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Consider the facts that a blackhole:

  1. Eats everything that passes through its event horizon.

    In layman's terms, it is defined as the shell of "points of no return", i.e., the boundary at which the gravitational pull of a massive object becomes so great as to make escape impossible.

  2. Disintegrates into "energetic nothingness".

    Hawking radiation reduces the mass and energy of black holes and is therefore also known as black hole evaporation. Because of this, black holes that do not gain mass through other means are expected to shrink and ultimately vanish. Micro black holes are predicted to be larger emitters of radiation than larger black holes and should shrink and dissipate faster.

Therefore, at varying sizes of a blackhole, you can get either an incinerator or an insane battery.


In the world of my Celestials, the Celestials are a posthuman race whose biotechnnology is composed of exotic matter composites, giving them cosmic-level magitek superpowers. I'm hinting massive phlebotinum usage that even I have little idea how to work with yet, hence where I'm gonna need help.

A baseline individual Celestial has a blackhole in its chest where its heart should be, aiding their exotic metabolisms, acting as either an energy source or a waste disposal system.

The idea would be that Celestials can eat anything to survive indefinitely, by having metabolisms that convert Hawking Radiation into more exotic matter or feeding any other matter to the blackhole


Considering that blackholes, in their classical definition, are still bound by physical laws, what methods might Celestials be employing in their bodies to safely store, refuel, and utilize the energy of blackhole hearts without overloading themselves with energy or collapsing in on themselves due to the gravity?


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  • $\begingroup$ The Hawking radiation produced by a black hole is inversely related to its mass. So it’s a positive feedback look. Microscopic black holes are the only ones that produce large amounts of radiation, and they tend to explode, violently. $\endgroup$ – Ethan Reesor Aug 7 '18 at 7:14
  • $\begingroup$ Watched a youtube video on this subject yesterday may not be precisely what you are looking for but I think is pretty close. If you repurpose the "perfect mirror" idea you could get this to work both ways I think. - youtube.com/watch?v=ulCdoCfw-bY $\endgroup$ – BMS21 Aug 7 '18 at 9:39
  • $\begingroup$ @BMS21 Yes, its pretty close. But no classical material can ever have perfect reflectivity, hence the phlebotinum-friendly suggestion. I once thought the solution would be to enclose the blackhole in a perfect shell made of materials with programmable optical properties (transparency, reflectivity, refractivity, etc.). The problem I found with that? The blackhole can only feed on electromagnetic energy. Dropping matter in it is like dropping a coin into an electric fan so, not safe as perfect recycler. $\endgroup$ – Kyle Zabala Aug 7 '18 at 16:53
  • $\begingroup$ Unless the perfect mirror is also a perfect armor, spinning blackhole hearts can still work as energy sources, but then they can't work as recyclers on demand. $\endgroup$ – Kyle Zabala Aug 7 '18 at 16:56
  • $\begingroup$ Since black holes are still theoretical, it gives you some creative latitude to define them as you like, within certain bounds... $\endgroup$ – worldbuilder Feb 1 at 1:43
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No advantages

An energy buffer should have a number of qualities to be considered useful. An energy buffer shall...

  • Accept energy on demand, at an acceptable rate
  • Give energy on demand, at an acceptable rate
  • Be available anywhere

Ok, so your black hole(ish) energy buffer can easily do the first point, no sweat. Then there is trouble...

How are you going to get energy out of there on demand? There is not dimmer installed on a black hole, no throttle, no on/off switch. You cannot poke it or shake it or squeeze it to get it to change its output.

And then there is the issue of mobility. How are your titan(esque) creatures going to move about? The black holes are not held in place in their bodies by scaffolding. Again: you cannot poke a black hole or in any way control it, other than to chuck more stuff into it.

It is easier to just have a Matter-to-Energy-to-Matter converter that operates on Einstein's mass/energy equivalence forumla, $E=mc^2$. These creatures take in matter... converts it into energy and then converts it back into some easilly storable matter. This could even be a "flavour" thing to distinguish between titans... one of them stores it as Gold (because: why not? Dense and compact)... one as diamond... one as Osmium.

But black holes.... that just is not viable if you want to maintain some kind of physical realism. They simply do not fulfill the requirements as viable energy buffers.

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    $\begingroup$ Ive commented on the main post but just to say the video talks about the "perfect mirror" method which should be a viable way of getting energy on demand. $\endgroup$ – BMS21 Aug 7 '18 at 9:41
  • $\begingroup$ Good answer, I actually misread the question thinking "recycler" as "trash" instead of "resusable". You are correct with your answer and I like it. Personally I think that they are the perfect trash cans. If they even exist, which they probably don't. $\endgroup$ – worldbuilder Feb 1 at 1:38
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What is certain is that these black holes would have to be extremely tiny, possibly microscopic. In order to transform the Earth into a black hole, you'd have to compress it to the size of a marble. So to what size would you need to compress an object to become a black hole which does not exert tremendous amounts of gravity or weight on the host body?

