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New Debate for Collider that Create Black Holes May Destroy Us All
:: 21 April, 2008
The Large Hadron Collider is a particle accelerator collider being built at the European Laboratory for Particle Physics, or CERN, straddling the French-Swiss border near Geneva. It should be completed and ready to start producing data sometime this summer. In it, scientists will be able to smash protons travelling at more than 99.99 percent of the speed of light with protons traveling in the opposite direction at the same speed.
more stories like thisProtons are actually pretty complicated objects, made of little bits and pieces, and in a collision of two protons it can happen that two of the little pieces find themselves very close together. Those pieces carry a lot of energy, and due to Einstein's E=mc{+2} one might imagine that a lot of mass in a little space could lead to a black hole.
The odds of this actually happening are pretty much zero for several reasons. First of all, the theorists who worry about such things happening make assumptions that the energy needed to make a black hole is vastly less than what we would expect in the real world as we know it. This possibility only arises in theories with what are called "large extra dimensions," and there is no evidence at all that these describe reality.
A second reason: Black holes, strictly speaking, are theoretical constructs. Nobody has ever seen a black hole. Things that are black hole candidates are objects which are known to be small and to have very high masses, but if one is very honest, there are a lot of problems with the black hole concept, and we don't yet know for sure that they really exist. One particularly vexing problem is that time is predicted to slow down as one approaches a heavy object, so that bits of matter falling into a heavy collapsing object actually take an infinite amount of time to fall in from the point of view of an observer outside.
A third reason is that while we physicists are all excited about the collisions to take place at CERN soon, such collisions take place all the time on Earth, the moon, and everywhere else due to ultrahigh energy cosmic rays. In other words, the experiments people worry about at CERN have been going on now and then at random all over the place for billions of years, and things seem to be fine!
Note for Large Hadron Collider
The Large Hadron Collider (LHC) is a particle accelerator located at CERN, near Geneva, Switzerland. It lies in a tunnel under France and Switzerland.
It is currently in the final stages of construction, and commissioning, with some sections already being cooled down to their final operating temperature of ~2K. The first beams are due for injection mid June 2008 with the first collisions planned to take place 2 months later. The LHC will become the world's largest and highest-energy particle accelerator. The LHC is being funded and built in collaboration with over two thousand physicists from thirty-four countries as well as hundreds of universities and laboratories.
When activated, it is theorized that the collider will produce the elusive Higgs boson, the observation of which could confirm the predictions and "missing links" in the Standard Model of physics and could explain how other elementary particles acquire properties such as mass. The verification of the existence of the Higgs boson would be a significant step in the search for a Grand Unified Theory, which seeks to unify the three fundamental forces: electromagnetism, the strong nuclear force and the weak nuclear force. The Higgs boson may also help to explain why gravitation is so weak compared to the other three forces. In addition to the Higgs boson, other theorized novel particles that might be produced, and for which searches are planned, include strangelets, micro black holes, magnetic monopoles and supersymmetric particles.
The collider is contained in a circular tunnel with a circumference of 27 kilometres (17 mi) at a depth ranging from 50 to 175 metres underground. The tunnel, constructed between 1983 and 1988, was formerly used to house the LEP, an electron-positron collider.
The 3.8 metre diameter, concrete-lined tunnel crosses the border between Switzerland and France at four points, although the majority of its length is inside France. The collider itself is located underground, with many surface buildings holding ancillary equipment such as compressors, ventilation equipment, control electronics and refrigeration plants.
The collider tunnel contains two pipes enclosed within superconducting magnets cooled by liquid helium, each pipe containing a proton beam. The two beams travel in opposite directions around the ring. Additional magnets are used to direct the beams to four intersection points where interactions between them will take place. In total, over 1600 superconducting magnets are installed, with most weighing over 27 tonnes.
