere will become a choking mix of steam & CO2. Way, way before the sun consumes the Earth, the planet will be turned into a Venus like environment.

And interestingly, our once benevolent magnetic shield will become our enemy. As Venus heated up, the solar wind blasted most of its water vapour out into space. On earth, the magnetosphere will prevent that from happening, which means our atmosphere will become much hotter & denser even that Venus' is today. The jury's out on exactly how long it'll take to play out, but life on Earth probably doesn't have more than 1 or 2 billion years left.

Indeed, so we need to become a multi-planetary species asap.

 

[littlebabyjesus]

Indeed, so we need to become a multi-planetary species asap.

There's still a lot of time, though. Even taking the bottom end of ee's estimate, there's more time left between now and then than the time it has taken for the very first multi-cellular life forms to evolve into us.

We have rather more pressing concerns atm regarding our survival.

 

[NoXion]

The planet does, we don't. In a billion years time the sun will have increased in luminosity by about 10% - doesn't sound like much, but it's enough to shift the habitable zone beyond our current orbit. The Earth will slowly heat up, the oceans will evaporate, the atmosphere will become a choking mix of steam & CO2. Way, way before the sun consumes the Earth, the planet will be turned into a Venus like environment.

And interestingly, our once benevolent magnetic shield will become our enemy. As Venus heated up, the solar wind blasted most of its water vapour out into space. On earth, the magnetosphere will prevent that from happening, which means our atmosphere will become much hotter & denser even that Venus' is today. The jury's out on exactly how long it'll take to play out, but life on Earth probably doesn't have more than 1 or 2 billion years left.

But will the core be as active in 1-2 billion years as it is today?

 

[NoXion]

Another thing, if the biosphere sequesters CO2, as it has done in the past, then the degree of heating may not be all that great after all.

 

[littlebabyjesus]

Applying the Copernican principle, it seems very likely that, whatever life there is on Earth in 1 billion years' time, humans will be long-extinct.

 

[EastEnder]

But will the core be as active in 1-2 billion years as it is today?

According to this: How long until Earth's core solidifies? the core has only cooled by 450K since the earth formed! So I'd guess the magnetic field will be around long after the earth's been rendered uninhabitable.

 

[weltweit]

.. We have rather more pressing concerns atm regarding our survival.

Trump and North Korea sizing each other up makes me want us to expand starwards sooner rather than later

 

[EastEnder]

Another thing, if the biosphere sequesters CO2, as it has done in the past, then the degree of heating may not be all that great after all.

That process can only occur whilst there's life to absorb the CO2, most of which happens in the oceans. The CO2 cycle is robust but not infallible, with enough heating, over a long enough period, we'll get a runaway greenhouse effect, which will eventually vaporise the oceans, effectively ending the CO2 cycle.

That's assuming we don't act first - if our species survives long enough, and masters the art of chucking about huge rocks in space, we could use their gravity to slowly move Earth out into an ever wider orbit. It's very simply in principle, just carefully direct a large asteroid to pass close to, but not too close, the Earth, on just the right trajectory & it will steal a tiny bit of Earths orbital momentum, slowing our orbit a little bit, and widening it in the process. If you do that every couple of million years, the Earth can be gently inched out, ever further from the Sun, thereby avoiding being cooked. Obviously that'll only buy us a few more billion years - after the Sun's red giant stage, it'll shrink to a tiny white dwarf & it won't matter where the Earth is, life will become impossible here.

 

[NoXion]

I've been meaning to say this in the Stephen Hawking thread, but I'll say it here while I remember:

I think a good reason to not only explore space and other planetary bodies, but to exploit them and establish permanent settlements there, is not so much for the sake of ensuring the survival of the human species within the next 100 years (as bad as climate change could be I don't think it will wipe us out), but to make better use of the resources available to us. Earth is the only planet we know of with a compatible biosphere, but the rest of the Solar system contains a great many resources that an advanced industrial society needs to function. Therefore surely it makes sense that we should take the opportunity and try to establish as much resource extraction and industrial activities in the extraterrestrial regions of the Solar system as we can, where there is no ecosystem to worry about unbalancing with our activities (barring possible places like Europa, Titan, and Encleadus, but in that case we could still exploit the asteroids to the hilt).

