Pt. 2
Overview/Black Hole Factories
Black holes need not be gargantuan, ravenous monsters. Theory implies that they can come in a huge variety of sizes, some even smaller than subatomic particles. Tiny holes should be wracked by quantum effects, and the very smallest would explode almost as soon as they formed.
Small black holes might be left over from the early stages of the big bang, and astronomers might be able to detect some of them exploding today.
Theorists have recently proposed that small black holes might be created in collisions in the present universe, even on Earth. They had thought that the requisite energies were too high, but if space has extra dimensions with the right properties, then the energy threshold for black hole production is much lower. If so, holes might be produced by the Large Hadron Collider (LHC) at CERN and in cosmic-ray collisions high in the atmosphere. Physicists could use the holes to probe
the extra dimensions of space.
THE RISE AND DEMISE OF A QUANTUM BLACK HOLE
BIRTH
Time 0
If conditions are right, two particles can collide to create a black hole. The newborn hole is asymmetrical. It can be rotating, vibrating and electrically charged. (Times and masses are approximate; 1 TeV is the energy equivalent of about 10-24 kilogram.
Mass: 10 to 8 TeV
BALDING PHASE
Time 0 to 1 x 10-27 second
As it settles down, the black hole emits gravitational and electromagnetic waves. To paraphrase physicist John A. Wheeler, the hole loses its hair becomes an almost featureless body, characterized solely by charge, spin and mass. Even the charge quickly leaks away as the hole gives off charged particles.
SPIN-DOWN PHASE
Time 1 to 3 x 10-27 second
The black hole is no longer black: it radiates. At first, the emission comes at the expense of spin, so the hole slows down and relaxed into a spherical shape. The radiation emerges mainly along the equatorial plane of the black hole.
Mass: 8 to 6 TeV
SCHWARZSCHILD PHASE
Time 3 to 20 x 10-27 second
Having lost its spin, the black hole is now an even simpler body than before, characterized solely by mass. Even the mass leaks away in the form of radiation and massive particles, which emerge in every direction.
Mass: 6 to 2 TeV
PLANCK PHASE
Time 20 to 10-27 second
The hole approaches the Planck mass�the lowest mass possible for a hole, according to present theory and winks into nothingness. String theory suggests that the hole would begin to emit strings, the most fundamental units of matter.
PHOTO (COLOR): SIMULATED DECAY of a black hole shows a particle accelerator and detector in cross section. From the center of the accelerator pipe emerge particles registered by layers of detectors.
MORE TO EXPLORE
Black Holes and Time Warps: Einstein's Outrageous Legacy. Kip S. Thorne. W. W. Norton, 1995.
High Energy Colliders as Black Hole Factories: The End of Short Distance Physics. Steven B. Giddings and Scott Thomas in Physical Review D, Vol. 65, Paper No. 056010; 2002. Preprint available at arxiv.org/abs/hep-ph/0106219
Black Holes at the LHC. Savas Dimopoulos and Greg Landsberg in Physical Review Letters, Vol. 87, Paper No. 161602; 2001. hep-ph/0106295
Black Holes from Cosmic Rays: Probes of Extra Dimensions and New Limits on TeV-Scale Gravity. Luis A. Anchordoqui, Jonathan L. Feng, Haim Goldberg and Alfred D. Shapere in Physical Review D, Vol. 65, Paper No. 124027; 2002. hep-ph/0112247
Black Holes at Accelerators. Steven B. Giddings in The Future of Theoretical Physics and Cosmology. Edited by G. W. Gibbons, E.P.S. Shellard and S. J. Rankin. Cambridge University Press, 2003. hep-th/0205027
Primordial Black Holes. Bernard Carr. Ibid. Similar paper available at astro-ph/0310838
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By Bernard J. Carr and Steven B. Giddings
BERNARD J. CARR and STEVEN B. GIDDINGS first met in person at a conference to celebrate Stephen W. Hawking's 60th birthday in 2002. Carr traces his enthusiasm for astrophysics to the famous 1969 BBC television documentary by Nigel Calder entitled "The Violent Universe." He became a graduate student of Hawking's in the 1970s, was one of the first scientists to investigate small black holes and today is a professor at Queen Mary, University of London. Giddings says he caught the physics bug when his father first told him about the weird properties of quantum mechanics. He went on to become an expert on quantum gravity and cosmology, was among the first to study the possibility of creating black holes in particle accelerators and is now a professor at the University of California, Santa Barbara. When not theorizing about gravity, he defies it by rock climbing.
A TALE OF TWO BLACK HOLES
ASTROPHYSICAL BLACK HOLES are thought to be the corpses of massive stars that collapsed under their own weight. As matter Falls into them, they act like cosmic hydroelectric plants, releasing gravitational potential energy--the only power source that can account for the intense x-rays and gaseous jets that astronomers see spurting out of celestial systems such as the x-ray binary shown here.
Mass: 1031 kilograms
Radius: 20 kilometers
Evaporation time: 1067 years
Companion star
Black hole
Accretion disk
Jet
MICROSCOPIC BLACK HOLES have masses ranging up to that of a large asteroid. They might have been churned out by the co lapse of matter early in the big bang. If space has unseen extra dimensions, they might also be created by energetic particle collisions in today's universe. Rather than swallowing matter, they would give off radiation and decay away rapidly.
Mass: 10-23 kilogram
Radius: 10-19 meter
Evaporation time: 10-26 second
Proton
Black hole
DIAGRAM: ASTROPHYSICAL BLACK HOLE
DIAGRAM: MICROSCOPIC BLACK HOLE
WAYS TO MAKE A MINI BLACK HOLE
PRIMORDIAL DENSITY FLUCTUATIONS
Early in the history of our universe, space was filled with hot, dense plasma. The density varied from place to place, and in locations where the relative density was sufficiently high, the plasma could collapse into a black hole.
Black hole
COSMIC-RAY COLLISIONS
Cosmic rays highly energetic particles from celestial sourcesmcould smack into Earth atmosphere and form black holes. They would explode in a shower of radiation and secondary particles that could be detected on the ground.
Cosmic ray
Exploding black hole
Detector
PARTICLE ACCELERATOR
An accelerator such as the LHC could crash two particles together at such an energy that they would collapse into a black hole. Detectors would register the subsequent decay of the hole.
Detector
DIAGRAM: Primordial Density Fluctuations
DIAGRAM: Cosmic-Ray Collisions
DIAGRAM: Particle Accelerator
MAKING HOLES IS HARD TO DO
How much do you need to squeeze a piece of matter to turn it into a black hole? The lighter a body is, the more you must compress it before its gravity becomes strong enough to make a hole. Planets and people are farther from the brink than stars are (graph). The wave nature of matter resists compression; particles cannot be squeezed into a region smaller than their characteristic wavelength (diagram), suggesting that no hole could be smaller than 10-8 kilogram. But if space has extra dimensions, gravity would be inherently stronger over short distances and an object would not need to be squeezed as much, giving would-be hole makers hope that they might succeed in the near future.
DIAGRAM: Region into which particles must squeeze to make a black hole.
GRAPH: Black holes in 9-D space
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Source: Scientific American, May2005, Vol. 292 Issue 5, p48, 8p
Item: 16729947
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Name: William Charles Simpson
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