The Earth is Dying! What Does That Look Like?

I don't see why it atmosphere would be colder as gravity would be unchanged and that's what keeps the atmosphere in place. The main effect would be loss of the Earth's magnetic field which would lead to increased exposure to radiation.

Among other things, the Earth would be rather level. The mountains would have worn down, and there wouldn't have been any new ones for a rather long time. By that time the Moon might have moved away, so the tides would be less. Will the Sun have gone nova yet? It'll be close. Will the Earth be a one-face?

What do you want the Earth to look llike?

I would think that humans will be long dead before what you described will happen what you are describing would result in major ice age.

Unless an odd lot manages to survive by hiding in a hole in the ground, and that is entirely possible an artificial environment underground but technology will have to make some major leaps between now and then.

waylander said:

I don't see why it atmosphere would be colder as gravity would be unchanged and that's what keeps the atmosphere in place. The main effect would be loss of the Earth's magnetic field which would lead to increased exposure to radiation.

Click to expand...

Which would also lead to erosion of the atmosphere from the effects of solar wind. That's what is thought to have happened on Mars, long ago, when it cooled and lost a significant magnetic field.

But without that magnetic protection from the bombardment of charged particles from the sun, the loss of atmosphere would be almost a secondary problem; humans, and probably all other surface organic life would have been fried sooner.

caw

As far as I know, the Earth's core cooling would not affect the surface temperature of the Earth. We get most of our warmth from the sun (...I think; feel free to correct me, anyone who knows better), so there's no need for protective clothing against cold.

Edit: I just did some back-of-the-envelope calculations based on this article's weird claim about boiling 200 cups of water for each person on Earth every hour, and -- unless I've borked my math, which is entirely possible -- the core delivers about 0.22 Watts of energy to each square meter of the planet. Thus, given an electric blanket might deliver 200 W of power to warm up a few square meters by ten degrees, I really doubt the core is helping keep us warm.

As others have noted, a cold core wouldn't immediately affect the air density, so no need for pressure suits or oxygen masks either (where would the oxygen come from, anyway, if the whole planet is lacking air?) although Blacbird's point about the solar radiation stripping away the atmosphere is a good one. Earth is bigger however; I would think it would retain its atmosphere a little better than Mars did.

As for what temperature the core would have to cool to before we start to suffer for it, scientists think the magnetic field of the Earth is due to the circulation of its molten iron-nickel core, so you just need the core to get cool enough to stop moving easily. The melting temperature of iron is a bit over 1500C, but that's at atmospheric pressure. At higher pressure, the melting point tends to go up in temperature.

Radiation would be the biggest issue, for sure. I think everything else would be gradual changes.

The Sun isn't expected to go nova, but it will expand into a red giant and overheat or perhaps even swallow the Earth, but that will be in billions of years.

I'm wondering how long it would take for the core to cool so it would no longer generate Earth's magnetic field. This would surely be many millions of years. To me it gets sketchy to say what "human" will be by then, but whatever.

jjdebenedictis said:

As far as I know, the Earth's core cooling would not affect the surface temperature of the Earth. We get most of our warmth from the sun (...I think; feel free to correct me, anyone who knows better), so there's no need for protective clothing against cold.

Edit: I just did some back-of-the-envelope calculations based on this article's weird claim about boiling 200 cups of water for each person on Earth every hour, and -- unless I've borked my math, which is entirely possible -- the core delivers about 0.22 Watts of energy to each square meter of the planet. Thus, given an electric blanket might deliver 200 W of power to warm up a few square meters by ten degrees, I really doubt the core is helping keep us warm.

Click to expand...

For comparison, the Sun shining directly overhead gives something like 1200 to 1500 watts per square meter. Of course that's only for about a third of the day, but that's still orders of magnitude greater than the Earth's internal heat.

benbradley said:

The Sun isn't expected to go nova, but it will expand into a red giant and overheat or perhaps even swallow the Earth, but that will be in billions of years.

