And it may find the "God" particle, the Higgs Boson:
If we find it, it will be monumental. If we don't find it, it will require a major overhaul of elementary theoretical physics.
Take your pick which is more exciting.
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If we find it, it will be monumental. If we don't find it, it will require a major overhaul of elementary theoretical physics.
Take your pick which is more exciting.
The Large Hadron Collider (LHC) currently under construction at CERN is the greatest basic science endeavor in history. Roughly half of the world's particle physicists, 7,000 individuals, make the Collider their workplace. This single-minded group of men and women hails from more than 80 countries. They represent almost every religion and ethnicity on Earthâembodying curiosity, cooperation, brilliance and ingenuity on the grandest scale.
The LHC is a circular tunnel 27 km around, bisected by the Franco-Swiss border. Over 100-billion protons will traverse its pathways at near-light speed, guided by some 9,300 superconducting magnets, each weighing several tons and chilled to temperatures colder than deep space. At four points in the tunnels, the counter-revolving protons are to smash into one another at a rate of nearly one billion per second.
At the crossing points, huge detectors are in place to register the tiny wisps of debris that emerge from each of the collisions. One of these instruments has enough iron to re-construct the Eiffel Tower; another is two-and-a-half times larger than the Parthenon and taller than the Colossus of Rhodes. Information from these subatomic traffic accidents will be sped around the globe on the largest computer grid in existenceâthe nervous system for all the brains that will struggle to make sense of the myriad data. All these superlatives exist for one reason: To understand the universe.
Seed asked those with the greatest stake in discerning nature's wonders to share their hopes, questions and wildest fantasies for the LHC.
Are There Other Dimensions?
The smashingly successful Standard Model of particle physics describes matter's most basic elements and the forces through which they interact. Physicists have tested its predictions to better than 1% precision. Yet despite its many successes, we know the Standard Model is not the whole story. If we apply the known principles of quantum mechanics and special relativity to compute what we expect masses to be, we find the result is 16 orders of magnitude bigger than measured valuesâso big that gravitational effects would be comparable to the strength of other particle forces. But, for the known particle masses, gravity is negligible when compared to other forces. To avoid this problem, the Standard Model relies on an enormous fudgeâwhat we physicists call a "fine-tuning."
Since the 1970's particle physicists have been searching for a natural explanation for known particle masses and the weakness of gravity. But they have not succeeded in finding an elegant solution with only three dimensions of space. A universe with extra dimensions might provide an answer. Gravity could be extremely weak in our region of a higher-dimensional universe, but strong somewhere else.
The magnificent thing is that we know there should be an answer to the question of the weakness of gravity, and that it should be revealed at the LHC, whatever the explanation turns out to be. If it is warped extra dimensions, to cite just one possibility, the experimental evidence would be particles that travel in extra-dimensional space but reveal themselves in our three-dimensional experiments. And the signal will be spectacular. Experimenters think it could be one of the easiest new phenomena to produce and discover. But no matter what the explanation for the weakness of gravity turns out to be, the LHC is prepared. And we're eagerly waiting the answer.
âLisa Randall, Harvard University, author of Warped Passages: Unveiling the Mysteries of the Universe's Hidden Dimensions
...
How Is Symmetry Broken?
One of the big mysteries of physics is why the electromagnetic and weak interactions, which are two of the main elementary particle forces, are so different. We literally see electromagnetic effects with our eyes in the form of light. On the other hand, it takes sensitive modern equipment to detect and study the weak interactions. Yet the modern Standard Model says that at a fundamental level, these two forces are on an equal footing, described by very similar equations (Maxwell's equations for electromagnetism, the Yang-Mills equations for the weak interactions). The difference between these two forces only arises from a process of "symmetry breaking," whereby nature spontaneously picks one force over anotherâeven though fundamentally they are equivalent. The LHC will tell us whether this notion is correct, and if so, how it works.
Understanding how the symmetry is broken is the key to understanding how the weak and electromagnetic interactions are unified in nature. This is believed to be an important step toward understanding a broader unification of the laws of nature.
âEdward Witten, Fields Medal winner, Institute for Advanced Study, Princeton University
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Is The Universe Anthropic?
I see only two possible outcomes of the LHC projectâeither there will be low energy supersymmetry, or there won't. If there isn't, I would expect that the minimal Standard Model will prevail. In either case, the Higgs particleâa still-hypothetical particle postulated in the 1960'sâwill be shown to exist, thus explaining the fundamental particles' masses.
The main conceptual issue is the one having to do with fine-tuning. Conventional wisdom that has prevailed since the early 80's is that the pure Standard Model requires ultra-fine-tuning to keep the masses of elementary particles, such as quarks and electrons, from being sucked up to the higher energy unification or Planck scales. (It's called the "gauge hierarchy" problem.) There have been several solutions proposed including technicolor and extra dimensions (really the same thing), but they don't look viable. Supersymmetry can prevent the gauge hierarchy disaster, which is indeed a disaster: Were it to have existed, it would certainly have precluded life as we know it.
Similar logic says that the cosmological constant should also be sucked up to some large scale, which would also have proved disastrous to life. At the present time, the only explanation for the size of the cosmological constant is the anthropic principleâthe dreaded "A word" that means if the universe weren't as it is, we wouldn't be here to observe it. So for me, the big question is whether the gauge hierarchy fine-tuning is similar to the cosmological constant fine-tuning, or if it has a more conventional supersymmetric explanation. Either will be incredibly interesting.
âLeonard Susskind, Stanford University,
author, The Cosmic Landscape: String Theory and the Illusion of Intelligent Design
Read rest here:
http://seedmagazine.com/news/2006/07/why_a_large_hadron_collider.php?page=all&p=y
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