THE PHYSICS OF TRAFFIC JAMS. German scientists have shown that the changeover from free-flowing traffic to a traffic jam (in which cars on a highway are greatly slowed or halted, at least temporarily) conforms to the well-known physics of phase transitions, an example of which is the transition from water to ice. In other words, traffic jams are not random patterns, but are deterministic in nature; that is, when a parameter exceeds a threshold value---such as the flux of cars---then local perturbations can grow, possibly leading to jams, analogous to the nucleating effect of tiny ice grains in a body of water being frozen. Once formed the jam moves along the highway as if it were a kind of "solid," with identifiable edges and with a "vapor" of comparatively free cars in front of and behind it. The information gained in this sort of research, the researchers believe, might lead to more accurate traffic forecasts and could be used in future "intelligent" transport systems. (B.S. Kerner and H. Rehborn, Physical Review Letters, 3 Nov. 1997; contact Boris Kerner, Daimler-Benz AG, kerner@dbag.stg.daimlerbenz.com.)

INDUCED TRANSPARENCY IN A SOLID OBJECT . An atom generally moves between two energy states by absorbing or emitting a photon---a red-light photon to take one example. If one of those states is itself a doublet of closely spaced states (the energy difference corresponding to a microwave photon, say), then an interesting interference effect can occur. By shining microwaves at the atom, resonance between the twin states becomes paramount, and the atom forgets about absorbing or emitting red light. In effect the atoms become transparent to red light. This electromagnetically induced transparency has previously been demonstrated in gases and figured in the Nobel Prize-winning effort to produce dark-state atoms---see Update 343. Now the effect has been achieved in a solid by scientists at Wayne State University, who reported a 20% drop in the absorption of light in ruby when they also shone microwaves at the resonance frequency into their sample (Zhao et al., Physical Review Letters, 28 July 1997). It is unlikely that this method will allow one to see through thick objects since the microwave power would have to be prohibitively high. The process might, however, create useful modifications in the material's refractive index. (Physics World, October 1997; Science, 15 August)

PRODUCING ELEMENT 114 is the goal of groups at Berkeley, Dubna, and Damrstadt. This element, at least the isotope containing 184 neutrons and 114 protons, is expected to be stable compared to its neighbors in the chart of the nuclides, with an expected lifetime of years rather than milliseconds or microseconds. The longevity of the nucleus, like the chemical inertness of the noble gases, is attributable to closed shells, in this case completed configurations of neutrons and protons. The three groups all plan new experiments for the coming year. In Berkeley, for example, they will collide calcium ions with plutonium to try and make an isotope of element 114. (Science, 24 October 1997.)

THE MOON FORMED IN ABOUT A YEAR, following a catastrophic collision between the Earth and some other body twice the size of Mars, according to a new model by Colorado astronomers. In this scenario, the giant off-center crash flung up a largely silicate cloud, of which eventually part rained back down on Earth and part coalesced into the Moon. This would explain, among other things, the Moon's curious lack of iron. (Nature, 25 Sept.)