What cosmological event could snuff out the sun without destroying Earth?

[Ryan_m_b]

1) It doesn't have to build them. Just maintain.

Given the huge variety and complexity of equipment inherint in modern life this doesn't change much. Also part of maintenance will be replacing damaged parts that innevitable wear and tear will damage, these are going to have to be built.

I'm not just talking about the systems to maintain the ecosystem here, I'm talking about all the technology we need in everyday life and all the technological industry required to provide that from factory robotic arms to MRI machines.

2) The other question is how closed does the ecosystem really have to be. For example, if you have a spaceship and you leak oxygen, then you are dead. Even with a dead Earth there are going to be supplies of oxygen lying around. It might be frozen oceans of oxygen. It could be ice that can be broken down by electrolysis.

Sure there are advantages of being able to harvest from the world but you've still got to keep an ecosystem going. That's no mean feat juggling so many species interactions when failure will result not just in habitat destruction but possibly the end of the human race.

3) Finally my gut feeling is that the small the number of people, the more easier it will be to maintain a closed ecosystem

I'm sure there's an optimum number decided by the carrying capacity for the ecosystem and the labour force needed to maintain it but that's ignoring every other part of industry.

From a "mouths to feed" people are easy to replace. The reason I think that "life will be cheap" is that when resources are limited, one less person is one less user of oxygen.

There's a lot you're not taking into account. A skilled worker requires a significant investment, you can't just execute your uppity neurosurgeons and replace them in 9 months time. For a skilled worker you need at minimum one full time adult for 5-10 years to make sure it doesn't die from starvation, disease or accident. For support this requires the input of specialist products e.g. vaccines, nutritious food, developmental toys which all rely on other workers and industries for everything from child psychologists to chemical factories. Then you need 10-15 years of education to get them to graduate level (with all the associated industry and workers) which makes them entry level tea-making-person for a period of years until they have the relevant experience to be considered a fully fledged skilled worker in their field.

Bottom line a high tech civilisation has a wealth of hidden complexity (just look at your smartphone and try to think of how many industries and skilled workers have had a hand in it e.g. exotic material mining, software writers, transport logistics etc) filled by skilled labourers and both they and the infrastructure are huge investments in resources. You can't just stick anyone onto a training course and in a short amount of time get a skilled worker. It takes years and it takes a large education sector stocked with current skilled workers (in other words you need to keep a pool of every speciality perpetually to prevent the loss of noncodified and tacit knowledge).

 

[twofish-quant]

I'm not just talking about the systems to maintain the ecosystem here, I'm talking about all the technology we need in everyday life and all the technological industry required to provide that from factory robotic arms to MRI machines.

I think that if the sun goes out people won't be worried too much about factory robotic arms or MRI machines. Given the difficulties involved in merely surviving I don't think there would any energy to do any more than that.

Sure there are advantages of being able to harvest from the world but you've still got to keep an ecosystem going. That's no mean feat juggling so many species interactions when failure will result not just in habitat destruction but possibly the end of the human race.

I think people will give up on trying to maintain species diversity and just merely do what it takes to keep a small number of people (100,000 at most) alive. Probably closer to 3000.

There's a lot you're not taking into account. A skilled worker requires a significant investment, you can't just execute your uppity neurosurgeons and replace them in 9 months time.

Frankly, I don't think there would be much need for neurosurgeons. Anyone that needs neurosurgery would be assumed to be dead already.

For support this requires the input of specialist products e.g. vaccines, nutritious food, developmental toys which all rely on other workers and industries for everything from child psychologists to chemical factories.

I think that all of that would be gone. We'd end up with medieval conditions, with only the bare knowledge needed to maintain life support. Anything and anyone else will be expendable.

Bottom line a high tech civilisation has a wealth of hidden complexity (just look at your smartphone and try to think of how many industries and skilled workers have had a hand in it e.g. exotic material mining, software writers, transport logistics etc) filled by skilled labourers and both they and the infrastructure are huge investments in resources.

Sure. That's why I don't think that we will end up with a high tech civilization. What I envision is a small group of people underground near a geothermal energy source that provides heat. Once you have heat, you can generate enough electric power to electrolyze water so that you can replace oxygen losses. Now if you can replace oxygen, then food, water, and heat are things that don't require a huge amount of high technology to maintain.

Low tech with the KISS principle. Oxygen, water, food, heat, with simple robust technology. I think that anything that requires any sort of specialist technological expertise to fix is going to be non-functional in a year.

 

[twofish-quant]

Also, if we have 100 years to prepare, I think it would be a terrible idea to have one settlement. What you really want are thousands of settlements, so that any thing that destroys one settlement doesn't destroy everything. You probably want a settlement that takes a high tech strategy and one that takes a low tech one, so that someone will survive.

 

[Ryan_m_b]

I think you're right except for the fact that your entire idea of returning to a quasi-hunter-gatherer state fails in the face of the need for a closed ecosystem. It's nowhere near as simple as just having some heat and oxygen. Have you ever looked into how complex an ecosystem is? You've got to produce one able to healthily sustain a human population for a long time in a small area. That's going to require highly advanced technology to monitor and manipulate at the required level.