I'm wondering how long it would take for the core to cool so it would no longer generate Earth's magnetic field. This would surely be many millions of years.

Click to expand...

Given the known rate of the slowing of the planet's rotation, and the known rate of core cooling, we don't need to worry about either of these things. The sun will bloat into its red-giant phase long before that. This is the way the world ends: not with a bang, but with a hot whimper.

caw

Lhowling said:

That's a beautiful line.

Click to expand...

It might be more like a choked squeak. I'm not planning to be around to find out.

caw

I think this is based on some hypotheses that the Earth's magnetic field deflects solar wind and allows us to retain a relatively thick atmosphere. Proponents of this idea claim that Mars lost its atmosphere and oceans after it became tectonically dead and lost its magnetic field for this reason. It's an alternative to the idea that planetary mass alone is what allows a planet to hold onto its atmosphere at a given distance from the sun.

Talking to my husband, though (he teaches astronomy at a college and took a number of planetary and atmospheric sciences classes in grad school), he thinks it's full of holes, because:

1. Mercury has a magnetic field and no atmosphere.
2. Venus has no magnetic field and a very thick atmosphere (runaway greenhouse effect)
3. Mars has no magnetic field and no atmosphere.

He says that the evidence still suggests that size (mass) of a planet probably has more to do with whether or not it has an atmosphere than its magnetic field (though magnetic field may play a role) and that this interacts with the composition of its atmosphere and its distance from the sun. So the idea is possible, but far from definitive at this point.

Probably more importantly, though, is that the Earth's core will be going strong for at least a billion years or so. The thing that's actually likely to drive the extinction of most life on Earth will be the increasing luminosity of the sun. In around 600 million years, the increased luminosity will disrupt the carbon/silicate cycle and decrease the amount of CO2 available for photosynthesis. Plants may well adapt for a while (since there are different photosynthetic pathways, and some can function with lower CO2 levels than others), but there are limits. Once photosynthesis ends, of course, nearly all animal life will go extinct, including any mammals (assuming mammals still exist in 600 million years--that's longer in the future than the Cambrian explosion is in the past). Eventually, the earth will grow warm enough (47 degrees centigrade average temp) for Earth to become a moist greenhouse and for the oceans to evaporate. Microbial life may persist in some locales, but complex, multicellurlar life will eventually be hosed long before the sun goes red giant.

This is still a looooong time in the future, though.

So you can see that the loss of our magnetic field in a billion years or so will be the least of life on Earth's worries. But humans will be long gone by then (if any descendents of ours have survived 600 million years in the future, they won't be anything like us, certainly, any more than we're like Pikaia).

If you want something that could happen in the not too distant future and be sudden and undeniable enough to allow people to live the way we do now more or less until the bitter end (and engage in an orgy of hedonistic debauchery when death is certain), maybe a meteor hitting the Earth would do the trick.

There's a pretty well-developed "People Before the End" subgenre, including On the Beach and Childhood's End.

1) Do any of the characters know why the planet is dying? Is the science important to the story (hard vs soft SF)?

2) Is it critical to the story for it all to happen on a future Earth, or can it be happening to a completely fictional planet and/or society?

In addition to to what Roxxsmom says, it's expected that in about 600 million years all the surface water on Earth will probably have vanished. Not only will the evaporation rate have increased, but the heat of the core is the primary driver of plate tectonics, which is the main engine of the long-term water cycle (water from the surface gets pulled down in subduction zones, later re-emerges through volcanic action). Cooling planet = no more recycling of ocean plates & water = everything dries out permanently. And life on a bone-dry planet is very very hard for the types of organisms that require water.

I highly doubt there will still be humans of any sort around at that time. The average lifespan of a species is shorter by more than an order of magnitude. But there could be other types of people

A point no one has yet mentioned: the heat of the Earth's core is ultimately what drives volcanoes (as well as other geothermal processes). And volcanoes, in turn, emit carbon dioxide. With a cold core, there would be no more volcanic eruptions, so there would be less carbon dioxide in the atmosphere; and, since carbon dioxide is a greenhouse gas, atmospheric temperatures would decrease. You'd get an ice age. The effect would take tens of thousands of years to kick in, however.

