Fuente: CERN Document Server: News Articles
Expuesto el: martes, 24 de abril de 2012 12:05
Autor: Emma Sanders
Asunto: Much ado about Nothing - exploring the vacuum with the LHC
Empty space is anything but. Remove everything you can from an area of space and it will still bustle with activity. A veritable abundance of particles and all-pervasive fields fill space with energy. Empty space even weighs something. Indeed, studying ‘nothing’ can tell us almost everything about the universe we live in. Setting the stage The 54 km of LHC beam pipes are pumped down to one of the best vacuums humankind can produce. Air pressure is higher on the moon than inside the LHC. This engineering feat is worthy of articles in itself, but the kind of vacuum we ask you to imagine here is something altogether different. It is quite simply the emptiest the laws of Nature allow. The constantly changing contributions to the vacuum from quantum chromodynamics, the theory of the strong interaction (click to see animations and credit). The cast of particles The laws of quantum mechanics allow particles to pop in and out of existence for undetectably small fractions of time. The more massive these “virtual” particles, the shorter the amount of time they can exist. This quantum fuzziness animates the vacuum with a constant buzz of particles and anti-particles.
Leading role - the Higgs In addition to the fluctuating activity of quantum fields, the vacuum is also filled with something far more substantial – the Higgs field. Omnipresent and permanent, even in the vacuum, this is the field that could be responsible for the different masses of all fundamental particles. The existence of the Higgs field would be definitively proven with the discovery of its accompanying particle - the Higgs Boson - and after promising signs from ATLAS and CMS last December, results from 2012 data are eagerly awaited. Waiting in the wings - Supersymmetry Whatever the findings this year for the Higgs, it will certainly not be the last surprise the vacuum has in store. One unsolved mystery arises from the incessant activity of virtual particles, because although they may not be directly detectable, they do interact with the Higgs field. Being virtual, quantum mechanics allows all kinds of interactions to take place. In fact, the sum of all possible interactions of heavy virtual particles with the Higgs field should contribute an infinite energy to the vacuum. A full house - Dark energy The power of nothing is not restricted to the minute world of particles, it can also be seen on cosmic scales. The energy in the vacuum, although tiny on laboratory scales, becomes considerable on astronomical ones, where great voids of space are filled with mere pin pricks of matter. Indeed, it is the energy of the vacuum – collectively known as dark energy - that causes the expansion of the universe to get faster and faster. Last year’s Nobel prize in physics was awarded to the astronomers who made the first large scale measurements of this acceleration by studying the light emitted from supernova explosions.
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