The Sun suddenly "turns off"

This is an extremely abstract question I’ve wondered about for many years but have had little success researching even a even a hint of an amswer, so I now turn to the “teeming millions”. Hey, what the heck…

What if the Sun where to suddenly “turn off” as if some celestial light switch was flicked? It would still exist as a celestial body, so our orbit would be maintained, it’s just “off”. Besides no longer seeing the moon (unless the streetlights from Earth illuminate it to some meager degree) nor the other planets, what phenomena would be observed? How long would life survive? Would our technology be able to still produce enough electricity to continue to grow food, melt water, build batteries and flashlights? Would the Earth’s inner warmth allow some to survive in underground caves or would the core heat also somehow cease to exist? Would the atmosphere remain intact despite Earth’s gravity? Do I have waaaay too much time on my hands? Questions abound.

Thanks folks. I look forward to your input.
Let’s have some fun with this.


Well nothing at all would happen for the first 7 minutes, or however long it is light from the sun takes to get here.

8min, 19sec.

I think the atmosphere would remain intact, but it’s because of Earth’s gravity, not despite it. Why would Earth’s gravity tend to disrupt the atmosphere?

Light and heat take about 8 minutes to reach Earth from the sun.

Following that, things would start to get cold. Everyone and everything would die. How long? Good question. The earth does retain heat but I’m estimating about 2 days for the entire planet to be a block of ice.

IANAS, but my reasoning is this: Generally, air temperature at night drops about 10-30 degrees cooler. That’s a discussion in itself, so I’ll just say 20 degrees for this scenario. So, when day hits, it warms back up to its previous temperture. So if it’s 80 degrees today, the sun goes out, then it turns to night, cools to 60, the “dawn” breaks 12 hours later, but drops to 40, then 20…etc.

I’m leaving out what factor the sun has in warming the nightside of the planet…is the Sun’s warmth recieved only during daylight hours?

I really, really need another beer.

Well usually the sun warms up the earth which then cools down more slowly than the sorrounding air.

Still I think it would take a week atleast before temperatures begin to drop drastically and the oceans begin to freeze.

Without the power of the sun there is no hydro electric power to be had, so we can take that out of the equation.

We may be able to continue to use atomic power, but I don’t know for how long.

All plant life and animal life would eventually die off so we would all starve. PERHAPS a few of us could create some sort of underground city, perhaps using the heat of some magma floes to survive. Couple with some sort of nuclear power source we may tough it out for a while longer…

I figure the folks who’d survive the longest would be those at the Artic weather stations or those on a fully provisioned nuclear submarine.

If you only turned of the visible light, but allowed infrared (heat) and probably UV, things might not be so bad… not sure what wavelengths of light plants require, but infrared is pretty important for most things.

Well, a very few of us might be able to live off of fungus.

I think a geothermal or nuclear power station can keep a small group of people alive almost indefinitely. The power will mostly be used for illumination of crops. Atomic power needs a lot of infrastructure (uranium mining and refining facilities) in the long term, so geothermal may be a better bet.

Oxygen level in the atmosphere will slowly decline, because there will be no more plants to produce oxygen and oxygen is a very unstable (highly reactive) substance. Eventually a Biosphere-II style enclosed ecosystem will become necessary. I have no idea how long it’ll take before the atmosphere becomes unbreathable.

Soon after Pauly Shore sneaks in.

You do realize that Earth has in the range of 326 million trillion (3.26 × 10^20) gallons of water, give or take a few right? (]cite .

IANAS either, but what your saying sounds ludicrous.

If the thermonuclear reactions in the core of the sun were halted right now, it would take a very long time to feel the effects. Because of the density in the reactive part of the sun, it takes a photon generated by the fusion process a VERY long time to make its way to the “surface” of the sun, the photosphere. This number seems to range from about 17,000 years to hundreds of thousands of years. I’m going to say that a good number seems to be about 40,000, as in the article below.

So if the thermonuclear fire were extinguished, the sun wouldn’t stop radiating energy for a very long time. We would have a while

And we ought to have warning of this. Because even though the EM radiation would continue uninterrupted for a long time, we could, hypothetically, detect an instant decline in neutrino emission. Since neutrinos aren’t bounced around by the densely packed atoms in the sun’s core, they zip right through, making the journey from sun’s core to Earth in minutes.

If we suddenly discover one day that the Sun isn’t giving off neutrinos anymore, it’s time to start making preparations. But we’d have tens of thousands of years to pack.


Having been directly involved with Biosphere 2 I can safely say they didn’t perfect the recipe for a sustainable sealed environment on the first try. The problem wasn’t making a breathable atmosphere but making sure it doesn’t become unbreathable. Unsealed concrete surfaces (it was sealed from the outside by a stainless steel liner) and extremely microbe rich soil resulted in low oxygen levels and high carbon dioxide.

Food was an issue. Even with Arizona sunshine coming in the windows they were barely able to grow enough food to sustain the eight people inside. The eight biospherians emerged much thinner than when they entered and very hungry. Trying to replicate sunshine with artificial light will consume vast amounts of power.

Even more important the eight of them were unable to perform all of the maintenance required by the apparatus themselves. After the first crew came out we had several months of work by a very large staff to make it ready for the next crew to inhabit.

Still it was quite an accomplishement as no one has ever built and operated a sealed habitat on a scale near the size of Biosphere 2.

Unforrunately the second crew only stayed in a few months due to external circumstances. The current management no longer operates it as a sealed environment.

Anyone else wondering how Striss has 0 posts, yet wrote this OP?


When Bio Dome came out I saw it with several co-workers including a few who lived inside Biosphere 2. We were the only ones in the theater laughing. It was by no means an accurate representation but there were enough inside jokes about certain aspects of the place and specific people that we figure the producers of the movie had a spy on the inside.

Such a thing is not possible in our universe.

At the time I post this, the OP has posted a question, yet has a post count of zero. How…???

Are there any SF stories along these lines? I.E., The sun has “died”, (fusion at the core has ceased), and Humanity has a few thousand years to migrate to another star or make preparations for the freezing of the Earth. Would make an interesting read.

Arthur C. Clarke’s “The Songs of Distant Earth” had a similar premise. Basically, humanity found that the sun would expand to a red giant in a few hundred years; In order to preserve the species they sent embryos to another solar system and robots to raise them to be a new civilization. Later, a bunch of humans actually did figure out a way to travel to the planet themselves, and much of the book dealt with the relationship between the new arrivals from Earth and the people who had never known Earth.

His/her post counter “turned off”. In 8 minutes it will be 0 kelvin.