# Without the sun how long would it take for earth to freeze solid

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Alan McDougall, Jun 13, 2010.

1. ### Alan McDougallAlan McDougallRegistered Senior Member

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Hi

If our planet could be removed from all external heat sources such as the sun , how long would it take to freeze solid?

Alan

3. ### James RJust this guy, you know?Staff Member

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Which part of it? The oceans?

The Earth's outer core is thought to be liquid iron, which still hasn't solidified 4.5 billion years after the Earth's formation.

5. ### Alan McDougallAlan McDougallRegistered Senior Member

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Agreed James but given an eternity to cool down within an absolute zero environment it must finally dissipate all its heat into the void.

Maybe a googleplex of years will do the job?

Alan

7. ### Michael歌舞伎Valued Senior Member

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What is causing the heat inside of the earth? Is that force dissipating?

8. ### Alan McDougallAlan McDougallRegistered Senior Member

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It has been postulated that nuclear energy and radiant heat are involved that gives the core its energy and heat

We know the half-life of some elements are billions of years, by extrapolating this means that it might take something like a trillion billion years to cool of.

Think of the enormous heat energy trapped in our oceans to cool them down if looked at them in isolation, would alone take maybe a billion years to freeze

Mars had no metal core, it must have had one billions of years ago, earth is a much larger planet than earth so the earth should take much longer to freeze

I think we should take a vote to see what each of us think would be the final outcome

Alan

9. ### EnmosValued Senior Member

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The surface of the planet would "freeze solid" pretty quickly and, really, that's all that matters.

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Alan

11. ### eburacum45Valued Senior Member

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Underneath the surface ice, which would include not only water ice but also oxygen and nitrogen ice, Earth would continue to be warm. Volcanoes would erupt, plate tectonics would continue while the heat deep inside the Earth continues to find its way to the surface. Around sources of geothermal heat there would be pockets and lakes of liquid water; it is possible that life will continue to thrive in these pockets, although I think the water would become more and more toxic over time. Perhaps life would adapt to these new conditions and persist indefinitely.

On a similar note it is conceivable that a human population could persist within the frozen crust, using geothermal energy to grow crops and recycle waste withing limited habitats. Such a population could survive for a long time, until geothermal energy was no longer available, and even longer if hydrogen fusion technology was available. But maintaining a closed ecological life support system in such circumstances would be tricky.

12. ### superstring01Moderator

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The Earth's core is expected to "cool down" (with the sun) in about another 2 billion years.

Without the gravity of the Sun, assisting the Moon, in churning about the insides of our planet, maybe a third less. Perhaps half. Who know.

~String

13. ### Fraggle RockerStaff Member

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Not quite. According to the Wikipedia section on the Earth's core, the major source of heat from radioactive decay is Thorium-232, which has a half-life of ten billion years. This means that after ten trillion years, 99.9% of the mass of this element will have decayed into stable isotopes and stop producing heat.

Potassium-40 and Uranium-236 also produce considerable radioactivity, but their half-lives are an order of magnitude shorter and therefore their long-term contribution to the Earth's temperature are irrelevant.

The article states the earth's total heat loss through radiation (there's no other way to dissipate heat in a vacuum) as 10 terawatts. It also lists the heat release of each of the major radioactive isotopes and their concentration within the core. If you can find the mass of the core and do some math, you can figure out how long it will take the planet to cool to any arbitrary temperature, with or without the heat of the sun. But I doubt that it will take a trillion billion years (10^21, a sextillion in U.S. terminology) to freeze.

I would guess that by then the temperature at the core will be a couple of degrees above zero Kelvin. In a sextillion years, would even a red dwarf be cool to the touch?

James can probably do this math.

14. ### Alan McDougallAlan McDougallRegistered Senior Member

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Hi Rocker,

A great post but what about proton decay, a proton is said to decay in more than 1 year to the power of 35,
1 year to the power of 35 zeros which are 35;1000000000000000000000000000000000000

Is that as long as your sextrillion years?

Alan

15. ### Janus58Valued Senior Member

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There is no evidence that the proton ever decays. The number given is the experimental lower limit for its decay. In other words, all we know it that if the proton were to decay. its half-life could not be any less than that.

16. ### Michael歌舞伎Valued Senior Member

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I was thinking of humanity huddled around these geothermal vents - but, I'd imagine humanity would be living in an artificial virtual world, one that was so utterly life-like as to be indistinguishable from THIS one

17. ### Fraggle RockerStaff Member

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What you're trying to say is: 10 to the 35th power;
We write that more compactly in scientific notation, adapted to the ASCII character set, as: 10^35.
It's sextillion, from Latin sextus, "sixth." There's no R in it. All of the prefixes for the higher powers-of-one-thousand series are derived from the Latin ordinal numerals: tri-, quadri-, quinti-, sexti-, septi-, octi-, etc. (In the American system anyway. In the European system they're powers of one million.)

So a 1 with 33 zeros is a decillion in the USA, and your number is one hundred decillion.

18. ### Alan McDougallAlan McDougallRegistered Senior Member

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Thank you you are correct I meant 10 to the of 35

19. ### joepistoleDeacon BluesValued Senior Member

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Earth will, ceterus paribus, be long gone before the Earth's core cools signficantly. If let's say the planet were to be spun off into the abys because of intergalactic collisions, we would not be completely deprived of energy. The core will continue to emit abundant energy for some time to come.

20. ### Alan McDougallAlan McDougallRegistered Senior Member

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The core will remain hot for countless billions of years much longer than the present age of the earth.

I believe that there has been some computer modeling on this question I will go and see if I can find it on the web