A god switchs off the nuclear fires in our sun tonight, do I have to worry?

In summary, the conversation discusses the potential effects of a hypothetical scenario in which a god turns off the nuclear reactions in the sun. The experts agree that it would take several thousand years, possibly even millions, for the Earth to freeze due to the core still being hot and radiating. They also discuss the possibility of the sun collapsing and becoming a white dwarf, but conclude that it is unlikely due to the remaining gravitational potential energy. The experts also mention that the sun will continue to radiate for a long time without fusion, but may eventually become a red giant.
  • #1
Spinnor
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Say a god got mad and could and did turn off the nuclear fires in our sun. About how long till Earth freezes?

We read that it takes an incredibly long to for the average photon produced in near the center of the sun until the time it scatters for the last time and leaves the sun, does that mean the sun will take a while to cool down, that time lengthened somewhat by the slow gravitational collapse of a shut down sun?

Say we look only at the volume of the sun where most energy is produced. Particles leave this volume (photons and anti neutrinos). The number of particles in this volume reduces, four protons and two electrons go to one helium nucleus. Does this change in particle number have thermodynamic consequences?

We know that a large flux of neutrinos can blow a star apart that goes supernova?

Does this flux of neutrinos tend to polarize the positively charged matter and the negativley matter? If so are large electric fields generated in a supernova?

From this does it follow that the constant flux of neutrinos in our sun give rise to some very small but constant outward force to the matter in the sun?




Thank you for your thoughts.
 
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  • #2
Intuitively, it seems that something similar to a core-collapse supernova would happen. After all, those happen because the nuclear power "turns off" due to poisoning with iron and nickel.
 
  • #3
Spinnor said:
We read that it takes an incredibly long to for the average photon produced in near the center of the sun until the time it scatters for the last time and leaves the sun, does that mean the sun will take a while to cool down, that time lengthened somewhat by the slow gravitational collapse of a shut down sun?

Yup. It will take several thousand years.

Say we look only at the volume of the sun where most energy is produced. Particles leave this volume (photons and anti neutrinos). The number of particles in this volume reduces, four protons and two electrons go to one helium nucleus. Does this change in particle number have thermodynamic consequences?

Yes. Over time the core contracts and more energy goes into the envelope. Once it reaches a tipping point, it turns into a red giant.

We know that a large flux of neutrinos can blow a star apart that goes supernova?

Yes.

Does this flux of neutrinos tend to polarize the positively charged matter and the negativley matter? If so are large electric fields generated in a supernova?

No. Neutrinos have no charge so they don't have any electromagnetic effects on the star.

From this does it follow that the constant flux of neutrinos in our sun give rise to some very small but constant outward force to the matter in the sun?

Yes. but I suspect if you run the numbers, you'll find the force too small to matter.
 
  • #4
truth is life said:
Intuitively, it seems that something similar to a core-collapse supernova would happen. After all, those happen because the nuclear power "turns off" due to poisoning with iron and nickel.

Except that in the sun, there isn't enough mass or pressure to cause the star to collapse once everything in the center is compressed to white dwarf matter.

In a supernova, the collapse is not caused merely by the existence of iron, it's that once you get past iron the nuclear reactions that happen actually absorb energy, so you get this feedback until everything is compressed to neutrons or possibly until you have a black hole.
 
  • #5
twofish-quant said:
Except that in the sun, there isn't enough mass or pressure to cause the star to collapse once everything in the center is compressed to white dwarf matter.

In a supernova, the collapse is not caused merely by the existence of iron, it's that once you get past iron the nuclear reactions that happen actually absorb energy, so you get this feedback until everything is compressed to neutrons or possibly until you have a black hole.

I know that, but I figured the sudden stopping of the nuclear reactions would cause the Sun to collapse somewhat dramatically into a white dwarf as the radiation pressure holding it up against gravity is suddenly removed. It's not going to collapse to a neutron star or anything, but that's why I said "like" a core-collapse supernova.
 
