I was recently looking at the control panel for the Universe Simulation, and I noticed a switch labeled

Sun - On/Off

I don't really want to turn off the sun without knowing what would happen.

Assuming I turn off the sun, it stops giving off light and heat, but its gravity remains the same - I know, physically impossible, but hypothetically speaking, assuming there was no supernova or other event that made the sun stop shining, it just suddenly was turned off How long could humans survive? I know the earth would get really dark after the ~8 minutes go by and the light that was emitted by the past sun reaches the earth, but how cold would it get?

I know things like growing crops would be quite impossible whit no light, but there is still quite a lot of potential energy stored up on the earth, and surely some humans could stay warm for a little while? What if someone was in a bunker, burred deep underground with thick, insulated walls, had enough compressed oxygen, clean water, plenty of food, and some way to safely expel waste, How long could this human survive? Granted, life in a bunker like this would be boring, but just think of it - you could be the last person alive

Or could you? Is it remotely possible to keep a well insulated room on earth with a heatless sun, remotely close to a normal room temperature?


4 Answers 4



Well, considering the Earth has gone through several ice-ages with the Sun ON including a "snow ball Earth" stage early in its formation: yeah, it'd get real cold on the surface. Dead cold.

Anything food chain based on a photosynthesizing autotroph would die (or go into hibernation then die).

However, there is another food chain based on chemosynthesis. Most famously tubeworms (actually their bacteria) that live on sulfur from deep sea vents. There are also caves like Movile Cave that are ecologically isolated from any photosynthetic input that have chemosynthetic bacteria supporting a number of flora and fauna. Sure they're all tiny, but they are alive.

Basically, that's the hope of Jupiter's moon Europa. Frozen surface, possibly liquid water underneath, powered by chemosynthesis.

So, in theory, humans could generate power from geothermal: using earth's heat to generate steam to turn a dynamo. With power, you can melt ice, or filter potable water from sea water and also electrolyze water for oxygen.

You can also power hydroponic farms if you raid the seed bank--and use the plants to feed regular underground animal farms. But you could also generate additional food from some kind of food chain based on chemosynthsis.

Might be nice to do this in a habitat that is connected to a facility near a hydrothermal vent.

I think we'd need Vitamin D supplements though. Also, I'm not sure how you'd scrub CO2 from an enclosed atmosphere indefinitely, so you'd probably vent air to the surface.

Who wants fried tubeworms!

  • $\begingroup$ Interesting, so it is technically possible that some humans could survive for a while? $\endgroup$ Sep 1, 2016 at 19:09
  • $\begingroup$ @X-27 - just after posting I was wondering whether you were going to give any heads up about the sun going OFF. Without warning, no. There would be riots and all services (food, power, water, waste) would cease. Any survivors would eventually starve or freeze. But if humans had time to build proper facilities, survival can be indefinite. Think of a nuclear powered sub. They say the only reason it has to surface is to load more food for the crew (though I bet periodic maintenance also is a good idea). Power source takes care of a lot of issues. $\endgroup$
    – Xplodotron
    Sep 1, 2016 at 19:15
  • $\begingroup$ maintenance can be done underwater, underwater mechanics exist for a reason... $\endgroup$
    – Charon
    Sep 1, 2016 at 19:20

Surprised no one has mentioned "A Deepness in the Sky", where this is a major plotpoint. Basically, things get dark, things on the surface freeze, the atmosphere collapses into a liquid, etc., as the surface temperature goes to absolute zero. But if you prepare (are far underground, hibernate, etc.) you are OK. Most exciting (in the book) is when the sun blasts back on again!

  • 1
    $\begingroup$ Nothing in the universe will reach 0 K all by itself. It will approach the temperature of the cosmic background radiation, which last I looked was somewhere on the order of 2.7 K. To get anything cooler than that, you have to run a heat pump, similar to how a refrigerator (a heat pump plus an enclosure) can keep its interior cooler than the exterior. Of course, thanks to the laws of thermodynamics and conservation of energy, the heat has to go somewhere, which is why it's usually not recommended to run a refrigerator without proper ventilation. And getting rid of waste heat in space is HARD. $\endgroup$
    – user
    Sep 1, 2016 at 21:30

Just last month, science gave us a pretty good answer with observations of Jupiter's moon, Io... the moon enters the planet's shadow, gets cut off from the sun, and its entire atmosphere crashes down so suddenly, it causes geologic pressure enough to generate geysers. Kind of amazing: http://arstechnica.com/science/2016/08/jupiters-moon-io-loses-its-atmosphere-when-eclipsed/


The sun is turned OFF:

-3 minutes pass

-Mercury freezes

-6 minutes pass

-Venus freezes

-8:30 minutes pass

-Earth freezes

-Almost Everything on earth dies

-After 6 hours the entire solar system would be frozen

Only humans who where prepared for the event would survive, they would be living underground, warm up with geothermal energy and feed on underground farms.Other survivors are the bacteria inside humans and the bacteria producing nitrogen plants.

  • 2
    $\begingroup$ This article from, ahem, Popular Science, says that popsci.com/science/article/2013-07/… the oceans would stay warm for hundreds of thousands of years. Also, Europa. Not that I disagree with you. You did say "almost" everything on Earth dies. $\endgroup$
    – Xplodotron
    Sep 1, 2016 at 19:24
  • 7
    $\begingroup$ I downvoted. Not having the Sun's light hit Earth doesn't mean everything immediately freezes. For instance, the night side of Earth retains a substantial amount of heat even though it's in the dark. $\endgroup$
    – HDE 226868
    Sep 1, 2016 at 19:27

Not the answer you're looking for? Browse other questions tagged .