The Top Physics Stories of 2003

The first three on our list concern the sharpening of our understanding of the big bang era, evidence for new quark groupings, and progress in manipulating quantum gases. At the largest size scale, new observations from the Wilkinson Microwave Anisotropy Probe (WMAP), the Sloan Digital Survey and other telescopes have reduced the uncertainties in the values of such cosmic parameters as the Hubble constant, the age of the universe, and the fractions of total energy vested in the form of dark and luminous matter (PNU #624; 659). Going to the opposite extreme, at the level of elementary matter, new data indicate that quarks needn't appear only in clumps of three (baryons) or two (mesons). Work at SLAC (US) and KEK (Japan) hint that quarks might also exist in "tetraquark" states (643), while experiments in Japan, the US, Russia, and elsewhere provide evidence for a "pentaquark" state (644). The third top story concerns the creation of the first ever Bose Einstein condensate (BEC) consisting of paired-fermion-atom molecules. This work is potentially important because mastering the interactions between fermion atoms in the BEC state might provide insights into the nature of superconductivity and superfluids (663). Other notable physics stories from the past year include the controversy over the use gravitational lensing of distant radio waves by Jupiter to measure the speed of gravity (620); advances in the use of attosecond laser pulses in studying chemical reactions (625); the use of microfluidics---essentially the science of fluids on a chip---in processing bio-particles such as blood cells and DNA molecules (627); evidence for the focusing of light in left-handed materials, materials with a negative index of refraction, and vindication of earlier research in this area (628); first fusion reactions in Sandia's Z machine (632); LIGO's first scientific publications report no gravity wave events but do succeed in establishing new upper limits on various wave production processes (632); building a laser based on a single atom at rest (654); amphoteric refraction, both positive and negative refraction, in a single material (657); and new work with photonic crystals, including the effects of shock waves (634) and energy shifting (646).