Energy Storage - Revision history

Lwcamp: /* Carbon super-materials */

2026-03-31T00:33:52Z

Carbon super-materials

← Older revision		Revision as of 17:33, 30 March 2026
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	However, if you only care about charging up the energy storage system <i>once, ever</i>, you can store more energy in it. Taking it all the way up to the failure stress of 200 GPa for perfect armchair nanotubes could, in principle, allow you to store close to 120 MJ/kg for tension-limited devices like flywheels or SMES. This could be promising for charging up advanced energy storage systems for use as explosives; at 120 MJ/kg your energy storage device has approximately 28 times more energy than an equal mass of TNT, and its sudden failure and release of that energy would thus provide an explosive yield roughly equivalent to the detonation of 28 times its mass of that high explosive. The ability of any real material to ever reach this limit is questionable. Even if such a material existed storing this much energy in it would put it at the limit of failure, such that slight bumps or changes in temperature could cause an explosion. Nonetheless, it is useful to science fiction authors as an upper limit to the amount of energy (explosive or otherwise) that can be stored in a device held together by chemical bonds.		However, if you only care about charging up the energy storage system <i>once, ever</i>, you can store more energy in it. Taking it all the way up to the failure stress of 200 GPa for perfect armchair nanotubes could, in principle, allow you to store close to 120 MJ/kg for tension-limited devices like flywheels or SMES. This could be promising for charging up advanced energy storage systems for use as explosives; at 120 MJ/kg your energy storage device has approximately 28 times more energy than an equal mass of TNT, and its sudden failure and release of that energy would thus provide an explosive yield roughly equivalent to the detonation of 28 times its mass of that high explosive. The ability of any real material to ever reach this limit is questionable. Even if such a material existed storing this much energy in it would put it at the limit of failure, such that slight bumps or changes in temperature could cause an explosion. Nonetheless, it is useful to science fiction authors as an upper limit to the amount of energy (explosive or otherwise) that can be stored in a device held together by chemical bonds.

	When considering carbon nanotube yarns as spring energy storage, the stress and strain limits give an energy of about 2 MJ/kg (from ½ × stress at elastic limit × strain at elastic limit / density). Unlike other energy storage methods such as flywheels or SMES, charging the system up beyond its elastic limit offers no benefit – you need to put in more energy to deform it to those levels, but the relaxation back to its new equilibrium deformed shape only gives you back about the amount of energy that can be stored elastically.		When considering carbon nanotube yarns as spring energy storage, the stress and strain limits give an energy of about 2 MJ/kg (from ½ × stress at elastic limit × strain at elastic limit / density)<ref name="CNT_springs"></ref>. Unlike other energy storage methods such as flywheels or SMES, charging the system up beyond its elastic limit offers no benefit – you need to put in more energy to deform it to those levels, but the relaxation back to its new equilibrium deformed shape only gives you back about the amount of energy that can be stored elastically.

	Other carbon supermaterials are also possible. Nanotubes are rolled up graphene sheets whose edges are joined to make a cylinder. This suggests that graphene would have similar elastic behavior to carbon nanotubes and plastic or brittle behavior beyond that point that depends on its orientation. And thus, re-usable energy storage made with graphene sheets would likely have similar constraints on its specific energy. Simulations support this, with stress-strain curves not strongly different from that of carbon nanotubes<ref>[https://www.mdpi.com/1996-1944/10/2/164# Fan, Na & Ren, Zhenzhou & Jing, Guangyin & Guo, Jian & Peng, Bei & Jiang, Hai. (2017). "Numerical Investigation of the Fracture Mechanism of Defective Graphene Sheets." Materials 10(2):164. DOI:10.3390/ma10020164.]</ref>. However, large sheets of graphene are more prone to brittle fracture, as they don't have the convenient limits of being confined to a tube to limit crack propagation.		Other carbon supermaterials are also possible. Nanotubes are rolled up graphene sheets whose edges are joined to make a cylinder. This suggests that graphene would have similar elastic behavior to carbon nanotubes and plastic or brittle behavior beyond that point that depends on its orientation. And thus, re-usable energy storage made with graphene sheets would likely have similar constraints on its specific energy. Simulations support this, with stress-strain curves not strongly different from that of carbon nanotubes<ref>[https://www.mdpi.com/1996-1944/10/2/164# Fan, Na & Ren, Zhenzhou & Jing, Guangyin & Guo, Jian & Peng, Bei & Jiang, Hai. (2017). "Numerical Investigation of the Fracture Mechanism of Defective Graphene Sheets." Materials 10(2):164. DOI:10.3390/ma10020164.]</ref>. However, large sheets of graphene are more prone to brittle fracture, as they don't have the convenient limits of being confined to a tube to limit crack propagation.

