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Micro black hole

Micro black hole

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Micro black holes are tiny black holes, also called quantum mechanical black holes or mini black holes, for which quantum mechanical
Quantum mechanics
Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...

 effects play an important role.

It is possible that such quantum primordial black holes were created in the high-density environment of the early Universe (or big bang
Big Bang
The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in...

), or possibly through subsequent phase transitions. They might be observed by astrophysicists in the near future, through the particles they are expected to emit by Hawking radiation
Hawking radiation
Hawking radiation is a thermal radiation with a black body spectrum predicted to be emitted by black holes due to quantum effects. It is named after the physicist Stephen Hawking, who provided a theoretical argument for its existence in 1974, and sometimes also after the physicist Jacob Bekenstein...

.

Some theories involving additional space dimensions predict that micro black holes could be formed at an energy as low as the TeV
TEV
TEV may refer to:* TeV, or teraelectronvolt, a measure of energy* Total Enterprise Value, a financial measure* Total Economic Value, an economic measure* Tobacco etch virus, a plant pathogenic virus of the family Potyviridae....

 range, which will be available in particle accelerators such as the LHC (Large Hadron Collider
Large Hadron Collider
The Large Hadron Collider is the world's largest and highest-energy particle accelerator. It is expected to address some of the most fundamental questions of physics, advancing the understanding of the deepest laws of nature....

). Popular concerns have then been raised over end-of-the-world scenarios (see Safety of particle collisions at the Large Hadron Collider). However, such quantum black holes would instantly evaporate, either totally or leaving only a very weakly interacting residue. Beside the theoretical arguments, we can notice that the cosmic rays bombarding the Earth do not produce any damage, although they reach center of mass
Center of mass
In physics, the center of mass or barycenter of a system is the average location of all of its mass. In the case of a rigid body, the position of the center of mass is fixed in relation to the body...

 energies in the range of hundreds of TeV
Electronvolt
In physics, the electron volt is a unit of energy equal to approximately joule . By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt...

.

Minimum mass of a black hole


In principle, a black hole can have any mass equal to or above the Planck mass.
To make a black hole, one must concentrate mass or energy sufficiently that the escape velocity
Escape velocity
In physics, escape velocity is the speed at which the kinetic energy plus the gravitational potential energy of an object is zero gravitational potential energy is negative since gravity is an attractive force and the potential is defined to be zero at infinity...

 from the region in which it is concentrated exceeds the speed of light. This condition gives the Schwarzschild radius
Schwarzschild radius
The Schwarzschild radius is the distance from the center of an object such that, if all the mass of the object were compressed within that sphere, the escape speed from the surface would equal the speed of light...

, , where G is Gravitational constant and c is the speed of light, of a black hole of mass M. On the other hand, the Compton wavelength
Compton wavelength
The Compton wavelength is a quantum mechanical property of a particle. It was introduced by Arthur Compton in his explanation of the scattering of photons by electrons...

, , where h is Planck's constant
Planck constant
The Planck constant , also called Planck's constant, is a physical constant reflecting the sizes of energy quanta in quantum mechanics. It is named after Max Planck, one of the founders of quantum theory, who discovered it in 1899...

, represents a limit on the minimum size of the region in which a mass M at rest can be localized. For sufficiently small M, the reduced Compton wavelength (, where ħ is Dirac's constant
Planck constant
The Planck constant , also called Planck's constant, is a physical constant reflecting the sizes of energy quanta in quantum mechanics. It is named after Max Planck, one of the founders of quantum theory, who discovered it in 1899...

) exceeds half the Schwarzschild radius, and no black hole description exists. This smallest mass for a black hole is thus approximately the Planck mass.

Some extensions of present physics posit the existence of extra dimensions of space. In higher-dimensional spacetime, the strength of gravity increases more rapidly with decreasing distance than in three dimensions. With certain special configurations of the extra dimensions, this effect can lower the Planck scale to the TeV range. Examples of such extensions include large extra dimension
Large extra dimension
In particle physics, models with universal extra dimensions propose that there are one or more additional dimensions beyond the three spatial dimensions and one temporal dimension that are observed...

s, special cases of the Randall-Sundrum model
Randall-Sundrum model
In physics, Randall–Sundrum models imagine that the real world is a higher-dimensional Universe described by warped geometry...

, and String theory
String theory
String theory is an active research framework in particle physics that attempts to reconcile quantum mechanics and general relativity. It is a contender for a theory of everything , a manner of describing the known fundamental forces and matter in a mathematically complete system...

 configurations like the GKP solutions. In such scenarios, black hole production could possibly be an important and observable effect at the LHC
Large Hadron Collider
The Large Hadron Collider is the world's largest and highest-energy particle accelerator. It is expected to address some of the most fundamental questions of physics, advancing the understanding of the deepest laws of nature....

