BOILING TOPOLOGY . If Einstein hadn't introduced the so-called cosmological constant (a fudge factor, denoted by the Greek letter Lambda, meant to preserve the then-apparent static density of the universe) into his gravitational equations, nature might have invented one anyway. For one thing, according to modern field theories, the vacuum is not empty but filled with virtual particles which (through a process called quantum fluctuations) zip into and out of existence, and Lambda has come to be seen as the energy density of the vacuum. Furthermore, the "inflationary" version of the big bang model calls for something like a nonzero Lambda in order to expand the early universe at a rate much higher than we observe today. The universe having evolved to its present state, however, it would now be convenient if Lambda were very close to zero. Although not presenting a complete theory of quantum gravity, Steven Carlip (UC Davis, 916-752-8786,carlip@dirac.ucdavis.edu) has at least sought to explain the Lambda mystery in a model which spans the distance scales from near the Planck realm (10^-35 m), where space becomes granular (and where the fluctuations arise), all the way up to the cosmological scale (10 billion light years). Carlip compares the universe to a pot of water being heated. The addition of energy makes the water hotter, but only up to the boiling point. Thereafter, more energy serves only to boil the water faster. Analogously, larger Lambdas only make the universe "boil" more. That is, the topology of space-time is merely driven into an ever more complicated tangle of subtle distortions and wormholes. Carlip's framework, which calls upon recent developments in group theory and non-Euclidean geometry, makes it very unlikely that Lambda would have a negative value, and may well explain why Lambda is so close to zero.(Physical Review Letters, tent. 24 Nov.; as usual, journalists can obtain copies of PRL articles by contacting AIP Public Information at physnews@aip.org)