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Matter to energy

  1. Jul 13, 2010 #1
    Kan the matter that falls into a black hole be crushed so hard that it is converted to energy?
  2. jcsd
  3. Jul 13, 2010 #2
    As described by einstein's most famous equation, there is no line between matter and energy---from a general relativity standpoint, they are the same.
    We don't know enough about singularities to give much of an answer to your question; saying anything about the matter that has fallen is pretty difficult.
  4. Jul 13, 2010 #3
    I'm going to rephrase your question as a physicist would interpret it, and then ask yourself if it makes any sense:

    "Can the 'energy' that falls into a black hole be crushed so hard that it is converted to energy?

    Matter 'is' energy; no converting needed. I'm guessing what you probably meant was, 'can matter that falls into a black hole be crushed so hard that it is 'converted' into pure radiation?' Unfortunately, the only known way (that I am aware of) to completely convert matter into pure radiation is to 'annihilate' it with antimatter (yes, it exists). Since I have never ventured into a black hole and subsequently been able to return to tell you about it, I'll send you off by saying "Your guess is as good as mine"! Cheers! :wink:
  5. Jul 13, 2010 #4
    I will rephrase in popsci: The energy which falls into a black hole is eventually just mass, charge, spin, and gravity. You can convert matter into photons and neutrinos through annihilation, and shoving it into a black hole, whichever. As for the rest, matter-energy equivalence is one of the pillars of GR; you can't just get around that.
  6. Jul 13, 2010 #5
    can i ask a dumb question from someone whos only venture into physics is what he heard from Kaku, Susskind, Hawking and the like... is it possible that black holes are just that, holes? could there be a "Surface Tension" to space/time and supernova are the ripping of that fabric? just something ive been kicking around
  7. Jul 13, 2010 #6
    First, welcome to PF, and second, when you don't pretend to knowledge you don't have you can't ask a stupid question in an educational setting. In this case, I don't think "tear" is the way to look at it... more like a partitioning away from the rest of the universe. Then again, if Einstein-Rosen Bridges and other wormholes exist, you would have a "hole" within the same universe. Even in M-Theory and Brane Cosmology, I don't believe there is a notion of surface tension or tearing, just inescapable gravity and a region where current physical theories break down.

    Then again, some people still believe in White Holes, and probing a BH is pretty much impossible so... who knows? I doubt there will be a conclusive answer in the lifetime of our species, but if they were tears in the universe, I would think that would be detectable; thus far there is no evidence of that which I know of.
  8. Jul 13, 2010 #7
    but thats my question: a "surface tension" to the fabric of space/time is logical since everything else seems to have a surface tension. i know it cant be experimentally verified, but since there are A LOT smarter people here, i thought it was a perfect place to "kick the ball around" so to speak. but thank you for the info...and the kindness of not being dumb =)
  9. Jul 14, 2010 #8
    Ok, I see I need to rephrese my question. What I initially wanted to know was this: Instead of bombarding the the Uranium atom with nuetrons to make it split and get vasts amounts of energy, can it be accomplished by say "crushing" that energy out of the atom?
  10. Jul 14, 2010 #9
    Remember that surface tension is a function of two mediums interacting, and a universe is either infinite, or a closed system surrounded by ???. There is nothing to form a surface tension with AFAIK. Even if the universe is embedded in a membrane, there wouldn't be the kind of effect you're talking about. Anyway, once again welcome to the forums. :)
  11. Jul 14, 2010 #10
    Energy is energy, you can't crush energy out of energy even if its in the form of matter. You could annihilate it with anti-uranium, or in fantasy you could crush it past its Schwarzschild radius and *bam*.... black hole. You could crush Uranium atoms together (apply heat and pressure) beyond what can be done and achieve fusion, which would release binding energy. The only way to achieve 100% efficiency of energy in the form of matter to energy in the form of Photons and neutrinos etc... is annihilation with antimatter.

    Matter = Energy, it's just a change of state.
  12. Jul 14, 2010 #11
    Let me end this debate by just saying "No". There will become a point where your Uranium will either become degenerate which will 'stop the crush', the electrons will begin to 'fuse' (if you will) to the protons forming neutrons (as in the formation of a neutron star) which will 'stop the crush', or lastly, you will create a black hole of some known 'mass' which is where the discussion of 'crushing' ends. Once we dive into the black hole we cannot have an intelligent discussion of what is occurring there because we cannot extract information from it (spare me the entropy/hawking radiation statement). I've never been inside of one to tell you about it, you never will, nor will anyone else. As previously stated, to turn matter into radiative energy like you want to do, you have to 'annihilate it' with an equal amount of anti-uranium; but to do this we are no longer talking about 'crushing' it, we are talking about 'annihilating' it. Hope this helps.
  13. Jul 14, 2010 #12


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    Gravity, and especially BHs, are the most effective known way (except annihilation) of turning matter into energy. For example if you arrange for violent collisions near the EH. Simply falling into the BH obviously won't do the trick.
    The process can be much more effective than fission or even fusion.
  14. Jul 14, 2010 #13
    Are we "turning [energy] into energy" or "turning matter into [radiation]"? The issue of being mindful on how we make statements such as this was pointed out earlier as it is a point-of-clarification with respect to answering the questions as they were 'intended' to be asked. I only point this out in an effort to avoid further confusion for those that asked the questions as they already seem to not understand the difference, or better put, the 'similarity'/equivalence of these two terms (matter and energy).

