The Sun turns off! How long do we have?

[Stranger_On_A_Train]

@Anne Neville

This was in a class I took over ten years ago- I could also be mis-remembering the number or the exact conditions the professor was talking about.

It was probably quoted wrong in the class, too. I got the 10Myr figure in basic Astronomy, too, and only recently learned of the correct range. Actually if you read Stephen Baxter (hard, modern physics based SF writer) he gets it wrong as well in “Liserl” and other related stories.

Stranger

[Eve]

Brad and Angelina and billions of others freeze to death!!

[lokij]

This reminds me of a short story I read once in an older compilation I had. “A pail of air” by Fritz Leiber, in fact after a google I find it can be read here…

http://www.webscription.net/chapters/0743498747/0743498747___6.htm

[drachillix]

@Anne Neville

Several years ago, the major highway connecting Santa Cruz and San Jose was shut down during the morning commute because there were a few inches of snow on the summit of the Santa Cruz Mountains, we didn’t really have the snowplows to deal with it, and people living in Santa Cruz or San Jose don’t typically have snow tires or snow chains unless they drive in areas where there typically is snow.

:eek: OMFG like highway 17 isn’t already 31 flavors of treacherous, on a clear, dry, light, summer day.

[mamboman]

How much longer would Venus stay warm, with it’s thicker atmosphere, than Earth?

mm

[Anne_Neville]

@Stranger On A Train

Sans Sun, the Earth would freeze rapidly. We’re not talking about Antarctic winter cold, either, but cold like Triton.

Does anybody have any idea how long that would take? Hours, days, weeks?

[Lemur866]

Judging by how much things cool off at night, I’d guess we’d cool about 10-20 degrees every day. Or maybe that should be half day. If we cooled off 20 degrees per day then within a week we’d go from 70 degrees to 70 below. But that seems a bit too fast to me, since the polar regions don’t cool off that fast when they have 24 hour darkness. But then the polar regions are getting warm air from sunlit parts of the world. People on the coasts would last longer due to the high specific heat of water. But once the oceans froze over the ice would insulate the oceans so there wouldn’t be much heat transfer from the ocean to the air.

One more thing…once the air freezes out, the concept of “temperature” loses meaning. You lose heat by radiation, conduction, or convection. Once the air freezes there’s no more heat loss through convection, just radiation into space and conduction to the ground. Of course, you’ll have to have airtight buildings, but at least you’ll be able to go out in a space suit and shovel up frozen air, unlike on the moon.

[groman]

@Lemur866

One more thing…once the air freezes out, the concept of “temperature” loses meaning. You lose heat by radiation, conduction, or convection. Once the air freezes there’s no more heat loss through convection, just radiation into space and conduction to the ground. Of course, you’ll have to have airtight buildings, but at least you’ll be able to go out in a space suit and shovel up frozen air, unlike on the moon.

Are we convinced the air will freeze out? The earth is pretty much a huge RTG and it’s not just going to drop down to 3 K and stay there. The rock it’s made off and the water it’s covered with are good conductors of heat so I would guess near-surface temperature would be cold but not as cold as just a rock floating in space. It might be enough to keep the air a mixed liquid or even a gas.

[Lemur866]

Well, melting point for oxygen is 54 K, boiling point is 90 K. Nitrogen is 63 K for melting, 77 K for boiling.

So that’s well above 3 K. Admittedly we don’t have any examples of bodies as massive and radioactive as the earth way out in the Kuiper belt. But according to Wikipedia, Pluto has a mean surface temperature of 44 K.

@wikipedia

Pluto does not have a significant atmosphere. It has a thin envelope of gas that is most likely made up of nitrogen, methane, and carbon monoxide, that develops in equilibrium with solid nitrogen and carbon monoxide ices on the surface as it approaches the Sun. As Pluto moves away from its perihelion and farther from the Sun, more of its atmosphere freezes and falls to the ground. When it returns to a closer proximity to the Sun, the temperature of Pluto’s solid surface will increase, causing the nitrogen ice to sublimate into gas—creating an anti-greenhouse effect. Much as sweat evaporating from the surface of human skin, this sublimation has a cooling effect and scientists have recently discovered,[11] by use of the Submillimeter Array, that Pluto’s temperature is 10 kelvins less than they expected.

So it’s hard to say how warm geothermal heating would keep the crust. But it seems it would take at least months or maybe even years to freeze out the atmosphere.