Of course it's still worth doing for the long-term survival of the human species, but the above is a good reason for doing it within the next century or two.

 

[EastEnder]

I've been meaning to say this in the Stephen Hawking thread, but I'll say it here while I remember:

I think a good reason to not only explore space and other planetary bodies, but to exploit them and establish permanent settlements there, is not so much for the sake of ensuring the survival of the human species within the next 100 years (as bad as climate change could be I don't think it will wipe us out), but to make better use of the resources available to us. Earth is the only planet we know of with a compatible biosphere, but the rest of the Solar system contains a great many resources that an advanced industrial society needs to function. Therefore surely it makes sense that we should take the opportunity and try to establish as much resource extraction and industrial activities in the extraterrestrial regions of the Solar system as we can, where there is no ecosystem to worry about unbalancing with our activities (barring possible places like Europa, Titan, and Encleadus, but in that case we could still exploit the asteroids to the hilt).

Of course it's still worth doing for the long-term survival of the human species, but the above is a good reason for doing it within the next century or two.

Asteroids are where it's at. Mining other planets is daft when there's trillions of tons of mineral bearing rocks just floating around there for the taking. Plus it'd be super crazy cool. Let's do it! Do it now!!

 

[NoXion]

That process can only occur whilst there's life to absorb the CO2, most of which happens in the oceans. The CO2 cycle is robust but not infallible, with enough heating, over a long enough period, we'll get a runaway greenhouse effect, which will eventually vaporise the oceans, effectively ending the CO2 cycle.

That's assuming we don't act first - if our species survives long enough, and masters the art of chucking about huge rocks in space, we could use their gravity to slowly move Earth out into an ever wider orbit. It's very simply in principle, just carefully direct a large asteroid to pass close to, but not too close, the Earth, on just the right trajectory & it will steal a tiny bit of Earths orbital momentum, slowing our orbit a little bit, and widening it in the process. If you do that every couple of million years, the Earth can be gently inched out, ever further from the Sun, thereby avoiding being cooked. Obviously that'll only buy us a few more billion years - after the Sun's red giant stage, it'll shrink to a tiny white dwarf & it won't matter where the Earth is, life will become impossible here.

Aren't white dwarfs still very hot and only cooling down very slowly? If the Earth has been moved out once, just move it back again, just further inward this time. The fact that the Earth would have to orbit very close could also be useful in itself, since by that time it's possible that the core of the planet will have become quiescent by that time, and tidal forces might be able to keep the tectonic plates going.

 

[NoXion]

Asteroids are where it's at. Mining other planets is daft when there's trillions of tons of mineral bearing rocks just floating around there for the taking. Plus it'd be super crazy cool. Let's do it! Do it now!!

Although since almost all other planetary bodies with solid surfaces are significantly less massive than the Earth, mining other planets and then transporting the resources elsewhere in the Solar system would still be cheaper than mining resources on Earth and then dragging them all the way up its deep gravity well for the rest of the Solar system to make use of.

 

[weltweit]

.. That's assuming we don't act first - if our species survives long enough, and masters the art of chucking about huge rocks in space, we could use their gravity to slowly move Earth out into an ever wider orbit. It's very simply in principle, just carefully direct a large asteroid to pass close to, but not too close, the Earth, on just the right trajectory & it will steal a tiny bit of Earths orbital momentum, slowing our orbit a little bit, and widening it in the process. If you do that every couple of million years, the Earth can be gently inched out, ever further from the Sun, thereby avoiding being cooked. Obviously that'll only buy us a few more billion years - after the Sun's red giant stage, it'll shrink to a tiny white dwarf & it won't matter where the Earth is, life will become impossible here.