The smaller an ecosystem is the less stable it is going to be as there is greater chance for individual or small groups of species to become critical to the food web meaning that when something happens to lower their numbers it sends catastrophic shockwaves. The smaller and more isolated the ecosystem the more disasterous this will be for humans.

This is of course tapdancing past how ecosystems would be build in underground caverns capable of sustaining humans.

 

[twofish-quant]

I think you're right except for the fact that your entire idea of returning to a quasi-hunter-gatherer state fails in the face of the need for a closed ecosystem. It's nowhere near as simple as just having some heat and oxygen. Have you ever looked into how complex an ecosystem is?

Yes, but since we are creating an artificial one, it's probably best to use the KISS principle and create a minimal surviable system rather than even begin to try to replicate a complex ecosystem. The model I was using was that of a Mars colony or spacecraft to Mars. I can imagine how a spacecraft to Mars with say 50 people would work. I couldn't imagine the complexity of trying to create a spacecraft with a million people, so at least for one of the colonies, I'd suggest not even trying.

 

[Ryan_m_b]

Yes, but since we are creating an artificial one, it's probably best to use the KISS principle and create a minimal surviable system rather than even begin to try to replicate a complex ecosystem.

The minimum complexity for a redundant, sustainable ecosystem is likely to be huge. Even systems that seem simple have a wealth of hidden complexity; just think of crops and how they rely on soil fauna (all the thousands of species) or insect polinators and then how each of those species requires others etc etc. Mentioning that also makes me think of the human (and all animals for that matter) microbiome and how we'd have to somehow ensure the environment could provide this.

The best idea I can think of would be to investigate some of the most isolated ecosystems that can sustain humans and try to replicate them.

The model I was using was that of a Mars colony or spacecraft to Mars. I can imagine how a spacecraft to Mars with say 50 people would work. I couldn't imagine the complexity of trying to create a spacecraft with a million people, so at least for one of the colonies, I'd suggest not even trying.

I wasn't using a spacecraft model because they aren't sustainable. You may have some recycling and repair facilities but at the eventually they will run out of their stockpiled resources and die.

Considering the goal here is the continued survival of the species I don't think this action of delaying the innevitable would help.

 

[Maiklas]

I have a few ideas...

I like the idea of a steampunk sort of colony. Almost every mine in the world is going to be taken over by refugees. Deep down, the Earth is hot, of course, from its formation and radioactive decay, so refugees are going to look to live in the Goldilocks zone of temperatures, not too shallow or deep. They would drill deeper for hot water and steam to turn to power. With power comes light, which can produce plants, which can produce oxygen and food. Maybe it's all really hard to make this work, and tens of thousands of mining colonies would fail to survive. Still, some colonies could have found a way. I don't think it's so hard as some of the above posters say, as it need not be a truly closed system. They can dig to expand their underground world and resources. They might be able to wear arctic clothing and carry oxygen tanks to go topside for short expeditions. If I were writing the story, I'd alternate the narrative between two underground colonies: a nuclear-powered colony created by a superpower like America, and a steampunk colony founded by miners, like in an African diamond mine or California gold mine. It would be interesting to see the nuclear-powered colony having social problems and the steampunk colony having technical breakthroughs.

Idea #2 is that the underground colonies would have to defend themselves from those still surviving topside. You might get some inspiration from the mysterious Sea People, who invaded/migrated into many of the Mediterranean civilizations circa 1600 B.C. "Coincidentally," around that time there was a major volcanic eruption that probably blocked out the Sun.

Idea #3 is that aliens could be responsible for the calamity. Analogous to how we used gravitational slingshotting to get Voyager and other probes to the outer planets, the aliens could have set up a masterful "billiards shot", perturbing small objects in the Oort cloud that result in more and more powerful interactions that eventually result in the Earth being ejected from the Solar System. There has to be a reason they don't simply send a dinosaur-killer asteroid at Earth, so how about that they want to colonize and they are cold-loving aliens? Maybe cold-fusion based biology or some cold-based biology beyond our current understanding. Their cold-natured ways would explain why they are so darn patient with the decades or centuries that their "billiard shot" would need to play out - they live a very long time and move slowly. The Earthlings would not know about the aliens; it would be just one theory to explain the extraordinary bad luck of a shower of Oort cloud objects destabilizing the orbits of Mercury, Venus, and ultimately the Earth. You can wait to reveal the aliens in the second novel, when, a couple centuries later, colonizing aliens are surprised when Earthlings start popping out of the ground to interfere with their efforts. The aliens would be ill-prepared for conflict, lacking a military, FTL spacecraft , and the speed to react, but they would have their own tricks.

 

[Ryan_m_b]

Welcome to the forums Maiklas.

