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

[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.

 

[CCWilson]

Let me rekindle this discussion with a further question. We have the Earth slung out of its orbit by a passing black hole of 3 solar masses. By the way, this would probably - according to Dr Stupid's gravity simulator - disrupt the entire solar system, tossing planets and even the Sun hither and yon, depending on how close to the Sun it passes. Although the moon is not included in the simulator, I suspect that it would also be thrown asunder, with the possibility of even crashing into the Earth, which would introduce complications that I don't think the story needs. Another possibility is that the black star would sling us into the Sun, which would be dramatic but a novel-killer.

My question is this: Since the black hole would not pass too close to the Earth, it would probably have no more direct tidal effects than the moon does. But the slingshot effect - the Earth going in one direction, then suddenly whipped in another direction - it seems to me that an observer on Earth would feel like he was on a carnival ride and experience a lot of centrifugal/centripetal force. Agree? And it seems obvious that the change in direction would also cause massive tidal waves. Am I right about that?

 

[mjacobsca]

LONG before people would feel any sort of "carnival-ride" forces, the Earth would experience tremendous tidal effects from the 3 solar mass black hole, causing ruptures in tectonic plates and mass devastation. One could envision Yosemite's super-volcanoe and other volcanoes erupting all at once, high tides that travel miles inland, and the release of a ton of carbon dioxide into the atmosphere (hey'll, we'll need that warmth as we travel out of the solar system).

If the BH got close enough to syphon atmosphere or compete with the gravity of the Earth itself to change our gravitational field, the Earth would be in serious trouble. You might not want to have it come that close, or your story would be over before it started.

One interesting effect of a BH, for which I don't know the math, is that it would probably disrupt satellites in orbit enough to destroy world-wide communication. A cool possibility would be most of the "good countries" satellites being sent out of orbit or crashing into the Earth, but an enemy's satellites somehow survived, giving the enemy a tremendous advantage over the "good" side. Spy operations would have to return to basics for the duration of the novel.

 

[Evo]

LONG before people would feel any sort of "carnival-ride" forces, the Earth would experience tremendous tidal effects from the 3 solar mass black hole, causing ruptures in tectonic plates and mass devastation. One could envision Yosemite's super-volcanoe and other volcanoes erupting all at once, high tides that travel miles inland, and the release of a ton of carbon dioxide into the atmosphere (hey'll, we'll need that warmth as we travel out of the solar system).

If the BH got close enough to syphon atmosphere or compete with the gravity of the Earth itself to change our gravitational field, the Earth would be in serious trouble. You might not want to have it come that close, or your story would be over before it started.

One interesting effect of a BH, for which I don't know the math, is that it would probably disrupt satellites in orbit enough to destroy world-wide communication. A cool possibility would be most of the "good countries" satellites being sent out of orbit or crashing into the Earth, but an enemy's satellites somehow survived, giving the enemy a tremendous advantage over the "good" side. Spy operations would have to return to basics for the duration of the novel.

What about the lack of a sun? Might put a damper on things...just saying.

 

[CCWilson]

I'm not so sure about huge tidal and tectonic effects from the gravitational effects of the black hole. The Sun, for example, has much less tidal effect than the moon, because the distance from one side of the Earth to the other is a significant part of the distance from Earth to moon, but a very small part of the distance from Earth to Sun. So unless the black hole passed fairly close, it would affect all parts of the Earth more or less similarly. That's why I think the effect due to the Earth's change in direction would be the significant factor.

 

[Evo]

I'm not so sure about huge tidal and tectonic effects from the gravitational effects of the black hole. The Sun, for example, has much less tidal effect than the moon, because the distance from one side of the Earth to the other is a significant part of the distance from Earth to moon, but a very small part of the distance from Earth to Sun. So unless the black hole passed fairly close, it would affect all parts of the Earth more or less similarly. That's why I think the effect due to the Earth's change in direction would be the significant factor.

Are you saying that the Earth would remain in it's exisiting orbit around the sun?

 

[CCWilson]

No. The premise of the story is that the Earth is slung out of solar orbit and loses its energy source, and with around five years lead time, a number of huge underground cities are built using mostly geothermal energy to generate electricity and keep our species going.

 

[mfb]

Tidal effects scale with M/r^3, orbital influence scales with M/r^2 - if we fix the orbital influence (enough to kick Earth out of the solar system), a bigger mass reduces tidal effects. We know that our sun influences the path of Earth in a significant way (we orbit it), so a black hole with 3 solar masses in a distance of about 1 AU (and a velocity of the order of 30km/s) could kick us out, while its tidal influence is smaller than the moon's. Completely negligible compared to the influence on the orbit.

 

[CCWilson]

mfb, what about the effects of the change in direction on the Earth, both on an observer sitting in a lawn chair and on the tides? In other words, if you're jogging along holding a pail of water and a cat carrier and then make a sharp right turn, the water sloshes up on the outside of the pail, and the cat is thrown toward the side of the carrier to the outside of your turn. I also wonder whether there would be geological effects that would predispose to earthquakes. Obviously the magnitude of those effects would depend on whether the Earth was whipsawed around the black hole or simply pulled into a slightly different path.

 

[mfb]

Those are all tidal effects. If the moon does not tilt your cat, a black hole in 1 AU distance would not do that either. Similar with earthquakes.

