A Frozen Earth

[Talitha]

A Friend asked me something very interesting today. She wanted to know how long it would take the Earth to freeze solid if the Sun suddenly 'went out'. I told her we wouldn't even know the Sun had gone out till about 8 minutes after the fact, but that was about all I could offer. However, I promised to pop in here and find out.

So, here we go.. the original question, with a few added for fun.

1) How long would it take the Earth to freeze solid if the Sun suddenly 'went out'?

2) How long would it take living things to die?

3) How long would it take till all of the oceans were frozen solid?

4) Would the thermal difference cause the Moon's orbit to be affected somehow?

Feel free to add more questions, and thanks for letting me pick your brains again.

[Jamie]

if the Sun suddenly 'went out'?

1 - I don't think that is physically possible

2 - Not long (compound the situation)

3 - Don't have a clue

4 - The only way the moons orbit would be effected would be if the earth split because of the temperature change.

[Talitha]

if the Sun suddenly 'went out'?

1 - I don't think that is physically possible

Yeah I know.. it's a "let's pretend" question.

[gurney]

On question 3: I don't think the sea can freeze solid at all. There would be a thick crust of ice, but the pressure of the water lower down would prevent it from ever freezing I think - not to mention the salt content. So I think even in the lowest almost zero K temperatures of space there would always be liquid water trapped deep below somewhere.

Q4: Again, I'm not really sure. But obviously there's at two major influences on the moon's orbit: 1)The gravitational pull of the earth, and 2)The gravitational pull of the sun.

Now if the sun's light suddenly goes out I suppose we've got to assume that something awful has happened to it. I suppose it could technically still be a dead mass in space, in which case perhaps it would retain most of its gravitational influence. but if the sun were to effectively disappear altogther then the earth would end up hurtling through space. The moon would retain it's primary orbit as a satellite around the earth but I would imagine it's orbit would change because of the loss of the gravitational compnent from the sun. I'm not sure if it would increase or decrease to be honest.

[astro_dt]

3.

Not an expert on geology but if there is still tectonic plate movement and the influence of the Moon's gravity then the core would remain hot, so the Earth would not completely freeze.

Danny

[Talitha]

Thanks for the responses, this is interesting. One thing I didn't realize was that "even in the lowest almost zero K temperatures of space there would always be liquid water trapped deep below somewhere." The 'disappearing' Sun scenario sounds interesting, too.

[ChrisEdu]

For it to become totally solid, you'd have to wait for the core to cool down enough for the production of magma to cease and the molten metals, etc.. to solidify. Even without sunlight, the Earth would retain its internal heating and therefore not totally freeze, especially places with geothermal activity. Mind you, there surface would become blooming cold in the absence of sunlight!

All the while that there was geothermal actvity, you can be pretty sure that life would survive in some from or another.

I'm pretty sure that the thermal change wouldn't affect the Moon's orbit. That's only likely to change as a result of gravity altering.

Another interesting thing to consider would be what the effect would be like if the greenhouse effect went wild and we had an atmosphere similar to Venus. I wonder how long the greenhouse could keep the temperature high?

[Sam]

Radio active decay provides quite a bit of heat and it would be sometime (a long long time) before that ran out. Things on the surface would be quite grim, quite quickly I would imagine.

[Astroman]

ChrisEdu and lightbucket are correct-it would take thousands of years for the Earth to "freeze solid". The oceans would remain liquid for millions of years for reasons stated, just as Europa and Titan's oceans are believed to be liquid, even further from the Sun.

Orbiting bodies do so because of their relative masses. The Sun influences the Moon's orbit about the Earth comparatively little. Currently, the Moon is moving away from us at about 2cm/yr. If "something bad" happened to the Sun, that rate may increse measurably, but not noticable. (We'd surely have bigger fish to fry!) I like to ask people what would happen if, hypothetically, the Sun turned into a black hole, suddenly. Their answer is, invariably, "We'd be sucked in!" Actually, practically nothing would happen, except it'd get very cold. This part falls directly onto this discussion.

In darkness, we'd get very cold in weeks. Weather would go bonkers, practically no predicting what would happen. Weather satellites would die quickly, deprived of the solar energy for batteries. Fossil fuels would generate power and heat and so on for some time, but I'm fairly sure humans would expire in a few decades. (There was an interesting program on US public broadcasting about how the Earth would look if humans disappeared. I didn't get to see it, but hope to catch it sometime.) Anyway, life would continue for probably centuries, but we fragile humans would soon expire, imho.

