On the permanent tide and the Earth dynamical ellipticity

<p>As other relevant quantities related to the Earth dynamics, the Earth dynamical ellipticity is influenced by tidal effects. In particular, it is affected by the permanent tide due to the time independent part of the Earth redistribution tidal potential. Hence, it is necessary to distinguish between its tide-free and non tide-free values (e.g., Burša 1995) when determining it from observations (e.g., Marchenko & Lopushanskyi 2018). This question is seldom considered in Earth rotation studies. For example, neither IAU2000/AIU2006 nutation/precession model nor IERS Conventions specify explicitly whether the dynamical ellipticity is a zero-tide parameter or not. However, current accuracy goals might be sensitive to that difference.</p><p>Within the framework of a Hamiltonian approach (Baenas, Escapa, & Ferrándiz 2019), we present a consistent treatment of the influence of the permanent tide on the dynamical ellipticity. In particular, we develop an analytical expression of the redistribution tidal potential based on Andoyer canonical variables and a semi-analytical theory of the orbital motions of the Moon and the Sun, following the same procedure as that given in Kinoshita (1977).</p><p>This method allows obtaining an expression of the zero frequency term of the redistribution tidal potential that updates that of Zadro & Marussi (1973), usually employed in reporting parameters of common relevance to Astronomy, Geodesy, & Geodynamics (e.g., Burša 1995, Groten 2004). In addition, it clarifies the procedure that must be followed in order that the dynamical ellipticity, fitted to the observations, contains the effects of the permanent tide avoiding in this way potential inconsistencies.</p>

Sentrum og snikksnakk. Luther i bruk - i samfunn og skole

Approaching the 500-year Reformation anniversary, the article discusses what might legitimize Luther as a topic in today’s society and educational practice. Are his crucial ideas an exclusively religious heritage, or could they be converted to issues of common relevance? Referring to the ways Luther was used by the GDR state and church in the 1983 anniversary, the article questions the potential for recontextualizing his specifically theological issues. By this, it relates to a current debate in religion didactics whether stories could be taught according to their religiously specific or universal, existential dimensions – cf. the question of learning about or from religion. The cultural and political impact of Luther’s theology obviously makes it relevant as common heritage. His theological issue, however – man’s lack of free will (De servo arbitrio), and his view on «theological man» as defined solely by God’s justification (De homine), which Luther considers to be his primary concern – appears to be counter-intuitive, i.e. different from what seems right or natural. Hence, it challenges the concept of cultural heritage, but proves a critical corrective to common, essentialist justifications of human dignity, cultural identity and superiority – which makes it an issue to be learnt from and not only about.Emneord: Luther, reformasjonen, kulturarv, fagdidaktikk, religionsdidaktikk.