I don't think it's so hard as some of the above posters say, as it need not be a truly closed system

If he's going with realistic science then it's going to be pretty hard to build a sustainable ecosystem with a carrying capacity sufficient for the population. Whilst it doesn't have to be completely closed (waste could be dumped, resources harvested) a lot of the knowledge, techniques and technology is going to be the same. This set up is comparable to trying to set up self-sufficient colony on another planet; you get the resources of the planet but you've got to do a lot of work to use them to keep the ecosystem alive.

 

[twofish-quant]

The minimum complexity for a redundant, sustainable ecosystem is likely to be huge.

I'm not entirely convinced of that. If this is true, then we are going to be stuffed if we try to colonize Mars.

The best idea I can think of would be to investigate some of the most isolated ecosystems that can sustain humans and try to replicate them.

Submarines and spacecraft .

I wasn't using a spacecraft model because they aren't sustainable.

Now. But any spacecraft that goes out of Earth orbit has got to be sustainable for months at a time. If you have a Mars colony or something around Jupiter, it's got to be sustainable indefinitely.

Considering the goal here is the continued survival of the species I don't think this action of delaying the innevitable would help.

One thing to consider is that if the sun were going out, then it might not make much sense to stay on Earth at all. The missing element is energy. With enough energy anything is possible. So if the sun were going out, it might make more sense to relocate to Io where you have volcanos which are powered by Jupiter's gravity field. Or you could have hydrogen fusion generators with Jupiter giving an essentially infinite source of hydrogen.

Even getting as many people out of the Earth's gravity well as possible would be useful. If you stay in the Earth's gravity well, then you are trapped. Once you get as many people as possible into "deep space" then you can start colonizing as many asteroids and comets as you can to maximize the odds that someone is going to survive.

 

[mfb]

If science jargon is not your forte, don't try to explain it. Just have the brightness of the Sun diminish for "no reason". If heat takes a million years to escape from the core, then the core quenched a million years ago and now we're seeing the effect.

Well, this would be a slow effect, slightly reducing solar radiation over the timescale of hundred thousand of years. In addition, solar neutrino observations can directly measure the rate of fusion in the core.

We are talking about something happening decades in the future, and I would expect that a significant amount of working hours can be spent for preparation, assuming the society remains intact. I would expect that roboters can do a lot of mechanical tasks. If you can train a robot to replace one specialist, you can train the robot to replace 10000. Not with the same output as 10000 workers, of course, but you can simply copy the memory to "train" more robots. Those robots would need a significant infrastructure, but (at least in theory) they are able to maintain this, perhaps with the help of humans. You need years of practice for neurosurgery, but if you can build some parts of a car and have a good guide, you might be able to build other parts of it, too.

The alternative would be to implement everything low-tech. Design cars so simple that 10 humans can build them. However, I think this approach will be doomed the day the oxygen runs out, as burning fossil fuels would probably be the only heat/energy source for the whole environment. Fission or even fusion are too complex to maintain.

 

[twofish-quant]

Something to point out here is that some of the best science fiction assumes something weird happening and looks at the consequences rather than trying to figure out the cause. One thing that you can do is to say "the sun is going out, and no one knows why." The fact that no one knows why the sun is going out would have some interesting consequences.

The alternative would be to implement everything low-tech. Design cars so simple that 10 humans can build them. However, I think this approach will be doomed the day the oxygen runs out, as burning fossil fuels would probably be the only heat/energy source for the whole environment. Fission or even fusion are too complex to maintain.

Fission reactors would be probably be impossible to maintain, but radiothermal generators could be maintained with minimal skills. The trouble is that I don't know what the energy requirements would be. The energy output of RTG's have been low, but traditionally they have been intended for space use where there are weight requirements.

And I'm not even sure that it would be impossible to design a fission reactor that would be need minimal intervention. Natural managed to create one at Oklo, Gabon.

That actually would be a good place to start. How much *energy* does it take to keep a human alive and how much of that comes from the sun.

 

[Ryan_m_b]

I'm not entirely convinced of that. If this is true, then we are going to be stuffed if we try to colonize Mars.

Yup.

Submarines and spacecraft .

These are not sustainable isolated ecosystems. Once their food stocks are gone it's game over. Think more along the lines of an ecosystem that cycles from autotrophs to detritivores via enough animals to sustain a human population.

Now. But any spacecraft that goes out of Earth orbit has got to be sustainable for months at a time. If you have a Mars colony or something around Jupiter, it's got to be sustainable indefinitely.

By definition I'd say that a spacecraft is not sustainable. Sustainability is linked to recycling, a biosphere can recycle it's resources potentially indefinitely with constant energy input. A spacecraft cannot, a colony would need to (else it's a dependant outpost).

One thing to consider is that if the sun were going out, then it might not make much sense to stay on Earth at all. The missing element is energy. With enough energy anything is possible. So if the sun were going out, it might make more sense to relocate to Io where you have volcanos which are powered by Jupiter's gravity field. Or you could have hydrogen fusion generators with Jupiter giving an essentially infinite source of hydrogen.

