Seems to me a volcanic area would have a tremendous heat gradient, from "way hotter than boiling" dropping quickly to "around absolute zero," and the area of Miami Beach weather would be too narrow for much to live in.

Can you use an artificial power source (see the story "A Pail of Air")?

How about putting it under water? It takes a while for oceans to freeze (way more than 12 hours -- consider that some open-water areas get almost no sun throughout the winter; and if they freeze over, they've just made themselves a layer of insulation). If you need it long-term, you could have underwater geothermal vents, warm enough to melt some particular area, if you can keep pressure from building up so that water no longer comes out of the pipe. You'd certainly have a lot of insulation (ice) to keep the absolute-zero away.

As to the original question, the surface of our Earth would become so cold as to be uninhabitable by animal or plant life except inside artificial habitats.

Some forms of underwater life might survive for a long time near volcanic vents.

As for the oceans freezing? Keep in mind, there is a big differance between the Earth facing away from the sun, and there being no sun at all. If the Earth were essentially exposed to the cold of space, I could easily see the oceans freezing up in twelve hours. At least to a very great depth.

Some forms of bacteria have been shown to be able to survive the vacum of space, so it is possible that something might survive without artificial help if the sun went away. Of course, this all depends very much on exactly how the sun goes away.

You probably already know this, but for the sake of realism in your story, keep in mind that if the sun did disappear, we wouldn't lose our "gravitational rope" for about 8 minutes.

"Let's say this particular planet is fairly volcanic. Would that matter at all?"

Questions like this really boil down to how much of our heat is produced by the sun, and how much is geothermal? There have got to be rough figures on that available. At any rate, I'd agree that you'd have to dig pretty deep to have access to geothermal heat. And you'd have to get there before the oceans froze--we don't have the technology to dig that far.

Also, I recommend the book _What If The Moon Didn't Exist?_ by Neil F. Comins. It looks at some similar questions to yours, and may help discover consequences you may not have considered.

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If the Earth were essentially exposed to the cold of space, I could easily see the oceans freezing up in twelve hours.

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You probably already know this, but for the sake of realism in your story, keep in mind that if the sun did disappear, we wouldn't lose our "gravitational rope" for about 8 minutes.

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You probably already know this, but for the sake of realism in your story, keep in mind that if the sun did disappear, we wouldn't lose our "gravitational rope" for about 8 minutes.

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As it rotates on the spit the warmth of the fire continuously bakes the roast as it rotates in front of that fire. So that the surface is continually rewarmed. The backside of the roast does not freeze because it is being indirectly heated by the fire and it is constantly rotating back into the heat.

Now drop that roast into negative 170 degrees uniformly. In a few seconds it will freeze solid. If sun vanished the effect would be the same as immersing the earth into liquid nitrogen. Aboslute zero on all surfaces uniformally. The atmosphere would collapse and many gases like oxygen would liquify.

The rate of freezing rises exponentially as the world grows colder.

My curt answer would be that if general relativity is correct, then gravity propagates at c. However, as we all know general relativity is not complete (it doesn't incorporate quantum mechanics well, for one), so you are right. There is no reputable experimental measure of light speed. If anyone's interested, I stumbled on this article, which goes into more detail: http://math.ucr.edu/home/baez/physics/Relativity/GR/grav_speed.html.

As for the original question, I'd like to point scm288 to the all-knowing Google: http://answers.google.com/answers/threadview?id=29757. The replies show, to me anyway, that there is enought wiggle room in our knowledge of geothermal energy that you could keep it warm enough for whatever purpose in your novel.

EDIT: The URL opens with an extra period at the end that I can seem to get rid of. Delete it and the link should work.

If the sun, meaning Sol, were to disappear, then the vast majority of life in the galaxy would be completely unaffected, including the vast majority of intelligent life. There would be some pretty darn confused astronomers, and humans wouldn't be too happy, but that's about all that would happen.