Lwcamp: /* Springs */

2026-03-31T00:33:03Z

Springs

← Older revision		Revision as of 17:33, 30 March 2026
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	The specific energy is the energy density divided by the mass density ρ		The specific energy is the energy density divided by the mass density ρ
	<div class="center" style="width: auto; margin-left: auto; margin-right: auto;"> E / M = ½ σ ε / ρ.</div>		<div class="center" style="width: auto; margin-left: auto; margin-right: auto;"> E / M = ½ σ ε / ρ.</div>
	For example, a hypothetical material with a yield strength of σ = 1 GPa and a mass of ρ = 1000 kg/m² could store a specific energy of 1 MJ/kg when used to build a flywheel rim, if it could only elongate by 10% before failure then as a spring it could store at most 5% of that, or 50 kJ/kg. While this example is highly simplified (springs are going to involve tension, compression, and shear, each of which will have different yield strengths) it shows that for good spring storage what you want are high yield strengths, low densities, and high elongations before failure. A high quality spring steel might be able to store about 10 kJ/kg as a spring, Kevlar might store about 45 kJ/kg, while a hypothetical perfect carbon nanotube yarn might be able to support around 2 MJ/kg.		For example, a hypothetical material with a yield strength of σ = 1 GPa and a mass of ρ = 1000 kg/m² could store a specific energy of 1 MJ/kg when used to build a flywheel rim, if it could only elongate by 10% before failure then as a spring it could store at most 5% of that, or 50 kJ/kg. While this example is highly simplified (springs are going to involve tension, compression, and shear, each of which will have different yield strengths) it shows that for good spring storage what you want are high yield strengths, low densities, and high elongations before failure. A high quality spring steel might be able to store about 10 kJ/kg as a spring, Kevlar might store about 45 kJ/kg, while a hypothetical perfect carbon nanotube yarn might be able to support around 2 MJ/kg<ref name="CNT_springs">S. Utsumi <i>et al.</i>, "Giant nanomechanical energy storage capacity in twisted single-walled carbon nanotube ropes"
			Nature Nanotechnology volume 19, pages 1007–1015 (2024) doi: [https://doi.org/10.1038/s41565-024-01645-x 10.1038/s41565-024-01645-x].</ref>.
	Springs also have the usual specific power limits from the [[Energy_Storage#Motors and generators \| electric motor]] or mechanical drivetrain. You have the benefit of nearly no self-discharge, and no need to worry about gyroscopic forces. However, this is a largely untested technology and its limitations are not well understood yet.		Springs also have the usual specific power limits from the [[Energy_Storage#Motors and generators \| electric motor]] or mechanical drivetrain. You have the benefit of nearly no self-discharge, and no need to worry about gyroscopic forces. However, this is a largely untested technology and its limitations are not well understood yet.

Lwcamp: /* Penrose process */

2026-03-13T03:05:38Z

Penrose process

← Older revision		Revision as of 20:05, 12 March 2026
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	===Penrose process===		===Penrose process===

			(Main article [[Black_Hole_Engineering#Penrose_process]])

