The Tox Uthat would do it.
I am not a physicist, but it's my uneducated opinion that the sun can't just "go out". I mean, it's a nuclear reaction, right? What would it take to stop the fusion process?
A really big fire hose?
A million person march on DC with the support of Hollyweird politicos!
The Tox Uthat would do it.
An extreeeeeemly large explosion!!!!
There was some cafeteria speculation a couple years ago that the sun has already gone out. It is dark inside and the surface is glowing from residual heat. Won't be long until we notice, maybe a few thousand years.
It is estimated the sun has about 4 billion more years of life left in it. Of course the sun can't just go out, but this was a hypothetical question: What if? If, by some strange quirk of fate, it went out, we would all die. End of story.
Exactly, lol! Just what I was thinking. In order for nuclear fusion to stop at the Sun's core, someone would have to turn off gravity in the universe, or the Sun would have to collide with another star, or something equally catastrophic, in all of which cases we'd have a lot more to worry about than getting cold and starving!
Well, for someone who writes a 'science' blog, this guy is pretty ignorant.
The fate of our sun is well know to anyone who has taken an astronomy 101 course.
A billion or so years from now, the hydrogen fusion reaction in the sun will no longer be able to support the weight of the core.
At that point the core, which will be mostly helium at that point, will collapse until it becomes so dense that a helium fusion reaction begins.
The sun will then swell up into a large red start who's size will be so large that it will reach to about the orbit of Mars.
IOW, the Earth is going to get fried and swallowed up before the Sun finally burns out. I suggect investing in sun screen, not winter clothing.
First, core contraction as pressure at the core falls. That allows ignition of elements beyond hydrogen. Helium burning would then support a larger, more tenuous sun - a red giant - with a higher power output but for a much shorter period of time than hydrogen burning. Eventually that too runs out, and the same repeats.
The next to trigger is carbon burning, and after that it goes very fast. The final elements up to iron (the most stable nuclei) take only days. When it is all gone, assuming the mass isn't enough to ignite the energy consuming trans-iron elements, you have only gravitional collapse pushing temperature up.
The sun shrinks to a white dwarf, stabilizing there as Pauli exclusion pressure counteracts infalling weight. It then takes millions of years for the resulting fusionless but white hot star remnant to cool off by radiation.
The sun needs fusion to maintain its state and to prevent gravitational collapse, but not to be hot. Infall of matter - shrinkage - can release plenty of additional energy. And the interior of dense, white hot bodies do not exactly cool off in an instant.
As for the scientist's musings, photosynthesis drives earth life by capturing about 0.5% of sunlight energy that hits the earth. Total human energy use is a fraction of that amount, about one quarter of it last I checked. We would have a substantial amount of energy from existing sources, for a while. But not enough to maintain the biosphere (it is less than currently does, and plants have very low mechanical efficiency, and we'd have no easy way of pumping our own power into them, rapidly).
On the other hand, given enough warning time there is plenty we could do. Fission energy release is basically unlimited - the amount of uranium in the earth's crust would suffice to replace solar power for millions of years, if we had access to it (which is a matter of capital for extraction etc). With enough lead time and capital, any power source can be used to feed plants e.g. in hydroponic tanks under UV light.
The total biosphere and thus population we can support is set by our income, not the form in which is arrives. Free sunlight is a huge "gift" portion of our income. But one kind can replace another - with adapation costs (thus net income reduction) and lead time.
Consider what (or Who) made it start up in the first place.
If solar fusion stopped today, it would be about 1,000,000 years before the sun cooled sufficiently that we might even begin to know about it, strangely enough. Fusion takes place deep inside the core of the sun. It takes millions of years for the heat generated to make its way to the surface where it radiates and we can feel it.
That's a very good point, and we appreciate the additional rigor you have brought to the discussion. The question should therefore be re-phrased as "What if the sun went away?"