One can assume that a small number of humans would survive, along with samples of any other terrestrial species they particularly cared to preserve. The main obsticle to human survival would be other human activity. Fortunately, while the oceans wouldn't freeze overnight or anything like that, most humans would be dead inside of six months, and only those with considerable technical resources and the discipline to use them correctly would be alive within a couple of years. One would hope that people in that situation would have better things to do than try and kill each other, but humans are fickle. Besides, if everyone were cooperating, it would only take a few to doom them all. That would happen sooner or later.

As for the natural environment, Earth's surface is heated by the sun's radience. However, there is also an enourmous amount of energy already contained in the planet itself. Because the exact mass of the planet and its moon isn't known, it would be difficult to give a precise figure, but it's a lot. A lot of this is simply heat both left over from various sources and generated by some ongoing processes (radioactive decay, incidental muon induced fusion, and of course the tidal effect of the unusually large moon). It's slowly leaking through the rather effective insulation of the crust all the time, and several ecologies of various levels of complexity on this planet actually derive all their energy from these geothermal sources. Some of the more complex ones would probably be badly disrupted by the destruction of all other life, but not necessarily. They could very well benefit from the elimination of all competition, after all.

Even if the ecologies collapsed entirely, the basic archaeotica at the base would survive.

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If sun vanished the effect would be the same as immersing the earth into liquid nitrogen.

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When we say that we feel cold, its a subjective feeling that we've invented ourselves. It's not actually cold. It's really pretty warm. We're just used to calling anything less than our body temparature cold. The total lack of heat is what is called absolute zero. This temparature has got nothing to do with 0 degrees centigrade which is the temperature at which water freezes. Absolute zero is minus 273 degrees centigrade. I guess that if the sun was removed totally, then we'd get pretty close to that. I dont know how much temperature your volcanic planet would still spew out if the sun were removed though.
The reason that the sea doesn't freeze at night time is that the sun is still present, its just around the other side of the earth. It's still warming the atmosphere indirectly.

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The reason that the sea doesn't freeze at night time is that the sun is still present, its just around the other side of the earth. It's still warming the atmosphere indirectly.

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you were doing pretty well.

In a vacuum, the only way heat is transferred is through radiation. Convection requires a circulating medium to transfer heat, and conduction requires contact with an object. Neither of these conditions applies to space.

Therefore, in the vacuum of space an object illuminated by the sun gets hot on the side facing the sun due to radiant energy.

The side facing away from the sun recieves no radiant energy. Therefore, without any other source of heat, it will cool down toward absolute zero.

How fast will it cool down? Assuming no other source of heat, it will cool down based on how fast it radiates heat away. That depends on its temperature and on the extent to which it is insulated.

As it turns out, atmospheres act as insulators. So for example, six hours after a sunset on the moon, the temperature will have dropped considerably more than the temperature on Earth drops six hours after sunset.

To believe that the presence of the sun on the other side of the Earth is what keeps the night side from freezing requires believing that either convection or conduction of heat from the day side is of sufficient magnitude as to forestall a large temperature drop.

First, let's rule out convection. The only things that could plausibly transfer heat to the dark side of the earth by convection are the water in the oceans and the air in the atmosphere.

At the equator, the rotational speed of the earth is close to a thousand miles per hour. Thus, six hours after sunset on an equinox day, a point at the equator is approximately six thousand miles from any point on earth receiving sunlight. Any heat it recieves through convection from the day side would have to travel six thousand miles. Even if we're generous and allow the convection six hours to travel, and ignore the fact that such travel would be on the night side and therefore losing heat the whole time, it would require currents or winds of 1000 miles per hour to transfer heat from the day side to a point in the middle of the night side. Feel free to do research on your own, but I suggest you take my word for it: that ain't happening.

So we are left with conduction. Water is a fairly good conductor of heat, so could conduction of heat through the oceans from the day side explain why the oceans don't freeze on the night side?

No. If that were the case, then bodies of water unconnected to the oceans would freeze overnight. Swimming pools, the Great Salt Lake, the Dead Sea. More mundanely, if water was a good enough heat conductor to do that, then you wouldn't ever notice warm or cold pockets of water, because the heat would be distributed too evenly.

