Number 70, March 5, 1992 by Phillip F. Schewe and Ben Stein CHAOTIC BEHAVIOR IN THE SOLAR SYSTEM has been under study for a number of years. Usually the studies show that chaotic orbits---orbits which, because of a great sensitivity to initial conditions, cannot be predicted with much confidence for more than a certain time interval---are more likely to occur in the outer solar system; e.g., some studies have shown that Pluto's orbit is chaotic. But three recent independent calculations (Paris, Toronto, MIT) suggest that chaotic effects may be at work in the inner solar system as well. Although the new calculations hardly imply that Earth's journey around the Sun will soon go awry, they may lead to an understanding of how minor changes in the Earth's orbit may cause climate change. (Science News, 22 Feb. 1992.) THE HADRON-ELECTRON RING ACCELERATOR (HERA) in Hamburg, Germany will be ready to do physics later this spring. At the 6.3-km-circumference HERA 30-GeV electrons will collide with 820-GeV protons. Because the electrons do not feel the strong nuclear force, they serve as excellent probes of the proton's inner structure; they are able to penetrate deep inside the proton, often so deep that they scatter not from the proton itself but from one of its constituent quarks. Two parameters, the total center-of-mass energy and the momentum transfer, will be at least a factor of ten higher at HERA than at other accelerators, which must depend on fixed-target experiments for exploring lepton-hadron collisions. Larger momentum transfers allow scientists to probe the distribution of matter inside protons down to very small distance scales, in HERA's case down to 10-17 cm, 10,000 times smaller than the size of the proton. (Physics Today, March 1992.) BUCKYBALL ARTICLES were the most cited of all scientific topic areas in 1991. In a study conducted by the Institute for Scientific Information, Buckyball articles ranked 1st, 3rd, 4th, and 9th among the top ten most-cited science stories. These papers included those on C-60 superconductivity (#1: A.F. Hebard et al., Nature, 18 April 1991), conducting films of C-60 and C-70 (#3: R.C. Haddon, Nature 28 March 1991), and crystal structure of C-60 (J.M. Hawkins et al., Science, 12 April 1991). Several other buckyball articles published before 1991, such as Kratschmer et al., Nature, 27 Sept. 1990, continue to be quite popular. (Science Watch, Jan. 1992.) "THE LHC PROJECT NOW EXISTS." These are the words of CERN Council president Sir William Mitchell commenting on the recent declaration by CERN's governing body that the Large Hadron Collider "is the right machine for the advance of the subject and of the future of CERN." The LHC, which like the SSC would collide protons against protons at TeV energies, would be built in the 27-km tunnel of the existing LEP collider. Despite Sir William's assertion, further approval steps will be necessary before construction of the machine would begin. (CERN Courier, Jan/Feb.)