What Would Happen if the Sun Disappeared?

For some reason this question gets asked a lot on Yahoo Answers. I’m not sure why, but people seem to be curious about what would happen to Earth if the sun disappeared. The times we live in maybe? Morbid curiosity? I don’t know, it is an odd question. I’ve thought about it a lot, and it is an exercise in science and logic, so here is my best guess as to our fate should the sun mysteriously vanish. As an aside, this isn’t a particularly likely fate for Earth. Stars don’t just go out, so there’s no chance of the sun just turning off. A cloud of some sort of thick interstellar gas could conceivably suddenly blot out the sun, but where such a cloud could suddenly come from defies reason, again, astronomers haven’t noticed any stars in the sky suddenly being blotted out by clouds of gas. So for the sake of argument we are simply going to postulate that in some unknowable way, the Sun simply vanishes one day. What would be our fate?

In short: We’d be hosed. The actual details might be somewhat variable, but it’s still pretty easy to predict. How much does the temperature drop between sunset and sunrise? If the Sun vanishes, it will simply keep dropping at the same rate or an even higher rate as the water freezes out of the atmosphere and Earth loses its cloud cover. At high elevations and arctic areas this means within days the temperature would be several hundred degrees below zero. In the tropics it might take a week or longer, but it’s safe to say that in at most two weeks the entire globe would have cooled to hundreds of degrees below zero, and all surface life as we know it would be impossible. Most humans, as well as most life on the planet, would have frozen to death.

Would the Earth be lifeless? No. The Earth itself would remain warm from radioactive decay for billions of years, so microbes deep in the crust would survive. The oceans would freeze over, but they likely wouldn’t freeze solid. Tidal action, volcanism, and the aforementioned heat from the Earth’s core would likely keep some water liquid. Deep sea life, especially that around sea floor vents that don’t rely on the Sun, would very possibly survive or even thrive.

On the surface though, nada. In fact most of the atmosphere would soon freeze and fall to the earth as snow. Different components would freeze out at different times, so there would be layers of colored snow, methane snow is orange for example. The almost airless sky would be awash with stars, brighter than the starriest night on Earth now. The Moon wouldn’t have phases but it would still be visible as a gray ghost hanging in the cloudless sky, dimly illuminated by starlight. In fact the Earth’s surface would likely be stunningly beautiful in a silent still way, like a frozen dream.

We wouldn’t be around to appreciate it though. Some humans might survive for awhile in deep shelters or nuclear submarines, but unless there were a lot of them in a well equipped base, their chances of long term survival would be almost nil. Still, if there was enough of a society left to support an industrial base, maybe humanity would survive. Nuclear power would last forever, and the entire Earth’s surface would be littered with useful artifacts, not to mention frozen food in one form or another.

Ice skating would be popular. There’d likely be a lot of morbid global warming jokes. The Sun disappearing would certainly put humanity’s current problems in perspective. Conceivably, it might even interfere with the publication of this blog.

(Above image of a 1999 solar eclipse is used legally: Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation license, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation license“. Credit and copyright: Luc Viatour. I didn’t even mention what would happen to the rest of the solar system, but if the Sun vanished the solar system’s various planets etc. would simply sail off in all directions. The Earth would keep the Moon and maybe a few captured asteroids as it spun off into deep interstellar space, alone among the stars.)