IS THE UNIVERSE CRYSTALLINE? As astronomers measure redshifts for additional galaxy superclusters, the three-dimensional architecture of the universe becomes more evident. New redshift surveys, reaching ever further into space, are benefiting from fiber optics and increasing automation. A fresh analysis of current redshift catalogs offers some evidence for a periodic arrangement of superclusters, separated by voids, on a scale of 120 megaparsecs (about 390 million light years). Great walls of galaxies on this scale have been discerned before but the apparent periodicity is new. The researchers suggest that a new theory might be needed to explain the sort of immense 3D- chessboard structure they seem to be finding in the data. (J. Einasto et al., Nature 9 January 1997.)

OUR LOCAL CLUSTER OF GALAXIES IS STILL FORMING. For decades astronomers have wondered about the origin of certain fast-moving clouds of atomic hydrogen in the vicinity of the Milky Way. In some cases the clouds appeared to be plunging into the plane of the galaxy (at speeds as large as 500 km/sec), and could not be considered as rotating with the galaxy. Later observations showed that some clouds actually seemed to be moving away from the Milky Way. A synthesis of new radio- telescope measurements plus re-evaluated data from COBE and the Hubble Space Telescope indicates that the clouds may be raw material left over from the formation of the entity known as the Local Group of galaxies, whose largest shareholders are the Andromeda galaxy (with 65% of the mass of the group) and our own Milky Way (30%). Reporting at last week's American Astronomical Society meeting in Toronto, Leo Blitz of UC Berkeley and David Spergel of Princeton said that the high velocity clouds will continue of feed the Milky Way (providing fuel for future star formation) and might even harbor dark matter, a hypothesis which would account for the continued stability of the clouds and their unexplained large internal velocities. Spergel said that the features of his theory for nearby high velocity clouds might apply also to larger, more distant hydrogen clouds in the cosmos.

METAL INCLUSIONS COME IN SPECIAL SIZES. Gold does not come out of the ground as ingots, but rather as misshapen lumps ensconced in a rocky ore. One can ask whether, in general, nature dictates the size and shape of chunks of one element embedded in another solid. This issue is especially important at the microscopic level since the melting point of some materials can be raised or lowered considerably by burying particles of one type within the sample. A Berkeley-Copenhagen- Rio de Janeiro collaboration (contact Uli Dahmen, uli_dahmen@macmail.lbl.gov) has now shown, for the first time, that nanoscopic three-dimensional lead inclusions, having come to equilibrium inside an aluminum matrix, assume only special ("magic") sizes. These preferred shapes, the researchers believe, are imposed by the crystalline mismatch between the two elements. In time, this magic-size phenomenon might be useful for tailoring specific thermodynamic, magnetic, electronic, or optical properties. (U. Dahmen et al., Physical Review Letters, 20 January 1997.)