  • #6
Spinnor said:
Say a god got mad and could and did turn off the nuclear fires in our sun. About how long till Earth freezes?

A long long time. Someone already said "thousands of years". There would be no dramatic or sudden change as the core would still be hot---like 15 million kelvin--and would continue to radiate. And the thermal Xray from the core would continue to percolate gradually out. No noticeable change at first.
At least thousands of years, might be one or more orders of magnitude more, before Earth freezes.

truth is life said:
I know that, but I figured the sudden stopping of the nuclear reactions would cause the Sun to collapse somewhat dramatically into a white dwarf as the radiation pressure holding it up against gravity is suddenly removed...

I think your guess is unphysical. Why would radiation pressure from the core suddenly be removed? The core, the inner 10 percent, is still hot. It still radiates.

Two-fish quant already gave excellent response so it is superfluous for me to chime in. But just wanted to express agreement.
 
  • #7
marcus said:
I think your guess is unphysical. Why would radiation pressure from the core suddenly be removed? The core, the inner 10 percent, is still hot. It still radiates.

Two-fish quant already gave excellent response so it is superfluous for me to chime in. But just wanted to express agreement.

I was indeed partially wrong. I forgot that the Sun will still have a tremendous amount of gravitational potential energy, and without fusion (I'm assuming higher-energy processes will still be forbidden somehow) the outer envelope will not suddenly be blown off as it would be if the Sun were a red giant. Thus, the Sun should still be able to radiate for perhaps millions of years. However, I still maintain that without fusion, the core will not be able to produce nearly as much radiation as it did and will therefore collapse inwards with the rest of the Sun until the overall Sun heats up enough to balance it's own weight with radiation pressure. It will necessarily be much denser than before, though maybe not to the white dwarf level.
 
  • #8
Without radiation pressure from nuclear reactions the Sun will collapse, but compression heating due to gravitational pressure will replace fusion as the heat source for millions of years. However the very outer layers which presently convect will collapse eventually and the Sun will probably shrink singificantly in the short term before eventually settling into a slow contraction. Since the Sun is below the Chandrasekhar mass limit it will only collapse to white dwarf density, becoming a sphere about 10,000 km in radius. If its heat dribbled out at its present luminosity then that process would take ~ 1 billion years. However there's no nuclear energy being generated so there's no "thermostat" like in Main Sequence stars, thus the Sun will probably brighten significantly. The Eddington Limit is the only constraint, which is at about 33,000 times present luminosity.

Maybe turning off fusion is not such a good idea, if you're a god.
 

1. What would happen if a god switched off the nuclear fires in our sun tonight?

If a god were to suddenly switch off the nuclear fires in our sun tonight, it would result in the immediate collapse of the sun. This would lead to a catastrophic supernova explosion, releasing a tremendous amount of energy and potentially destroying our entire solar system.

2. Is there any scientific evidence to support the idea of a god switching off the nuclear fires in our sun?

As a scientist, I cannot comment on the existence or actions of any god. However, there is no scientific evidence to support the idea of a god actively controlling or manipulating the physical processes of the sun or any other celestial body.

3. Would we have any warning if a god were to switch off the nuclear fires in our sun?

No, there would be no warning if a god were to switch off the nuclear fires in our sun. The collapse of the sun would happen instantaneously, without any detectable changes or signs beforehand.

4. How likely is it that a god would switch off the nuclear fires in our sun?

As a scientist, I cannot speculate on the likelihood of a god intervening in the natural processes of the universe. However, based on our current understanding of physics and the laws of nature, it is highly unlikely that a god would or could interfere in such a way.

5. Should I be worried about a god switching off the nuclear fires in our sun tonight?

No, you should not be worried about a god switching off the nuclear fires in our sun tonight. This is a highly unlikely scenario and there is no scientific basis or evidence to support it. Instead, we should focus on understanding and studying the natural processes of the sun and the universe as a whole.

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