Could the ground be conducting enough heat around the world? Go outside on a sunny day and feel a patch of ground that has been in the sun for a while. Then feel a patch of ground that has been in the shade a while. Do they feel about the same temperature? If not, then the ground is not a good enough conductor of heat to even out the temperature.

What keeps the night side of the earth's temperature from dropping drastically is insulation, not the sun shining on the day side. Therefore, if the sun disappeared, the oceans would not freeze solid in twelve hours.

Earth would continue rotating on its axis at about the same rate it does now. Although "day" would have little meaning, the rotational period could be measured based on when a particular star rose above the horizon, and that period would be about 24 hours. It would be slightly different from a sun-measured day, because one component of that was the Earth's orbit around the sun.

> It would lose its normal orbit due to the
> sun's disappearance, right?

Assuming the sun wasn't replaced with a dark body with the same mass, then the center of Mass of the Earth-Moon combo would move in essentially a straight line from the moment the sun disappeared, at the speed of about eight miles per second.

> Would it be attracted to orbit Jupiter or
> would it just spin off until it got
> trapped into some other star's gravity
> well?

Unless Jupiter and the Earth happened to be at the right points in their orbits such that their vectors of travel after the sun's disappearance would get very close to each other, Jupiter capturing Earth is very unlikely.

As for being captured by another star, it's possible, after a very long time. Consider that at 8 miles per second, it would take over 1300 years to travel one light year. The only stars that could possibly capture the Earth would be those with a declination of about 0 degrees. The nearest star within one degree of 0 is Ross 128 (FI Virginis), which is a bit over ten light years away, or 13000 years of travel for the earth. And there's only a 1/180 chance Earth would head within a degree of that star.

Even if Earth passes close to a star, it's probably going to just swing around the star and continue on its way. Something other than the star's gravity would have to interact with Earth to slow it down enough for capture.

I'm going to nitpick myself and say that this is incorrect. While eight miles per second is the speed at which it would move relative to the last position of the sun, the sun isn't there any more. The Earth-Moon system would actually begin orbiting the galactic center at approximately the same speed the sun was, with minor variation due to its speed and angle in orbit around the sun at the moment the sun disappeared. That speed is about 135 miles per second.

Does the Earth inherit its gravity from the sun? I don't see how this is so, because if it were true, then the atmosphere wouldn't form about the Earth, it would form about the sun.

It's wouldn't "strip" the Earth of its atmosphere, but as the temperature fell low enough, gasses in the atmosphere would turn to liquid or solid and fall as "rain" or "snow." For example, carbon dioxide might begin to turn to dry ice at -78 degrees Celsius (195 degrees Kelvin.) We might get liquid oxygen rain at 90 degrees Kelvin, and nitrogen rain at 77 degrees. Since nitrogen makes up over three quarters of our atmosphere, there wouldn't be much left after that.

There is basically no chance whatsoever that we could come any closer to Jupiter, or any of the other planets with regular orbits. Consider that the ones further out than us all have higher orbital velocities and the ones closer in all have lower orbital velocities. Mercury has a bit of an odd-ball orbit, it might be able to catch us if the sun disappeared at just the right time (though that exact time doesn't exactly come around every year or even every thousand years). Some of the outer planets might catch Pluto and sling it back towards us eventually. But those are long-shots at enourmous odds.

Also, it should be noted that the oceans contain a lot more heat than the atmosphere, and more is being added on a pretty constant basis (the "constant" here is actually more of a summation of "half-life" curves, but all of them have billion year scales, hence "pretty constant"). The seas will be capped inside a year or two. But ice is a very good insulator. And once the oceans are capped, atmospheric weather as we understand it will essentially cease, reducing convection transfer to almost nothing. That means that the atmosphere will be acting almost entirely as an insulator too. It will contract and condense over time, rain wouldn't be likely, it would be more like accumulating dew from a mist.

But nothing still living would care, under the ice there would be livable contitions for a good long time. For members of the Archaea, at any rate (as for what "Archeotica" means, I'm not going to explain it, it's just too silly on too many levels).