The definition and creation of black holes

Hawking radiation InStephen Hawking argued that, due to quantum effects, black holes "evaporate" by a process now referred to as Hawking radiation in which elementary particles such as photonselectronsquarksgluons are emitted.

The definition and creation of black holes

It spins because the star from which it formed was spinning, and it is now thought that this is actually likely to be the most common form in nature.

A rotating black hole would bulge outward near its equator due to its rotation the faster the spin, the more the bulge. Spinning and non-spinning black holes Source: Penrose and Wheeler went on to prove that any non-rotating starhowever complicated its initial shape and internal structure, would end up after gravitational collapse as a perfectly spherical black holewhose size would depend solely on its mass.

In the late s, Penrose collaborated with his Cambridge friend and colleague, Stephen Hawkingin more investigations into the subject. Such theorems provided a set of sufficient conditions for the existence of a gravitational singularity in space-timeand showed that, far from being mathematical curiosities which appear only in special cases, singularities are actually a fairly generic feature of general relativity.

Although it may seem a very complex, peculiar and perhaps counter-intuitive object, a black hole can essentially be described by just three quantities: Brandon Carter and Stephen Hawking proved the No-Hair Theorem mathematically in the early s, showing that the size and shape of a rotating black hole would depend only on its mass and rate of rotation, and not on the nature of the body that collapsed to form it.

They also proposed four laws of black hole mechanics, analogous to the laws of thermodynamics, by relating mass to energyarea to entropyand surface gravity to temperature. Hawking radiation as particle pairs are created near a black hole Source: University of St Andrews: According to this theory, black holes are not completely black, and neither do they last forever.

Hawking showed how the strong gravitational field around a black hole can affect the production of matching pairs of particles and anti-particles, as is happening all the time in apparently empty space according to quantum theory. If the particles are created just outside the event horizon of a black holethen it is possible that the positive member of the pair say, an electron may escape - observed as thermal radiation emitting from the black hole - while the negative particle say, a positronwith its negative energy and negative mass may fall back into the black holeand in this way the black hole would gradually lose mass.

Stellar black holes — small but deadly

This was perhaps one of the first ever examples of a theory which synthesized, at least to some extent, quantum mechanics and general relativity. Hawking vigorously defended this paradox against the arguments of Leonard Susskind and others for almost thirty years, until he famously retracted his claim ineffectively conceding defeat to Susskind in what had become known as the " black hole war".

He suggests that, as an object falls into a black holea copy of the information that makes it up is sort of scrambled and smeared in two dimensions around the edge of the black hole. Furthermore, Susskind believes that a similar process occurs in the universe as a whole, which raises the rather alarming idea that what we think of as three- dimension al reality is in fact something like a holographic representation of a "real" reality, which is actually contained in two dimensions around the edge of the universe.

It is also theoretically possible that "primordial" or "mini" black holes could have been created in the conditions during the early moments after the Big Bangpossibly in huge numbers.

No such mini black holes have ever been observed, however - indeed, they would be extremely difficult to spot - and they remain largely speculative. It is anyway likely that all but the largest of them would have already evaporated by now as they leak away Hawking radiation. But it is hoped that such mini black holes might be experimentally re-created in the extreme conditions of the Large Hadron Collider at CERN, which, among other things, would lend much-needed credence to some of the current theoretical predictions of superstring theory regarding gravity.Black holes may solve some of the mysteries of the universe.

A black hole is a place in space where gravity pulls so much that even light cannot get out. Black holes are some of the strangest and most fascinating objects found in outer space.

They are objects of extreme density, with such strong gravitational attraction that even light cannot. A black hole formed in this way is called a primordial black hole and is the most widely accepted hypothesis for the possible creation of micro black holes.

Computer simulations suggest that the probability of formation of a primordial black hole is inversely proportional to its mass. Creation of Black Holes.

Topic Index: Black Holes and Wormholes Introduction - Stars, Supernovas and Neutron Stars - Creation of Black Holes By definition, we cannot observe black holes directly, but they can be detected by the gravitational effect they exert on other bodies or on light rays.

The definition and creation of black holes

Black hole definition: Black holes are areas in space, where gravity is so strong that nothing, not even light, | Meaning, pronunciation, translations and examples.

It seems likely that the early universe, in which very large, short-lived stars were the norm, was scattered with many, many black holes, which gradually merged together over time, creating larger and larger black holes.

The definition and creation of black holes
Creation of Black Holes - Black Holes and Wormholes - The Physics of the Universe