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Using the process of 'pair production' and using the nature of a blackhole to separate and destroy one of the particles from that pair, would surrounding blackholes with heavy metals (which increase the chances of pair production occurring) allow, over a long enough period of time, enough mass to be 'freed' from the blackhole that it loses enough gravity to 'fail'?

The inspiration for this idea was, among many things, from this line on Wikipedia: "The probability of pair production in photon-matter interactions increases with photon energy and also increases approximately as the square of atomic number of the nearby atom."

https://en.wikipedia.org/wiki/Pair_production

I posted this here because I believe the mass 'freed' from a blackhole could literally be used to build entire galaxies, not just worlds.

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    $\begingroup$ "which increase the chances of pair production occurring" - how?.. Also, this is not discussion board, and "idea pooling" is generally considered too broad, so please consider removing your last paragraph. $\endgroup$
    – Mołot
    Mar 13 '17 at 14:32
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    $\begingroup$ Unfortunately anti-matter is still matter, just the opposite of it's 'particle pair', and when it annihilates with it's opposite it still conserves energy. All of which will be 'consumed' by the blackhole and make it grow. $\endgroup$ Mar 13 '17 at 14:42
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    $\begingroup$ I think this is better for the physics stack exchange. $\endgroup$ Mar 13 '17 at 14:54
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    $\begingroup$ @TheBlackCat This does not belong at Physics.SE. That is for real physics, while this is speculative. This is the place to get your speculative physics dismantled, at Physics.SE they would just close the question outright without bothering to reply. $\endgroup$
    – kingledion
    Mar 13 '17 at 15:18
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    $\begingroup$ @JanIvan anti-matter is still mass. It is not negative matter. Antimatter will make a BH bigger, as will massless particles. $\endgroup$
    – JDługosz
    Mar 13 '17 at 15:38
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None of your "liberated" matter will come from the black hole.

The pair production mode you're describing comes from an interaction between photons and atomic nuclei. Essentially, when I high energy photon interacts with a nucleus, it has a chance of converting into a pair of particles, generally an electron and a positron.

You could, hypothetically, create some additional matter from high energy photons by doing this near a black hole and dumping all of the antiparticles into the black hole, preserving only the "regular" matter. However, doing so won't be liberating anything from the black hole, which is impossible. Black hole emissions are determined only by the mass of the black hole, as per the formula for Hawking radiation.

Instead, you're converting energy already outside the black hole (high energy photons) into another form of energy (elementary particles). Your conversion rate is 50% at best since you're getting rid of the anti-particles.

While it's certainly easier to build things out of particles than out of photons, you need to find a good way of concentrating your photons into a small space around a black hole, and then find a good way of getting your matter outside of the gravity well of the black hole. You also need to find a way of producing photons to feed into a black hole. All of this will net you a small amount of mass, since you're likely to be getting lots of high energy electrons out of your interactions, which are difficult to use as a construction material. Certainly not galaxies worth of mass.

At the end of the day, this is also probably something that's already happening at scales that would be difficult for you to replicate. Black holes, especially big black holes, tend to be surrounded by accretion disks of inspiralling matter. These disks are filled with lots of high energy particles compressing against one another and heating up. They certainly emit lots of high energy photons, and those photons likely interact with the particles in the disk to create particles through pair production. In really big black holes, lots of matter shoots out at the poles of the black hole in immense jets of high energy particles. Most of these particles are bits of the accretion disk that get launched free, but some are probably created by pair production. The amount of mass created, though, is far less than the amount of mass that falls into the black hole.

At the end of the day, yes, you can create mass through pair production near a black hole, but not very much, and it's not liberated from the black hole. You certainly can't create new galaxies this way, and are better off finding an existing galaxy and using that for whatever you need a galaxy for. There's certainly plenty to choose from.

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If you pour (cold) gasoline on a fire, you'll cool the fire, right? I believe that is an apt analogy. Anything you place near a BH will orbit into the BH. There is no break-even distance: Hawking Radiation occurs very near the Event Horizon and stable orbits must be much much further away. see this: https://space.stackexchange.com/questions/1911/is-there-any-stable-orbit-around-a-black-hole

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No. You can’t change the Hawking radiation by any means, period.

The analytic estimate on the linked page includes a crutial result:

$$P = \frac{\hbar c^6}{15360 \pi G^2 M^2}$$

Look what it depends on: universal constants, and the mass of the black hole. Nothing else.

Now look at the pair production you refer to: photons with sufficient energy will reverse the process of anniliation.

pair production

This affects high-energy gamma rays that happen to be present, not any black hole.

Building an entire galaxy? That would be some black hole! Supermassive BH’s are generally 0.5% of the mass of the host galaxy. Meanwhile, about 10% of the primordial gas has been used to make stars.


※ if you really want that in your story, invent something that's beyond the standard model. Invoke quantum gravity.

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    $\begingroup$ This formula does indeed depend only on constants and mass of the black hole, but your answer does not show when it is applicable and what assumptions was made to derive it. Thus, you didn't show it is even applicable when there is a lot of mass next to the event horizon. Please, be more elaborate. $\endgroup$
    – Mołot
    Mar 13 '17 at 15:39
  • $\begingroup$ You just have to trust that Hawking got it right as it's an accepted mainstream result now, or read the analysis on the Wikipedia page I ref'ed. Really, I could have stopped with “No.” $\endgroup$
    – JDługosz
    Mar 13 '17 at 15:43
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    $\begingroup$ You could have stopped with "no" and get it deleted as VLQ. As far as I've seen he derived it for vacuum. And I trust he got it right. But just like speed of light is c, except in water it isn't, I'm not sure this formula is also true for black hole in lead. $\endgroup$
    – Mołot
    Mar 13 '17 at 15:52
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    $\begingroup$ I agree with Molot, that isn't the full equation for Hawking Radiation. That is "a crude analytic analysis" on Wikipedia of "the power emitted by a black hole in the form of Hawking radiation... estimated for the simplest case of a nonrotating, non-charged Schwarzschild black hole of mass M.". A non-rotating, non-charged black hole is the "spherical horse" of astrophysics; every black hole rotates and has charge. $\endgroup$
    – Schwern
    Mar 13 '17 at 18:28
  • $\begingroup$ @JDługosz Whilst I appreciate the input and whilst you may be correct in relation to Hawking radiation and I respect you may have a lot of scientific background and knowledge... this is a creative exchange, is it not? $\endgroup$ Mar 13 '17 at 18:57
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The crux of the question is, I surmise:

Can we increase the rate at which a blackhole decays by increasing the rate of pair production and could this method of increasing the rate be due to heavy metals.

There are a couple of points to make:

  • Yes increasing the rate of pair production would increase the rate at which the blackhole "evaporates" - Assuming no other process is adding mass to the black hole we decrease the life-time.

  • Nuclei with large numbers of protons do increase the rate of pair production from photons passing close by.

So that all seems to support you, right?

However we have some problems:

  • We aren't sure what process it is which creates these pair productions. It could just be an increase in the potential energy at a point. It could be other particles decaying. There are different theories but the point is that the heavy nuclei only help when we're looking at protons.

  • The pair production mean getting a couple of fundamental particles, it really depends on what you're making but the stuff will probably be several orders of magnitude smaller than the nuclei you're putting in (only not the case for the top quark whose mass will probably be of the same order).

  • In other words, if the pair production was all electron-positron, even if you're increasing the pair production by 100 for every nuclei you add - if even one in a thousand nuclei are falling into the black hole they're going to counter this effect.

  • It is more than likely the black-hole would pull in more than this so this process would make them grow rather than shrink.
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