I don't see why one couldn't just construct solar panels across swathes of Earth's now frozen surface or use fusion (or any other energy source) on Earth. Moving to space would make the whole endevour hugely more complicated and expensive through the added headache of having to get it there (or designing and shipping equipment to build it all there).

Even getting as many people out of the Earth's gravity well as possible would be useful. If you stay in the Earth's gravity well, then you are trapped. Once you get as many people as possible into "deep space" then you can start colonizing as many asteroids and comets as you can to maximize the odds that someone is going to survive.

I don't see why moving to space would change any chance of survival. You're going to need precicely the same resources and innovations only if you try for space you have to make it all work there or ship it there.

 

[twofish-quant]

These are not sustainable isolated ecosystems. Once their food stocks are gone it's game over. Think more along the lines of an ecosystem that cycles from autotrophs to detritivores via enough animals to sustain a human population.

I don't see food as a big problem. The fact that we digest plants and vegetable matter is an accident of evolution. It's possible to get all your nutrition injected via an IV, and there are people who end up living for years at a time with all their nutrition supplied that way.

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

I don't see why one couldn't just construct solar panels across swathes of Earth's now frozen surface or use fusion (or any other energy source) on Earth.

Solar panels won't work. No sun. The thing about Jupiter is its this huge gravity engine which leaks out energy in several different ways, which might be collectable.

Moving to space would make the whole endevour hugely more complicated and expensive through the added headache of having to get it there (or designing and shipping equipment to build it all there).

Right. But it's best to do it when the lights are still shining.

Also a lot depends on when the lights start to go out. If the sun starts to fade when we already have a solar system infrastructure in place, then what we can do is to use solar power satellites to store as much of the energy of the sun as we can, so that we can tap into it once the lights go out.

I don't see why moving to space would change any chance of survival. You're going to need precicely the same resources and innovations only if you try for space you have to make it all work there or ship it there.

More options. Also with the larger planets you get a source of energy. There's also the "now or never" situation. Even in the best case scenario I can't imagine an post-sun Earth based civilization *ever* getting the ability to go into space, and if everyone stays on earth, then it's going to be the end sooner or later.

The other thing that could be done is genetic engineering. You could start engineering people that would be most likely to survive the lights going out.

 

[Ryan_m_b]

I don't see food as a big problem. The fact that we digest plants and vegetable matter is an accident of evolution. It's possible to get all your nutrition injected via an IV, and there are people who end up living for years at a time with all their nutrition supplied that way.

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

I think you're mistaking the product for the process here. The nutrients that go into IV still have to be produced like regular food. I don't know too much about IV but if it's anything like culture medium then it isn't defined either which is an extra barrier to any artificial synthesis (and if we could synthesise such things we could use it to make in vitro foods if we wanted).

Solar panels won't work. No sun. The thing about Jupiter is its this huge gravity engine which leaks out energy in several different ways, which might be collectable.

Geothermal or nuclear then. I don't see Jupiter as being a more attractive option given then sheer cost involved in any space endeavour (as well as the extra R&D needed).

More options. Also with the larger planets you get a source of energy. There's also the "now or never" situation. Even in the best case scenario I can't imagine an post-sun Earth based civilization *ever* getting the ability to go into space, and if everyone stays on earth, then it's going to be the end sooner or later.

Why would it end on Earth sooner or later? Also I don't see any realistic way that this could be accomplished. I know that sounds strange considering the topic of this thread but hear me out: proposing that mankind has the ability to build sustainable underground cities that can house all the ecology, industry and societies we need is one thing considering that all of those things are here on Earth but considering doing it in space (where we would have to seriously ramp up our in-situ resource allocation and fab lab technologies) just adds orders of magnitude of difficulty.

The other thing that could be done is genetic engineering. You could start engineering people that would be most likely to survive the lights going out.

Perhaps though that's so far into the realms of science fiction there isn't much to discuss. Right now if we tried we might be able to swap one allele for another but significant phenotypic engineering is way out there.

 

[Czcibor]

When I was playing with a simulation where merely putting an object of size of an underweight star was making havoc in our system. (actually in the simulation that I run the mess wasn't immediate) My idea?

Apocalypse rider: burnt out brown dwarf - massive enough, popular enough, damn hard to detect

Way: it crosses the system and immediately destabilizes orbits. However, the doom on Earth is not immediate it first is moved to much higher orbit/more eccentric. Later it is ejected from the system by interactions with Jupiter.

(so you can get a few decades in which the situation is degrading somewhat)

Possible energy sources: geothermal and nuclear. Iceland becomes surprisingly hospitable ;) Nuclear power plant - the safest place to live ;)

Political system - who got saved? Military? A few rich people and those who they hired? Democratic gov selected? By random from all citizens? By some meritocratic exam?

I would not worry too much about carbon dioxide. If the planet got colder it would freeze at places where temperature would be below -78C.

 

[CCWilson]

Guys, I appreciate all the speculation; gets my brain wheels turning. A couple of points.

