Gravitational Lensing in Astronomy

Deflection of light by gravity was predicted by General Relativity and observationaly confirmed in 1919. In the following decades various aspects of the gravitational lens effect were explored theoretically, among them the possibility of multiple or ring-like images of background sources, the use of lensing as a gravitational telescope on very faint and distant objects, and the possibility to determine Hubble's constant with lensing. Only relatively recently gravitational lensing became an observational science after the discovery of the first doubly imaged quasar in 1979. Today lensing is a booming part of astrophysics. In addition to multiply-imaged quasars, a number of other aspects of lensing have been discovered since, e.g. giant luminous arcs, quasar microlensing, Einstein rings, galactic microlensing events, arclets, or weak gravitational lensing. By now literally hundreds of individual gravitational lens phenomena are known. Although still in its childhood, lensing has established itself as a very useful astrophysical tool with some remarkable successes. It has contributed significant new results in areas as different as the cosmological distance scale, the large scale matter distribution in the universe, mass and mass distribution of galaxy clusters, physics of quasars, dark matter in galaxy halos, or galaxy structure.Comment: Review article for "Living Reviews in Relativity", see http://www.livingreviews.org . 41 pages, latex, 22 figures (partly in GIF format due to size constraints). High quality postscript files can be obtained electronically at http://www.aip.de:8080/~jkw/review_figures.htm

Evaluating the therapeutic effects of museum object handling with hospital patients: A review and initial trial of wellbeing measures

Arts therapy interventions within health care produce positive outcomes for patients, staff and carers, though little rigorous evaluation of these activities is conducted using clinically accepted measures. Similarly, heritage-specific therapeutic interventions offer comparable potential to increase well-being. Although museums and galleries have significant capacity to contribute to health and social care, widespread implementation is impeded by lack of robust clinical data quantifying the impact of such interventions. Measurement scales for psychological well-being, quality of life and health status were reviewed for their suitability to evaluate well-being in hospital patients before and after 30-minute museum object handling sessions. Measures were short-listed using selection criteria of internal and external validity, practicality and sensitivity. Focus on usage in health care, breadth of application, ease of administration and degree of responsiveness informed the choice of optimum measures for preliminary research with female oncology patients (n=40). Findings indicated effectiveness of selected measures (Positive Affect Negative Affect Scale; PANAS and Visual Analogue Scale; VAS) for heritage-specific interventions