The construction of LHC was originally approved in 1995 with a budget of 2.6 billion Swiss francs, with another 210 million francs (140 M€) towards the cost of the experiments. However, cost over-runs, estimated in a major review in 2001 at around 480 million francs (300 M€) in the accelerator, and 50 million francs (30 M€) for the experiments, along with a reduction in CERN's budget pushed the completion date out from 2005 to April 2007. 180 million francs (120 M€) of the cost increase has been the superconducting magnets. There were also engineering difficulties encountered while building the underground cavern for the Compact Muon Solenoid, due to, in part, the allegedly "faulty" parts lent to CERN by fellow laboratory and home to the world's largest particle accelerator, (until CERN finishes the Large Hadron Collider) Argonne National Laboratory, or FermiLab, located in Batavia, Illinois, outside of Chicago. The total cost of the project is anticipated to be between $5 and $10 billion (US Dollars).
Note for Black Hole
A black hole is a region of space in which the gravitational field is so powerful that nothing, not even light, can escape its pull after having fallen past its event horizon. The name comes from the fact that, at a certain point, even electromagnetic radiation (e.g. visible light) is unable to break away from the attraction of these massive objects. This renders the hole's interior invisible or, rather, black like the appearance of space itself.
Despite its interior being invisible a black hole hole may betray its presence through in interaction with matter that lies in orbit outside its event horizon. For example, a black hole may be perceived by tracking the movement of a group of stars that orbit its center. Alternatively, one may observe the product of gas (from a nearby star, for instance) that has been drawn into the black hole. The gas spirals inward, heating up to very high temperatures and emitting large amounts of radiation that can be detected from earthbound and earth-orbiting telescopes. Such observations have resulted in the general scientific consensus that — barring a breakdown of our understanding nature— black holes do exist in our universe.
While the idea of an object with gravity strong enough to prevent light from escaping was proposed in the 18th century, black holes, as currently understood, are described by Einstein's general theory of relativity, which he developed in 1916. This theory predicts that when a large enough amount of mass is present in a sufficiently small region of space, all paths through space are warped inwards towards the center of the volume, preventing all matter and radiation within it from escaping.
While general relativity describes a black hole as a region of empty space with a pointlike singularity at the center and an event horizon at the outer edge, the description changes when the effects of quantum mechanics are taken into account. Research on this subject indicates that, rather than holding captured matter forever, black holes may slowly leak a form of thermal energy called Hawking radiation. However, the final, correct description of black holes, requiring a theory of quantum gravity, is unknown.
Popular accounts commonly try to explain the black hole phenomenon by using the concept of escape velocity, the speed needed for an vessel starting at the surface of a massive object to completely clear the object's gravitational field. Using Newton's law of gravity it is straight forward to show that if you take a sufficiently dense object its escape velocity will equal or even exceed the speed of light. Citing that nothing can exceed the speed of light they then infer that nothing would be able escape such a dense object. Of course, this argument has a flaw in that it doesn't explain why light would even be effected by a gravitating body, let alone why it wouldn't be able to escape. Sometimes some arguments are added arguing that in general relativity light is affected by gravity and that indeed the energy required to escape a black hole is infinite. This makes the argument slightly better, but still this really does not explain what is going on.
To really understand what is going on we need two lessons taught to us by Albert Einstein. The first is that time and space are not two independent concepts, but are interrelated forming a single continuum, spacetime. This continuum has some special properties. An object is not free to move around spacetime at will, instead it must always move forwards in time. In fact, not only must an object move forwards in time, it also cannot change its position faster than the speed of light. This is the main result of the theory of special relativity.
The second lesson we need is the main message of general relativity, mass deforms the structure of spacetime. Loosely speaking, the effect of a mass on spacetime is to slightly tilt the direction of time towards the mass. As a result, objects tend to move towards masses; we experience this as gravity. As you get closer to a mass this tilting effect becomes stronger. At some point close to the mass this effect becomes so strong that all the possible paths an object can take lead towards the mass. That is, you can no longer get further away from the black hole no matter how much you try; you are trapped. This is precisely what happens at the event horizon of a black hole.
In figure, Visitors stand in front of the ATLAS detector at the Large Hadron Collider near Geneva
Tags: Large Hadron Collider , particle accelerator , Particle Physics , or CERN , black hole ,