	If a black hole is spinning, you get an effect vaguely like a space-time blender that whips up a region around the hole just outside the event horizon where the space time is, figurative speaking, "spinning around" the black hole. This is called the <i>ergosphere</i>. If you drop an object so that it falls into the ergosphere on an orbit in the same direction the egrosphere is spinning, and if at the bottom the object launches part of itself backwards (like the impulsive burn of a rocket, say, shooting out propellant for thrust) so that the ejected material falls past the event horizon, the extra kick at low gravitational potential will send the remainder of the object zipping back out faster than it came in. If you do this right, it adds more kinetic energy to the ejected object than the mass energy of the stuff that was dropped in!<ref>[https://ntrs.nasa.gov/api/citations/20180005592/downloads/20180005592.pdf Jeremy D. Schnittman, "The Collisional Penrose Process", NASA GSFC]</ref> This extra energy comes from the rotational energy of the black hole. You can then spin the black hole back up again by throwing stuff in off-center so that it gains angular momentum.		If a black hole is spinning, you get an effect vaguely like a space-time blender that whips up a region around the hole just outside the event horizon where the space time is, figurative speaking, "spinning around" the black hole. This is called the <i>ergosphere</i>. If you drop an object so that it falls into the ergosphere on an orbit in the same direction the egrosphere is spinning, and if at the bottom the object launches part of itself backwards (like the impulsive burn of a rocket, say, shooting out propellant for thrust) so that the ejected material falls past the event horizon, the extra kick at low gravitational potential will send the remainder of the object zipping back out faster than it came in. If you do this right, it adds more kinetic energy to the ejected object than the mass energy of the stuff that was dropped in!<ref>[https://ntrs.nasa.gov/api/citations/20180005592/downloads/20180005592.pdf Jeremy D. Schnittman, "The Collisional Penrose Process", NASA GSFC]</ref> This extra energy comes from the rotational energy of the black hole. You can then spin the black hole back up again by throwing stuff in off-center so that it gains angular momentum.

Lwcamp: /* Black hole creation */

2026-03-13T03:04:50Z

Black hole creation

← Older revision		Revision as of 20:04, 12 March 2026
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	===Black hole creation===		===Black hole creation===

	if moderate amounts of matter or energy can somehow be crushed into a black hole, that black hole will almost instantly evaporate via the Hawking process to produce a flash of ~~electromagnetic~~ radiation. The fact that no one can figure out any way to cause such a collapse is a bit of a hitch in this plan, but we can speculate on the results of what would happen if you did so.		if moderate amounts of matter or energy can somehow be crushed into a black hole, [[Black_Hole_Engineering#Hawking_radiation\|that black hole will almost instantly evaporate via the Hawking process to produce a flash of energetic radiation]]. The fact that no one can figure out any way to cause such a collapse is a bit of a hitch in this plan, but we can speculate on the results of what would happen if you did so.

	A small black hole cannot be fed. Its radiation produces so much pressure than incoming matter is pushed away from the hole, and even without that matter bunches up in a jam trying to get into the tiny hole so that it can only feed at a trickle. So such a hole is in some sense "safe" – you made it, it can't eat the planet, and no matter what you do it is going to evaporate in a flash of energetic radiation. The minimum mass at which a black hole can start eating material is a bit under 100 million metric tons; but not until approximately 100 million tons can it absorb matter faster than it radiates away the energy it is getting. So if you keep your hole at significantly less than 100 million tons, you won't be endangering the planet. And just for reference, that 100 million ton black hole will be spitting out a variety of 100 MeV radiation particles (gamma rays, neutrinos, electron, positrons, muons, various mesons, and gravitational waves) at a rate of 1.4 TW (of which about 700 GW of which is capable of interacting with matter), with a lifetime (if it doesn't eat anything) of about 67 million years. If it is allowed to eat stuff, it will stabilize to a usable power output of around a TW between its hawking radiation and the radiation from its accretion disk. And that 100 million tons will be compactified into a radius five times smaller than a proton, so there is no way that you can actually hold on to it in any kind of gravitational field – it will simply fall into the planet with little resistance, eating a few micrograms of stuff each second and putting out as much power as a large power station as harsh radiation as it plunges into the Earth.		[[Black_Hole_Engineering#Feeding_a_black_hole\|A small black hole cannot be fed]]. Its radiation produces so much pressure than incoming matter is pushed away from the hole, and even without that matter bunches up in a jam trying to get into the tiny hole so that it can only feed at a trickle. So such a hole is in some sense "safe" – you made it, it can't eat the planet, and no matter what you do it is going to evaporate in a flash of energetic radiation. The minimum mass at which a black hole can start eating material is a bit under 100 million metric tons; but not until approximately 100 million tons can it absorb matter faster than it radiates away the energy it is getting. So if you keep your hole at significantly less than 100 million tons, you won't be endangering the planet. And just for reference, that 100 million ton black hole will be spitting out a variety of 100 MeV radiation particles (gamma rays, neutrinos, electron, positrons, muons, various mesons, and gravitational waves) at a rate of 1.4 TW (of which about 700 GW of which is capable of interacting with matter), with a lifetime (if it doesn't eat anything) of about 67 million years. If it is allowed to eat stuff, it will stabilize to a usable power output of around a TW between its hawking radiation and the radiation from its accretion disk. And that 100 million tons will be compactified into a radius five times smaller than a proton, so there is no way that you can actually hold on to it in any kind of gravitational field – it will simply fall into the planet with little resistance, eating a few micrograms of stuff each second and putting out as much power as a large power station as harsh radiation as it plunges into the Earth.