The story begins just a few years from now, so that the reader can easily imagine himself living it, and the warning is only five or seven years before a black hole passes by, initially with uncertainty as to whether it will sling us into space, so that this generation is the one facing extermination. Forget genetic engineering and traveling to a moon of Jupiter and building fusion reactors and such; not enough time.

One of the issues is going to be maintaining a livable atmosphere underground. Anybody know much about oxygen generators? I do think that geothermal power plants have a lot to recommend them as a semi-permanent source of energy and perhaps a source of water as well; can't forget about water.

You'd want a farm and ranch as part of the bunker city, for dining variety, and the choice of which plants and animals to take underground would be difficult; all others would go extinct, forever.

The economic system would probably be one of central control, at least initially, and a new currency would be established. Your old money is no good here.

The process of selecting underground residents would be wrenching. After choosing scientists and doctors and other technical people, a lottery to give everyone else some small chance? Winners to bring their families? Age restrictions? No one over 40? Would rich people build their own cities underground? Could average citizens band together and survive for a while in caverns?

 

[mfb]

Fission reactors would be probably be impossible to maintain, but radiothermal generators could be maintained with minimal skills. The trouble is that I don't know what the energy requirements would be. The energy output of RTG's have been low, but traditionally they have been intended for space use where there are weight requirements.

And I'm not even sure that it would be impossible to design a fission reactor that would be need minimal intervention. Natural managed to create one at Oklo, Gabon.

The issue is not the heat generation, but the general management with radioactive stuff and so on. RTGs might work, I would try to build them with long-living material on the surface.

That actually would be a good place to start. How much *energy* does it take to keep a human alive and how much of that comes from the sun.

That is the issue. Sun gives us free ~100-500 W/m^2, averaged over a year and depending on the position and weather conditions.
Wheat production is ~1000tons/(km^2 * year), therefore it gets 3GJ/kg of light (here I used 100W/m^2). This can be improved, of course, so maybe we can assume 1GJ/kg. Light generation is not 100% efficient, but the solar spectrum is not ideal for wheat growth, so this should cancel in some way. 1GJ is 280kWh, if you would have to pay for this wheat would be very expensive, even with current power plants.
Ok... do not use wheat for food production ;).

I do think that geothermal power plants have a lot to recommend them as a semi-permanent source of energy and perhaps a source of water as well; can't forget about water.

Fun fact: They work even better without the sun, as the surface is now a cheap and very cold reservoir. And they will continue to be possible for a few billion years.
Water: Recycling. Make your complete system water-tight, and recycle everything. The ISS already uses this.

 

[CCWilson]

I wonder how fast the temperature would drop as the Earth leaves the solar system - maybe not as fast as we'd think. All that heat stored in the core would continue to warm the planet's surface for millions of years and therefore also the atmosphere, with greenhouse gases holding the heat in. So cold as hell, but probably not cold enough to freeze oxygen and nitrogen for a long, long time. A lot would depend on whether carbon dioxide and methane and other greenhouse gases would stick around. How long, I wonder, could people walk around without space suits, wearing the kind of clothing climbers of Everest use?

 

[Ryan_m_b]

This wiki page might help, especially the information regarding the head content of the Earth and the fact that the majority of heat comes from radioactive material.

 

[onomatomanic]

I did some back-of-the-envelope seasonal temperature modelling recently, which I think should work for this case.

• If I simply switch off the Sun and neglect internal heat completely, the (global average) temperature drops below 200K after about 10 weeks and below 100K after about 30 weeks.
  
  
• If I make it slightly more realistic by sending Earth directly away from the Sun with the same speed at which it orbits now, the temperature drops below 200K after about 20 weeks and is still a little above 100K by the end of the first year.
  
  
• I have a dim recollection that the equilibrium temperature of Earth due to internal heat alone would be about a tenth of its present value, i.e. around 30K. If someone could confirm or correct that value, I can incorporate that into the model.

According to the wikipedia pages, the melting and boiling points of both nitrogen and oxygen lie between 50K and 100K, for preliminary reference.

 

[CCWilson]

What do we know about frozen oxygen and nitrogen?

In a novel I've started, the Earth has been flung out of solar orbit and is chilling down. Eventually it gets cold enough to freeze the component gases of our atmosphere. Anyone know what frozen oxygen and frozen nitrogen are like? Would they be more snow-like or ice-like? Among the significant components of the atmosphere, water vapor would obviously freeze first, then carbon dioxide, then argon, oxygen, and nitrogen. I'm trying to find out what the surface of the Earth would be like at the point that all the atmospheric gases froze. Would there be a layering of the frozen gases, or intermixing? Any idea what the texture of the icy covering would be - slushy, rock hard, snowy? And I'd appreciate any help in figuring out how deep that mess would be worldwide.

 

[JohnRC]

If the Earth were flung out of orbit, it would cool down very slowly -- the core of the Earth is still hot, and a few thousand kilometres of rock is a good insulation shield. There would also be quite a lot of heat generated by the Earth's remaining reserves of uranium, potassium-40, and thorium. The oceans are also a large heat reservoir; the atmosphere is not!

