|Virtual particle-pairs appear fleetingly around a black hole, the nearer the hole, the more virtual particles. Shown is one created on the Schwarschild Radius of the black hole, when one particle is swallowed by the hole becoming a real anti-particle and annihilating part of the black holes mass, the other escapes as a real particle.|
For a large mass Black Hole, the curvature of space at the Schwarzschild radius is only gentle, and few virtual particle pairs are created which can go on to perform this feat. The Black Hole radiates only faintly. But as it gets smaller, the curvature of space increases, intensifying the polarisation of the vacuum, which creates more virtual particle pairs, and more virtual particle pairs find themselves on the Schwarzschild radius - it radiates ever more energetically. The particles aquire the energy from the gravitational field, which gets weaker. The radiation conforms to the spectrum of a Black Body whose characteristic temperature is inversely proportional to the mass of the Black Hole. For a solar-mass Black Hole, this temperature is 60 nanoKelvin, but as it gets smaller, it gets hotter, radiates faster, and gets ever smaller ever faster until, when it is the size of a proton, explodes in the last 1/10 th second with the energy equivalent of 107 one-megaton H-bombs. The Black Hole has evaporated itself. This process is called Hawking evaporation. This takes aeons for a stellar-mass Black Hole, but any Everest-mass Black Holes created in the Big Bang should be exploding now.
The lifetime (through Hawking evaporation) of a Black Hole is proportional to the cube of its mass. For a Black Hole of 1 solar mass, the lifetime would be approximately 1071 seconds (approximately 3×1063 years).
The characteristic temperature of a black hole is inversely proportional to its' mass. In the above example, a 1 solar mass black hole would have a black-body temperature of 6×10-8 Kelvin. i.e. very cold indeed; colder even than the Cosmic Microwave Black Body radiation that pervades the universe which theorists suggest arose because of the Big Bang.
It has been calculated that the particles that a Black Hole evaporates by Hawking Radiation will be comprised of photons, neutrinos and gravitons. Only about 1% being gravitons. The energy of the emitted gravitons will depend upon the mass of the Black Hole; the gravitons emitted by Black Holes of mass less that 10 15 tons will have insufficient energy to be detectable here on Earth.
There may be hidden curled-up dimensions in spece-time that subtly alter the effect of gravity over extremely short distances. If so, and the hidden dimensions are large enough, then this may allow microscopic Black Holes to form in ultra-high-energy particle collisions. But even if a such a microscopic Black Hole was formed within a particle accelerator by a very high energy collision, that Black Hole would be so small as to evaporate by Hawking Radiation almost as quickly as it could form, if not quicker, thus eliminating the possibility of such an occurrance. If, however, any microscopic Black Hole were formed within a quark-star, perhaps by a high-energy cosmic ray or neutrino impinging upon it, then it would rapidly accumulate more matter much faster than it could evaporate, creating a monster Black Hole; the whole quark star would be transformed into a Black Hole within 10 seconds. The resulting explosion would release prestigious quantities of energy, easily enough to account for a gamma-ray burst.
Gamma Ray Bursts
A gamma ray burst is a phenomena observed in the sky. About once a day a highly energetic burst of gamma rays lasting from a few milliseconds to several minutes is observed to come from apparently random areas of the sky. Such bursts are thought to occur at extreme distances from Earth, in other far away galaxies, and if so, this means they are immensely powerful fluxes of gamma rays, the gamma ra flux being about 100 times as bright as that from a supernova explosion. The source of gamma rays is a mystery, but there are several theories to account for them. They are somertimes associated with peculiar supernovas, or 'hypernova'. They could be caused by the gravitational collapse of the fast-rotating core of a massive star, or 'collapsar'.
If a gamma ray burst occurred within our own galaxy relatively near to the Sun, the proximity of such an extremely powerful source of gamma rays would be enough to cause a mass extinction on Earth.It is likely that many gamma ray bursts have occurred in our galaxy in the last billion years. It is also likely that at least one was near enough to the Earth to cause a mass extinction. The mass extinction of 433 million years ago, in the late Ordovician period has found strong support that it was caused by a gamma ray burst. A typical 10 second burst of gamma rays at such high intensities would have reacted with atmospheric nitrogen creating ozone-destroying compounds such as nitrogen dioxide in sufficient quantity to deplete the protective upper ozone layer by up to 50% for a decade. This would have exposed organisms to increased ultra-violet rays from the sun which could have caused a mass extintion. Also, the nitrogen dioxide absorbs light, and this would have reduced sunlihht overall by 1% and by up to 30% at the poles, leading to significant global cooling.