Say that the Earth’s orbit was disrupted for one reason or another and our mudball goes hurling out of the solar system. How long does it take for the magma to cool and reach absolute zero (or whatever the lowest possible temp is)?
Assume we have a year to prepare. It’s happening in Jan 2017 and theres nothing we can do to prevent it. How long could humanity survive? Days? Years?
Not sure things would happen in the sequence you describe; if the Sun goes nova, it will quickly expand to a size larger than the Earth’s orbit.
If we presciently construct a few geothermal taps, we’ll have adequate heat for our lifetimes, probably (I doubt the Earth’s core will ever reach absolute zero), but water and food will be immediate concerns. How large a group of survivors are you thinking of planning for?
A Popular Science article from 2008 addresses this:
Complete article here:
If The Sun Went Out, How Long Would Life On Earth Survive?
ETA: The article says that humans could live in submarines for hundreds of years, but in the paragraph right above that it says that plant life would die off quickly. Herbivores are going to die off when the plants do, and carnivores will die off when their food (the herbivores) runs out. So what exactly do they think these humans in submarines are going to eat?
That is cool (no pun intended). It sounds like it would be theoretically possible for humans to live in such a world. We would “just” need undersea bases that are bigger and more self-sufficient than a nuclear submarine plus a fleet of submarines to mine for resources and catch food. I am not sure what the menu would consist of exactly but it would have to be mostly seafood that can live in really cold water plus whatever can be grown under artificial and very space-limited conditions. Again, this is just in theory. Living that way would probably be horrible in practice but I assumed that it was all but impossible. That seems easier than a manned Mars base.
What about underground bases? If you dig a deep enough hole, the ground itself warms up due to heat radiating from the Earth’s mantle and core. How deep would you need to go on average before you achieve comfortable and stable temperatures in such an environment?
Frozen sea men.
Sushi! 
I don’t know how long the ocean’s marine lifecycle would last, but there’s no sunlight in the deep ocean, and of the various mechanisms that sustain deep sea communities in the absence of sunlight, chemosynthesis would presumably still be operative for quite some time.
How about submarine sandwiches?
We’d need as much help as we could get, so a first step would be to bury the hatchet with the anemones.
It would eventually be -400F.
You might want to read this recent thread:
Without the Sun Would All Life on Earth Really End?
We had a discussion about this several years ago; I was wondering if you could eat the tube worms and other organisms that obtain nutrients from the chemosynthetic bacteria around the “black smokers.” If I recall (can’t find the thread at the moment), the sulfur components make them likely poisonous to humans.
If I only have a short time to live I hope the answer is pussy, but I’m just being cute.
I’m surprised by these claims that hint we may be able to survive a while from a complete change in orbit or the extinction of the sun when just the slightest tilt away from ol sol turns half the globe into a frozen mess that’s survivable but miserable.
But I must confess I’m having a self pity party. It was in the upper 40’s and mid 50’s and dry here all through December so I hesitated to store my Vette. I went down to New Orleans for NYE to come home to it buried in 9 inches of snow. :eek::mad::smack:
I can’t imagine what it would be like if it were -400. Hopefully I’d be dead or at least still drunk in the FQ!
Depending on our ingenuity, it could be days or eons.
The article mentions that deep water would stay liquid but how quickly would the temperature decrease 1 or more kilometers underground?
Yes, yes, make your Fallout 4 and Dr. Strangelove references now.
As for food:
We’d eat algae/mushrooms* and organisms that feed on algae/mushrooms I suppose. We’d need to find an energy-efficient way to transform algae into 2000 kilocalories/person and the essential nutrients out bodies can’t make.
With nuclear power, we could keep heated for a long while, especially if we found a way to keep machinery warm enough to mine more nuclear material and perhaps coal.
Whether food or light, it’s all energy. If we find ways to extract and conserve enough energy, we can live.
Might it help to release lots of greenhouse gases to conserve more of the earth’s heat? Might we save the species with pollution?
*Whatever can feed on just about anything and needs little light.
The limiting factor will be the amount of primary foodstuff we could grow using geothermal power alone. Geothermal power could power lighted growrooms, which could produce crops to feed humans directly. Note that mushrooms and other fungi are secondary producers of edible protein, and live off waste - if you want to grow them you need a primary producer as well. The same goes for animal life; we could keep a population of shellfish or other animals to eat material that we can’t eat directly, but there must be some photosynthetic or chemosynthetic primary food source.
Iceland produces about 700 MW of geothermal power; convert that into light for growrooms and you’d get about fifty hectares of growing space - enough to support a small population. This may be no more tha a few hundred, or as many as tens of thousands, depending on whether an efficient closed ecological life-support system could be established.
Exploiting all the Earth’s geothermal vents and geothermal power sources might allow as many as a million people to live on the planet for an indeterminate period - not many compared to today’s population, and they’d still need other resources like trace elements and rare earths for any technology they might want to build - but the mines would mostly be under 4km of ice, so there would be severe problems acquiring new material.
Bolding mine.
**eburacum45 **really nailed it.
There’s a big difference between “we” as in current society versus “we” as in a comparative handful of *de facto *colonists.
And between “survive” as in “live out our ordinary prosaic lives in the midst of a plentiful natural ecosystem” versus “everyone is locked in a continual struggle to maintain our little band and its totally artificial life support systems against failures, continuous wearing out, and an ever-encroaching utterly hostile and unsurvivable natural environment.”
And between “a while” as in “millennia upon millennia into the indefinite future” versus “your young kids might live to reproduce, but their kids mostly won’t.”
The very tech that could, given enough warning, be deployed to keep a few hundred thousand humans alive on the otherwise dead Earth would be far more complex than that few humans could maintain into the indefinite future.
Posit us having a cohort of intelligent self-replicating robots that “live” on electricity and we’d stand a chance. Current or near future tech? Forget it, at least over a span of, say, 75+ years.