1,721,389 research outputs found
The Impact of the Temporal Distribution of Communicating Civilizations on Their Detectability
No full textWe used a statistical model to investigate the detectability (defined by the requirement that causal contact has been initiated with us) of communicating civilizations within a volume of the Universe surrounding our location. If the civilizations are located in our galaxy, the detectability requirement imposes a strict constraint on their epoch of appearance and their communicating life span. This, in turn, implies that our ability to gather empirical evidence of the fraction of civilizations within range of detection strongly depends on the specific features of their temporal distribution. Our approach illuminates aspects of the problem that can escape the standard treatment based on the Drake equation. Therefore, it might provide the appropriate framework for future studies dealing with the evolutionary aspects of the search for extraterrestrial intelligence (SETI). Key Words: Astrobiology-Extraterrestrial life-SETI-Complex life-Life detection-Intelligence. Astrobiology 18, 54-58
Measurement of cosmological parameters
No full textThe study of the cosmic microwave background (CMB) has played a crucial role in establishing a new standard of precision in the determination of cosmological parameters. The full-sky, high-resolution maps of the CMB recently produced by the WMAP space mission, have reinforced the evidence in favor of a fiat universe, dominated by dark matter and dark energy, and consistent with the predictions of the inflationary scenario. Further high-precision observations of the CMB, such as those that will be carried on by ESA's Planck Surveyor, will further strengthen our knowledge of the Universe
The music of the Big Bang: the cosmic microwave background and the new cosmology
No full textThe cosmic microwave background radiation is the afterglow of the big bang: a tenuous signal, more than 13 billion years old, which carries the answers to many of the questions about the nature of our Universe. It was serendipitously discovered in 1964, and thoroughly investigated in the last four decades by a large number of experiments. Two Nobel Prizes in Physics have already been awarded for research on the cosmic background radiation: one in 1978 to Arno Penzias and Robert Wilson, who first discovered it, the other in 2006, to George Smoot and John Mather, for the results of the COBE satellite. Most cosmological information is encoded in the cosmic background radiation by acoustic oscillations in the dense plasma that filled the primordial Universe: a "music" of the big bang, which cosmologists have long been trying to reconstruct and analyze, in order to distinguish different cosmological models, much like one can distinguish different musical instruments by their timbre and overtones. Only lately, this amazing cosmic sound has been unveiled by such experiments as BOOMERANG and MAXIMA and, more recently, by the WMAP satellite. This led to a giant leap in our understanding of the Universe, but the investigation is not ended yet. The book focuses on how the exploration of the cosmic background radiation has shaped our picture of the Universe, leading even the non-specialized readers towards the frontier of cosmological research, helping them to understand, using a simple language and captivating metaphors, the mechanisms behind the Universe in which we live. "This non-technical tour of the discovery and significance of the whispers of creation, the fossil radiation from the Big Bang, is a delight to read." Prof. Joe Silk, University of Oxford, a pioneering contributor to understanding the structure of the cosmic background radiation
Cosmology from Planck
No full textI briefly review some of the main scientific outputs expected from the upcoming Planck mission. Planck will map the CMB sky with 5' resolution and mu K sensitivity, with minimal foreground contribution and superb control on systematics. It will collect the entire information enclosed in the temperature primary anisotropy signal and will also get a good measurement of the polarized component of the CMB. This will have profound implications on our knowledge of the physics of the early universe and on the determination of cosmological parameters. (c) 2006 Elsevier B.V. All rights reserved
Copernicanism and the typicality in time
No full textHow special (or not) is the epoch we are living in? What is the appropriate reference class for embedding the observations made at the present time? How probable -- or else -- is anything we observe in the fulness of time? Contemporary cosmology and astrobiology bring those seemingly old-fashioned philosophical issues back into focus. There are several examples of contemporary research which use the assumption of typicality in time (or temporal Copernicanism) explicitly or implicitly, while not truly elaborating upon the meaning of this assumption. The present paper brings attention to the underlying and often uncritically accepted assumptions in these cases. It also aims to defend a more radical position that typicality in time is not -- and cannot ever be -- well-defined, in contrast to the typicality in space, and the typicality in various specific parameter spaces. This, of course, does not mean that we are atypical in time; instead, the notion of typicality in time is necessarily somewhat vague and restricted. In principle, it could be strengthened by further defining the relevant context, e.g., by referring to typicality within the Solar lifetime, or some similar restricting clause
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