# The Naked Scientists Forum

### Author Topic: How many gravitons does it take to change a light bulb?  (Read 1603 times)

#### jeffreyH

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##### How many gravitons does it take to change a light bulb?
« on: 31/01/2014 20:12:18 »
Interesting title? Well if we have a universe containing only a light bulb, and we instantaneously add a large mass somewhere near to it, how many gravitational waves would be needed to affect the photons emitted from our magic bulb? This question is not trivial. It is like what came first the chicken or the egg?

#### syhprum

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##### Re: How many gravitons does it take to change a light bulb?
« Reply #1 on: 31/01/2014 21:09:34 »
The only vaguely intelligent answer I can give is how much energy is given out in the form of gravity waves I under stand Jupiter emits about 25 Watts !

#### jeffreyH

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##### Re: How many gravitons does it take to change a light bulb?
« Reply #2 on: 31/01/2014 21:33:32 »
The only vaguely intelligent answer I can give is how much energy is given out in the form of gravity waves I under stand Jupiter emits about 25 Watts !

Well as there would be no length contraction or time dilation before the first wave hit the bulb, apart from the generated by the bulb itself, how would the effect propagate through the bulb?

#### yor_on

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##### Re: How many gravitons does it take to change a light bulb?
« Reply #3 on: 31/01/2014 23:26:11 »
There might be, or there might not be, gravitational waves. But the 'field energy' described by, and in, such a wave is 'non localized', meaning that you can transform any gravitational field away, just by imagining yourself 'free falling' in it. So I don't expect anyone to be able to turn on light bulbs by its 'energy'. It would become very strange if a gravitational wave didn't allow geodesics in it. Depending on views you can use time symmetry to suggest all sorts of thing for such a wave, as using the Wheeler-Feynman theory where all light move two ways simultaneously, meeting itself at the middle as it is. Depending on ones views the 'energy' may be there, or it may not. Today most people expect a gravitational wave to be measurable, but it won't be until we get a experiment showing us a 'energy localization' we can find out how a gravitational waves 'energy' will be stored in it, or out of it. That experiment I don't think exist.
=

The same goes for any gravitational field as far as I see. All gravitational 'energy' is possible to transform away, just by a free fall. Gravity is frame dependent. Depending on views one also can transform away a EM field, at least if split it into a electrical and magnetic part. It depends on how you look at such a field it seems, if made of two parts, or as a EM field of one whole entity. When of two parts you can transform away one, if a 'entity' then you just see one of its functions. At least you can state that it is frame dependent.

And a frame dependence is a local definition, expressed best by a 'black box scenario', as I think of it. It's not defining what happens over frames of reference, relative ones local clock and ruler, instead being about what one can measure, inside that black box, being 'at rest' with it.
« Last Edit: 01/02/2014 00:23:41 by yor_on »

#### syhprum

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##### Re: How many gravitons does it take to change a light bulb?
« Reply #4 on: 01/02/2014 14:22:34 »
"There might be, or there might not be, gravitational waves"
I did not think there was any doubt as to the existence of gravitational waves simply that detection is very difficult because of the very low frequency very low power of any nearby sources.
It is calculated neutron stars in close orbit would be emitting 100 times the energy than a star such as the sun emits in the electromagnetic range but it would only be for a very short time before they merged into a black hole.
if it happened nearby we would certainly detect it !
« Last Edit: 01/02/2014 14:25:46 by syhprum »

#### yor_on

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##### Re: How many gravitons does it take to change a light bulb?
« Reply #5 on: 02/02/2014 14:16:18 »
I don't know, as you say the evidence we have is the ones from observing binary stars. At least as far as I know? And the ideas building up to it is, to say the least, intricate. I will wait and see myself.
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Take a look here
http://arxiv.org/abs/gr-qc/9704002

« Last Edit: 02/02/2014 14:20:25 by yor_on »

#### jeffreyH

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##### Re: How many gravitons does it take to change a light bulb?
« Reply #6 on: 03/02/2014 00:06:16 »
I don't know, as you say the evidence we have is the ones from observing binary stars. At least as far as I know? And the ideas building up to it is, to say the least, intricate. I will wait and see myself.
=

Take a look here
http://arxiv.org/abs/gr-qc/9704002

The cylindrical waves are not only cylindrical but spiral in nature. This is exactly what I have found.

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##### Re: How many gravitons does it take to change a light bulb?
« Reply #6 on: 03/02/2014 00:06:16 »