The first stage, I suspect, would be a substantial glaciation, in which a normal ice-age type climate would be followed by a freezing over of all the oceans, which would progress downward to the ocean floor. All plant life would die. I would expect this part of the process to take somewhere between a month or two and a decade or two, but that is just a wild guess on my part.

There would then be a significant "pause", because nothing much else would happen between T(surface average) ~ -10°C and T(surface average) ~ -150°C. Carbon dioxide would fall as hoar frost during this period, forming a layer about 1 or 2 centimetre thick; would pack down to an ice about 4 or 5 millimetre thick.

When the surface average temperature falls below ~150°C condensation from the air will start to produce liquid argon, oxygen, and nitrogen. At this stage the ground will be warmer than the air (radioactive decay energy still reaching the surface), so that the condensation will start in the atmosphere as a fine mist, and that mist will drift to the surface as the atmosphere becomes much thinner, eventually forming oceans of liquid air on top of the frozen water oceans. These oceans would contain a fairly uniform mixture of 78% nitrogen, 21% oxygen, and 1% argon, and would average roughly 30 metre deep.
The oceans would form when the temperature reached about -190°C, and would initially be rich in oxygen and argon.

The ocean would be a pale duck-egg blue colour -- if there were any light to see it with.

Only when the temperature fell below about 210°C would solid start to form at the carbon dioxide/water ice floor of the liquid air ocean -- probably starting with large crystals of argon, followed with smaller crystals of nitrogen, and eventually by tiny crystallites of a mixture of oxygen and nitrogen (separate very small crystals in a eutectic mixture). The whole effect would be ice-like with a blue surface layer.

However, there is a steady state of surface temperature that would be achieved when the energy flow from radioactive decay from the Earth's interior matched the rate of energy loss from the Earth's surface arising from blackbody-type low frequency radiation (as a radiating body at this stage, the Earth would be far from black). With a little bit of research (which I am not prepared to do) it should be possible to calculate (or at least estimate) what this temperature might be. I do not know, but I would hazard another wild guess that this would be around about -200°C, so that the oceans of liquid water might or might not form, and probably would not freeze.

 

[chill_factor]

the atmosphere can form a convective adiabat and have an upper atmospheric temperature in thermal equilibrium with space while trapping internal heat. The amount of radiated energy would be absolutely tiny because radiation scales to temperature to the 4th power and due to convection the top of the atmosphere is the only thing that's going to be in thermal equilibrium, which is at a low temperature of something like 30 degrees - and the only way to get heat off Earth is through radiation. if the atmosphere is sufficiently opaque to far IR (which it is) then the absolute only way to radiate is by convecting warm air to the top of the atmosphere where it radiates; everything below the top layer is not going to radiate effectively because the far IR is going to be absorbed again.

Meanwhile there'll still be tidal stresses from the moon, internal heat and human heat.

Its very likely that a liquid ocean could survive and there'd only be massive glaciation instead of total freeze over.

Here's an article:

http://arxiv.org/abs/1102.1108

 

[JohnRC]

Here is the basis for some estimates:

Mass of atmosphere: 5.2 E 18 kg
density of liq nitrogen: 808 kg/m³ at boiling point -196°C
density of liq oxygen: 1142 kg/m³ at boiling point -183°C
estimated density of liquid air: 900 kg/m³ at boiling point
volume of liquefied atmosphere: 5.8 E 15 m³ = 5.8 E9 m.km²
surface area of Earth's (water) oceans: 3.6 E 8 km²

therefore average depth of liquefied atmosphere overlying present oceanic area: 16 metre

fraction by volume of carbon dioxide 390 ppm

mass of CO2 in atmosphere 390 * 44/29 * 5.2 E 12 = 3.05 E 15 kg
total surface area of Earth = 5.1 E 8 km² = 5.1 E 14 m³
density of solid CO2: 1560 kg/m³ at sublimation point –78°C
volume of solid CO2 frozen from atmosphere 2.9 E 12 m³
thickness of compact CO2 ice is therefore 0.0057 m or 5-6 mm.

----
reply to chill's post above:

Your scenario is the warmest possibility, chill. The problem with it is that the present structure of the atmosphere would not survive separation from the sun -- specifically the stratosphere which is warmed by the absorption of sunlight by ozone.

The top of the atmosphere is the thermosphere which is very very hot indeed! I presume that by "the top" you were meaning the mesopause at around 85 km altitude, which is the coldest part of the atmosphere.

If the sun were no longer in the act, then solar radiation which heats the stratosphere and the thermosphere is no longer in the action, and ozone will fairly rapidly disappear in a continuing cycle of atmospheric chemistry. There will also -- after a while -- be no cloud cover. Tidal stresses from the moon will continue to warm the Earth's from below, but they are a relatively small factor compared with continuing radioactive decay are they not?

Presumably the thermal structure of the Earth's atmosphere would revert to a simple one with decreasing temperature at increasing altitude, and you might be right that that would make radiative heat loss a very small factor; I had expected larger, with a steady state temperature around -200 °C.

