Direct Contact Among Galactic Civilizations by Relativistic Interstellar Spaceflight

Direct contact among galactic populations by relativistic interstellar spacefligh

Microenvironments for Life on Mars

Possible extraterrestrial life on mars in micro- environmen

The pre- and post-accretion irradiation history of cometary ices

Comets Halley and Wilson exhibited similar 3.4 micron emission features at approx. 1 AU from the Sun. A simple model of thermal emission from organic grains fits the feature, provides optical depths in good agreement with spacecraft measurements, and explains the absence of longer-wavelength organic features as due to spectral heliocentric evolution (Chyba and Sagan, 1987). The model utilizes transmission spectra of organics synthesized in the laboratory by irradiation of candidate cometary ices; the authors have long noted that related gas-phase syntheses yield polycyclic aromatic hydrocarbons, among other organic residues (Sagan et al., 1967). The authors previously concluded (Chyba and Sagan, 1987) that Halley's loss of several meters' depth with each perihelion passage, combined with the good fit of the Halley 3.4 micron feature to that of comet Wilson (Allen and Wickramasinghe, 1987), argues for the primordial - but not necessarily interstellar - origin of cometary organics. The authors examine the relative importance to the formation of organics of the variety of radiation environments experienced by comets. They conclude that there is at present no compelling reason to choose any of three contributing mechanisms (pre-accretion UV, pre-accretion cosmic ray, and post-accretion radionuclide processing) as the most important

Comets and the Origin of Life

Dr. Carl Sagan is the David Duncan Professor of Astronomy and Space Sciences and the Director of the Laboratory for Planetary Studies at Cornell University. He played a leading role in the Mariner, Viking and Voyager expeditions to the planets, for which he received numerous awards including the NASA Medal for Exceptional Scientific Achievement. His scientific research has enhanced mankind\u27s understanding of the greenhouse effect on Venus, dust storms on Mars, the origin of life, and the search for life elsewhere. Dr. Sagan is author, co-author or editor of more than 20 books, including The Dragons of Eden for which he was awarded the Pulitzer Prize. His Emmy and Peabody Award winning television series Cosmos became the most widely watched science series in the history of American public television and has been seen in 60 countries by more than 400 million people. The accompanying book, also called Cosmos, is the best-selling science book ever published in the English language. A longtime advocate for science and technology education, the ethical applications of science, and increased scientific literacy for the general public, Dr. Sagan has called IMSA a gift from the people of Illinois to the human future. Dr. Sagan is a member of IMSA\u27s National Advisory Board

Planetary Exploration (Lecture Two)

Requested by: Standing order from Science Planetary Exploratio

One Reality: Augmenting How the Physical World is Experienced by combining Multiple Mixed Reality Modalities

International audienceMost of our daily activities take place in the physical world, which inherently imposes physical constraints. In contrast, the digital world is very flexible, but usually isolated from its physical counterpart. To combine these two realms, many Mixed Reality (MR) techniques have been explored, at different levels in the continuum. In this work we present an integrated Mixed Reality ecosystem that allows users to incrementally transition from pure physical to pure virtual experiences in a unique reality. This system stands on a conceptual framework composed of 6 levels. This paper presents these levels as well as the related interaction techniques

Scintillation-Induced Intermittency in SETI

We consider interstellar scintillations as a cause of intermittency in radio signals from extraterrestrial intelligence (ETI). We demonstrate that scintillations are very likely to allow initial detections of narrowband signals from distant sources (> 100 pc), while making redetections improbable. We consider three models in order to assess the non-repeating, narrowband events found in recent SETI and to analyze large surveys in general: (I) Radiometer noise; (II) A population of constant Galactic sources undergoing interstellar scintillation,; and (III) Real, transient signals (or hardware errors) of either terrestrial or ET origin. We apply likelihood and Bayesian tests of the models to The Planetary Society/Harvard META data. We find that Models II and III are both highly preferred to Model I, but that Models II and III are about equally likely. Ruling out Model II in favor of Model III requires many more reobservations than were conducted in META *or* the reobservation threshold must be much lower than was used in META. *We cannot rule out the possibility that META events are real, intrinsically steady ETI signals.* We recommend that future surveys use thresholds far below the typical false-alarm threshold to lessen the effects of intermittency. The threshold level is best defined in terms of the recording and computational technology that is available at a cost commensurate with other survey costs.Comment: 59 pages, LaTeX using aaspp4 style file, 12 figures in 14 PostScript figures, ApJ, in press, 1997 Oct.

Thinking like a man? The cultures of science

Culture includes science and science includes culture, but conflicts between the two traditions persist, often seen as clashes between interpretation and knowledge. One way of highlighting this false polarity has been to explore the gendered symbolism of science. Feminism has contributed to science studies and the critical interrogation of knowledge, aware that practical knowledge and scientific understanding have never been synonymous. Persisting notions of an underlying unity to scientific endeavour have often impeded rather than fostered the useful application of knowledge. This has been particularly evident in the recent rise of molecular biology, with its delusory dream of the total conquest of disease. It is equally prominent in evolutionary psychology, with its renewed attempts to depict the fundamental basis of sex differences. Wars over science have continued to intensify over the last decade, even as our knowledge of the political, economic and ideological significance of science funding and research has become ever more apparent