Ancientphilosophers thought wind, water, fire and earth were the most basic elementsof the cosmos, but the study of the small has since grown up. Physicistscontinue to carve the known universe into particles to describe everything frommagnetism to what atoms are made of and how they remain stable. Yet strikingsimilarities in the world of quantum mechanics, as the study of particles andtheir forces is known, has led to a one of the most important questions in modernscience: Is there a single theory that can describe everything?
"Weunderstand a lot about the universe up to the first few energetic microseconds,but earlier than that our physics break down," said Mark Jackson, atheoretical physicist at Fermilab in Batavia, Illinois. "But those firstmoments are where the really interesting things happened."
If a theorycan be designed to withstand the incredible energies of the early universe aswell as incorporategravity, Jackson said, then a universal theory of physics could become areality.
The"standard model" of physics views particles as infinitesimal points,some of which carry basic forces. In spite of the fact that it fails to includegravity and becomes gibberish at high energies, the time-tested theory is thebest tool scientists have for explaining physics.
"Youhear people complain about how good the standard model is," said MichaelTurner, a cosmologist at the University of Chicago. "It's an incompletemodel, and yet we can't findflaws in it."
Turnerexplained that discovering a mass-inducing particle, called the Higgs boson,remains the next big test for the standard model. If discovered, the heavyparticle would definitively show that properties like electromagnetism andradioactivity are really different facets of the same force.
"It'sthe miracle that allows us to combine them together," Turner said of theHiggs, which may be found someday in the collisions of particle acceleratorsthat "rewind" matter to the intense energies of the early universe.
Thestubbornness of the standard model has been too much for some physicists,however, leading to new theories that include gravity and work at extremelyhigh energies.
Perhaps themost popularized of them all is stringtheory, which describes particles as strands of energy vibrating atdifferent "frequencies." To explain the point-like nature ofparticles, string theory holds that strings are wrapped up in 10 or 11dimensions?six to seven more than are currently recognized.
The idea issimilar to viewing a building from far away. At great distances it looks like apoint, but moving closer it appears flat and eventually as a three-dimensionalstructure. Wrapped within the building are extra dimensions that become smallerand smaller: pipes, and nooks and crannies within the pipes, the spaces betweenthe nooks and crannies and so on.
The inabilityso far for string theory to prove up to 11 tiny dimensions exist is a hang-upfor many, but Jackson thinks some strings could have been stretched across theuniverse into "superstrings"--ones large enough to detect in space today.
In spite ofa present lack of such evidence, Jackson is confident string theory willweather the storm.
"It'shard to imagine that the universe has two different sets of rules for physics.When does it turn one off and the other one on?" Jackson reasoned."We know there is quantum mechanics and we know there is gravity, so itseems there should be one overall theory. I'm betting my career that it'sstring theory."
Fermilabcosmologist Scott Dodelson also finds a unified theory logical, but doesn'tthink a big departure from the standard model is required to conjure one up.
"Thereare basically two approaches; one is the bottom-up, which is taking data andfixing pieces of a theory to make it more elegant," said Fermilabcosmologist Scott Dodelson. "The other approach is top-down, starting withan elegant theory and working down toward the data. My chips are on the bottom-uppeople wanting to get down and dirty with data."
In eithercase, physicists, theorists and cosmologists alike are waiting for high-energyexperiments such as the Large Hadron Collider (LHC) in Europe to go online.They hope to find not only the Higgs in the aftermath of colliding particles,but also particle"super-partners" that Dodelson described as the overweight,hidden cousins of more familiar electrons, neutrinos and the like.
"They'retoo heavy to have been seen so far," Dodelson said, adding that theintense energies LHC-like machines may be enough to get them to "popout" of colliding particles. If so, the mystery of darkmatter (much of the universe's missing mass) could be solved in addition tocreating a more formidable standard model of physics.
"Wemay eventually pierce the 'cloak' of dark matter and detect supersymmetricparticles in the lab," Dodelson said. "It would introduce a whole newclass of particles and create a new standard model."
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