Question: how long would we survive without the sun?

Laurence Perreault Levasseur answered on 17 Jun 2014:

If the sun was to suddenly disappear, at first, we wouldn’t realize anything. For the first 8 minutes and 19 seconds, everything would be as if the sun was still there, we would still see it shining in the sky. This is because it would take 8 minutes and 19 seconds for the last rays of light emitted by the sun to travel to us. Similarly, for 8 minutes and 19 seconds, the Earth would still orbit around the place where the sun used to be. This is because gravity (and information in general) travels at the speed of light.

After those 8 min 19 sec, the sun would disappear in the sky and the Earth would start moving along a straight line from that point, drifting into deep space. Then chaos and panic would probably take over human society, but lets put that aside for now.

Interestingly, even if we wouldn’t see the sun anymore, in the sky we would still be able to see the planets that are further away from the sun than us for a little while, orbiting the sun that no longer exist as if nothing happened. That’s because even if planets don’t emit light per say, but reflect only reflect light from the sun, the light the last rays of light form the sun would take longer to travel to them then to us than to us that direct. So first the sun would shut down, then Mars, then Jupiter (30 min later), then Saturn, the Uranus and finally Neptune…

Then for us, it would be like an endless night. We would still be able to see around a bit using light from stars, though. And we would still be able to use things like electricity and fossil fuels, so cities, at first, would continue working like normal.

Photosynthesis, however, would stop immediately. That means all plants would stop producing O2 and eventually die. But this is ok for us, since even though all humans on the planet use about 6 trillion of O2 per year, the atmosphere right now already contains 1 quintillion of O2. So that means that even without photosynthesis, and including EVERY living thing that uses O2, it would take 1000s of years to run out of O2 (oufff!! so we won’t die from lack of O2!)

One of the first consequences of the disappearance of the sun would be that the temperature would start to drop exponentially fast. This means very quickly at first, and then more and more slowly as the days, weeks and months pass by. By the end of the first week, the average temperature would be freezing. So for the first few weeks or months, we, humans would probably still be fine, since it’s no worse than a bad dark winter (I’m Canadian, so I’ve seen worse!). By the end of the first year, the temperature would have dropped down to -73C. That’s starting to be cold.

By that time, we’d have to move to places that are hot because of the core of the Earth is active (it’s kept hot by pressure and radioactive decay, at about 5000C), like close to geothermal sources or deep inside the Earth or close to the bottom of oceans.

After 10 to 20 years, it would be so cold outside that air would become liquid, so it would start ‘raining liquid air’. By that time, the earth will be covered in a thick layer of ice. That is very good for us – or at least for life- , because ice float and it is a very good insulator, so it means that for BILLIONS of years after the sun would have disappeared, there would still be liquid water at the bottom of the oceans, which could pockets of protected life.

I’m not sure we, humans, would make it there, because by the time it’s raining and snowing O2 outside, it’s going to be hard to get something to breath, but still, it’s fascinating that life could make it long enough to travel to say, another star and be heated up again!

The above is a summary from:

(which is awesome)