Daily Earth rotation determinations from IRIS very long baseline interferometry
Classical optical determinations of Earth rotation (UT1) require several weeks of observations to achieve an accuracy of ∼1.5 ms of time, whereas modern techniques have demonstrated an accuracy of 0.7–0.9 ms on timescales of 1–5 days l,2. Here we have probed the limits of the accuracy and time resolution of very long baseline inteferometry (VLBI) determinations of UT1 by conducting a series of 1-h observing sessions using only one baseline. Comparison of the results from the 1-h sessions with corresponding determinations from 24-h multi-baseline sessions establishes that the accuracy of the 1-h determinations is close to 0.1 ms of time. These observations were scheduled as part of the project MERIT (monitor earth rotation and intercompare techniques of observation and analysis3) intensive observing campaign.
Variations in atmospheric angular momentum on global and regional scales and the length of day
Twice-daily global analyses of the zonal winds prepared by the U.S. National Meteorological Center for the period from January 1, 1976, through December 31, 1981, have been used to construct a time series of the atmosphere's angular momentum (M). This series is spectrally analyzed and compared with independent observations of changes in the solid earth's rate of rotation. The most prominent feature in the M time series is an annual signal, and this is mirrored by similar behavior in changes in the length of the day (l.o.d.). Other noteworthy fluctuations in M and l.o.d. on time scales of less than a year also occur, however, and these too agree well with each other. In this regard, a near 50-day fluctuation in both time series, also noted in other studies, is especially visible. We conclude on the basis of these comparisons that indeed most of the variability in our time series for M is real and that, as others have suggested, the atmosphere plays a dominant role in forcing changes in l.o.d. on time scales of about a year and less. We divide the globe into a number of belts to investigate the contributions made by different parts of the atmosphere to the changes found in the global statistic M. Our approach is to calculate empirical orthogonal functions that define the major spatial modes of variation among the regional time series of angular momentum. As expected, we find the annual cycle in M is associated with seasonal changes in the major jet streams of the two hemispheres, with the larger of these changes occurring in the northern hemisphere. Nonseasonal changes in M emerge from the imbalances among regional variations in momentum, with the largest contributions on time scales less than a year coming from the regions 10°–25°S and 20°–35°N.
Between identity and difference: Three ways of reading Nishida's non-dualism
The philosophy of Nishida KitarŌ offers the reader today not only a paradigm for a comparative philosophy, but also a methodological framework to construct a Buddhist philosophy. The key and, at the same time, the obstacle to his philosophy is the concept of the "self-identity of the absolute contradiction." This conceptual cornerstone of Nishida's philosophy is as controversial among scholars today as it is central to his philosophy. Critics, such as Tanabe Hajime and Takahashi Satomi, argue that Nishida's philosophy privileges the principle of identity over that of difference and falls into a monism; his supporters, most of all Nishitani Keiji and Ueda Shizuteru, to the contrary, claim that it comprises the key to philosophical non-dualism. In general, I am convinced that even his "self-identity of the absolute contradiction," if it is read carefully within the context of Nishida's philosophy, will render a paradigm that falls neither into a logical contradiction nor into a monism but that provides the foundation for a non-dualist philosophy. To this end, I will reread it first in the context of Nishida's overall project and, then, on the background of Nishida's debates with his critics.