Suppose the sun stoped heating the earth, how long will it take till the earth is completely frozen?, also could humanity somehow surivive?, i think we could survive for a few thousand years at least in isolated pockets near nuclear plants, oil rigs and geotermal energy sources, i am wrong?
Frodo.
While I don’t know the answer to this I’d like to know:
How dark would it be with no sun? I mean we get new moons but how much light do we still see from the sun even at night?
I assume you’re looking to find out the time that the atmosphere would take to cool off; the Earth’s core would stay molten due to radioactive deacy processes.
In this case, I think that this formula could be adapted: most of the heat in the Earth’s atmosphere is due to the sun, and if the sun went out it would cool radiatively (to a first approximation.) Plugging in the numbers and approximating the atmosphere as a uniform layer of gas (10 km high with a density of 0.5 atm), I get… 7 x 10^9 sec, or about 200 years for the atmosphere to cool from about 300 K (27 C) to about 250 K (-23 C.)
This is probably a vast overestimate, though. Look for someone who knows what they’re talking about (i.e. a geologist or meteorologist, not a physicist like me) to tear my calculation to shreds sometime soon.
The normal seasonal cooling of the earth takes about 6 months, june-january. Since this comes about as a result of minor variation in the amount of solar heating that a hemisphere gets, the cooling due to a total absence of the solar heating should take place on about the same timescale.
Wouldn’t we need to find out the total amount of heat energy in the atmosphere, oceans, and surface rocks, in order to figure out how long it would take to escape to space?
Upon further consideration, my calculation above is probably a pile of bovine ordure; it only takes a few hours for the atmosphere to cool down significantly from daytime to nighttime, which would be a pretty close analogy to what the OP is talking about.
You’d also have to factor in the effects of the oceans giving off their heat into the atmosphere; my WAG would be that we would have at most a year before the entire surface got Arctic-like. But since my credibility is pretty much shot here, I’ll step aside for now and hope that someone else can answer this more authoritatively.
IMO, the atmospheric cooling would be logarithmic. In the first couple hours it would cool down quickly to night time like temperatures, and then over a couple hundred years the temperature would slowly go down. It would probably take millions (or billions) of years for the earth to be completely frozen though, because of the heat that’s in there now and the heat that’s being produced from radioactive decay. Remember, there’s still heat in there from when earth was formed over 4 billion years ago.
Could humanity somehow survive? That’s a great debate.
…Or on a much shorter timescale. At a rough estimate based on how quickly it can cool down at night, I wouldn’t give it longer than a week before it was below freezing over the entire planet.
I suspect that the flaw in MikeS’s argument is that he neglected the ground. The atmosphere is in thermal contact with the ground, and the ground can radiate energy much more efficiently than a gas can.
I agree, may be i made a mistake posting the thread in this forum, [pathetic attemp at flattery]if so i hope the mods in their infinite wisdom will move it [/paaf]
But i think that before we can debate that, we need to solve the freezing time question wich seems to be still in doubt.
Frodo.
It’s theoretically possible, if you had enough money and time, to construct a gigantic underground base with a fully self sufficient water and air filtration system, using nuclear and/or geothermic power to keep things going, that could support a small number of people.
The radiative loss from the upper atmosphere would not drop directly, as Chronos has pointed out. The ground would heat the air, as would the seas, and convection would continue to take warmer air higher into the atmosphere. That would maintain the rate until the entire atmosphere, and the surface land and water were all cooled.
A single year with reduced solar input from volcanic particles can drop the surface average temperature by several degrees. With everything shut off, there would be much more rapid cooling. Also a lot of rain, at first, followed by some snow. After that, the rate of cooling would moderate some.
But snow over the entire land mass represents a pretty drastic change in climate. The poles would not be effected more by this. In fact the loss rate near the equator would be the highest, resulting in the most dramatic change in temperature. The distribution of deep water heat sinks would be the main driving force behind atmospheric conditions until things settled down.
My wild assed guess: Bitter cold weather all the time within six months, freezing of the shallows of the oceans within a decade, and total freezing of the ocean surfaces within a century. Freezing the deeps would take a lot longer, and volcanic heat would slow that down a lot. You would have venting of liquid water onto the frozen surfaces here and there, for millions of years. During that time the atmosphere would condense, and then freeze as well, perhaps falling as snow in certain cases.
Oh, and moonlight, the light of planets, etc. are all solar reflection. Nothing but starlight remains to see by. Probably spooky, to watch the moon occlude stars, being otherwise invisible, up there.
Tris
There is also the option of dragging our sorry asses (the entire planet) closer to the sun (it would need to be very close now after all that mass lost during the ‘black-out’) and take advantage of gravitational friction… Perhaps.
The Bad Astronomergives the following answer
in this thread.
They covered this on one of my favourite radio programs, Quirks and Quarks just a few months ago. I can’t find the interview they did with some university professor where he described a timeline for the events following the sun going out… but I did find this:
Ah! Here it is! I’ll go download the audio file and come back with a report.
Holy cow… it’s going to take nearly two hours to download on my connection. Don’t expect my report soon…