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Sun Question

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Sun Question

Light from the Sun takes about 8 minutes to reach us so if the Sun suddenly went out we wouldn't know about it immediately.
If the Sun was powered by electricity from a socket on Earth and the socket was switched off how long before we would see the Sun go out bearing in mind that electricity theoretically 'travels' at approximately the speed of light.
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Re: Sun Question

Would it even be possible to run a cable that far on AC? Even at the speed of light it would take minutes for each sinewave to move along the cable to the sun. At the speed of light and at that distance you'd surely run into problems where the sinewave can't keep up surely? - AC is basically the polarity being swtiched and the flow of electrons being reversed. Now there is no way that in a split second you could suddenly reverse the flow of electrons all the way from earth, to the sun, back to earth and then switch the polarity to the same in reverse all in 1/60th of a second.
Well.. thats my take on it..
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Re: Sun Question

Run it on DC then.
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Re: Sun Question

Ah but....does electricity travel at the speed of light?
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pwatson
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Re: Sun Question

I thought 2/3rds the speed of light was a working approximation for electricity through copper.
The reply from 7up misses the point that it isn't the time taken for a single electron to traverse the entire length of the cable and AC/DC makes no difference (ignoring cable losses etc). 
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Re: Sun Question

I Guess it's like these stars that are hundreds of light years away, they may have ceased to exist yet we continue to see them, so we might be seeing something that is not really there but as it used to be. Wink
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Re: Sun Question

OK I'll bite ...............20.805 minutes
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Re: Sun Question

No trick journeys.....I don't know the answer.
Is electricity like water in that when the source is cut the pressure drops along with the flow.
Or does the electrical flow continue along the wire even after the source is cut.
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Re: Sun Question

Quote from: Strat
If the Sun was powered by electricity from a socket on Earth

With the current price hikes I wouldn't want to be the one paying that bill.
Are we assuming that the sun does dark immediately?  As far as I know the sun is quite large so it would take quite a while to cool down after the power was switched off and until it cooled down a fair bit it would still emit light.  Even an incandescent light bulb doesn't go dark immediately on loss of power (though it doesn't take very long).
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Re: Sun Question

Yes, the Sun would go off immediately.
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Re: Sun Question

Quote from: pwatson
The reply from 7up misses the point that it isn't the time taken for a single electron to traverse the entire length of the cable and AC/DC makes no difference (ignoring cable losses etc). 

So what you're saying is that at the exact moment the polarity switches here on earth, it would also switch at the sun - at that exact moment?
Of course it won't. If it takes light something like 6.5 minutes to get here from the sun and electricity is marginally slower than that sinewave swap will not take affect at the suns end of the cable for several minutes. In the meantime it's swapped here on earth again and thus a positive sinewave thats now switched to a nexgative will almost certainly cancel out the previous wave at the load (the sun).
A simple way of thinking of AC is like a pull-push mechanism. In the case of the sun, you might pull or push but that won't happen instantaneously at the sun will it. Meanwhile you've switched and so somewhere along the line that energy will cancel itself out before it even gets there.
Of course you're quick enough to claim I'm wrong but didn't come up with an answer yourself..
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Re: Sun Question

now I see where your coming from:-
have a look at http://amasci.com/miscon/eleca.html
specifically item 6
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Re: Sun Question

Well, if I may paraphrase no less an authority than Patrick Moore. I recall reading an article by him describing a star (don't remember which one) that we see the light from it as it was at the time of the Battle of Hastings it having taken that long to travel to us on Earth, more remote stars take even longer. The nearest star to us (other than the Sun) Proxima Centuri at 4.24 light years away, we see as it was in 2009ish.
So following that logic Strat, yes, we wouldn't know about it or start to get very cold for about eight and a half minutes.
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Re: Sun Question

As I said in my opening post Wink
The question boils down to the action of the Earth bound switch, the subsequent reaction of the Sun and the time delay.

Science is attempting to look further in space and therefore further back in time to the theoretical Big Bang.
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Re: Sun Question

By the Sun going out, it would mean that nuclear fusion at the core would somehow of miraculously have ceased.
As for taking eight minutes for the effect to be noticed, that's an interesting cosmic question. Certainly Neutrinos produced at the core would stop flowing immediately and, eight minutes later, these solar Neutrinos would no longer be passing through you, me, the Earth's and beyond. And that's detectable, even with our primitive technology. However, the solar core is surrounded by a dense envelope of hydrogen gas which, is not part of the fusion reaction - it's the sun's fuel store. This acts like an insulating blanket; hence it takes thousands of years for photons produced at the core, to migrate their energy outwards through the dense atmosphere to the visible photosphere. The energy from this year's summer sun, could be as old as the end of the last Ice Age. Thus if the Sun went out, we'd probably see it fade over ten thousand years.
However, there is a situation when the core can literally switch off in the blink of an eye. At the heart of a blue giant star, the core will become so hot and so dense, nuclear fusion starts fusing the element Iron. This is a dead end scenario with only one spontaneous outcome. Within hours, the core goes into melt down and the star explodes - at close on the speed of light. A very bad day indeed. The only warning of the impending supernova event is a massive flux of gamma rays that makes everything in the planetary neighbourhood glow purple.
As for the speed of light along a power cable 1AU long? You're probably in the realm of Special Relativity where the gravity of the sun affects the length of the space and time along the flex. Ouch.
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