If a human looks at the clear blue sky from which light with high enough degree of polarization d originates, an 8-shaped bowtie-like figure, the yellow Haidinger's brush can be perceived, the long axis of which points towards the sun. A band of high d arcs across the sky at 90° from the sun. A person can pick two points on that band, observe the yellow brushes and triangulate the position of t...

This theoretical paper introduces a new way to view and characterize teaching and learning astronomy. It describes a framework, based on results from empirical data, analyzed through standard qualitative research methodology, in which a theoretical model for vital competencies of learning astronomy is proposed: Reading the Sky. This model takes into account not only disciplinary knowledge but a...

Current X-ray observatories, archival X-ray data, and the Sloan Digital Sky Survey (SDSS) represent a powerful combination for addressing key questions about active galactic nuclei (AGN). We describe a few selected issues at the forefront of X-ray AGN research and the relevance of the SDSS to them. Bulk X-ray/SDSS AGN investigations, X-ray weak AGN, red AGN, hard X-ray selected AGN, high-redshi...

Radiative sky cooling reduces the temperature of a system by promoting heat exchange with the sky; its key advantage is that no input energy is required. We will review the origins of radiative sky cooling from ancient times to the modern day, and illustrate how the fundamental physics of radiative cooling calls for a combination of properties that may not occur in bulk materials. A detailed co...

Spinning particles in curved space-time can have fermionic symmetries generated by the square root of bosonic constants of motion other than the Hamiltonian. We present a general analysis of the conditions under which such new supersymmetries appear, and discuss the Poisson-Dirac algebra of the resulting set of charges, including the conditions of closure of the new algebra. An example of a new...

The MAGIC telescope, with its 17-m diameter mirror, is currently the largest single-dish Imaging Air Cherenkov Telescope. It is located on the Canary Island of La Palma, at an altitude of 2200 m above sea level, and is operating since 2004. The accessible energy range is in the very high energy (VHE, E > 100 GeV) γ-ray domain, and roughly 40% of the duty cycle is devoted to observation of extra...

We present the results of our methods to “mine” the blazar sky, i.e., select blazar candidates with very high efficiency. These are based on the crosscorrelation between public radio and X-ray catalogs and have resulted in two surveys, the Deep X-ray Radio Blazar Survey (DXRBS) and the “Sedentary” BL Lac survey. We show that data mining is vital to select sizeable, deep samples of these rare ac...

Europe’s Lisbon strategy has reinforced eGovernment as a potential provider of major entomic boost by facilitating new and better services for all citizens and companies and reinforcing eDemocracy developments. The NMS are invited to play an active role in elaborating the new Information Society policy issues identified. This paper will explore the e-Readiness of NMS services environment, focus...