	But what about a smaller hole. Like, one that is formed from only a kg of matter. Such a hole will completely evaporate in less than one ten-thousandth of a trillionth of a second, releasing on the order of 20 megatons of energy in the process in the form of extremely high energy particles; gamma rays and hadrons and leptons of all kinds, weak vector bosons, Higgs particles, and perhaps other exotic paticles we haven't detected yet, all at energies so high that we don't really know how they would behave because we lack any experimental evidence at that energy scale, but which would probably produce extensive hadronic and gamma air showers scattering intense radiation over many kilometers in all directions. But at least anyone affected by the radiation will also have been burned to a crisp by the thermal flash before being blown to crumbly bits by the blast wave.		But what about a smaller hole. Like, one that is formed from only a kg of matter. Such a hole will completely evaporate in less than one ten-thousandth of a trillionth of a second, releasing on the order of 20 megatons of energy in the process in the form of extremely high energy particles; gamma rays and hadrons and leptons of all kinds, weak vector bosons, Higgs particles, and perhaps other exotic paticles we haven't detected yet, all at energies so high that we don't really know how they would behave because we lack any experimental evidence at that energy scale, but which would probably produce extensive hadronic and gamma air showers scattering intense radiation over many kilometers in all directions. But at least anyone affected by the radiation will also have been burned to a crisp by the thermal flash before being blown to crumbly bits by the blast wave.

Lwcamp: /* Accretion disks */

2026-03-13T03:02:06Z

Accretion disks

← Older revision		Revision as of 20:02, 12 March 2026
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	===Accretion disks===		===Accretion disks===

			(Main article [[Black_Hole_Engineering#Accretion_disks_and_astrophysical_jets]])

	If you drop matter at a black hole but somewhat offset from a direct line, conservation of angular momentum dictates that the stuff dropped will start to orbit around the black hole instead of falling straight through the event horizon. As the matter approaches the hole, those parts of the object that are closer will experience higher gravity than those farther away, making them orbit faster. These tidal forces rip the object apart, spreading it out into a disk around the hole, and the way that the tidal forces squeeze and shear this material heat the matter up. As the matter gets hot, it radiates away some of that heat, causing it to lose energy and fall closer in to the hole, which in turn generates more heat. This process can convert between about 5% to 40% of the mass energy of an infalling object into radiation (depending on the spin of the black hole). Although less efficient than antimatter or baryon decay, it has the advantage that a lot of the emitted energy is easier to use – infrared to x-rays rather than high energy gamma rays and exotic penetrating particles. It has the disadvantage of requiring a black hole.		If you drop matter at a black hole but somewhat offset from a direct line, conservation of angular momentum dictates that the stuff dropped will start to orbit around the black hole instead of falling straight through the event horizon. As the matter approaches the hole, those parts of the object that are closer will experience higher gravity than those farther away, making them orbit faster. These tidal forces rip the object apart, spreading it out into a disk around the hole, and the way that the tidal forces squeeze and shear this material heat the matter up. As the matter gets hot, it radiates away some of that heat, causing it to lose energy and fall closer in to the hole, which in turn generates more heat. This process can convert between about 5% to 40% of the mass energy of an infalling object into radiation (depending on the spin of the black hole). Although less efficient than antimatter or baryon decay, it has the advantage that a lot of the emitted energy is easier to use – infrared to x-rays rather than high energy gamma rays and exotic penetrating particles. It has the disadvantage of requiring a black hole.

