Number 70 (Story #1), 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.)