black hole A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts that a sufficiently compact mass can defo ...

theory, the black hole membrane paradigm is a simplified model, useful for visualising and calculating the effects predicted by

quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, q ...

for the exterior physics of black holes, without using quantum-mechanical principles or calculations. It models a black hole as a thin, classically radiating surface (or membrane) at or vanishingly close to the black hole's

event horizon In astrophysics, an event horizon is a boundary beyond which events cannot affect an observer. Wolfgang Rindler coined the term in the 1950s. In 1784, John Michell proposed that gravity can be strong enough in the vicinity of massive compact ob ...

. This approach to the theory of black holes was created by

Kip S. Thorne Kip Stephen Thorne (born June 1, 1940) is an American theoretical physics, theoretical physicist known for his contributions in gravitation, gravitational physics and astrophysics. A longtime friend and colleague of Stephen Hawking and Carl ...

, R. H. Price and D. A. Macdonald.

Electrical resistance

Thorne (1994) relates that this approach to studying black holes was prompted by the realisation by Hanni,

Ruffini Ruffini is an Italian surname. Notable people with the surname include: * Alessandro "Sandro" Ruffini (1889–1954), Italian actor and voice actor * Angelo Ruffini (1864–1929), Italian histologist and embryologist *Attilio Ruffini (1924–2011), ...

, Wald and Cohen in the early 1970s that since an electrically charged pellet dropped into a black hole should still ''appear'' to a distant outsider to be remaining just outside the event horizon, if its image persists, its electrical fieldlines ought to persist too, and ought to point to the location of the "frozen" image (1994, pp. 406). If the black hole rotates, and the image of the pellet is pulled around, the associated electrical fieldlines ought to be pulled around with it to create basic "electrical dynamo" effects (''see:''

dynamo theory In physics, the dynamo theory proposes a mechanism by which a celestial body such as Earth or a star generates a magnetic field. The dynamo theory describes the process through which a rotating, convection, convecting, and electrically conductin ...

). Further calculations yielded properties for a black hole such as apparent electrical resistance (pp. 408). Since these fieldline properties seemed to be exhibited down to the event horizon, and general relativity insisted that no dynamic exterior interactions could extend ''through'' the horizon, it was considered convenient to invent a surface ''at'' the horizon that these electrical properties could be said to belong to.

Hawking radiation

After being introduced to model the theoretical electrical characteristics of the horizon, the membrane approach was then pressed into service to model the

Hawking radiation Hawking radiation is theoretical black body radiation that is theorized to be released outside a black hole's event horizon because of relativistic quantum effects. It is named after the physicist Stephen Hawking, who developed a theoretical ar ...

effect predicted by

. In the coordinate system of a distant stationary observer, Hawking radiation tends to be described as a quantum-mechanical particle-

pair production Pair production is the creation of a subatomic particle and its antiparticle from a neutral boson. Examples include creating an electron and a positron, a muon and an antimuon, or a proton and an antiproton. Pair production often refers ...

effect (involving

virtual particle A virtual particle is a theoretical transient particle that exhibits some of the characteristics of an ordinary particle, while having its existence limited by the uncertainty principle. The concept of virtual particles arises in the perturba ...

s), but for stationary observers hovering nearer to the hole, the effect is supposed to look like a purely conventional radiation effect involving real particles. In the membrane paradigm, the black hole is described as it should be seen by an array of these stationary, suspended noninertial observers, and since their shared coordinate system ends at the event horizon (because an observer cannot legally hover at or below the event horizon under general relativity), this conventional-looking radiation is described as being emitted by an arbitrarily thin shell of hot material at or just above the event horizon, where this coordinate system fails. As in the electrical case, the membrane paradigm is useful because these effects should appear all the way down to the event horizon, but are not allowed by GR to be coming ''through'' the horizon – attributing them to a hypothetical thin radiating membrane at the horizon allows them to be modeled classically without explicitly contradicting general relativity's prediction that event horizon surface is inescapable. In 1986,

, Richard H. Price and D. A. Macdonald published an anthology of papers by various authors that examined this idea: "Black Holes: The membrane paradigm".

References

* *

Leonard Susskind Leonard Susskind (; born June 16, 1940)his 60th birthday was celebrated with a special symposium at Stanford University.in Geoffrey West's introduction, he gives Suskind's current age as 74 and says his birthday was recent. is an American physicis ...

, "Black holes and the information paradox", ''Scientific American'', April 1997
cover story
. Also reprinted in th
special edition "The edge of physics"
*

, R. H. Price and D. A. Macdonald (eds.) "Black Holes: The Membrane Paradigm" (1986) * Thorne, Kip, '' Black Holes and Time Warps: Einstein's Outrageous Legacy'', W. W. Norton & Company; Reprint edition, January 1, 1995, , chapter 11, pp. 397–411 {{Black holes Black holes Quantum gravity Holonomic brain theory

Electrical resistance

Hawking radiation

See also

References