.
It would also be a common natural phenomenon induced by the cosmic rays.

Hawking radiation



In 1974 Stephen Hawking
Stephen Hawking
Stephen William Hawking, CH, CBE, FRS, FRSA is an English theoretical physicist and cosmologist, whose scientific books and public appearances have made him an academic celebrity...

 argued that due to quantum
Quantum
In physics, a quantum is the minimum amount of any physical entity involved in an interaction. Behind this, one finds the fundamental notion that a physical property may be "quantized," referred to as "the hypothesis of quantization". This means that the magnitude can take on only certain discrete...

 effects,
black holes "evaporate" by a process now referred to as Hawking radiation
Hawking radiation
Hawking radiation is a thermal radiation with a black body spectrum predicted to be emitted by black holes due to quantum effects. It is named after the physicist Stephen Hawking, who provided a theoretical argument for its existence in 1974, and sometimes also after the physicist Jacob Bekenstein...

 in which elementary particles (photons, electrons, quarks, gluons, etc.) are emitted. His calculations show that the smaller the size of the black hole, the faster the evaporation rate, resulting in a sudden burst of particles as the micro black hole suddenly explodes.

Any primordial black hole of sufficiently low mass will Hawking evaporate to near the Planck mass within the lifetime of the Universe. In this process, these small black holes radiate away matter. A rough picture of this is that pairs of virtual particle
Virtual particle
In physics, a virtual particle is a particle that exists for a limited time and space. The energy and momentum of a virtual particle are uncertain according to the uncertainty principle...

s emerge from the vacuum
Vacuum state
In quantum field theory, the vacuum state is the quantum state with the lowest possible energy. Generally, it contains no physical particles...

 near the event horizon
Event horizon
In general relativity, an event horizon is a boundary in spacetime beyond which events cannot affect an outside observer. In layman's terms it is defined as "the point of no return" i.e. the point at which the gravitational pull becomes so great as to make escape impossible. The most common case...

, with one member of a pair being captured, and the other escaping the vicinity of the black hole. The net result is the black hole loses mass (due to conservation of energy
Conservation of energy
The nineteenth century law of conservation of energy is a law of physics. It states that the total amount of energy in an isolated system remains constant over time. The total energy is said to be conserved over time...

). According to the formulae of black hole thermodynamics
Black hole thermodynamics
In physics, black hole thermodynamics is the area of study that seeks to reconcile the laws of thermodynamics with the existence of black hole event horizons...

, the more the black hole loses mass the hotter it becomes, and the faster it evaporates, until it approaches the Planck mass. At this stage a black hole would have a Hawking temperature of TP / 8π (5.6×1032 K), which means an emitted Hawking particle would have an energy comparable to the mass of the black hole. Thus a thermodynamic description breaks down. Such a mini-black hole would also have an entropy of only 4π nats
Nat (information)
A nat is a logarithmic unit of information or entropy, based on natural logarithms and powers of e, rather than the powers of 2 and base 2 logarithms which define the bit. The nat is the natural unit for information entropy...

, approximately the minimum possible value. At this point then, the object can no longer be described as a classical black hole, and Hawking's calculations also break down.

While Hawking radiation is sometimes questioned, Leonard Susskind
Leonard Susskind
Leonard Susskind is the Felix Bloch Professor of Theoretical Physics at Stanford University. His research interests include string theory, quantum field theory, quantum statistical mechanics and quantum cosmology...

 summarizes an expert perspective in his recent book: "Every so often, a physics paper will appear claiming that black holes don't evaporate. Such papers quickly disappear into the infinite junk heap of fringe ideas."

Conjectures for the final state


Conjectures for the final fate of the black hole include total evaporation and production of a Planck mass-sized black hole remnant. It is possible that such Planck-mass black holes, no longer able either to absorb energy gravitationally like a classical black hole because of the quantised gaps between their allowed energy levels, nor to emit Hawking particles for the same reason, may in effect be stable objects. In such case, they would be WIMPs (weakly interacting massive particles); this could explain dark matter
Dark matter
In astronomy and cosmology, dark matter is matter that neither emits nor scatters light or other electromagnetic radiation, and so cannot be directly detected via optical or radio astronomy...

.

Formation in the early Universe


Production of a black hole requires concentration of mass or energy within the corresponding Schwarzschild radius
Schwarzschild radius
The Schwarzschild radius is the distance from the center of an object such that, if all the mass of the object were compressed within that sphere, the escape speed from the surface would equal the speed of light...