I'm afraid I find it hard to imagine how the Earth's core could ever cool suddenly enough to have a dramatic impact over a few years or even a few decades. You'd probably have to posit some phenomenon well outside of what's currently known to science.

If I may make a suggestion: The catastrophe could take the form of a black hole randomly flying through the Solar System and disrupting Earth's orbit. Earth could wind up being flung out into deep interstellar space, far away from the Sun. That's a perfectly possible scenario, albeit highly improbable. The catastrophe would unfold over a period of several years, so it would very much be on a human time-scale. The astronomer Greg Laughlin discusses this sort of possibility in his blog, here. (Though note that he assumes the interloper is an ordinary star, which could be seen thousands of years before it encountered the Solar System; a black hole wouldn't be detectable so long in advance.)

I believe that heat driving plate tectonics (and volcanism) comes primarily from radioactivity in the mantle itself, not from the core., so the driving force for plate tectonics and the cooling of the core can be decoupled. In contrast, heat in the core comes mainly from the exothermic crystallization of molten iron. This heat can only escape to the surface via movement through the mantle, a process speeded up by plate tectonics. Perhaps a time could be imagined when plate tectonics shut down while the core is still molten, and this causes heat to build up in the interior (slower heat loss), which ultimately leads to a geologically sudden "overturn" that could be catastrophic to surface-dwellers. As several folks have pointed out, though, geologically sudden events don't seem very sudden to short-lived humans, and any complete freezing of the Earth's core is billions of years in the future, possibly after the Sun has entered it's stage of burning H in its outer shell (if it does) which will cause much greater problems on Earth than a cold core.

Kevin Nelson said:

A point no one has yet mentioned: the heat of the Earth's core is ultimately what drives volcanoes (as well as other geothermal processes). And volcanoes, in turn, emit carbon dioxide. With a cold core, there would be no more volcanic eruptions, so there would be less carbon dioxide in the atmosphere; and, since carbon dioxide is a greenhouse gas, atmospheric temperatures would decrease. You'd get an ice age. The effect would take tens of thousands of years to kick in, however.

Click to expand...

CO2 is a minor greenhouse gas about one percent as effective as water vapor. A lack of surface would have a much greater cooling effect, but there would be other factors, including the expansion of the Sun and the loss of internal heat.

King Neptune said:

CO2 is a minor greenhouse gas about one percent as effective as water vapor. A lack of surface would have a much greater cooling effect, but there would be other factors, including the expansion of the Sun and the loss of internal heat.

Click to expand...

That doesn't sound right to me, though it might depend on just how you measured effectiveness. Also, there would be a multiplier effect--with less carbon dioxide, the temperature would be lower, which in turn would mean less water vapor in the atmosphere, which would lower temperatures even more.

Kevin Nelson said:

That doesn't sound right to me, though it might depend on just how you measured effectiveness. Also, there would be a multiplier effect--with less carbon dioxide, the temperature would be lower, which in turn would mean less water vapor in the atmosphere, which would lower temperatures even more.

Click to expand...

You might want to research the matter. What appears in the press is not accurate. One should use multiple sources.

We will have to wait a while, but it might turn out that the late stage Earth will be hot, muggy, and dead. There is a good chance that the Earth would have been thoroughly irradiated by the dying Sun before the Sun will swallow the Earth. The irradiation would leave the Earth lifeless in addition to being worn smooth, but we will have to wait to know for sure.

One thing bothering me about this thread (and thus the OP's idea) that I recall there are thousands, perhaps millions of potential events that could wipe out humanity well before any significant effects from the Earth's core cooling or the Sun's output changing.

If any story is set on Earth millions (much less over billion) of years in the future, I'd also wonder that what survived would be what we know of as human today (even without taking into account future "technological evolution" which would make changes orders of magnitude faster).

