Physics.

Gimme five! New finds forced theorists to reexamine models of interaction among fundamental particles called quarks. Previously found only in twos or threes, quarks turned up in possible four- and five-particle groupings at several accelerator laboratories (164: 3 *, 245 *, 381). New evidence also turned up for unexpectedly light quark combinations (163: 333).

Supermolecules Physicists induced clouds of trapped, ultracold molecules to form Bose-Einstein condensates. This state of matter, in which all particles are in the stone quantum state, had been achieved only with atoms (164: 324 *).

Matter's momma? An analysis of particle collisions inside an accelerator strengthened indications that those impacts briefly recreated a fiery soup of matter that permeated the universe just after the Big Bang and then condensed into the bulk of subatomic particles known today (163: 387 *).

Ups and downs Landmark particle-accelerator experiments provided physicists with long-sought data needed to better understand up and down quarks, the building blocks of ordinary matter (163: 227 *).

One-atom laser Sandwiched between mirrors and stimulated by intense light, a single, ultracold cesium atom let loose its own infrared laser beam, which was the most orderly beam of laser light ever produced (164: 181 *).

Doppler toppler After 60 years of anticipation, experimenters finally created an inverse Doppler effect, an increase in the frequency of an electromagnetic wave, rather than the usually observed decrease in frequency, from a receding source (164: 358).

Spin doctored Using electrical signals to manipulate a magnetic property of electrons known as spin, researchers took a major step toward a new type of spin-based electronics and, possibly, toward computers that exploit the strangeness of quantum mechanics to do calculations (163: 118).

Humpty-dumpty The first measurements of how people's bodies scatter sound waves indicated that, acoustically, a human body resembles an elongated chicken egg (164: 308 *).

Crack stoppers Recognizing that cracks stretch rather than propagate in some rubbery solids, researchers developed a new theory of failure resistance for stretchy materials such as skin and adhesives (163: 261).

Molecular command A technique that triggers specific vibrations in individual molecules enabled scientists to sever selected bonds in those particles and to make some molecules slide along a surface or pop free of it (163: 339).

Warm, slow light By dramatically slowing laser pulses in a room-temperature ruby, researchers brightened prospects that slow-moving or even stopped light may attain practical use in optical communications or other applications (163: 252).

Scientists probing the origins of superfluidity, or frictionfree flow, found that an accumulation of just seven atoms of liquid helium appears sufficient to trigger that exotic state (164: 262).

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