Lwcamp: /* Accretion disks */

2026-03-13T03:00:11Z

Accretion disks

← Older revision		Revision as of 20:00, 12 March 2026
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	===Accretion disks===		===Accretion disks===

	If you drop matter at a black hole but somewhat offset from a direct line, conservation of angular momentum dictates that the stuff dropped will start to orbit around the black hole instead of falling straight through the event horizon. As the matter approaches the hole, those parts of the object that are closer will experience higher gravity than those farther away, making them orbit faster. These tidal forces rip the object apart, spreading it out into a disk around the hole, and the way that the tidal forces squeeze and shear this material heat the matter up. As the matter gets hot, it radiates away some of that heat, causing it to lose energy and fall closer in to the hole, which in turn generates more heat. This process ~~will~~ convert about 40% of the mass energy of an infalling object into radiation. Although less efficient than antimatter or baryon decay, it has the advantage that a lot of the emitted energy is easier to use – infrared to x-rays rather than high energy gamma rays and exotic penetrating particles. It has the disadvantage of requiring a black hole.		If you drop matter at a black hole but somewhat offset from a direct line, conservation of angular momentum dictates that the stuff dropped will start to orbit around the black hole instead of falling straight through the event horizon. As the matter approaches the hole, those parts of the object that are closer will experience higher gravity than those farther away, making them orbit faster. These tidal forces rip the object apart, spreading it out into a disk around the hole, and the way that the tidal forces squeeze and shear this material heat the matter up. As the matter gets hot, it radiates away some of that heat, causing it to lose energy and fall closer in to the hole, which in turn generates more heat. This process can convert between about 5% to 40% of the mass energy of an infalling object into radiation (depending on the spin of the black hole). Although less efficient than antimatter or baryon decay, it has the advantage that a lot of the emitted energy is easier to use – infrared to x-rays rather than high energy gamma rays and exotic penetrating particles. It has the disadvantage of requiring a black hole.

	==Space-time storage==		==Space-time storage==

Lwcamp at 19:00, 7 March 2026

2026-03-07T19:00:27Z

← Older revision		Revision as of 12:00, 7 March 2026
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	==References==		==References==
	[[Category:Physics & Engineering‏‎]][[Category:Engineering‏‎]]		[[Category:Physics & Engineering‏‎]][[Category:Physics & Math & Engineering]][[Category:Engineering‏‎]]