Let's assume you start off with a heart with a generous 10kg. If you'd want to compress it to a become a black hole, it will keep its weight and gravitational pull (basically nothing), but become microscopically tiny.

If you consider to have anything heavier than that, let's say 1000kg, you'd need a lot of muscles and body size in order to carry that weight around. It wouldn't even have any significant gravitational pull of its own yet, and the Hawking Radiation wouldn't be remotely sufficient to make it worthwhile. It's more likely that the lifespan would be quite short.

In order to compensate that, you'd need some form of anti-gravity. That way you could justify a lot of mass, and possibly a sizable black hole. But if it fails even for a second, the entire mass would fall through the body towards the planet the host is standing on. Not only that, it would also draw objects around it as if it had the gravity of the Earth. It would be like a pacemaker that may never fail, or else everything around it would die.

I am not sure how much value you could pull off from a black hole heart that is either invisible to the eye (and have little sense to be a black hole given the low mass), or massive enough to be a ticking bomb of planetary mass destruction (which would make it somewhat fictionally usable).

But generally speaking I would say, even in fiction loosely bound to reality, a black hole within the body of an alien of any level of advancement is not a feasible luxury (given that it is not a (natural) necessity).

Remember, there is plenty of magical fiction out there which utilizes the name "black hole" to portray magic that pulls in things into some dark magical entity. But that has nothing to do with actual black holes.

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  • $\begingroup$ The amount of Hawking radiation produced by a black hole is inversely proportional to its mass $\endgroup$ – Ethan Reesor Aug 7 '18 at 7:12
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    $\begingroup$ But if the total mass of the black hole is too small, the total energy it could exert over its lifetime would be minuscule relative to what may be expected to make it worthwhile. And you are right, it would "evaporate" quickly as well, and even with the size of one Earth it wouldn't last too long either, unless it is "fed" in time... with moons or planets... And I assume a longevity of those black hole hearts would be a concern too. $\endgroup$ – Battle Aug 7 '18 at 7:31
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    $\begingroup$ One way, you have too little energy. The other, you have too little power. $\endgroup$ – Ethan Reesor Aug 7 '18 at 7:33
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    $\begingroup$ Theoretically you could balance evaporation and ‘feeding’, thus using the black hole as a matter to energy engine. But practically you’d most likely just blow yourself to bits. $\endgroup$ – Ethan Reesor Aug 7 '18 at 7:36
  • $\begingroup$ * actual theoretical black holes, since they are still unproven and may not even exist. Even Stephen Hawkins now doubts their existence. $\endgroup$ – worldbuilder Feb 1 at 1:40
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It might be feasible but the creatures would be quite weird and I am not sure whether the classical laws of physics would actually still be applicable in this realm.

I once created a python script that performs the calculations, see at the end of this post.

If I input a mass of 1e12 kgs, I get the following output:

Enter mass [kg]1e12
Schwardschild Radius: 1.4851297e-15 m
Surface gravity     : 3.0258475e+31 N
Surface temperature : 1.2269853e+11 K
Power dissipation   : 3.5621128e+08 W
Will evaporate in   : 8.4103192e+19 s
Energy released      : 8.9875518e+28 J

In other words, a steady rate of 350 Megawatts of power due to Hawking Radiation alone with a lifetime that is in excess of the known lifetime of the universe. Also note that the black hole itself is only slightly larger than an atomic nucleus. However, to construct the black hole you would have to squeeze a volume of 10 x 10 x 10 kilometers of water into that space.

While the surface gravity is tremendous, the gravity at a distance of say 1 meter is only a few newtons / kg so static structures at that distance should be safe from gravitational collapse. To keep the black hole in place with respect to the creature you could give the black hole a positive charge (done at construction time) and encase it in a metal sphere with with an almost equal positive charge at say 1 meter from the black hole center, the charge distribution on the outer metal sphere could then be used to compensate for local gravity or to accelerate or decelerate the black hole to compensate for the creatures acceleration and deceleration.

Note that the charges involved would be in the order of several tens of coulombs and while easily achieved for the black hole itself (only several moles of protons in the input material to be added, negligible to the total input number), the encasing metal in the outer shell would have to be stripped from at least one electron per metal atom and I am pretty sure that that does not count as a metal anymore and the metal bonding properties would seriously deteriorate. Of course you can put the encasing metal sphere further away to lower the charge density per amount of metal.

If the creature needs more power, it can always feed the black hole with negatively charged particles by aiming in the neighborhood of the black hole at relativistic speeds so that the particles start orbiting the black hole in close proximity. The combination of bremsstrahlung and collisions between the particles in orbit and the virtual particles and photons near the schwarzschild radius are thought to be a fairly efficient mass to energy converter, converting up to 10% of the incoming mass to energy, though it should be noted that at these scales and timeframes classical or even relativistic laws of physics may no longer be applicable.

