Strong Dependence of the Inner Edge of the Habitable Zone on Planetary Rotation Rate

Planetary rotation rate is a key parameter in determining atmospheric circulation and hence the spatial pattern of clouds. Since clouds can exert a dominant control on planetary radiation balance, rotation rate could be critical for determining mean planetary climate. Here we investigate this idea using a three-dimensional general circulation model with a sophisticated cloud scheme. We find that slowly rotating planets (like Venus) can maintain an Earth-like climate at nearly twice the stellar flux as rapidly rotating planets (like Earth). This suggests that many exoplanets previously believed to be too hot may actually be habitable, depending on their rotation rate. The explanation for this behavior is that slowly rotating planets have a weak Coriolis force and long daytime illumination, which promotes strong convergence and convection in the substellar region. This produces a large area of optically thick clouds, which greatly increases the planetary albedo. In contrast, on rapidly rotating planets a much narrower belt of clouds form in the deep tropics, leading to a relatively low albedo. A particularly striking example of the importance of rotation rate suggested by our simulations is that a planet with modern Earth's atmosphere, in Venus' orbit, and with modern Venus' (slow) rotation rate would be habitable. This would imply that if Venus went through a runaway greenhouse, it had a higher rotation rate at that time.Comment: 7 pages, 4 figures, accepted at Astrophysical Journal Letter

Review of \u3ci\u3eLanguage Policy and Social Reproduction: Ireland 1893-1993\u3c/i\u3e, by Padraig Ó Riagáin

Ó Riagáin has produced the sort of book that many have wished for but doubted they would see: a scrupulously dispassionate, comprehensive account of Irish language fortunes since the late 19th century, and of Irish language policies and outcomes since independence in 1922. Reading his careful, low-key book, one could easily forget that he is writing from and about a country where language issues rouse strong feelings, and also about the single most discussed case of attempted language maintenance and restoration in our time. His meticulous study allows efforts on behalf of Irish to be seen, appropriately, within a broad general framework of national development, in which the effectiveness of language policies is dependent in good part on their fit or lack of fit with the economic and social conditions of a given period

Review of \u3ci\u3eSyntactic Transfer, Contact-Induced Change, and the Evolution of Bilingual Mixed Codes: Focus on Karelian-Russian Language Alternation\u3c/i\u3e, by Anneli Sarhimaa

The data that underlie Anneli Sarhimaa\u27s excellent study were gathered between 1989 and 1992, under restrictive field circumstances. Visits to Karelia required what the author terms “intricate co-operation with academic and public authorities in Russia” (p. 76), and the duration of any stay was limited to a few weeks. From her home base in Finland, she made short visits to three Central Karelian villages in the summers of 1989 and 1991, working with additional Central Karelian speakers resident in the capital city of Karelia in the winters of 1990 and 1991; in 1992, a two-week trip allowed her to work in nine Tver Karelian villages in central Russia. That these compressed visits produced 30-some hours of taped interviews and 31 sets of translation-task data (15 Central Karelian, 16 Tver Karelian) does credit to her careful advance planning; the frankness with which she points to limitations in the resulting data does equal credit to her scholarly scrupulousness

Review of \u3ci\u3eLanguage and the State: Revitalization and Revival in Israel and Eire\u3c/i\u3e, edited by Sue Wright; \u3ci\u3eThe Language Question in the Census of Population\u3c/i\u3e, by Mícheál Ó Gliasáin

Language and the state contains two formal papers, plus the questions and answers that followed each. The occasion was a Current Issues in Language and Society seminar held at the University of Birmingham in September 1995; the speakers were Bernard Spolsky of the Language Policy Research Center, Bar-Ilan University, Israel (“Conditions for language revitalization: A comparison of the cases of Hebrew and Maori”), and Muiris Ó Laoire of the Irish Language Department, University College Galway, Ireland (“An historical perspective on the revival of Irish outside the Gaeltacht, 1880–1930, with reference to the revitalization of Hebrew”). Perhaps because Israel and Ireland constitute a rare pair of cases in which the energies and resources of the state have been devoted to the promotion of a language spoken by relatively few at the time of the state\u27s official formation, the volume\u27s title is framed in terms of those two cases alone. But this seriously downplays the value of Spolsky\u27s discussion of Maori revitalization efforts, which greatly enhances the book\u27s contribution, and in fact makes this a book that no one deeply concerned with small-language revitalization efforts should miss