Cool idea, I had never heard of it before.

 

[DotCommunist]

Asteroids are where it's at. Mining other planets is daft when there's trillions of tons of mineral bearing rocks just floating around there for the taking. Plus it'd be super crazy cool. Let's do it! Do it now!!

could repeatedly throw giant lumps of water ice at mars to see what happens while we are at it

 

[EastEnder]

Aren't white dwarfs still very hot and only cooling down very slowly? If the Earth has been moved out once, just move it back again, just further inward this time. The fact that the Earth would have to orbit very close could also be useful in itself, since by that time it's possible that the core of the planet will have become quiescent by that time, and tidal forces might be able to keep the tectonic plates going.

White dwarfs are certainly hot, they take trillions of years to fully cool down. But they're very small - about the size of Earth - and all nuclear fusion has ended. They're also quite dangerous, much of the original mass of the star remains, but massively compacted. You wouldn't want to get too close to one - it's been theorised that they could have a habitable zone, incredibly close in, but at that distance the tidal forces involved might prove the undoing of any unwary planet.

 

[EastEnder]

could repeatedly throw giant lumps of water ice at mars to see what happens while we are at it

That would upset Yossarian, he goes into tree hugger mode at the idea of interfering with other planets. Personally I'm all for it, chuck big things at the poles, melt the permafrost, start the reactor, free Mars, etc.

 

[EastEnder]

There's still a lot of time, though. Even taking the bottom end of ee's estimate, there's more time left between now and then than the time it has taken for the very first multi-cellular life forms to evolve into us.

We have rather more pressing concerns atm regarding our survival.

This is true, but I do find it interesting that it's a sometimes overlooked factor in the potential evolution of complex life. Given how long life on Earth spent as little more than slime, if it'd "only" taken another billion years to make the leap from simple to complex, it might well have run out of time entirely. By the time dinosaurs were running around, the sun might already have been cooking the Earth. It's an interesting equation - the ratio of how long it takes for complex life to emerge, versus how long a planet will remain potentially habitable. Based on that comparison, planets orbiting long lived stars, such as red dwarfs, offer a much greater duration over which the planet might remain hospitable, but at the cost of a less dynamic environment.

We really need bigger telescopes - the more exoplanets we discover, the more it'll teach us about the variety of planetary types & the associated possibilities for life.

 

[DotCommunist]

also, large stored dead trees under the ground- the oil explosion could be said to have bootstrapped our species a bit. Not that we weren't already pretty fly for a prehistoric guy but still. How likely is it that such deposits would be found elsewhere or that the hypothetical alienz might even go down that particular technological route

 

[EastEnder]

also, large stored dead trees under the ground- the oil explosion could be said to have bootstrapped our species a bit. Not that we weren't already pretty fly for a prehistoric guy but still. How likely is it that such deposits would be found elsewhere or that the hypothetical alienz might even go down that particular technological route

Oil mostly comes from ancient marine organisms, the dead trees make coal!

But I would agree that fossil fuels made modern civilisation - trees most of all, given that without coal it's unlikely the industrial revolution would have kicked off in the way it did.

 

[littlebabyjesus]

This is true, but I do find it interesting that it's a sometimes overlooked factor in the potential evolution of complex life. Given how long life on Earth spent as little more than slime, if it'd "only" taken another billion years to make the leap from simple to complex, it might well have run out of time entirely. By the time dinosaurs were running around, the sun might already have been cooking the Earth. It's an interesting equation - the ratio of how long it takes for complex life to emerge, versus how long a planet will remain potentially habitable. Based on that comparison, planets orbiting long lived stars, such as red dwarfs, offer a much greater duration over which the planet might remain hospitable, but at the cost of a less dynamic environment..