Lwcamp: /* Black hole creation */

2026-02-03T07:00:24Z

Black hole creation

← Older revision		Revision as of 00:00, 3 February 2026
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	A small black hole cannot be fed. Its radiation produces so much pressure than incoming matter is pushed away from the hole, and even without that matter bunches up in a jam trying to get into the tiny hole so that it can only feed at a trickle. So such a hole is in some sense "safe" – you made it, it can't eat the planet, and no matter what you do it is going to evaporate in a flash of energetic radiation. The minimum mass at which a black hole can start eating material is a bit under 100 million metric tons; but not until approximately 100 million tons can it absorb matter faster than it radiates away the energy it is getting. So if you keep your hole at significantly less than 100 million tons, you won't be endangering the planet. And just for reference, that 100 million ton black hole will be spitting out a variety of 100 MeV radiation particles (gamma rays, neutrinos, electron, positrons, muons, various mesons, and gravitational waves) at a rate of 1.4 TW (of which about 700 GW of which is capable of interacting with matter), with a lifetime (if it doesn't eat anything) of about 67 million years. If it is allowed to eat stuff, it will stabilize to a usable power output of around a TW between its hawking radiation and the radiation from its accretion disk. And that 100 million tons will be compactified into a radius five times smaller than a proton, so there is no way that you can actually hold on to it in any kind of gravitational field – it will simply fall into the planet with little resistance, eating a few micrograms of stuff each second and putting out as much power as a large power station as harsh radiation as it plunges into the Earth.		A small black hole cannot be fed. Its radiation produces so much pressure than incoming matter is pushed away from the hole, and even without that matter bunches up in a jam trying to get into the tiny hole so that it can only feed at a trickle. So such a hole is in some sense "safe" – you made it, it can't eat the planet, and no matter what you do it is going to evaporate in a flash of energetic radiation. The minimum mass at which a black hole can start eating material is a bit under 100 million metric tons; but not until approximately 100 million tons can it absorb matter faster than it radiates away the energy it is getting. So if you keep your hole at significantly less than 100 million tons, you won't be endangering the planet. And just for reference, that 100 million ton black hole will be spitting out a variety of 100 MeV radiation particles (gamma rays, neutrinos, electron, positrons, muons, various mesons, and gravitational waves) at a rate of 1.4 TW (of which about 700 GW of which is capable of interacting with matter), with a lifetime (if it doesn't eat anything) of about 67 million years. If it is allowed to eat stuff, it will stabilize to a usable power output of around a TW between its hawking radiation and the radiation from its accretion disk. And that 100 million tons will be compactified into a radius five times smaller than a proton, so there is no way that you can actually hold on to it in any kind of gravitational field – it will simply fall into the planet with little resistance, eating a few micrograms of stuff each second and putting out as much power as a large power station as harsh radiation as it plunges into the Earth.

	But what about a smaller hole. Like, one that is formed from only a kg of matter. Such a hole will completely evaporate in less than one ten-thousandth of a trillionth of a second, releasing on the order of 20 megatons of energy in the process in the form of extremely high energy particles; gamma rays and hadrons and leptons of all kinds, weak vector bosons, Higgs particles, and perhaps other exotic paticles we haven't detected yet, all at energies so high that we don't really know how they would behave because we lack any experimental evidence at that energy scale, but which would probably produce extensive hadronic and gamma air showers scattering intense radiation over many kilometers in all directions. But at least anyone affected by the radiation will also have been burned to a crisp by the thermal flash before being ~~blow~~ to crumbly bits by the blast wave.		But what about a smaller hole. Like, one that is formed from only a kg of matter. Such a hole will completely evaporate in less than one ten-thousandth of a trillionth of a second, releasing on the order of 20 megatons of energy in the process in the form of extremely high energy particles; gamma rays and hadrons and leptons of all kinds, weak vector bosons, Higgs particles, and perhaps other exotic paticles we haven't detected yet, all at energies so high that we don't really know how they would behave because we lack any experimental evidence at that energy scale, but which would probably produce extensive hadronic and gamma air showers scattering intense radiation over many kilometers in all directions. But at least anyone affected by the radiation will also have been burned to a crisp by the thermal flash before being blown to crumbly bits by the blast wave.

	To get a hole that lasts for one second, it needs to be a bit over 1000 tons (with a yield of 25 trillion tons TNT equivalent) and will emit 10 TeV particles as its radiation. Holes that produce less than a megaton of yield will produce even more energetic and exotic radiation that the 1 kg variety, that will be likely to pose a radiation threat to the entire area. So black hole power sources seem to be a bit finicky to use.		To get a hole that lasts for one second, it needs to be a bit over 1000 tons (with a yield of 25 trillion tons TNT equivalent) and will emit 10 TeV particles as its radiation. Holes that produce less than a megaton of yield will produce even more energetic and exotic radiation that the 1 kg variety, that will be likely to pose a radiation threat to the entire area. So black hole power sources seem to be a bit finicky to use.

Lwcamp: /* Black hole creation */

2026-02-03T06:59:32Z

Black hole creation

← Older revision		Revision as of 23:59, 2 February 2026
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	if moderate amounts of matter or energy can somehow be crushed into a black hole, that black hole will almost instantly evaporate via the Hawking process to produce a flash of electromagnetic radiation. The fact that no one can figure out any way to cause such a collapse is a bit of a hitch in this plan, but we can speculate on the results of what would happen if you did so.		if moderate amounts of matter or energy can somehow be crushed into a black hole, that black hole will almost instantly evaporate via the Hawking process to produce a flash of electromagnetic radiation. The fact that no one can figure out any way to cause such a collapse is a bit of a hitch in this plan, but we can speculate on the results of what would happen if you did so.