. It is hypothesized that shortly after the big bang
Big Bang
The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in...

 the Universe was dense enough to fit within its own Schwarzschild radius. Even so, at that time the Universe was not able to collapse into a singularity
Gravitational singularity
A gravitational singularity or spacetime singularity is a location where the quantities that are used to measure the gravitational field become infinite in a way that does not depend on the coordinate system...

 due to its uniform mass distribution and rapid growth. This, however, does not fully exclude the possibility that black holes of various sizes may have emerged locally. A black hole formed in this way is called a primordial black hole
Primordial black hole
A primordial black hole is a hypothetical type of black hole that is formed not by the gravitational collapse of a large star but by the extreme density of matter present during the universe's early expansion....

 and is the most widely accepted theory for the possible creation of micro black holes.

Expected observable effects


Primordial black holes of initial masses around 1015 grams would be completing their evaporation today; lighter primordial black holes would have already evaporated. In optimistic circumstances, the Fermi Gamma-ray Space Telescope satellite, launched in June 2008, might detect experimental evidence for evaporation of nearby black holes by observing gamma ray bursts. It is unlikely that a collision between a microscopic black hole and an object such as a star or a planet would be noticeable. This is due to the fact that the small radius and high density of the black hole would allow it to pass straight through any object consisting of normal atoms, interacting with only few of its atoms while doing so. It has, however, been suggested that a small black hole (of sufficient mass) passing through the Earth would produce a detectable acoustic or seismic
Seismology
Seismology is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. The field also includes studies of earthquake effects, such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, oceanic,...

 signal.

Can we produce micro black holes?


In familiar three-dimensional gravity, the minimum energy of a microscopic black hole is 1019 GeV
Electronvolt
In physics, the electron volt is a unit of energy equal to approximately joule . By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt...

, which would have to be condensed into a region on the order of the Planck length. This is far beyond the limits of any current technology. It is estimated that to collide two particles to within a distance of a Planck length with currently achievable magnetic field strengths would require a ring accelerator about 1000 light years in diameter to keep the particles on track. Stephen Hawking
Stephen Hawking
Stephen William Hawking, CH, CBE, FRS, FRSA is an English theoretical physicist and cosmologist, whose scientific books and public appearances have made him an academic celebrity...

 also said in chapter 6 of his Brief History of Time that physicist John Archibald Wheeler
John Archibald Wheeler
John Archibald Wheeler was an American theoretical physicist who was largely responsible for reviving interest in general relativity in the United States after World War II. Wheeler also worked with Niels Bohr in explaining the basic principles behind nuclear fission...

 once calculated that a very powerful hydrogen bomb using all the deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...

 in all the water on Earth could also generate such a black hole, but Hawking does not provide this calculation or any reference to it to support this assertion.

However, in some scenarios involving extra dimensions of space, the Planck mass can be as low as the TeV
Electronvolt
In physics, the electron volt is a unit of energy equal to approximately joule . By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt...

 range. The Large Hadron Collider
Large Hadron Collider
The Large Hadron Collider is the world's largest and highest-energy particle accelerator. It is expected to address some of the most fundamental questions of physics, advancing the understanding of the deepest laws of nature....

  (LHC) has a design energy of 14 TeV for proton
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....

-proton collisions and 1150 TeV for Pb
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

-Pb collisions. It was argued in 2001 that in these circumstances black hole production could be an important and observable effect at the LHC
or future higher-energy colliders. Such quantum black holes should decay emitting sprays of particles that could be seen by detectors at these facilities. A paper by Choptuik and Pretorius, published on March 17, 2010 in Physical Review Letters
Physical Review Letters
Physical Review Letters , established in 1958, is a peer reviewed, scientific journal that is published 52 times per year by the American Physical Society...

, presented a computer-generated proof that micro black holes must form from two colliding particles with sufficient energy, which might be allowable at the energies of the LHC if additional dimensions are present other than the customary four (three space, one time).

Safety arguments


Hawking's calculation and more general quantum mechanical
Quantum mechanics
Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...

 arguments predict that micro black holes evaporate almost instantaneously.
Additional safety arguments beyond those based on Hawking radiation were given in the paper, which showed that in hypothetical scenarios with stable black holes that could damage Earth, such black holes would have been produced by cosmic rays and would have already destroyed known astronomical objects such as the Earth, Sun, neutron stars, or white dwarfs. Further, microscopic black holes generated from a particle accelerator are very small in size and are expected to have a high velocity, making it impossible for them to accrete a dangerously large amount of mass before leaving the earth for good.

Black holes in quantum theories of gravity


It is possible, in some theories of quantum gravity, to calculate the quantum corrections to ordinary, classical black holes. Contrarily to conventional black holes which are solutions of
gravitational field equations of the general theory of relativity, quantum
gravity black holes incorporate quantum gravity effects in the vicinity of
the origin, where classically a curvature singularity occurs.
According to the theory employed to model quantum gravity effects, there
are different kinds of quantum gravity black holes, namely loop quantum
black holes, noncommutative black holes, asympotically safe black holes. In
these approaches black holes are singularity free.