    Furthermore, what is the 'mechanism' by which "Gravity, and especially BHs" are turning matter into radiation? You state:

    By "violent collisions" are you talking about "annihilation" that results near the EH as matter falls into it (for example Hawking radiation?) or does your statement somehow lead to the ability of a macroscopic amount of matter becoming so densely packed that it spontaneously converts itself into one or more photons (i.e. somehow by 'colliding' BHs)? The reason I ask is because (i) if you meant the former (annihilation), then you only reiterated what I said to begin with and you cannot 'crush' matter into radiation because any macroscopic amount of matter will either become degenerate, form neutrons, or a BH before it spontaneously becomes pure radiation (ii) if you meant the latter (spontaneous pure conversion of matter to radiation via 'crushing'), then my question to you is, what 'mechanism' does the crushing?; is it 'space-time'? If this is the case I will simply state that space-time is a 'tool' that we use to understand our universe, it is nothing 'physical' in the sense that 'it' would create a 'force' on the matter capable of 'crushing' it past degeneracy, past neutron formation, past BH formation (into a region of science that for all practical purposes can be considered non-science; I say that with a glint of looseness) into spontaneous conversion of matter into pure radiation. GR did away with gravitational 'force'. Sure, matter tells space-time how to warp, and space-time tells matter what path to take, but since spontaneous matter breakdown into pure radiation would require a density so great it could only occur inside a BH, there would be no way to test it, and by extension it must be 'excluded' from 'scientific' discussions.

    I am not trying to be condescending, I am just trying to understand/rational how your point differs from the clarification I already provided: 'no', matter cannot be "crushed" into pure radiation, unless you can tell me the 'mechanism' by which it happens, and by excluding any discussion of the separate process of annihilation as being the cause. And for further clarification, I am assuming we are talking about 100% conversion, which as far as I am aware annihilation is the only 'known' way to do that. Please feel free to comment for clarification, I'm actually kind of curious what you meant, but to me the answers were provided with respect to the intended question(s) and at a level on par with the apparent knowledge of the person asking it.
    Last edited: Jul 14, 2010
  15. Jul 15, 2010 #14


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    Most obviously, neither I
    nor the OP
    are talking about exact 100% conversion. Only you claim now to do so, but this isn't obvious from your post.

    re partial conversion:
    Matter into useful energy, like photons or kinetic energy of decently interacting particles. Something which can drive (in principle) a power plant.
    Neither. I'm talking, in fact, about violent collisions. You throw in one (macrosopic) particle from the left, one from the right. When they collide near the horizon, they do so with almost arbitrary kinetic energy. Which turns into heat, which generates radiation. You collect the outgoing radiation and use it to warm your feet.
    The efficiency can be some 10 - 20 %. I think you can get even more energy from throwing matter into black hole with more sophisticated designs.
  16. Jul 15, 2010 #15
    Looking back at my other posts, I can see why the "100% efficiency" wasn't clear; I assumed that's what we were talking about. In response to:

    I must say that the purpose of my clarification-question has served its purpose; you've made me realize something that I had previously not considered; I have now been 'learned'. :wink: For that, 'thank you'.

    I will concede that a 'violent collision' is a rather effective way of converting the matter's KE into radiation. Furthermore, if we consider the fusion involved, then we are, figuratively speaking, 'crushing' radiative-energy from the rest mass of the colliding matter due to the presence of the BH. So long as we are converting rest mass to radiative energy, I am okay calling it 'crushing' by analogy. However, without clarification from Frannas, I am going to continue assuming that the question they were really wondering was if some sort of 'space-time mechanism' was capable of doing the 'crushing'; which of course the answer is 'no'.
    Last edited: Jul 15, 2010
  17. Jul 16, 2010 #16


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    If you drop the literal "crushing" requirement, there are a number of options to convert matter into energy or even extract rotational energy from the Black Hole. Magnetic fields shepherd accretion disks and jets and can induce particle-antiparticle creation. From the http://en.wikipedia.org/wiki/Penrose_process" [Broken], you can even get more energy than you threw in. With a bit of a stretch you could call this effect a 'space-time mechanism'.
    Last edited by a moderator: May 4, 2017
  18. Jul 16, 2010 #17
    I'll buy that. :wink:
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