Good question!

[Talitha]

Humans would last a few decades? I figured we'd all be gone in a week at best. It got down to -40°C the other night and I thought about this question while watching the thermometer slowly drop. If Sol had 'gone out' that night and wasn't around to warm the Earth at dawn, how much colder would the temp have dropped, and how fast? How long before I ran out of firewood and drained the LP tank's fuel? :shock:

Btw, public radio ran a very interesting interview with the author of The World Without Us a while ago... I'm guessing it's the basis for the tv production you heard about. Great book.

[philf]

Well, I guess one answer is, as the earth rotates at night it cools. From that you can probably work out the average rate of cooling (my guess would be its about 4 - 5 degrees colder at night than during the day).

I should think by the time it got to 100 below we'd be pretty stuffed - if its pitch black outside and you cant get out of your car for the cold.

My guess is, other than society breaking down very rapidly when we're all doomed, within a fortnight it would be too cold (as there's no sun there would be too "cooling down" periods a day rather than one) for the majority of people to survive - with most people gone by then and the rapid failing of any infrastructure for heating and lighting and with nothing growing I should thin kit woudl be game over very shortly thereafter.

Interesting premise for a novel though - what of the sun "sputtered", the nuclear reaction failed and it went out - how could you restart it from an earth thats in the dark and rapidly going nuts ?

Good thread and an interesting notion

Phil

[ChrisEdu]

In terms of how cold it would get, you could just consider the temperature on the far side of the Moon. As that is not bathing in sunlight, it would give a pretty good starting point for a comparison.

[Talitha]

(my guess would be its about 4 - 5 degrees colder at night than during the day).

Phil

4-5 degrees? Not where I am. The daytime high the other day was -18°C when it dropped down to -40°C just before dawn. In Fahrenheit that's a drop from 0° to -40° in less than 12 hours. I imagine those of us living inland on large land masses would be the first to go. (Whoever gets here first can have my scope and eyepieces.. I'll probably have burned my journals and atlases by then, though. )

In terms of how cold it would get, you could just consider the temperature on the far side of the Moon. As that is not bathing in sunlight, it would give a pretty good starting point for a comparison.

Good point Chris, IIRC the lunar surface fluctuates somewhere in the area of +121°C to -156°C but it has no atmosphere.. do you think Earth's atmospheric blanket would keep our temp higher for a while? We'd still freeze to death long before it gets down to -156°C, though.

[ChrisEdu]

Undoubtedly, the atmosphere would act as some sort of blanket, for a while at least. The amount of heat it would retain would probably be influenced by its composition at the time. Afterall, Venus is hotter than Mercury due to its atmosphere.

[ChrisEdu]

Another point that just pooped into my head - some heat is lost due to reflection (the old white vs black seat in summer situation). With no light, there'd be no reflection, so no heat lost through this way, which might have a slight influence on things.

[gurney]

Hmmm, I think you might be getting a little confused there Chris.

I think the reflection you're refering to is the reflection of radiation from the sun impacting on the space-side surface of the atmosphere. Certainly our atmosphere absorbs a percentage of sunlight, but reflects back a large amount of it also, which is then sunlight that effectively has no impact on our temperature because it's just bounced back outwards before it warms us up.

If the sun were to 'disappear' then obviously the reflection factor wouldn't come into it as there would be no sunlight to reflect. BUT equally there would be no sunlight to absorb either! So although there would be no heat lost through reflection, unfortunately there would be no heat AT ALL! ...other than what the earth produces of its own accord.

[Sam]

Ah.... but imagine the astronomy potential! (for a short time anyway).

[ChrisEdu]

Hmmm, I think you might be getting a little confused there Chris.

I think the reflection you're refering to is the reflection of radiation from the sun impacting on the space-side surface of the atmosphere. Certainly our atmosphere absorbs a percentage of sunlight, but reflects back a large amount of it also, which is then sunlight that effectively has no impact on our temperature because it's just bounced back outwards before it warms us up.

If the sun were to 'disappear' then obviously the reflection factor wouldn't come into it as there would be no sunlight to reflect. BUT equally there would be no sunlight to absorb either! So although there would be no heat lost through reflection, unfortunately there would be no heat AT ALL! ...other than what the earth produces of its own accord.

I might have been confused - it was late and I was dosed up!

[barkis]

It is a very scary prospect, even though hypothetical.