If the black hole comes closer, it can have significant tidal effects, but they are not required to remove Earth from its orbit.

 

[CCWilson]

Beg to differ. Tidal effects occur because of the differential gravitational forces of the moon on the oceans on the near side (greater) vs the oceans on the far side (lesser). That's why the moon has more tidal effect than the sun - because the diameter of the Earth - 13,000 km - is a significant percentage of the distance from moon to Earth (400,000 km) and a very small percentage of the distance from Sun to Earth (150,000,000 km) - so the difference in gravitational attraction from near to far side is greater for the moon, even though the Sun is much more massive than the moon.

But we're not talking here about a difference in gravitational attraction between two sides of the Earth. Our planet is being slung out of its orbit not by tidal effects but by the gravitational attraction of the black hole to the Earth overall. I agree that the tidal effects wouldn't necessarily be large, but the centrifugal/centripetal force from the change in direction would. I suspect that earthquake generating effects would be small, but the water in our oceans would, I think, be sloshed around, resulting in high tides, and I'll bet a human would feel those carnival-ride effects.

 

[mfb]

Our planet is being slung out of its orbit not by tidal effects but by the gravitational attraction of the black hole to the Earth overall.

You cannot feel an homogeneous gravitational field - one of the fundamental rules in General Relativity. You can feel the different gravitational attraction at different points, and those are tidal effects. Without those tidal effects, Earth could accelerate with whatever value in any coordinates - it does not matter, as all objects get the same acceleration.

 

[CCWilson]

I may be coming around to your opinion on this - but it's a brain twister. Thinking about the Earth in relation to the solar system, if the Earth got whipped around slingshot fashion, you'd think an observer on Earth would feel the change in direction. But I shouldn't think of the Earth in relation to the solar system, but more in relation to spacetime. The black hole would massively deform spacetime, and the Earth and everything on it would simply be along for the ride, floating along where the gravitational forces tell it to go. The only gravitational effects we would feel would be those of the Earth, as usual.

I'm still not sure of this, however. Bears further contemplation, especially since the gravitational fields are changing.

 

[onomatomanic]

I'm still not sure of this, however. Bears further contemplation, especially since the gravitational fields are changing.

The key concept here is "being in free-fall". You do not feel any gravitational forces with respect to which you are simply falling. That includes the Sun and the Moon, and, for someone in orbit, the Earth as well. Analogously, it includes the Black Hole. The only reason we do feel the gravitational force of Earth is that, not being in orbit, we aren't able to fall - because the pesky surface gets in the way, sooner or later (hopefully sooner, for practical reasons).

 

[Evo]

I may be coming around to your opinion on this - but it's a brain twister. Thinking about the Earth in relation to the solar system, if the Earth got whipped around slingshot fashion, you'd think an observer on Earth would feel the change in direction. But I shouldn't think of the Earth in relation to the solar system, but more in relation to spacetime. The black hole would massively deform spacetime, and the Earth and everything on it would simply be along for the ride, floating along where the gravitational forces tell it to go. The only gravitational effects we would feel would be those of the Earth, as usual.

I'm still not sure of this, however. Bears further contemplation, especially since the gravitational fields are changing.

How about the fact that life could not exist without the sun, no matter how far down you dig? How do you grow crops? How do you raise lifestock? How do you create an environment for humans? Waste disposal? Potable water? Breathable air? I assume the seas and all sea life were abandoned. Is this some silly Noah's Ark scenario?

Animals? Plants? How many humans did you plan to take underground out of all of the billions?

Medicine? Hospitals and medical care?

Even assuming some life is possible, what's the quality of life and how do you accomplish it?

 

[CCWilson]

Evo, that's what the novel is all about. I've worked out most of the issues you raise. If you're interested, scan this thread, unless its silliness puts you off your feed.

 

[mfb]

How about the fact that life could not exist without the sun, no matter how far down you dig?

What about 3km to find Desulforudis audaxviator?
Well, and an artificial environment might work as well.

 

[sadben]

I think that an extra solar object of sufficient mass is the best bet: Aliens are a silly way of implementing "Deus ex machina"

 

[JohnRC]

If you can afford to have a lead-in time of about 7-10 years while the Earth was slowly being ejected from the solar system, then the scenario that would least affect humanity would be a fly-by of some sort (from an object within or outside the solar system) that gently accelerated Earth into a rather more eccentric orbit, leading to gravitational whip effect ejecting it from the solar system when its path took it close to Jupiter on the first orbital pass-by.

This scenario would have the additional advantage that you would be free to do whatever you wanted with the moon -- destroy it, remove it, or leave it.

 

[FalseVaccum89]

Not without technology. There are no objects of sufficient mass to capture the black hole.

Actually, this is not accurate; unless one is near the event horizon of a black hole, one experiences the exact same level of spacetime curvature (thus the same level of gravitaitonal force) as with a normal body of comparable mass. A black hole should have the *exact* same effect as a star with comparable mass, unless it were to collide with something.

 

[Drakkith]

Actually, this is not accurate; unless one is near the event horizon of a black hole, one experiences the exact same level of spacetime curvature (thus the same level of gravitaitonal force) as with a normal body of comparable mass. A black hole should have the *exact* same effect as a star with comparable mass, unless it were to collide with something.

He's talking about our Sun capturing the black holes in an orbit. Since the Sun is much less massive than any known black hole, such a thing is not possible.