# How long would it take for earth's core to cool down and solidify?

Would earth go the same way as Mars by first losing its magnetic field followed by its atmosphere as its core solidifies and cools down ?

At what rate is the earth's core cooling down?.

Is it slow enough that it would be past time when the sun's temperature rises as it starts its journey into the red giant phase and heat up earth at which point it doesn't matter if earth has its magnetic field or not, or is it fast enough to happen within the next few hundred million years?

• That Mars has no magnetic field because it's core has solidified is an old and incorrect meme. That Mars's core is still partially molten means that not enough heat has escaped from the core to enable to core to freeze. A geodynamo can only exist if the heat flux out of the core exceeds some minimum value. Mars has no magnetic field and has a partially molten core because Mars has a stagnant lid. A stagnant lid (no tectonic plates, no volcanic activity) means the heat stays trapped inside for a long, long time. – David Hammen Nov 7 '15 at 10:49
• August, this is more of a question for the Earth Science SE, as @userLTK has suggested. – Aabaakawad Dec 5 '15 at 23:35

At what rate is the earth's core cooling down?

The inner core is cooling at the rate of around $55^{\circ} C$ every billion years.

Would earth go the same way as Mars by first losing its magnetic field followed by its atmosphere as its core solidifies and cools down ?

Given enough time, yes; But earth is constantly producing heat though multiple processes, the most important being the decay of radioactive elements with long half lives (for e.g., U-238 has a half life of around 4.5 billion years). As the present temperature of the inner core is estimated to be around $5000^{\circ} C$, this is going to take tens of billions of years.

The magnetic fields are generated by eddy currents in the outer core, which is a liquid layer about 2,300 km thickness. The inner core is growing at the rate of about 1 mm per year, so it is going to 'freeze over' (i.e. solidify) in about 2.3 billion years. Without its liquid outer core, the Earth's magnetic field shuts down, and charged particles emanating from the Sun gradually deplete the atmosphere, like Mars.

Is it slow enough?

Well, it is not slow enough for the sun to become a red giant and fry earth, which will happen in 4 billion years or so. But is certainly doesn't matter as we won't be around to witness it.

• what do you mean by "we" in "we wont be around"? – r2_d2 Nov 6 '15 at 18:10
• Is there a source to that 55 degrees C every billion years? It seems to me that number would change as the radioactive material remaining changes. I've seen it mentioned in the other thread as well, but I haven't seen it backed up by a source. – userLTK Nov 8 '15 at 12:18

Would earth go the same way as Mars by first losing its magnetic field followed by its atmosphere as its core solidifies and cools down ?

We don't know. The current popular belief is the Sun will engulf it long before that. It is merely a hypothesis, not a theory.

At what rate is the earth's core cooling down?.

According to today's set of popular superstitions, it all depends on how quickly the fuel inside the nuclear reactor that is the Earth's core (according to some people) depletes. Estimates vary. There are way too many unknowns, and way too many variables to come up with a concrete number (degrees or terawatts). 50 terawatts is a number that surfaces periodically in various publications, but there's just not enough empirical evidence for the hypothesis to become a theory.

Is it slow enough that it would be past time when the sun's temperature rises as it starts its journey into the red giant phase and heat up earth at which point it doesn't matter if earth has its magnetic field or not, or is it fast enough to happen within the next few hundred million years?

Again, according to what we seem to believe today, the Sun will get to us long before that. Which, by the way, is also a hypothesis rather than a theory. No matter how impressive the number of sources, it does not constitute proof. Not in science, anyway.

• "nuclear reactor that is the Earth's core"? Do you really mean this? I'm no geologist, but if you're simply referring to heat from decay, I wouldn't term it a" reactor". – Semidiurnal Simon Dec 8 '15 at 7:47
• Deforestation will cause a loss of cloud cover which will result in constant radiation from the Sun, The Oceans will begin to evaporate, The Earth's core will begin to heat up and become unstable causing a wobble in the Earth's Axis, The Rotation will decrease due to the wobble causing a slow roast effect.The core is now so hot it begins to lose its magnetism and the moon drifts off into space. Once the magnetic field is gone and radiation enters freely and destroys the atmosphere. – user5434678 Jan 5 '16 at 11:47
• The Earth is now almost at a stand still and open to all the elements.The core decays completely.This whole process could take as less as a hundred thousands of years.The Sun will take billions of years to transform into a red giant. – user5434678 Jan 5 '16 at 11:48