Heraclides of Pontus. Astronomical fragments

Heraclides of Pontus (c. 388–310 BCE), a Platonic philosopher, worked in various literary genres and wrote on such topics as psychology, politics, literature, history, geography, astronomy and the philosophy of nature. Nothing is preserved. The present publication contains a collection of the testimonies about Heraclides’ astronomical writings. He thought of an infinite universe, in fact believing that every star is a kosmos, located in the infinite either. He famously advanced the theory of terrestrial rotation, hypothesizing that the apparent diurnal rotation of the heavens is better explained by the rotation of the Earth, and in this context correctly observed that, unlike other planets, Venus as morning and evening star has the maximum elongation from the Sun’s position (that is to say is never located far from the Sun). The evidences are translated and numbered according to a new edition by Schütrumpf et al. 2008.

Magnetic field of the Hot Earth. Reversals, magnetic anomalies and mechanism of the magnetic poles drift.

Principally new model of the magnetic field of the Hot Earth is proposed. Unlike the commonly accepted approach which considers that the Earth’s temperature doesn’t increase because heat released under selfgravitation is removed through radiation our model assumes that early substance of the Earth heated up to 30 000 K was a superheated and overcompressed vapour. Cooling the Earth substance was condensing. The system was expanding adiabatically that governed the character of the Earth enlargement. This scheme origins from the phase transition (PT) of condensation-evaporation under the benefit of condensation. PT provides the heat, geodynamics of expansion and the Earth’s magnetic field (EMF). The high temperature of the substance causes its thermoionization, whereas PT operation relating to mass transfer initiates charges separation and generation of the double electric layer (DEL). A diurnal rotation of DEL induces a weak initial EMF which enhances then at the expense of the Hall dynamo (Hall current) inside PT area. The benefit of evaporation causes the Earth compression and reversal of the EMF polarity. The approach we develop provides an insight into features of the magnetic field of the planets and satellites at the Sun system.

Global patterns of synchronization in human communications

Social media are transforming global communication and coordination and provide unprecedented opportunities for studying socio-technical domains. Here we study global dynamical patterns of communication on Twitter across many scales. Underlying the observed patterns is both the diurnal rotation of the Earth, day and night, and the synchrony required for contingency of actions between individuals. We find that urban areas show a cyclic contraction and expansion that resembles heartbeats linked to social rather than natural cycles. Different urban areas have characteristic signatures of daily collective activities. We show that the differences detected are consistent with a new emergent global synchrony that couples behaviour in distant regions across the world. Although local synchrony is the major force that shapes the collective behaviour in cities, a larger-scale synchronization is beginning to occur.

Dynamical analysis of sea-breeze hodograph rotation in Sardinia

This study investigates the diurnal evolution of sea-breeze (SB) rotation over an island at the middle latitudes. Earlier research on sea breezes in Sardinia shows that the onshore winds around various coasts of the island exhibit both the theoretically predicted clockwise rotation as well as seemingly anomalous anticlockwise rotation. A non-hydrostatic fully compressible numerical model (WRF) is used to simulate wind fields on and around the island on previously studied sea-breeze days, and is shown to capture the circulation on all coasts accurately. Diurnal rotation of wind is examined, and patterns of clockwise and anticlockwise rotation are identified. A dynamical analysis is performed by extracting individual forcing terms from the horizontal momentum equations. Analysis of several regions around the island shows that the direction of rotation is a result of a complex interaction between near-surface and synoptic pressure gradient, Coriolis and advection forcings. An idealized simulation is performed over an artificial island with dramatically simplified topography yet similar dimensions and latitude to Sardinia. Dynamical analysis of the idealized case reveals a rather different pattern of hodograph rotation to the real Sardinia, yet similar underlying dynamics. The research provides new insights into the dynamics underlying sea-breeze hodograph rotation, especially in coastal zones with a complex topography and/or coastline.

Dynamical analysis of sea-breeze hodograph rotation in Sardinia

This study investigates the diurnal evolution of sea-breeze rotation over an island in the mid-latitudes. Earlier research on sea-breezes in Sardinia shows that the onshore winds around various coasts of the island exhibit both the theoretically predicted clockwise rotation as well as seemingly anomalous anti-clockwise rotation. A non-hydrostatic fully compressible numerical model (WRF) is used to simulate wind fields on and around the island on previously-studied sea-breeze days and is shown to accurately capture the circulation on all coasts. Diurnal rotation of wind is examined and patterns of clockwise and anti-clockwise rotation are identified. A dynamical analysis is performed by extracting individual forcing terms from the horizontal momentum equations. Analysis of several regions around the island shows that the direction of rotation is a result of a complex interaction between near-surface and synoptic pressure gradient, Coriolis and advection forcings. An idealized simulation is performed over an artificial island with dramatically simplified topography, yet similar dimensions and latitude to Sardinia. Dynamical analysis of the idealized case reveals a rather different pattern of hodograph rotation to the real Sardinia, yet similar underlying dynamics. The research provides new insights into the dynamics underlying sea-breeze hodograph rotation, especially in coastal zones with complex topography and/or coastline.

Conservative evaluation of the uncertainty in the LAGEOS-LAGEOS II Lense-Thirring test

We deal with the test of the general relativistic gravitomagnetic Lense-Thirring effect currently being conducted in the Earth’s gravitational field with the combined nodes Ω of the laser-ranged geodetic satellites LAGEOS and LAGEOS II. One of the most important sources of systematic uncertainty on the orbits of the LAGEOS satellites, with respect to the Lense-Thirring signature, is the bias due to the even zonal harmonic coefficients J ℓ of the multipolar expansion of the Earth’s geopotential which account for the departures from sphericity of the terrestrial gravitational potential induced by the centrifugal effects of its diurnal rotation. The issue addressed here is: are the so far published evaluations of such a systematic error reliable and realistic? The answer is negative. Indeed, if the difference ΔJ ℓ among the even zonals estimated in different global solutions (EIGEN-GRACE02S, EIGEN-CG03C, GGM02S, GGM03S, ITG-Grace02, ITG-Grace03s, JEM01-RL03B, EGM2008, AIUB-GRACE01S) is assumed for the uncertainties δJ ℓ instead of using their more-or-less calibrated covariances $$ \sigma _{J_\ell } $$, it turns out that the systematic error δμ in the Lense-Thirring measurement is about 3 to 4 times larger than in the evaluations so far published based on the use of the covariances of one model at a time separately, amounting up to 37% for the pair EIGEN-GRACE02S/ITG-Grace03s. The comparison among the other recent GRACE-based models yields bias as large as about 25–30%. The major discrepancies still occur for J 4; J 6 and J 8, which are just to which the zonals the combined LAGEOS/LAGOES II nodes are most sensitive.