Corvin Zahn

Explanatory and illustrative visualization of special and general relativity

This paper describes methods for explanatory and illustrative visualizations used to communicate aspects of Einsteins theories of special and general relativity, their geometric structure, and of the related fields of cosmology and astrophysics. Our illustrations target a general audience of laypersons interested in relativity. We discuss visualization strategies, motivated by physics education and the didactics of mathematics, and describe what kind of visualization methods have proven to be useful for different types of media, such as still images in popular science magazines, film contributions to TV shows, oral presentations, or interactive museum installations. Our primary approach is to adopt an egocentric point of view: the recipients of a visualization participate in a visually enriched thought experiment that allows them to experience or explore a relativistic scenario. In addition, we often combine egocentric visualizations with more abstract illustrations based on an outside view in order to provide several presentations of the same phenomenon. Although our visualization tools often build upon existing methods and implementations, the underlying techniques have been improved by several novel technical contributions like image-based special relativistic rendering on GPUs, special relativistic 4D ray tracing for accelerating scene objects, an extension of general relativistic ray tracing to manifolds described by multiple charts, GPU-based interactive visualization of gravitational light deflection, as well as planetary terrain rendering. The usefulness and effectiveness of our visualizations are demonstrated by reporting on experiences with, and feedback from, recipients of visualizations and collaborators.

X-Ray Pulses from Accretion Columns: Contributions to the Energy Dependence of the Pulse Shape

We study the pulse profiles of medium-luminosity binary X-ray pulsars in the framework of a column model. The model includes relativistic effects in a Schwarzschild spacetime and the dipolar shape of the accretion funnel. It takes into account mechanisms that are expected to be of major importance for the energy dependence of the pulse shape: energy-dependent local beaming of radiation leaving the column, the luminous halo formed by illumination of the neutron star surface, and magnetic scattering in the upper accretion stream. Beam patterns and pulse profiles are calculated for different values of mass and radius of the neutron star and different local beaming functions. The results illustrate that the energy dependence of the pulse profiles is to a large degree determined by the energy-dependent relative importance of the halo and column contributions to the observed flux.

Visualization in the Einstein Year 2005: a case study on explanatory and illustrative visualization of relativity and astrophysics

In this application paper, we report on over fifteen years of experience with relativistic and astrophysical visualization, which has been culminating in a substantial engagement for visualization in the Einstein Year 2005 - the 100/sup th/ anniversary of Einsteins publications on special relativity, the photoelectric effect, and Brownian motion. This paper focuses on explanatory and illustrative visualizations used to communicate aspects of the difficult theories of special and general relativity, their geometric structure, and of the related fields of cosmology and astrophysics. We discuss visualization strategies, motivated by physics education and didactics of mathematics, and describe what kind of visualization methods have proven to be useful for different types of media, such as still images in popular-science magazines, film contributions to TV shows, oral presentations, or interactive museum installations. Although our visualization tools build upon existing methods and implementations, these techniques have been improved by several novel technical contributions like image-based special relativistic rendering on GPUs, an extension of general relativistic ray tracing to manifolds described by multiple charts, GPU-based interactive visualization of gravitational light deflection, as well as planetary terrain rendering. The usefulness and effectiveness of our visualizations are demonstrated by reporting on experiences with, and feedback from, recipients of visualizations and collaborators.

Fremde Welten auf dem Graphikschirm : die Bedeutung der Visualisierung für die Astrophysik

Unsere Vorstellung von der uns umgebenden Welt ist im wesentlichen durch optische Eindrucke gepragt. Durch die Beschrankungen des menschlichen Auges konnen wir viele Bereiche nicht direkt visuell wahrnehmen, wie z. B. atomare und kosmische Objekte, mit Lichtgeschwindigkeit ablaufende Vorgange und elektromagnetische Strahlung auserhalb des sichtbaren Bereichs. Die Menschen versuchen aus diesem Grund seit Jahrhunderten durch kunstvolle Instrumente wie Mikroskope, Fernrohre sowie schnelle und multispektrale Detektoren die Grenzen ihrer Wahrnehmung zu erweitern . Dies ist jedoch aufgrund physikalischer Gesetze nicht im beliebigen Mase moglich. Obwohl auch die Computer selbst diesen grundsatzlichen physikalischen Beschrankungen unterliegen, sind sie doch ein Instrument, um mit Simulationsrechnungen im Rahmen der gultigen physikalischen Gesetze und durch Visualisierung der Ergebnisse diese fremden Welten sichtbar zu machen. Dies soll an einigen Beispielen, bei denen der Graphikschirm als Supermikroskop, als Riesenfernrohr und als Fenster zur Welt von Einstein dient, demonstriert werden. Our picture of the world around us is determined essentially by optical impressions. Due to the limitations of the human eye, we cannot directly perceive many fjelds visualIy, e .g. atomic and cosmic objects, processes occurring with the velocity of light, and electromagnetic radiation outside the visual range. For this reason, humans have tried for centuries to expand the limits of their visual perception with the help of imaginative instruments such as microscopes, telescopes, and fast und multispectral detectors. Because of the laws of physics, this is not possible to an arbitrary extent. Although the computer itself is restricted to these fundamental physical constraints, it is an instrument with which we, using simulation calculations within the framework of the physical laws and through visualization of the results, can make these strange worlds visible. This will be demonstrated by several examples in which the graphics display serves as super microscope, giant telescope and window to the world of Einstein.

Computersimulation in der Astrophysik

Unser Wissen uber die Struktur des Kosmos und die darin enthaltenen Objekte stammt aus der sorgfaltigen Analyse der einfallenden elektromagnetischen Strahlung, verbunden mit einer theoretischen Modellierung im Rahmen der von uns erforschten Naturgesetze. Die Beobachtungen erstrecken sich dabei heute vom Radiowellenbereich uber den Infrarot-, den optischen, den Rontgenbereich bis hin zum Hochstenergie-Gamma-Bereich, also uber mehr als 20 Dekaden des elektromagnetischen Spektrums. Eine realistische Modellierung der Systeme im Rahmen einer beobachtungsnahen Theorie erfordert vor allem bei Systemparameterstudien im allgemeinen den Einsatz der grosten verfugbaren Rechenleistungen.

Simulation mit Supercomputern: Ein neues Werkzeug der Physik

Unser Wissen uber die Struktur des Kosmos und die darin enthaltenen Objekte stammt aus der sorgfaltigen Analyse der auf der Erde einfallenden elektromagnetischen Strahlung, verbunden mit einer theoretischen Modellierung im Rahmen der von uns erforschten Naturgesetze. Die astronomischen Beobachtungen erstrecken sich dabei heute vom Radiowellenbereich uber den Infrarot-, den optischen, den Rontgenbereich bis hin zum Hochstenergie-Gamma-Bereich, also uber mehr als 20 Dekaden des elektromagnetischen Spektrums.