Straightening Out Mind- Bending Measurements Measuring time and space on the atomic scale requires quantum rulers and clocks. Gambini and Pullin are up to the challenge. News by MIKE PERRICONE
FQXi Awardees: Rodolfo Gambini, University of the Republic, Uruguay,& Jorge Pullin, Louisiana State University September 14, 2007
During tumultuous economic times in Start With an Not so at the quantum level. Argentina, Jorge Pullin’s Buenos Aires high Itty-Bitty Ruler… “There, one is dealing with a limited school had few resources. The library was This task is easier said than done. Quan- number of systems, and their interac- a cabinet with a few dozen old books. tum-level distances are smaller than an tions have considerably more freedom,” Science classes were undemanding and atomic nucleus (10 -15 m), while quan- says Pullin. “One sees behaviors that one uninspiring. A course in radio and TV re- tum-associated time increments shrink would never see in everyday life. Many pair was as close as he got to a laboratory. below 10 –23 seconds, the time it takes of these behaviors significantly contra- And an accounting class provided light (traveling at the “speed of light,” or dict our intuition, which is conditioned what passed for intellectual fulfillment. “I 3x10 8 meters per second) to move by our status as macroscopic observers. learned how to keep accounting books completely past an atomic nucleus. This makes quantum mechanics quite adjusted for inflation, which was running Further, the Heisenberg uncertainty difficult to visualize.” at thousands of percent in Argentina at principle states that at the quantum that time,” Pullin recalls. One day’s dol- level, we cannot accurately measure a At Least We Can Visualize lars were the next day’s pennies. particle’s position and its momentum Aristotle’s Pear But perhaps that early challenge of simultaneously, so scientists often use A quantum conception of time is espe- tracking a mind-bending phenomenon probabilities in their quantum calcula- cially difficult to imagine. Like the Greek served Pullin better than he realized. tions instead. But how does a ruler philosopher Aristotle, we associate time measure the probability of an outcome? with change. In a famous example of a How can a clock adapt to quantum fluc- ripening pear, Aristotle compared the tuations such as the slowing down of different states of a system with the time experienced by particles approach- revolutions of the earth on its axis: as ing the speed of light? each new day evolved, the pear changed. It is here that Gambini and Pullin hope to apply a semblance of order. Their pro- ject, “Relational Physics With Real Rods And Clocks, And The Measurement Problem Of Quantum Mechanics,” re- ceived an FQXi grant worth US$65,530. Gambini and Pullin begin by consider- RODOLFO GAMBINI ing the quantum world and the “real University of the Republic, world” as indivisible. “Our view is that Uruguay there is only one ‘world’ and it is quan- tum in nature,” says Pullin. Now holding the Horace Hearne Or, as Gambini, who achieved the first Chair in Theoretical Physics at Louisiana degree in physics ever awarded in Uru- State University in Baton Rouge, and co- guay, says, “classical behavior observed JORGE PULLIN directing the Horace Hearne Institute at a macroscopic level must be under- for Theoretical Physics, Pullin has em- Louisiana State University stood in terms of quantum mechanics.” barked on a long-term quest to measure According to Pullin, “one can probe mind-bending phenomena of the quan- Two thousand years later, Sir Isaac this world at different scales and see Newton’s theory of gravity regarded tum world. With his collaborator of different behaviors.” For example, “In nearly 20 years, Rodolfo Gambini of time as absolute, says Ahbay Ashtekar, everyday scales, one has enormous the Eberly Professor of Physics and Di- Uruguay’s University of the Republic in numbers of systems and subsystems Montevideo, Pullin seeks accurate meas- rector of the Institute for Gravitational interacting constantly. This limits the Physics and Geometry at Penn State. urements at subatomic scales. types of behaviors that one can see.”
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