24 June 2005

"Holy Grail" of Universe Still a Mystery

By Rusty Rockets

The Holy Grail of a single universal theory that unites all of the universe's fundamental forces still seems to elude physicists, but the quest has revealed some interesting bit players along the way. A peculiar force that works at the quantum level has been the subject of some intense examination, and it looks as though the findings could help nanotechnologists solve some troubling problems with future nanotechnology.

A group of researchers, including Purdue University's Ephraim Fischbach, have spent a lot of time looking at small objects and how they interact together. The group's experiment, which involves the behavior of a minuscule gold ball as it moves over different substances, shows that gravity behaves exactly as Isaac Newton predicted, even at small scales. It looks as though the old adage 'the simplest things are often best' is appropriate, because for those in search of the so-called "Theory of Everything," the finding would seem to rule out the exceptions to his time-honored theories that physicists believe might occur when objects are tiny enough.

The team measured a lesser-known force, a force that influences small objects and is more influential than gravity itself; the Casimir force. You'll be happy to know that the Casimir force does not involve a 'dark side' or Jedi Knights. It was named after Hendrik Casimir, a Dutch physicist, who in 1948 predicted that two uncharged parallel metal plates would be subject to a force pressing them together. The Casimir force can only be measured when the distance between the two plates is extremely small; the order of several atomic diameters. Though not a new discovery, Fischbach, Professor of physics in Purdue's College of Science, claims that the team "have measured the Casimir force with greater accuracy than has ever before been achieved."

The Casimir effect might best be described by analogy. Eighteenth century French sailors noticed an effect similar to that of the Casimir effect when ships became too close to one another on the high seas. As the ships got closer to each other the sea between them bacame calmer causing a lower energy density than the swell around the ships. As a result, a pressure was created that pushed the ships closer together, often causing them to become entangled. Fischbach explains how similar effects at a smaller scale cause concerns for researchers in nanotechnology: "Without compensating for the Casimir force, nanoparticles might clump together, nanogears might jam and adjacent nanowires might short out due to its attraction effects. Anyone creating a nanodevice will have to consider the Casimir force, just as a car manufacturer has to consider tyre friction and air resistance." This is an important discovery, but Fischbach and his team have much grander plans.

Ricardo S. Decca, the assistant professor of physics at Purdue University Indianapolis who designed the experiment, claimed that they: "We're doing work that could have cosmological implications." The team's new paper on the Casimir force, which appeared in the scientific journal Physical Review Letters, is a step closer to observing the fainter effects of attractive forces in the nanoworld. The team agrees that while this is great for nanoengineers and nanotechnology in general, such discoveries could lead to far more profound knowledge about the universe. "To this day, we still have to describe the behavior of the universe in terms of multiple forces - gravity, electromagnetism, and the strong and weak nuclear forces," Fischbach said. "Gravity often seems to be the odd force out because the others are primarily visible on the quantum scale. Connecting it with the quantum world is the holy grail of physics, and we hoped this experiment would give us a clue of how to do it."

No deviations from the expected behavior of gravity showed up in the team's experiment, but they plan to improve its methods to make even finer observations next time around. "We are trying to improve our experiment so it will be a million times more sensitive than it is now, which is already far more sensitive over this distance scale than anything done before," Decca said. "We think that is feasible with our technique. If we do find deviations then, it will give us a lead into what direction to look for the Theory of Everything."