Neither oxygen nor nitrogen nor argon gases can absorb infrared radiation. Once water vapour and carbon dioxide have snowed out, and methane and ozone have escaped their respective biological and photochemical replacement, and played out their chemical degradation, those are effectively the only gases left in the atmosphere -- the only reason the atmosphere is opaque to far infrared is ozone, methane, water, and carbon dioxide, as can be seen in any satellite observation through the Earth's atmosphere in the far infrared.

The Earth's low temperature darkness atmosphere would be quite transparent to far infrared.

 

[chill_factor]

yep that's true I hadn't thought of the carbon dioxide and water separating from the atmosphere.

would it be possible to pump huge amounts of methane into the atmosphere in amounts great enough to slow down the cooling?

 

[JohnRC]

yep that's true I hadn't thought of the carbon dioxide and water separating from the atmosphere.

would it be possible to pump huge amounts of methane into the atmosphere in amounts great enough to slow down the cooling?

I have checked up on the geothermal energy flux through the surface, and at present it amounts to about 0.1 watt per square metre. For that particular energy flux, the steady state emission temperature would probably be in the range of about 50-60 K if the emissivity of an ice-covered Earth were in the range 10-25%. The flux would increase with the geothermal gradient if the Earth's surface were to cool, but probably not by very much.

The steady state emission temperature is a firm number for a particular level of emissivity. Any remaining uncertainty and discrepancy between the picture that I have set out and that of chill_factor is down to the altitude and the "blackness" of the surface or atmospheric layer that the emission is effectively coming from.

There are two reasons, though, why pumping large amounts of methane might be unnecessary. The first is that the Earth is a huge thermal reservoir that would probably cool very slowly to reach this steady state. It should be possible to calculate how slowly; I have not yet done that. The second is that all of the plants are going to die in the darkness. They and the remaining microbiota will continue for awhile to metabolize and produce carbon dioxide, (and methane in some cases), until their environment gets too cool for them to continue. (Likewise the animals, but they are a much smaller part of the equation than plants and microbiota, which are roughly equal). This will prolong the period of high atmospheric carbon dioxide, and high level atmospheric emission from a layer much cooler than the surface.

 

[Borek]

Tidal stresses from the moon will continue to warm the Earth's from below, but they are a relatively small factor compared with continuing radioactive decay are they not?

I believe Andre (another user) posted links to papers that claimed radioactive decay plays much smaller role than it is commonly believed, and tidal heating is much more important. But I don't remember details and I can't find the thread where he posted it, so I can't check if I remember correctly.

 

[CCWilson]

Those answers are fantastic. Thanks.

Most discussions of why the Earth's core is so hot don't even mention tidal effects. They tell us that the three main causes are residual heat from the formation of the planet, frictional heat as iron and other dense materials sink, and radioactive decay.

What would happen if it did get cold enough to start raining oxygen all over the Earth? In particular, what if it rained oxygen over land that was cold enough to keep it liquid? Would it flow downhill? I'm trying to understand what the land surface would be like under those conditions. What would it be like to stand out there, warmly dressed, when oxygen and nitrogen rain starts to fall?

 

[Drakkith]

What would happen if it did get cold enough to start raining oxygen all over the Earth? In particular, what if it rained oxygen over land that was cold enough to keep it liquid? Would it flow downhill? I'm trying to understand what the land surface would be like under those conditions. What would it be like to stand out there, warmly dressed, when oxygen and nitrogen rain starts to fall?

Other than it flowing downhill like any normal fluid, I'm not sure what would happen honestly. Normal rainfall comes from clouds high in the sky. I'd expect that if you were standing outside as the oxygen started to liquify if would be similar to standing outside as mist formed around you. But I really don't know.

If that's true, it would be interesting for your characters to be standing outside and wiping this liquid off of them when they suddenly realize it's the oxygen in the atmosphere condensing.

 

[CCWilson]

Once water vapor and carbon dioxide and some others rain or snow, leaving mainly oxygen and nitrogen, would there be clouds? Would there be fierce wind storms, do you think? Would all the oxygen - and later nitrogen - leave the atmosphere as rain and mist, or might it snow as well? In the first case, I suspect it would mostly collect in oceans and lakes and depressions, and only freeze when the temperature dropped even lower, leaving most land areas with just a thin layer of frozen oxygen and, later, nitrogen. If it snowed oxygen and nitrogen, there might be snow drifts and maybe deep ice over land and sea.

 

[russ_watters]

That's a rough question:

Once water vapor and carbon dioxide and some others rain or snow, leaving mainly oxygen and nitrogen, would there be clouds?

That's odd because the water vapor in the air is always replenished by evaporation from the surface. We have a cycle in equilibrium. And carbon dioxide does not precipitate out.

Would there be fierce wind storms, do you think?

Off the top of my head, I'd say a lack of water vapor would reduce wind because water is partly a driver of the weather cycle. I could be wrong, though -- it is a pretty out-there hypothetical.