How much is the evolutionary dynamism of the environment dependent on the wider system, and how much is it generated by the life itself? For instance, all you need is uneven heating of the surface and an atmosphere to create weather, which is always dynamic. We have stuff like tides to create unique environments that have played important roles in evolution, but much of the dynamism comes from the existence of life itself, I would suggest - the most diverse places, such as rainforests or coral reefs, are actually places with very stable conditions.

 

[NoXion]

That would upset Yossarian, he goes into tree hugger mode at the idea of interfering with other planets. Personally I'm all for it, chuck big things at the poles, melt the permafrost, start the reactor, free Mars, etc.

I'd understand if it turns out that Mars has some kind of biosphere still going - but otherwise, what's the problem exactly? Terraform away.

 

[EastEnder]

How much is the evolutionary dynamism of the environment dependent on the wider system, and how much is it generated by the life itself? For instance, all you need is uneven heating of the surface and an atmosphere to create weather, which is always dynamic. We have stuff like tides to create unique environments that have played important roles in evolution, but much of the dynamism comes from the existence of life itself, I would suggest - the most diverse places, such as rainforests or coral reefs, are actually places with very stable conditions.

Absolutely, the evolution of Earth itself has been massively influenced by the life on it. Without the CO2 cycle, plate tectonics would likely grind to a halt, messing up continent formation and leading to periodic, vast planet wide volcanism, which would be unpleasant. I was thinking more with regard to putative life around long lived stars - red dwarfs are great candidates for this, but their habitable zone is much closer in to the star. Added to which, they're extraordinarily magnetic leading to regular, massive solar flares. All of which means that a planet like ours, with the biosphere open to the air, would not fare well under such conditions. More likely it would be ocean worlds, where life could evolve deep underwater, protected from the harmful radiation. Which would suit simple life, but probably not all that conducive to highly complex, intelligent life.

 

[littlebabyjesus]

Absolutely, the evolution of Earth itself has been massively influenced by the life on it. Without the CO2 cycle, plate tectonics would likely grind to a halt, messing up continent formation and leading to periodic, vast planet wide volcanism, which would be unpleasant. I was thinking more with regard to putative life around long lived stars - red dwarfs are great candidates for this, but their habitable zone is much closer in to the star. Added to which, they're extraordinarily magnetic leading to regular, massive solar flares. All of which means that a planet like ours, with the biosphere open to the air, would not fare well under such conditions. More likely it would be ocean worlds, where life could evolve deep underwater, protected from the harmful radiation. Which would suit simple life, but probably not all that conducive to highly complex, intelligent life.

It would pose challenges to ideas about escaping from your environment in the way we have managed it, for sure, but why would purely ocean worlds not be conducive to intelligent life? Various brainy problem-solvers have evolved in our oceans, such as octopuses. And while the evolution of cetaceans involved a great deal of time on land, they evolved their exceptional cleverness after the return to the water. Once brains have evolved, there does appear to be a wide variety of situations in which increasing cleverness is selected as it is worth the extra energy needed to run it.

 

[EastEnder]

It would pose challenges to ideas about escaping from your environment in the way we have managed it, for sure, but why would purely ocean worlds not be conducive to intelligent life? Various brainy problem-solvers have evolved in our oceans, such as octopuses. And while the evolution of cetaceans involved a great deal of time on land, they evolved their exceptional cleverness after the return to the water. Once brains have evolved, there does appear to be a wide variety of situations in which increasing cleverness is selected as it is worth the extra energy needed to run it.

Well it's certainly not guaranteed to stymie progress, but for life to exist on a watery planet close to a red dwarf, it would probably have to remain in the deep ocean. The solar radiation might even create a "dead" zone in the upper few hundred meters. When you think of all the attributes associated with intelligence - tool use, construction, settlements, farming, etc - it's not all that clear how such things could arise at the bottom of the sea. I'm not saying it's not possible, just that the challenges would be immense.

 

[NoXion]

Interesting discussion RE: intelligent ocean life here, here and here. Lots of interesting ideas.

Edit: Also this.