Ultracold Experiment Could Solve One of Physics’s Biggest Contradictions

[n2doc]

There’s a mysterious threshold that’s predicted to exist beyond the limits of what we can see. It’s called the quantum-classical transition.

If scientists were to find it, they’d be able to solve one of the most baffling questions in physics: why is it that a soccer ball or a ballet dancer both obey the Newtonian laws while the subatomic particles they’re made of behave according to quantum rules? Finding the bridge between the two could usher in a new era in physics.

We don’t yet know how the transition from the quantum world to the classical one occurs, but a new experiment, detailed in Physical Review Letters, might give us the opportunity to learn more.

The experiment involves cooling a cloud of rubidium atoms to the point that they become virtually motionless. Theoretically, if a cloud of atoms becomes cold enough, the wave-like (quantum) nature of the individual atoms will start to expand and overlap with one another. It’s sort of like circular ripples in a pond that, as they get bigger, merge to form one large ring. This phenomenon is more commonly known as a Bose-Einstein condensate, a state of matter in which subatomic particles are chilled to near absolute zero (0 Kelvin or ?273.15° C) and coalesce into a single quantum object. That quantum object is so big (compared to the individual atoms) that it’s almost macroscopic—in other words, it’s encroaching on the classical world.

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http://www.pbs.org/wgbh/nova/next/physics/ultracold-experiment-could-solve-one-of-physicss-biggest-contradictions/