Apart from it's major contributions to the survival of life on earth, light and heat, the sun is symbolic of creation. It's loss would spark untold adverse reactions on all life forms on the planet.

The survival question would be academic. The will to live amongst the majority of humans, would disappear in rapid style. Some major diehards may resist the inevitable, but the futility of it would soon be apparent.

Man has suffered many many disasters, wars, pestilence , famine, disease, and survived. The loss of the sun would not be survivable. The planet would freeze completely eventually, although the time scale is matterless. Some basic lifeforms would last for a long time, but then expire too. Not only will this planet cease, the whole solar system would be a graveyard.

So, unless someone somewhere can chuck a few obelisks at Jupiter and switch it on,

In the words of Private Fraser. "We're all doomed I tell you, doomed."

Ron. Pessimist. :crybaby:

[Tiny]

Best be somewhere else by then. Saving mankind - the job for some great leader - as in we will do anything to get away from him.

[timetraveller]

As Crazy as it sounds the Earth actually did once Milena ago freeze solid right down to the Equator Snowball Earth

and so to try and answer your questions .

Sea water does in fact freeze despite what others might think and has done so and in parts right now IE the seas of the bearing straights and of course the seas around the arctic and Antarctic

All thought the Earth does have internal heat generated by radioactive decay the majority of our heat comes from the sun so take that away and we have basically had it and the chain of events would not be pleasant

Day one all photo synthesis on planet Earth stops and with it the production of oxygen.

Within 3 to 4 weeks most vegetative life has died with the exception of fungal flora Temperatures on our planets surface would have dropped to around - 20 to -30 degrees.

All of our known weather patterns would have ceased no solar radiation to create high and low pressure zones and now no thermoclines, so evaporation ceases the gulf stream and other ocean currents shut down stopping oceangraphic warming .

We are also in total darkness, no moonlight only light we would see is from the stars.

Within 3 months nearly all Animal life has ceased to exist ,

Mass extinctions of all species including man .

I would suggest that within six months all life with the exception of anaerobic microbes has ceased no oxygen present in our atmosphere or insufficient to support life.

Massive new glaciers are now slowly but inexorable moving outwards from the polar regions Canada and North America and Britain are slowly being buried in ice sheets over a mile thick .The temps are now well below -60 degrees the oceans would have completely frozen over ,although the deepest parts would still be liquid mainly due to heating from sub aquatic volcanic activity and hydrothermal vents .

Within 6 months even the north and south African regions are now under glacial conditions and our blue marble is now a giant snowball devoid of all but the most basic life forms

If you think this scenario is science fiction try reading the geological records you may be very unpleasantly supprised.

Our last major ice age was only 26000 years ago and most of Britain was buried under a mile of ice and most inhabitants had retreated southwards without sunlight however even that ceases to be a viable strategy. Oh and it is now beginning to be understood that the ice ages are in fact very rhythmic and the trigger is almost certainly caused by precession caused by our slight wobble. And if your wondering how the hell the Earth escaped its icy grip of death last time it is estimated it took 40 million years to thaw out the snowball and the cause of the thawing was in fact global warming caused by massive volcanic eruptions ( flood Basalt eruptions )chucking dust and billions of metric tons of greenhouse gasses into our atmosphere

Basically folks without sunlight were all dead

[acey]

This is a very nice question. As others have said, all sorts of factors would influence things (internal radioactivity, tidal effects). But for a rough estimate you could start with the mass of the world's oceans (about 1.4. billion x 10**21 tonnes), the average temperature (a quick hunt suggests that 3 degrees C is a reasonable number - av. surface temp is much higher but most of the ocean is cold), and the temperature we want to get down to (about -2 degrees C, freezing point of sea-water). Problem is then to consider how long it takes for heat to radiate into space - again we need to estimate the temp of space (and if the Sun is meant to have disappeared then -270 seems OK).

We could use Newton's law of cooling, but the problem is that we need to know the coefficient of heat transfer that appears in the equation. So I suppose we'd consider the oceans as covering all of the Earth's surface and consider radiative transfer from a sphere (actually I suppose we'd be imagining the whole Earth to be made of water in determining the coefficient but as a first approximation I guess that'd be OK). To get the heat transfer from a sphere maybe we'd need the Stefan-Boltzmann law... Oh dear this is starting to sound like a morning's work...

If I come up with anything I'll let you know, but maybe someone else can do the calculation first!

[philf]

If it helps acey the answer is 42 (apparently) !