# The Naked Scientists Forum

### Author Topic: Does matter turn to energy in a black hole?  (Read 2242 times)

#### acecharly

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##### Does matter turn to energy in a black hole?
« on: 01/03/2014 18:44:05 »
When it gets crushed down its hard to comprehend matter going to a singularity but as it has a close relationship with energy then would it need any space at all if it changed to energy?

Does energy take up any space? I.e how much energy could fit inside a 1 cm2 container?

#### syhprum

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##### Re: Does matter turn to energy in a black hole?
« Reply #1 on: 02/03/2014 05:07:49 »
A 1cm cube of matter compressed to black hole density would have the energy equivalent 1.29*10^38 Joules

#### acecharly

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##### Re: Does matter turn to energy in a black hole?
« Reply #2 on: 02/03/2014 09:54:48 »
A 1cm cube of matter compressed to black hole density would have the energy equivalent 1.29*10^38 Joules

So is it possible to work out how much room 1.29*10^38 of energy takes up?

#### jeffreyH

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##### Re: Does matter turn to energy in a black hole?
« Reply #3 on: 02/03/2014 19:20:07 »
A 1cm cube of matter compressed to black hole density would have the energy equivalent 1.29*10^38 Joules

So is it possible to work out how much room 1.29*10^38 of energy takes up?

That depends upon the density of the matter. If you are thinking of solid matter then there is a limit to the density below which the solid would become small particles or gas. You would need to know roughly how many atoms were in the mass and which elements to determine a reasonable density. It isn't straightforward.

#### syhprum

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##### Re: Does matter turn to energy in a black hole?
« Reply #4 on: 02/03/2014 23:33:46 »
I made the proviso that it was compressed to black hole density and took my figures from the table of masses of black holes of various radii.

#### jeffreyH

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##### Re: Does matter turn to energy in a black hole?
« Reply #5 on: 03/03/2014 22:55:01 »
I made the proviso that it was compressed to black hole density and took my figures from the table of masses of black holes of various radii.

I was referring to uncompressed state. Sorry. Without knowing if singularities exist or not then working out volume for a black hole makes no sense.

#### yor_on

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##### Re: Does matter turn to energy in a black hole?
« Reply #6 on: 04/03/2014 01:23:56 »
matter is energy, although we only can free a very small part of it, even in a nuclear reaction. Energy in itself is ill defined as I see it. You can't really speak about a 'energy density' of a perfect vacuum, unless you go away from a measurement into theory. Waves constantly 'traverse' a vacuum though, as we define it, as does photons. But if you imagine a vacuum in itself then its 'energy' is something neutral. You have to introduce matter to measure those waves.

#### yor_on

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##### Re: Does matter turn to energy in a black hole?
« Reply #7 on: 05/03/2014 18:40:26 »
Actually 'energy', as per calculating the energy released in interactions is not ill defined. It's the idea of 'energy' on its own that I can't get around in my head. Energy expressed through transformations is a working tool in physics.

#### Cthetruth

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##### Re: Does matter turn to energy in a black hole?
« Reply #8 on: 07/03/2014 00:50:37 »
thank you

#### evan_au

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##### Re: Does matter turn to energy in a black hole?
« Reply #9 on: 10/03/2014 10:47:21 »
I saw an estimate that gas caught in the accretion disk around a black hole would radiate so strongly in X-Rays that perhaps 10% of its mass-energy would be radiated away. The twisted magnetic field in the accretion disk are thought to accelerate some percentage of the infalling matter to relativistic speeds, forming powerful jets.

If it were hydrogen gas, fusing it to helium only releases energy equivalent to <1% of its initial mass.
So a tamed black hole would be a powerful (and dangerous) source of energy.

So in a sense, matter does turn to energy in a black hole.
But this part of the process occurs before the matter reaches the event horizon.

#### The Naked Scientists Forum

##### Re: Does matter turn to energy in a black hole?
« Reply #9 on: 10/03/2014 10:47:21 »