Struggling to understand the strange implications of modern physics, readers in the 1930's and 40's turned to a popular children's book for adults called "Mr. Tompkins in Wonderland" by the physicist George Gamow. In a series of dreams, Mr. Tompkins finds himself in surreal surroundings where the constants of nature have been changed so that matter behaves in ways that defy common sense.
In one dream, a number known as Planck's constant, which governs the intensity of quantum theory's perplexing effects, is cranked up so high that ordinary objects behave like elementary particles, which have the curious ability to act like both hard little kernels and ethereal waves. Things as large as billiard balls suddenly behave like electrons, spreading out all over the table, following many different paths at once. A visit to a quantum pool hall leaves poor Mr. Tompkins feeling drunk. The reason "quantum elephantism" doesn't really happen, the book explains, is that Planck's constant is extremely small, affecting only the tiniest objects - electrons and photons but not billiard balls.
But nothing involving quantum theory is ever so clear-cut. Recent experiments are demonstrating that quantum weirdness is not limited to the atomic realm. In late September, a team of Danish physicists reported that a phenomenon called quantum entanglement - the "spooky action at a distance" that troubled Einstein - can affect not just individual particles but clusters of trillions of atoms. And last week, the Nobel Prize in Physics was awarded for experiments showing how quantum mechanics can be exploited to make a couple of thousand atoms crowd together into a single superatom - what the scientists called "a kind of smeared-out, overlapping stew."
Experiment by experiment, the abstractions of quantum theory are taking on substance, impinging on phenomena closer to home. Physicists are developing a new finesse - getting a feel for quantum mechanics by playing with atoms the way their predecessors mastered Newtonian physics by fooling around with swinging pendulums or marbles rolling down inclined planes.
The practice is paying off with a deeper understanding of reality's rules. In Mr. Tompkins's time, the difference between the mysterious quantum realm and the hard-edged world of everyday life was assumed to be simply a matter of size. Much beyond the magnitude of an atom, as quantum effects faded, objects took on definite positions in space and time. In recent years the situation has revealed itself as somewhat more subtle. Whether an object is dominated by quantum fuzziness has less to do with how big it is than with how well it can be shielded from outside disturbances - tiny vibrations, bombarding air molecules or even particles of light.
Larger things are indeed harder to isolate from the roiling environment - hence the predictable behavior of billiard balls. But with their delicate touch, physicists are steadily bringing the quantum ambiguities further into the macroscopic domain.
Consider the case of quantum entanglement. A subatomic particle can spin clockwise or counterclockwise like a top - but with a quantum twist. As long as it remains isolated from its environment, it lingers in a state of limbo, rotating both clockwise and counterclockwise at the same time. Only when it is measured or otherwise disturbed does it randomly snap into focus, assuming one state or the other. "And" becomes "either/or."
Stranger still, two subatomic particles can be linked so that they must rotate in opposite directions. Force one to spin clockwise and the other instantly begins spinning counterclockwise, no matter how far they are separated in space.
In the past, experimenters had entangled two photons this way, and last year, in a major leap, they quantum mechanically tethered four atoms together. The recent excitement came when physicists at the University of Aarhus in Denmark reported in the Sept. 27 issue of Nature that they had briefly entangled two clouds consisting of trillions of cesium atoms. In one cloud most of the atoms were spinning one way; in the other cloud most were spinning, mirrorlike, in the opposite direction.
Correlating groups of atoms this way may find a use in quantum computers, devices where calculations are performed using single atoms or particles as counters. (Think of them as quantum abacus beads.) Theoreticians have proved that a quantum computer, if one can be built, could solve problems now considered impossible.
The experiments that won this year's Nobel in physics involved synchronizing atoms in a different but equally counterintuitive way.
Because of their quantum nature, atoms (like the particles they are made of) act like waves. The slower they move, the more stretched-out they become, dropping in pitch like a musical note sliding down the scale. Take a rarefied gas - atoms darting around in a container - and cool it so that the motion becomes slower and slower. Each atom's wavelength will widen until finally, as the temperature nears absolute zero, they all overlap, forming an exotic substance called a Bose-Einstein condensate. Imagine 2,000 billiard balls merging into one.
It is impossible for us denizens of the macro world to really picture such a state. We would have to have grown up in a universe with different constants, like the ones in Mr. Tompkins's dreams. As Gamow put it in his preface, "Even a primitive savage in such a world would be acquainted with the principles of relativity and quantum theory, and would use them for his hunting purposes and everyday needs."
As for developing quantum instincts, physicists are working their way up to the level of savages, striking sparks, building their first fires.