http://www.scientificamerican.com/articl...-galaxies/
EXCERPT: [...] more evidence mounts that the warm, wet conditions for life as we know it prevail throughout the cosmos. Surely simple, single-celled life should be common out there [...but...] The possible existence of intelligent aliens and extraterrestrial civilizations [...] remains much more controversial and is scarcely funded at all. [...] SETI chiefly looks for chatty cosmic cultures that might be beaming messages around [...] But its interstellar eavesdropping has yet to detect any signals that withstand close scrutiny.
[...] Now, new results suggest this loneliness may extend out into the universe far beyond our galaxy or, instead, that some of our preconceptions about the behaviors of alien civilizations are deeply flawed. After examining some 100,000 nearby large galaxies a team of researchers lead by The Pennsylvania State University astronomer Jason Wright has concluded that none of them contain any obvious signs of highly advanced technological civilizations. [...] it is by far the largest of study of its kind to date.
[...James Annis:] “In some sense it doesn’t matter how a galactic civilization gets or uses its power because the second law of thermodynamics makes energy use hard to hide. They could construct Dyson spheres, they could get power from rotating black holes, they could build giant computer networks in the cold outskirts of galaxies, and all of that would produce waste heat. Wright’s team went right to the peak of the curve for where you’d expect to see any sort of waste heat, and they’re just not seeing anything obvious....”
[...] Annis suspects galaxy-sterilizing astrophysical explosions called gamma-ray bursts, which were more frequent in the cosmic past, until recently suppressed the rise of advanced civilizations and that we inhabit “the beginning of history.”
But as rich as the scientific literature is with ideas, some of the most fascinating ones come instead from science fiction. [...In author Karl Schroeder's] view the future of technology would not consist of star-hopping civilizations spreading like wildfire through galaxies, disassembling planets and smothering suns, but rather of slow-growing cultures becoming more and more integrated with their natural environments, striving for ever-greater efficiencies and coming ever-closer to thermodynamic equilibrium. Simply put, profligate galaxy-spanning empires are unsustainable and therefore we do not see them. “SETI is essentially a search for technological waste products,” Schroeder has written. “Waste heat, waste light, waste electromagnetic signals—we merely have to posit that successful civilizations don’t produce such waste, and the failure of SETI is explained....”
EXCERPT: [...] more evidence mounts that the warm, wet conditions for life as we know it prevail throughout the cosmos. Surely simple, single-celled life should be common out there [...but...] The possible existence of intelligent aliens and extraterrestrial civilizations [...] remains much more controversial and is scarcely funded at all. [...] SETI chiefly looks for chatty cosmic cultures that might be beaming messages around [...] But its interstellar eavesdropping has yet to detect any signals that withstand close scrutiny.
[...] Now, new results suggest this loneliness may extend out into the universe far beyond our galaxy or, instead, that some of our preconceptions about the behaviors of alien civilizations are deeply flawed. After examining some 100,000 nearby large galaxies a team of researchers lead by The Pennsylvania State University astronomer Jason Wright has concluded that none of them contain any obvious signs of highly advanced technological civilizations. [...] it is by far the largest of study of its kind to date.
[...James Annis:] “In some sense it doesn’t matter how a galactic civilization gets or uses its power because the second law of thermodynamics makes energy use hard to hide. They could construct Dyson spheres, they could get power from rotating black holes, they could build giant computer networks in the cold outskirts of galaxies, and all of that would produce waste heat. Wright’s team went right to the peak of the curve for where you’d expect to see any sort of waste heat, and they’re just not seeing anything obvious....”
[...] Annis suspects galaxy-sterilizing astrophysical explosions called gamma-ray bursts, which were more frequent in the cosmic past, until recently suppressed the rise of advanced civilizations and that we inhabit “the beginning of history.”
But as rich as the scientific literature is with ideas, some of the most fascinating ones come instead from science fiction. [...In author Karl Schroeder's] view the future of technology would not consist of star-hopping civilizations spreading like wildfire through galaxies, disassembling planets and smothering suns, but rather of slow-growing cultures becoming more and more integrated with their natural environments, striving for ever-greater efficiencies and coming ever-closer to thermodynamic equilibrium. Simply put, profligate galaxy-spanning empires are unsustainable and therefore we do not see them. “SETI is essentially a search for technological waste products,” Schroeder has written. “Waste heat, waste light, waste electromagnetic signals—we merely have to posit that successful civilizations don’t produce such waste, and the failure of SETI is explained....”