Fiction

  • In David Brin
    David Brin
    Glen David Brin, Ph.D. is an American scientist and award-winning author of science fiction. He has received the Hugo, Locus, Campbell and Nebula Awards.-Biography:...

    's novel Earth
    Earth (novel)
    Earth is a 1990 science fiction novel written by David Brin. The book was nominated for the Hugo and Locus Awards in 1991.-Plot introduction:...

    an artificial micro black hole slips into the core of the earth.
  • In Dan Simmons
    Dan Simmons
    Dan Simmons is an American author most widely known for his Hugo Award-winning science fiction series, known as the Hyperion Cantos, and for his Locus-winning Ilium/Olympos cycle....

    's novels Ilium and Olympos, a major landmark is "Paris Crater", the site where a man made micro black hole's containment field failed, and the black hole sank toward the centre of the earth before collapsing (presumably in accordance with the Hawking radiation
    Hawking radiation
    Hawking radiation is a thermal radiation with a black body spectrum predicted to be emitted by black holes due to quantum effects. It is named after the physicist Stephen Hawking, who provided a theoretical argument for its existence in 1974, and sometimes also after the physicist Jacob Bekenstein...

     theory), leaving a volcanic crater in its wake.
  • In the short story How We Lost the Moon, A True Story by Frank W. Allen, which is actually written by Paul J. McAuley, a micro black hole is accidentally created on the Moon and gradually consumes it.
  • Larry Niven
    Larry Niven
    Laurence van Cott Niven / ˈlæri ˈnɪvən/ is an American science fiction author. His best-known work is Ringworld , which received Hugo, Locus, Ditmar, and Nebula awards. His work is primarily hard science fiction, using big science concepts and theoretical physics...

    's Hugo Award
    Hugo Award
    The Hugo Awards are given annually for the best science fiction or fantasy works and achievements of the previous year. The award is named after Hugo Gernsback, the founder of the pioneering science fiction magazine Amazing Stories, and was officially named the Science Fiction Achievement Awards...

    -winning stories The Hole Man
    The Hole Man
    "The Hole Man" is a short story by American writer Larry Niven. It won the Hugo Award for Best Short Story in 1975.In this story, a team of explorers and scientists on Mars encounter an alien base, in which there is a still-functional communication device. One scientist believes that at the center...

    and The Borderland of Sol deal with "quantum black holes".
  • In Martin Caidin
    Martin Caidin
    Martin Caidin was an American author and an authority on aeronautics and aviation.Caidin wrote more than 50 books, including Samurai!, Black Thursday, Thunderbolt!, Fork-Tailed Devil: The P-38, Zero!, The Ragged, Rugged Warriors, A Torch to the Enemy and many other works of military history...

    's novel Star Bright, an object is created during an implosion-fusion
    Nuclear fusion
    Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...

     test that has essentially the properties of a micro black hole, though it is not given that name. The object is eventually destroyed, but the resulting explosion destroys a huge area around it.
  • In Steven R. Donaldson's 5 volume Gap series of books he presents singularity grenades as anti-spaceship cosmic weapons that release a micro black hole on impact with a ship.
  • In Bungie
    Bungie
    Bungie, Inc is an American video game developer currently located in Bellevue, Washington, USA. The company was established in May 1991 by University of Chicago undergraduate student Alex Seropian, who later brought in programmer Jason Jones after publishing Jones' game Minotaur: The Labyrinths of...

    's award-winning Halo Series, the method of faster-than-light
    Faster-than-light
    Faster-than-light communications and travel refer to the propagation of information or matter faster than the speed of light....

     travel for spacecraft is through an nondimensional domain known as 'Slipspace', and is made possible by ripping the space-time continuum by having slipspace drives artificially generating thousands of micro black holes that quickly evaporate via Hawking radiation
    Hawking radiation
    Hawking radiation is a thermal radiation with a black body spectrum predicted to be emitted by black holes due to quantum effects. It is named after the physicist Stephen Hawking, who provided a theoretical argument for its existence in 1974, and sometimes also after the physicist Jacob Bekenstein...

    .
  • In the Video game Master of Orion II one of the weapons a player can use is a micro black hole generator, which is used to immobilize and destroy enemy ships.
  • In a promotional video for the video game Portal 2
    Portal 2
    Portal 2 is a first-person puzzle-platform video game developed and published by Valve Corporation. The sequel to the 2007 video game Portal, it was announced on March 5, 2010, following a week-long alternate reality game based on new patches to the original game...

    , the Aperture Science Handheld Dual Portal Device is shown to have a miniature black hole and event horizon
    Event horizon
    In general relativity, an event horizon is a boundary in spacetime beyond which events cannot affect an outside observer. In layman's terms it is defined as "the point of no return" i.e. the point at which the gravitational pull becomes so great as to make escape impossible. The most common case...

    approximation ring.

External links