	A small black hole cannot be fed. Its radiation produces so much pressure than incoming matter is pushed away from the hole, and even without that matter bunches up in a jam trying to get into the tiny hole so that it can only feed at a trickle. So such a hole is in some sense "safe" – you made it, it can't eat the planet, and no matter what you do it is going to evaporate in a flash of energetic radiation. The minimum mass at which a black hole can start eating material is a bit under 100 million metric tons; but not until approximately 100 million tons can it absorb matter faster than it radiates away the energy it is getting. So if you keep your hole at significantly less than 100 million tons, you won't be endangering the planet. And just for reference, that 100 million ton black hole will be spitting out a variety of 100 MeV radiation particles (gamma rays, neutrinos, electron, positrons, muons, various mesons, and gravitational waves) at a rate of 1.4 TW (of which about 700 GW of which is capable of interacting with matter), with a lifetime (if it doesn't eat anything) of about 67 million years. If it is allowed to eat stuff, it will stabilize to a usable power output of ~~a bit over~~ a TW between its hawking radiation and the radiation from its accretion disk. And that 100 million tons will be compactified into a radius five times smaller than a proton, so there is no way that you can actually hold on to it in any kind of gravitational field – it will simply fall into the planet with little resistance, eating a few micrograms of stuff each second and putting out as much power as a large power station as harsh radiation as it plunges into the Earth.		A small black hole cannot be fed. Its radiation produces so much pressure than incoming matter is pushed away from the hole, and even without that matter bunches up in a jam trying to get into the tiny hole so that it can only feed at a trickle. So such a hole is in some sense "safe" – you made it, it can't eat the planet, and no matter what you do it is going to evaporate in a flash of energetic radiation. The minimum mass at which a black hole can start eating material is a bit under 100 million metric tons; but not until approximately 100 million tons can it absorb matter faster than it radiates away the energy it is getting. So if you keep your hole at significantly less than 100 million tons, you won't be endangering the planet. And just for reference, that 100 million ton black hole will be spitting out a variety of 100 MeV radiation particles (gamma rays, neutrinos, electron, positrons, muons, various mesons, and gravitational waves) at a rate of 1.4 TW (of which about 700 GW of which is capable of interacting with matter), with a lifetime (if it doesn't eat anything) of about 67 million years. If it is allowed to eat stuff, it will stabilize to a usable power output of around a TW between its hawking radiation and the radiation from its accretion disk. And that 100 million tons will be compactified into a radius five times smaller than a proton, so there is no way that you can actually hold on to it in any kind of gravitational field – it will simply fall into the planet with little resistance, eating a few micrograms of stuff each second and putting out as much power as a large power station as harsh radiation as it plunges into the Earth.

	But what about a smaller hole. Like, one that is formed from only a kg of matter. Such a hole will completely evaporate in less than one ten-thousandth of a trillionth of a second, releasing on the order of 20 megatons of energy in the process in the form of extremely high energy particles; gamma rays and hadrons and leptons of all kinds, weak vector bosons, Higgs particles, and perhaps other exotic paticles we haven't detected yet, all at energies so high that we don't really know how they would behave because we lack any experimental evidence at that energy scale, but which would probably produce extensive hadronic and gamma air showers scattering intense radiation over many kilometers in all directions. But at least anyone affected by the radiation will also have been burned to a crisp by the thermal flash before being blow to crumbly bits by the blast wave.		But what about a smaller hole. Like, one that is formed from only a kg of matter. Such a hole will completely evaporate in less than one ten-thousandth of a trillionth of a second, releasing on the order of 20 megatons of energy in the process in the form of extremely high energy particles; gamma rays and hadrons and leptons of all kinds, weak vector bosons, Higgs particles, and perhaps other exotic paticles we haven't detected yet, all at energies so high that we don't really know how they would behave because we lack any experimental evidence at that energy scale, but which would probably produce extensive hadronic and gamma air showers scattering intense radiation over many kilometers in all directions. But at least anyone affected by the radiation will also have been burned to a crisp by the thermal flash before being blow to crumbly bits by the blast wave.