[Lightnin]

So let’s say we’ve got a bit of warning. Could we produce a lot of cloudcover, by boiling seawater, and try make ourselves a nice comfy thermal blanket?

[Lemur866]

How will that stop heat from radiating out into space? And I think you drastically underestimate how much energy it would take to keep the oceans warm. The total amount of human produced energy is an infintesimal fraction of the amount of energy we get from the sun.

Yes, insulation is a good idea. But you want local insulation. Build a roof and cover it with foam/snow and get inside. There’s no point in worrying about anything outdoors any more, it’s going to freeze solid. You need to start thinking like you’re building a spaceship to travel through interstellar space, with the benefit that you’ve got a giant asteroid tagging along with you. You’d have to build grow lights for any plants anyway, it makes no sense to try to keep them exposed to interstellar space.

Sure, if you’re a Pierson’s Puppeter you can keep your planet warm in interstellar space just by the heat of your planetary industry. That’s not gonna work so well for humans.

[gazpacho]

@Lemur866

Sure, if you’re a Pierson’s Puppeter you can keep your planet warm in interstellar space just by the heat of your planetary industry. That’s not gonna work so well for humans.

I thought they brought along a working star to avoid just these problems.

[Lemur866]

The other terraformed planets in the rosette had miniature suns orbiting around them. But the Puppeterr homeworld was heated only by the waste heat of Puppeteer industry. If the homeworld was still orbiting its star the oceans would have boiled into steam.

[Stranger_On_A_Train]

@Anne Neville

Does anybody have any idea how long that would take? Hours, days, weeks?

I started to run a back-of-the-envelope calcuation based purely on radiative loss, and then realized that the emissivity will change dramatically once atmospheric gases start to condense. (I also couldn’t find an agreed upon number for the thermal load of the Earth, though I’m sure that climatologists or geophysicists must have a standard estimate.) Finger-in-the-wind guess is days rather than weeks, and certainly not months before you’re completely frozen. The amount of geothermal heating on the surface of the Earth is negligable, and energy loss will be progressive. Dirt is not an especially good thermal conduit, so it would take a while to cool but evaporative cooling as the atmosphere condenses will leach heat out quick, turning it into a tundra. The oceans might survive a bit longer, especially if an adiabatic layer of ice forms over and traps in the remaining liquid.

@Lemur866

Judging by how much things cool off at night, I’d guess we’d cool about 10-20 degrees every day. Or maybe that should be half day. If we cooled off 20 degrees per day then within a week we’d go from 70 degrees to 70 below.

Ever gone camping in the desert, toravich? Temperature drop at night can easily be 60-80F due to the arid climate, clear sky, and poor thermal mass properties of the sandy cover. I would guess that the temperature will drop quickly until water starts freezing out, then will stagnate owing to the enthalpy required for fusion (transition to a solid matrix, not nuclear fusion), then drop precipitously again until other gases start condensing. There’ll be a buffer once you get a radiation balance of thermal energy coming from the inner crust to the outer crust, and then once the whole crust freezes it’ll drop to equilibrium.

@Lemur866

One more thing…once the air freezes out, the concept of “temperature” loses meaning. You lose heat by radiation, conduction, or convection. Once the air freezes there’s no more heat loss through convection, just radiation into space and conduction to the ground. Of course, you’ll have to have airtight buildings, but at least you’ll be able to go out in a space suit and shovel up frozen air, unlike on the moon.

The Earth will still have a temperature, and will have to come to equilibrium with the 2.7K cosmic background. Lacking any significant external thermal source (and the aforementioned minimal geothermal heating) I’d guestimate somewhere in the mid to low double digits–maybe warmer in the oceans if they can remain liquid under an ice cap. But yeah, you’ll have all of the volitiles and oxidizers you want. Now you just have to figure out a way to stay warm. Suddenly, mad scientist plans to build a fortress in a live volcano don’t seem to bad, non?

Stranger

[Stranger_On_A_Train]

@Lemur866

The other terraformed planets in the rosette had miniature suns orbiting around them. But the Puppeterr homeworld was heated only by the waste heat of Puppeteer industry. If the homeworld was still orbiting its star the oceans would have boiled into steam.

Note that the Puppeteer’s also had to have the ability to make fine adjustments to the orbits of their entire worlds, as Klemperer rosettes are not stable and will (over relatively short timespans) become perturbed. So, any race that can move planets can probably manage to keep one pretty warm.

Stranger