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[en] The author suggests that Lyttletons's analysis of palaeomagnetic data to support the contracting Earth hypothesis is open to question. He discusses why some doubts must persist about the significance of the palaeoradii obtained and presents new data to constrain the hypothesis. (C.F.)
[en] Niobium metallogeny over the course of geological history has been considered on the basis of data from 45 largest deposits in the world belonging to any of three metallogenic types: alkaligranitic, foidic, and carbonatitic. The deposits were formed under variable intensity from the Middle Paleoproterozoic to the Cenozoic. The greatest resources of niobium are accumulated in the deposits formed during the Rodinian, Pangean, and Amasian supercontinent cycles. These cycles are characterized by the prevalence of deposits associated with carbonatite complexes.
[en] Observations of the Earth's rotation exhibit random, secular and periodic variations in rate (changes in the length of the day l.o.d.) and in direction (polar motion). These variations are of great significance, because they are probably associated with geophysical phenomena. A matter of particular interest is the question of whether these fluctuations in the l.o.d. and in polar motion can arise from a common geophysical cause. Comparison of the values of l.o.d. with the amplitude of Chandler wobble for the last 80 years indicates that this hypothesis cannot be disregarded; however the data on long period fluctuations are difficult to interpret and the evidence is too poor to permit any conclusion. Also the nature of these fluctuations is not at all clear, because apparent periodic variations can also arise from a random process. Periods of about 4 and 7 years found by us and other authors, however, should be real and associated with meteorological effects. (Auth.)
[en] A brief report on the final round of the first World Physics Olympiad (WoPhO) held in Lombok, West Nusa Tenggara, Indonesia is presented. The theoretical and experimental problems are presented and the mark distribution is discussed. (paper)
[en] A total of 43 Earth-crossing asteroids are now known. Twenty-five were discovered or recovered in the last decade. There were only six numbered Earth-crossing asteroids prior to 1970. Since then, twenty-one have been numbered. The Aten asteroids, a new group of Earth-crossing asteroids, have orbits smaller than that of the Earth. The largest Earth crosser, Hephaistos, has C-type UBV colors and is probably about 10 km in diameter. The smallest, Hathor, has unusual UBV colors and a probable diameter of about 200 m. (Auth.)
[en] Earth's radiation imbalance is determined from ocean heat content data and compared with results of direct measurements. Distinct time intervals of alternating positive and negative values are found: 1960-mid-1970s (-0.15), mid-1970s-2000 (+0.15), 2001-present (-0.2 W/m2), and are consistent with prior reports. These climate shifts limit climate predictability.