The python script:

import math
# manifest constants

SpeedOfLight = 2.99792458e8 # m/s^2
GravitationalConstant = 6.67384e-11 # Nm^2/kg^2
ReducedPlanckConstant = 1.054571726e-34 # Js
BoltzmannConstant = 1.3806488e-23 # J/K
CosmicBackgroundTemperature = 2.725 # K

def schwarzschildradius(mass):
    '''
    Compute the Schwarzshield radius of a given mass @mass. The Schwarzschild
    radius is the distance from the centre of the black hole to its even horizon,
    assuming a perfect sphere.
    '''
    global SpeedOfLight
    global GravitationalConstant

    rs = 2 * GravitationalConstant * mass / math.pow(SpeedOfLight, 2.0)
    return rs

def surfacegravity(mass):
    '''
    Gravity at the event horizon of a black hgole with given mass @mass.
    '''
    global SpeedOfLight
    global GravitationalConstant

    gs = math.pow(SpeedOfLight, 4.0) / ( 4.0 * GravitationalConstant * mass )
    return gs

def surfacetemperature(mass):
    '''
    Surface temperature at the event horizon of a black hgole with given mass @mass
    due to Hawking Radiation
    '''
    global SpeedOfLight
    global GravitationalConstant
    global ReducedPlanckConstant
    global BoltzmannConstant

    th = ReducedPlanckConstant * math.pow(SpeedOfLight, 3.0) / (
        8.0 * math.pi * GravitationalConstant * mass * BoltzmannConstant )
    return th


def willevaporate(mass):
    global CosmicBackgroundTemperature

    return surfacetemperature(mass) > CosmicBackgroundTemperature

def evaporationtime(mass):
    '''
    Black hole dissipation time (due to Hawking Radiation) at initial mass @mass
    '''
    global SpeedOfLight
    global GravitationalConstant
    global ReducedPlanckConstant

    tev = 5120.0 * math.pi * math.pow(GravitationalConstant, 2.0) * math.pow(mass, 3.0) / ( ReducedPlanckConstant * math.pow(SpeedOfLight, 4.0) )
    return tev

def evaporationenergy(mass):
    '''
    Total mass conversion is simple
    '''
    global SpeedOfLight

    return mass * math.pow(SpeedOfLight, 2.0)

def evaporationdissipation(mass):
    '''
    And dissipation is also simple
    '''
    global SpeedOfLight
    global GravitationalConstant
    global ReducedPlanckConstant

    p = ReducedPlanckConstant * math.pow(SpeedOfLight, 6.0) / ( 15360.0 * math.pi * math.pow(GravitationalConstant, 2.0) * math.pow(mass, 2.0) )
    return p



if __name__ == "__main__":
    print "Black hole calculations"
    print "======================="
    print "Example masses: 80 (average human male), 5.972e24 (Earth), 1.98892e30 (Sun), 7.3477e22 (Moon), 1.672621777e-27 (proton)"
    mass = float(raw_input("Enter mass [kg]"))
    print "Schwardschild Radius: %10.7e m" % schwarzschildradius(mass)
    print "Surface gravity     : %10.7e N" % surfacegravity(mass)
    print "Surface temperature : %10.7e K" % surfacetemperature(mass)
    print "Power dissipation   : %10.7e W" % evaporationdissipation(mass)
    if willevaporate(mass):
        print "Will evaporate in   : %10.7e s" % evaporationtime(mass)
        print "Energy released      : %10.7e J" % evaporationenergy(mass)
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  • $\begingroup$ So basically, you're saying the metal sphere is the one that needs to be made of phlebotinum so it can accumulate/generate insane amounts of static charge. Meanwhile, the blackhole needs to be positively charged so that it can be subjected to electrostatic forces, therefore making it relatively safer. The blackhole charging is no problem, but what exotic material can even fulfill the role of the metal sphere.. HHmmm... $\endgroup$ – Kyle Zabala Aug 7 '18 at 16:25
  • $\begingroup$ Also, cool program. Can it also account for the statistics of spinning blackholes (like the one commented by @BMS21? If so, even cooler. Now, where do I find a 1000 cu. km. of water $\endgroup$ – Kyle Zabala Aug 7 '18 at 16:47
  • $\begingroup$ A comet will do nicely. But please note that the amount of energy you need to compress that volume of water (or ice) to a volume only slightly larger than an atomic nucleus is at least equal to the total amount of energy released during the lifetime of the black hole, i.e. 8.9875518e+28 J (conservation of energy). I can think of no physical process that will do that except maybe slingshotting a comet between two tightly orbiting big black holes at precisely the right grazing angle and time but then we get deep into the realm of gravity waves and general relativity. $\endgroup$ – GretchenV Aug 8 '18 at 7:58

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