Geo-nuclear reactor versus red dwarf

[chrismb]

I am of the understanding that the earth's core is still molten because of nuclear decay of fissioning elements that formed the earth long ago.

(If it is otherwise, then please tell me why the earth's core is still molten. I have heard an idea about it getting heat from neutrinos, but that doesn't explain why mars has gone cold.)

My question is whether the earth will become uninhabitable due to inflation of the sun (all else being equal here on earth) before the earth's fissionable isotopes cool off.

I am guessing that given U238's half life of 4 billion years, then a significant internal cooling will be around the same timescale as the sun going red dwarf, so the earth's core solidifying will be the least of any earth resident's problems.

[Skipjack]

Actually earth will get a lot hotter, not colder...
The sun will get a lot hotter sooner than we will like (loong before it expands).

[pfrit]

Actually earth will get a lot hotter, not colder...
The sun will get a lot hotter sooner than we will like (loong before it expands).

More importantly, the cooler the earth's core gets, the less vocanic activity there will be. Less water and CO2 will be returned to the atmosphere and the decrease will occur at an ever quickening pace. The earth will become cooler as time passes. Maybe 1-2 Billion years before it becomes uninhabitable by the current crop of humans. Either way, We are not going to live to see it.

[KitemanSA]

I am guessing that given U238's half life of 4 billion years, then a significant internal cooling will be around the same timescale as the sun going red dwarf, so the earth's core solidifying will be the least of any earth resident's problems.

I do believe it goes red giant before winding up white dwarf. Red dwarfs start out small and stay there.

[Torulf2]

Earth will be unhabitable in 500 million years if not the thermal properties is changed, greenhouse gases and/or the albedo.

The difference inn inner heat of mars and earth is due to the relation between total heat production (radioactivity) and total heat radiation. A large planet have smaller surface relative to the volume compared to a small planet and radiates relatively less heat than a small one.

[Skipjack]

Most people believe that the sun will not become a problem before a few billion years have passed. According to Phil Plait, this is not true. It will get hotter long before that. I cant find his original article anymore (I tried Google, yes), but in his Blog, he once talked about it. I might recall it wrong, but the process was supposed to start some 500 million years from now (if I remember correctly, it might be longer, sorry, bad memory for numbers).
AFAIK, that would be long before the earths core cools down. So it will get warmer, before it would get colder, I am affraid.

[D Tibbets]

Uranium heats the core. Also an isotope of potassium (?) is a major contributor. The Sun is continually getting hotter as it ages and will possibly evaporate all of the oceans well before it goes off the main sequence and becomes a red giant. I recall ~ 500-1000 million years will make the Earth uninhabitable for us.

I don't know how fast the Earth's core will cool and how this will effect mantle thickness, plate tecktonics, and vulcanism. Perhaps more important is how much weaker the Earth's magnetic field will become as the dynamo winds down, decreasing protection from solar radiation.

Dan Tibbets

[CaptainBeowulf]

So, if we figure out how to move the planet with a heim gravity drive or woodward inertial drive, we can stay in the habitable zone (might have to put another drive on Mars and fly it out of the way, though). How do we deal with the core cooling? Anyone got any ideas about injecting more uranium, or whatever else?

[JLawson]

So, if we figure out how to move the planet with a heim gravity drive or woodward inertial drive, we can stay in the habitable zone (might have to put another drive on Mars and fly it out of the way, though). How do we deal with the core cooling? Anyone got any ideas about injecting more uranium, or whatever else?

I'm going to be lazy, and leave that problem for the next shift after they've moved Mars out of the way.

And they'd better be more careful with the gravity pliers this time! One Olympus Mons is quite enough!

[KitemanSA]

I hope they got the calibration better than they did on Minerva. Eros, Pallas, and the rest of those rocks just aren't quite the same.

[clonan]

So, if we figure out how to move the planet with a heim gravity drive or woodward inertial drive, we can stay in the habitable zone (might have to put another drive on Mars and fly it out of the way, though). How do we deal with the core cooling? Anyone got any ideas about injecting more uranium, or whatever else?

But then you have to change ALL the calanders! personally I am used to 365 days.

Instead why not just build a solar shade...Let most of the light through, reflect enough to keep the temp stable and transmit some down to the planet for power...

[IntLibber]

Actually earth will get a lot hotter, not colder...
The sun will get a lot hotter sooner than we will like (loong before it expands).

Actually, it will get colder first, as the trace remaining CO2 gets locked up in coral limestones, creating a permanent global ice house effect until the sun swells up. Permanent ice house is expected within only a few million years, even if we burn all the fossil fuels to compensate. We are overdue for the next ice age.

[Skipjack]

Actually, it will get colder first, as the trace remaining CO2 gets locked up in coral limestones, creating a permanent global ice house effect until the sun swells up. Permanent ice house is expected within only a few million years, even if we burn all the fossil fuels to compensate. We are overdue for the next ice age.

Got any reference regarding that? I would assume an ice age, yes, but not a "snowball earth" situation like we had once (and only once IIRC) in the history of the planet.
Also, the sun will heat up quite signifficantly, long before the expansion process starts. It will be enough to make the earth mostly uninhabitable.

[djolds1]

So, if we figure out how to move the planet with a heim gravity drive or woodward inertial drive, we can stay in the habitable zone (might have to put another drive on Mars and fly it out of the way, though). How do we deal with the core cooling? Anyone got any ideas about injecting more uranium, or whatever else?

But then you have to change ALL the calanders! personally I am used to 365 days.

Instead why not just build a solar shade...Let most of the light through, reflect enough to keep the temp stable and transmit some down to the planet for power...

Build a supramundane habitat around Saturn - 1g surface gravity. Or move the planets with mass stream technology.

[IntLibber]

Actually, it will get colder first, as the trace remaining CO2 gets locked up in coral limestones, creating a permanent global ice house effect until the sun swells up. Permanent ice house is expected within only a few million years, even if we burn all the fossil fuels to compensate. We are overdue for the next ice age.

Got any reference regarding that? I would assume an ice age, yes, but not a "snowball earth" situation like we had once (and only once IIRC) in the history of the planet.
Also, the sun will heat up quite signifficantly, long before the expansion process starts. It will be enough to make the earth mostly uninhabitable.

The past 12 million years of 100k year ice ages interspersed with short interglacials is an effect of this sequestration effect.

CO2's greenhouse capabilities are most significant at lower concentrations. The 260 parts per million that existed during the Little Ice Age were the bare minimum to support photosynthesis outside of equatorial areas. During main Ice Ages, the CO2 level drops to between 200-240 ppm or lower.

The higher CO2 levels go, warming effects drop off on a log scale of diminishing returns (hence, Arrhenius projected warming of between 0.5-1.0 C per CO2 doubling).

While land and swamp based photosynthesis stored CO2 only gets sequestered as coal fossil fuel deposits, which is easily re-released by volcanic intrusion into coal seams, or forest fire ignition of exposed seams, coral based sequestration of CO2 (which makes Calcium Carbonate, i.e. limestone) is a much more permanent sequestration of carbon, because while metamorphic tectonic subduction of plankton becomes oil, subduction of limestone metamorphs into marble (though usually the limestone remains as part of the continental rafts that float over subducted basaltic plates).

When the cold gets too cold for animal life on land to produce CO2, coral will sequester CO2, and without volcanism to return it to the atmosphere (which wont happen since most limestone remains on continental rafts and is not subducted), we are headed for Ice House.

See "Terraforming: Engineering Terrestrial Environments" by Martyn Fogg