Quoting The Fount Of All Human Knowledge:

The first humans with proto-Neanderthal traits are believed to have existed in Eurasia as early as 350,000 - 600,000 years ago[8] with the first "true Neanderthals" appearing between 200,000 and 250,000 years ago.[9]

Click to expand...

Even "surviving" that long doubtful without previous losses of humanity on Earth and repopulation from outer space/other planets. Presuming an even like this happens every 65 million years (we have no good way of knowing for sure, but I'm just saying), it could happen well over a dozen times in a billion years:

The Cretaceous–Paleogene (K–Pg) extinction event,[a] formerly known as the Cretaceous–Tertiary (K–T) extinction,http://en.wikipedia.org/wiki/Cretaceous–Paleogene_extinction_event#cite_note-3 was a mass extinction of some three-quarters of plant and animal species on Earth—including all non-avian dinosaurs—that occurred over a geologically short period of time 66 million years ago.[2][3]

Click to expand...

Or there could be future technology for those on Earth to survive or avert such disasters. If that's true, there should also be technology to live on a further-out planet (and not just half a dozen, but for billions) or in outer space further from the Sun, or even much further away such as near a younger star that will last for another billion years.

The story will then be about people who refuse to go into space for any reason, and are determined to stay on Earth and ride it out to its end. "The End" could well take many generations, so there could be lots of plausible denial, conspiracy theories about why "they" want to take us all into outer space, and what-not.

As others have said it would mean no more magnetic field. It's the outer liquid molten core that gives the earth it's magnetic field. It is believed every 300,000 years or so, the core changes direction and spins the other way, and this causes a shift in the poles.

I believe it would have a major effect on plate tectonics and the volcanic processes of the earth. Tectonic plates move because of convection currents within the mantle (cold rock sinks and warm rock rises) . Secondly the ocean floor is constantly expanding at "mid ocean ridges" in which molten lava pushes up from the mantle, pushing the oceanic plate apart at the ridge, creating more ocean floor. The oceanic plate then collides with other plates, continental plates and is subducted beneath the continental plate back into the mantle, this is a major driver in volcanic activity. I'm guessing with a cold core all these processes would stop. Who knows what problems this would cause. I'm guessing, for starters, no more earthquakes, volcanic activity or mountain building.

Earth would be indeed dying/dead.

King Neptune said:

You might want to research the matter. What appears in the press is not accurate. One should use multiple sources.

Click to expand...

I have already done a fair amount of research into this subject, and my information does not come from the press. Here are some sources from the peer-reviewed scientific literature.

Gaidos, Deschenes, Dundon et.al. "Beyond the principle of plenitude," Astrobiology 5(2):
"CO2 is the major greenhouse gas on the modern Earth." (p.111)

Selsis, Kasting, Levrard et.al. "Habitable planets around the star Gl 581?" Astronomy & Astrophysics 476, 2007:
"In the absence of CO2 (or a greenhouse gas other than H2O), the present Earth would be frozen." (p.2)

Kasting and Catling. "Evolution of a habitable planet," Ann.Rev. of Astronomy and Astrophysics 41, 2003:
"The difference between Te and Ts is the magnitude of the greenhouse effect: Delta Tg=Ts-Te= 33K....H2O is responsible for approximately two thirds of this warming; CO2 accounts for most of the remaining one third of the greenhouse effect. Lesser contributions, on the order of two to three degrees total, come from CH4, N2O, O3, and various anthropogenic chlorofluorocarbons." (p.438)

Boschi, Lucarini, and Pascale. "Bistability of the climate around the habitable zone," Icarus 226, 2013:
Their figure 3a, p.1730, shows that a reduction of the carbon dioxide level of Earth's atmosphere to 90 ppm would be associated with a global temperature drop of roughly 6 K.

Zsom, Seager, de Wit, and Stamenkovic. "Toward the minimum inner edge distance of the habitable zone," Astrophysical Journal 778, 2013:
"If CO2 were removed from the atmosphere of Earth, the global average temperature would be below the freezing point of water." (p.5)