Lwcamp: /* Electron degenerate matter */

2026-01-09T16:57:15Z

Electron degenerate matter

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	No two electrons can occupy the same quantum state. This can be expressed as no two electrons (with the same spin) can occupy the same place at the same time, but an equivalent statement is that you can't have more than one electron (with the same spin) in a given electron energy level. As you compress matter, you are trying to compress more and more electrons into the same number of available energy levels. Eventually you reach a state called a degenerate Fermi gas, where all the low-lying electron states are filled, and to cram in more electrons you need to put them in higher and higher energy states on top of the ones already filled. When a star runs out of fusion fuel, cools off, and contracts, it will get crushed under its own gravity to an electron degenerate state with densities on the order of a billion kilograms per cubic meter (10<sup>9</sup> kg/m<sup>3</sup>). Under these conditions, the degenerate electron gas will have a specific energy on the order of a kiloton per kilogram and a pressure of around 3×10<sup>21</sup> Pa (30,000 trillion times Earth atmospheric pressure).		No two electrons can occupy the same quantum state. This can be expressed as no two electrons (with the same spin) can occupy the same place at the same time, but an equivalent statement is that you can't have more than one electron (with the same spin) in a given electron energy level. As you compress matter, you are trying to compress more and more electrons into the same number of available energy levels. Eventually you reach a state called a degenerate Fermi gas, where all the low-lying electron states are filled, and to cram in more electrons you need to put them in higher and higher energy states on top of the ones already filled. When a star runs out of fusion fuel, cools off, and contracts, it will get crushed under its own gravity to an electron degenerate state with densities on the order of a billion kilograms per cubic meter (10<sup>9</sup> kg/m<sup>3</sup>). Under these conditions, the degenerate electron gas will have a specific energy on the order of a kiloton per kilogram and a pressure of around 3×10<sup>21</sup> Pa (30,000 trillion times Earth atmospheric pressure).

	Note that the electron degenerate gas is <i>unbound</i>. There is nothing keeping it together other than whatever is supplying the external pressure (usually the gravity of a dead sun). If removed from that pressure it will immediately expand. Violently. Immediately liberating that kiloton per kg in a massive explosion. There is no material that can contain those pressures – and even if there was, the most energetic electrons in the degenerate matter at that density are flying around at energies typical of [[Nuclear_radiation#Beta\|radioactive beta decay]] (about 150 keV, for the density discussed here), fast enough to simply ignore chemical bonds and go shooting through matter unhindered, except for the trail of ionization destruction that they would leave in their wake. So comparisons you often find like "one teaspoon of white dwarf material would weigh as much as a freight train" gloss over the fact that you simply can't take that teaspoon away from the white dwarf – such things are simply inconsistent with existence under conditions typical of Earth (or outer space, or the ~~even~~ core of an active sun).		Note that the electron degenerate gas is <i>unbound</i>. There is nothing keeping it together other than whatever is supplying the external pressure (usually the gravity of a dead sun). If removed from that pressure it will immediately expand. Violently. Immediately liberating that kiloton per kg in a massive explosion. There is no material that can contain those pressures – and even if there was, the most energetic electrons in the degenerate matter at that density are flying around at energies typical of [[Nuclear_radiation#Beta\|radioactive beta decay]] (about 150 keV, for the density discussed here), fast enough to simply ignore chemical bonds and go shooting through matter unhindered, except for the trail of ionization destruction that they would leave in their wake. So comparisons you often find like "one teaspoon of white dwarf material would weigh as much as a freight train" gloss over the fact that you simply can't take that teaspoon away from the white dwarf – such things are simply inconsistent with existence under conditions typical of Earth (or outer space, or even the core of an active sun).

	But if you have Sufficiently Advanced aliens in your setting, with access to non-molecular supermaterials or force screens or something; and if those are sufficient to contain electron degenerate matter, now you have some idea of what it would do.		But if you have Sufficiently Advanced aliens in your setting, with access to non-molecular supermaterials or force screens or something; and if those are sufficient to contain electron degenerate matter, now you have some idea of what it would do.