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Astronomy Question

B

BigJimbo

Golden Member
If all nuclear fusion in the CORE of the sun ceased immediately, how long would it take for us on the Earth to see the sun begin to get dark?

I thought it was 8 minutes but I guess I was wrong.

I'm pretty sure it takes 8 minutes for the light to go from the sun to Earth.

EDIT: The answer according to my teacher is approximatly 1 million years
 
I think it would take much longer, due to continuing reactions throughout the rest of the sun. Heck, the sun might just hiccup and catch again if the remaining reactions got the core going again.
 
Longer than 8 minutes, the sun is really big.

If the sun was just gone, it would take 8 minutes for us to notice, both from the light and the gravity.
 
its actually a few million years. dont have any links or anything but i did hear it when i was talking to an astrophysics professor
 
8 minutes, 37 seconds or so. The sun is appoximately 93 million miles from the Earth. Light travels approximately 180,000 miles per second. So, it takes 8 minutes and 37 seconds for the light from the sun to reach the Earth, and that is how long it would take to notice any visible change in the luminosity of the sun.
 
People, read the original post. He's not asking how much longer the Sun is projected to last before changing phases, he asked a hypothetical question of how long it would take humans to notice if the sun suddenly dimmed or went dark.
 
the answer isnt 8 minutes i guessed it and was wrong.

How ever it does take ~8 min for sun to reach Earth im stumped looked online and found nothing.
 
Originally posted by: bernse
It'd take thousands of years. Possibly hundreds of thousands of years.
Click to expand...

Keep in mind that before people had theorized the existence of nuclear fusion, Helmholtz had proposed the rather clever "contraction theory" which suggested that the heat of the sun was generated from its slow contraction (converting gravitational potential energy into heat). Without any contribution from fusion, this could maintain the heat and luminosity of the sun for 100 million years.

It was a great theory at the time, but eventually people discovered that the earth was billions of years old, which didn't fit very well with a sun less than a tenth that age.
 
Originally posted by: BigJimbo
the answer isnt 8 minutes i guessed it and was wrong.

How ever it does take ~8 min for sun to reach Earth im stumped looked online and found nothing.
Click to expand...

Then I don't understand the question. If the question is how long it takes to notice a change in luminosity of the sun, the answer IS approximately 8 minutes.
 
Originally posted by: DAGTA

Then I don't understand the question. If the question is how long it takes to notice a change in luminosity of the sun, the answer IS approximately 8 minutes.
Click to expand...

The question referred to a change at the core of the sun. Bear in mind that the mean free path of photons within the sun (and especially as you near the core) is extremely short. Estimates for how long it takes for a photon to make it from the center to the surface range from 25,000 to 100,000 years (!). Thus, even if we ignore the energy contribution of gravitational compression, a change in photon production in the center would still take thousands of years to cause a significant change in surface luminosity.

You would, of course, notice an abrupt change in neutrino flux after about 8 and a third minutes.
 
If fusion stopped then there would be a drastic decrease in pressure in the core as no new energy was being produced. The sun would contract fairly quickly but not very far. There'd be some serious effects 🙂

In fact, this WILL happen. The sun will burn through the hydrogen in its core in a few billion years and then fusion will stop. The sun will then contract until the core is hot enough to fuse helium and then that will start up.
 
Allright, so what's the corrrect answer? My answer would be 32 min, u know...8 + 8+ 8 + 8 😉 U need to give sun a little headroom for error 😀
 
READ THIS CAREFULLY: If all nuclear fusion in the CORE of the sun ceased immediately, how long would it take for us on the Earth to see the sun begin to get dark?

8 minutes
1 day
100 years
1 million years

being multiple choice i had to pick one of those following answers and being i guessed 8min i got it wrong but cannot find the correct answer
 
Originally posted by: BigJimbo
READ THIS CAREFULLY: If all nuclear fusion in the CORE of the sun ceased immediately, how long would it take for us on the Earth to see the sun begin to get dark?

8 minutes
1 day
100 years
1 million years

being multiple choice i had to pick one of those following answers and being i guessed 8min i got it wrong but cannot find the correct answer
Click to expand...

Well if you read the link I provided, the only answer you list which makes sense is 1 million years.
 
Originally posted by: WinstonSmith
Originally posted by: BigJimbo
READ THIS CAREFULLY: If all nuclear fusion in the CORE of the sun ceased immediately, how long would it take for us on the Earth to see the sun begin to get dark?

8 minutes
1 day
100 years
1 million years

being multiple choice i had to pick one of those following answers and being i guessed 8min i got it wrong but cannot find the correct answer
Click to expand...

Well if you read the link I provided, the only answer you list which makes sense is 1 million years.
Click to expand...

The link said 100,000 years and since it was multiple guess leaving the next highest option which would be 1 million years
 
Originally posted by: HappyPuppy
Originally posted by: bernse
It'd take thousands of years. Possibly hundreds of thousands of years.
Click to expand...


I'm willing to believe you if you have some proof.
😉
Click to expand...

Well, just heading off to bed and noticed this. Closest cite I can find with a quick google is a howstuffworks link...albeit not scientifically a recognized source like Nature, it'll do for now. 🙂

From: http://science.howstuffworks.com/sun2.htm

The convective zone, which is the final 30 percent of the sun's radius, is dominated by convection currents that carry the energy outward to the surface. These convection currents are rising movements of hot gas next to falling movements of cool gas, much like what you can see if you placed glitter in a simmering pot of water. The convection currents carry photons outward to the surface faster than the radiative transfer that occurs in the core and radiative zone. With so many interactions occurring between photons and gas molecules in the radiative and convection zones, it takes a photon approximately 100,000 to 200,000 years to reach the surface!
Click to expand...

If fusion were to somehow magically stop though, we would be able to tell earlier via Neutrinos.
 
Originally posted by: BigJimbo
Originally posted by: WinstonSmith
Originally posted by: BigJimbo
READ THIS CAREFULLY: If all nuclear fusion in the CORE of the sun ceased immediately, how long would it take for us on the Earth to see the sun begin to get dark?

8 minutes
1 day
100 years
1 million years

being multiple choice i had to pick one of those following answers and being i guessed 8min i got it wrong but cannot find the correct answer
Click to expand...

Well if you read the link I provided, the only answer you list which makes sense is 1 million years.
Click to expand...

The link said 100,000 years and since it was multiple guess leaving the next highest option which would be 1 million years
Click to expand...

That was one estimate, but if you read further, everything is based on guestimation of parameters. It mentions a million years as a possibility. Your science teacher doens't KNOW the correct answer because no one can. However when you look at the likely range of values for those parameters, a million years works.
 
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