Would all the oxygen - and later nitrogen - leave the atmosphere as rain and mist, or might it snow as well?

No. Water precipitates because it can exist as liquid or solid at our temperature and pressure.

 

[JohnRC]

Most of the weather is driven by solar energy; with no sun, there would be much less energy to drive weather systems. However, there would still be some instability in the air column because warmer, potentially less dense air is overlain by cooler, and so convection cells may well be set up.

Apart from local factors like volcanic eruptions, I think that the air circulation might be a fairly gentle trade wind type pattern, driven by geothermal warming at the surface, and by tidal effects on both land and air mass. With solid oceans there would be no oceanic circulation to interact with the atmospheric system.

When the surface temperature gets to about -150°C (and the upper atmosphere is somewhat cooler), condensation to liquid argon and liquid oxygen can begin in the upper atmosphere. This will actually have a local warming effect (release of latent heat), and any downward motion of liquid droplets will also have a (smaller?) warming effect (dissipation of gravitational kinetic energy).

So the actual cooling is likely to stall between -150° and -200° C surface temperature.
While the cooling only proceeds slowly, oceans of oxygen will start to form -- more likely from gently descending mists rather than actual rainfall. At this stage oxygen snow is unlikely, because oxygen has a good wide liquid range. Towards the end of this stage, though nitrogen will probably form as crystallites of snow or hoar frost as well as mist. And the other factor is that the atmosphere will become very thin.

At about -210°C = 63 K the oceans -- uniform depth of about 14 metre over the oceanic 71% of Earth's surface -- will start to freeze. The atmosphere at this stage will have a pressure of roughly 4 Pa, made up of about 60% neon, 25% nitrogen and falling, 13% helium and very slowly rising, and 1% hydrogen (this does not allow for any meteoric material that might have been picked up during Earth's escape from the solar system

 

[Borek]

That's odd because the water vapor in the air is always replenished by evaporation from the surface. We have a cycle in equilibrium. And carbon dioxide does not precipitate out.

Once we get to temperatures where nitrogen and oxygen are liquid, water and carbon dioxide become rock solid (pun intended). They will be still able to sublime, but I am not convinced their partial pressures will be high enough to be of any meteorological importance.

 

[CCWilson]

When the surface temperature gets to about -150°C (and the upper atmosphere is somewhat cooler), condensation to liquid argon and liquid oxygen can begin in the upper atmosphere. This will actually have a local warming effect (release of latent heat), and any downward motion of liquid droplets will also have a (smaller?) warming effect (dissipation of gravitational kinetic energy).

Wouldn't the liquid argon and oxygen that condense out initially at high altitude return to a gaseous state as they fall to warmer temperatures, resulting in no net heat loss or gain - until low altitudes are cold enough to maintain them in a liquid state?

So the actual cooling is likely to stall between -150° and -200° C surface temperature.
While the cooling only proceeds slowly, oceans of oxygen will start to form -- more likely from gently descending mists rather than actual rainfall.

Would the oxygen liquify preferentially over the oceans, or would it follow existing streams and rivers to run downhill to oceans and lakes?

Any rough guesses as to how long it might take before oxygen and later nitrogen begin to liquify?

Thanks a lot for your help.

 

[JohnRC]

Wouldn't the liquid argon and oxygen that condense out initially at high altitude return to a gaseous state as they fall to warmer temperatures, resulting in no net heat loss or gain - until low altitudes are cold enough to maintain them in a liquid state?


Would the oxygen liquify preferentially over the oceans, or would it follow existing streams and rivers to run downhill to oceans and lakes?

Any rough guesses as to how long it might take before oxygen and later nitrogen begin to liquify?

Thanks a lot for your help.

You are quite right -- there would be an initial period when high level condensate would evaporate again at lower levels. The overall effect would be a transfer of heat upward which would reduce the temperature gradient through the atmosphere.

The other thing, though, is that we are talking about 20% of the atmosphere potentially condensing out at high levels which would result in a fairly major updraught of lower level air to "fill" the resulting void. When the major gases in the atmosphere start to condense out there will be a fairly rapid drop in atmospheric pressure. My instinct for fluid dynamics is not good enough to guess at the overall consequences during this phase. It is quite possible that after a fairly quiet cooling phase from -50 °C to -150 °C, the condensation of major atmospheric gases will introduce a stormy and turbulent phase in the atmospheric behaviour.

Similarly for the rainout. On Earth at present, water rainfall is preferentially over land because air masses are driven upward by surface topography, with resulting cooling and condensation. So if there was major air circulation, and associated stormy weather, I think that oxygen precipitation would similarly occur mainly over land. If on the other hand, the atmosphere remained fairly calm and quiet during this phase, I think there would be even precipitation over land and ocean. I cannot at present think of any mechanism that might lead to preferential precipitation over ocean.

And no, I would not care to hazard a guess as to how long. Probably not less than a year, because this phase of the cooling is fairly close to the long term steady state temperature profile, and we cannot be sure how close. So the guess I would make if forced to would be anywhere between a year and a few millennia.