Winston
Lorenzo von Matterhorn
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Are we alone? Setting some limits to our uniqueness
April 28, 2016
https://phys.org/news/2016-04-limits-uniqueness.html
Excerpts:
...a new paper shows that the recent discoveries of exoplanets combined with a broader approach to the question makes it possible to assign a new empirically valid probability to whether any other advanced technological civilizations have ever existed.
And it shows that unless the odds of advanced life evolving on a habitable planet are astonishingly low, then human kind is not the universe's first technological, or advanced, civilization.
"Rather than asking how many civilizations may exist now, we ask 'Are we the only technological species that has ever arisen?" said Sullivan. "This shifted focus eliminates the uncertainty of the civilization lifetime question and allows us to address what we call the 'cosmic archaeological question'how often in the history of the universe has life evolved to an advanced state?"
That still leaves huge uncertainties in calculating the probability for advanced life to evolve on habitable planets. It's here that Frank and Sullivan flip the question around. Rather than guessing at the odds of advanced life developing, they calculate the odds against it occurring in order for humanity to be the only advanced civilization in the entire history of the observable universe. With that, Frank and Sullivan then calculated the line between a Universe where humanity has been the sole experiment in civilization and one where others have come before us.
"Of course, we have no idea how likely it is that an intelligent technological species will evolve on a given habitable planet," says Frank. But using our method we can tell exactly how low that probability would have to be for us to be the ONLY civilization the Universe has produced. We call that the pessimism line. If the actual probability is greater than the pessimism line, then a technological species and civilization has likely happened before."
Using this approach, Frank and Sullivan calculate how unlikely advanced life must be if there has never been another example among the universe's ten billion trillion stars, or even among our own Milky Way galaxy's hundred billion.
The result? By applying the new exoplanet data to the universe's 2 x 10 to the 22nd power stars, Frank and Sullivan find that human civilization is likely to be unique in the cosmos only if the odds of a civilization developing on a habitable planet are less than about one in 10 billion trillion, or one part in 10 to the 22th power.
"One in 10 billion trillion is incredibly small," says Frank. "To me, this implies that other intelligent, technology producing species very likely have evolved before us. Think of it this way. Before our result you'd be considered a pessimist if you imagined the probability of evolving a civilization on a habitable planet were, say, one in a trillion. But even that guess, one chance in a trillion, implies that what has happened here on Earth with humanity has in fact happened about a 10 billion other times over cosmic history!" (visualizing one billion - the height of a stack of one billion one dollar bills measures 358,510 feet or 67.9 miles. This would reach from the earths surface into the lower portion of the troposphere. - W)
For smaller volumes the numbers are less extreme. For example, another technological species likely has evolved on a habitable planet in our own Milky Way galaxy if the odds against it evolving on any one habitable planet are better than one chance in 60 billion.
But if those numbers seem to give ammunition to the "optimists" about the existence of alien civilizations, Sullivan points out that the full Drake equationwhich calculates the odds that other civilizations are around todaymay give solace to the pessimists.
"The universe is more than 13 billion years old," said Sullivan. "That means that even if there have been a thousand civilizations in our own galaxy, if they live only as long as we have been aroundroughly ten thousand yearsthen all of them are likely already extinct. And others won't evolve until we are long gone. For us to have much chance of success in finding another "contemporary" active technological civilization, on average they must last much longer than our present lifetime."
"Given the vast distances between stars and the fixed speed of light we might never really be able to have a conversation with another civilization anyway," said Frank. "If they were 20,000 light years away then every exchange would take 40,000 years to go back and forth."
But, as Frank and Sullivan point out, even if there aren't other civilizations in our galaxy to communicate with now, the new result still has a profound scientific and philosophical importance. "From a fundamental perspective the question is 'has it ever happened anywhere before?'" said Frank. Our result is the first time anyone has been able to set any empirical answer for that question and it is astonishingly likely that we are not the only time and place that an advance civilization has evolved."
Scientists discover potentially habitable planets
Just 40 light years from Earth, planets are best targets so far for search for extraterrestrial life.
May 2, 2016
https://news.mit.edu/2016/scientists-discover-potentially-habitable-planets-0502
Excerpts from that article and another:
Because the system is just 40 light years from Earth, co-author Julien de Wit, a postdoc in the Department of Earth, Atmospheric, and Planetary Sciences, says scientists will soon be able to study the planets atmospheric compositions, as well as assess their habitability and whether life actually exists within this planetary system.
These planets are so close, and their star so small, we can study their atmosphere and composition, and further down the road, which is within our generation, assess if they are actually inhabited, de Wit says. All of these things are achievable, and within reach now. This is a jackpot for the field.
Up to now, the search for Earth-like orbs in our Galaxy and beyond centred on stars like our Sun, more massive and hotter than the dwarf around which the newly-discovered worlds orbit.
But the discovery suggests that a significant fraction of ultracool dwarfs hold potentially habitable planets in their gravitational sway.
"At the scale of our Galaxy, this means billions of additional places where life might have developed," Gillon said.
April 28, 2016
https://phys.org/news/2016-04-limits-uniqueness.html
Excerpts:
...a new paper shows that the recent discoveries of exoplanets combined with a broader approach to the question makes it possible to assign a new empirically valid probability to whether any other advanced technological civilizations have ever existed.
And it shows that unless the odds of advanced life evolving on a habitable planet are astonishingly low, then human kind is not the universe's first technological, or advanced, civilization.
"Rather than asking how many civilizations may exist now, we ask 'Are we the only technological species that has ever arisen?" said Sullivan. "This shifted focus eliminates the uncertainty of the civilization lifetime question and allows us to address what we call the 'cosmic archaeological question'how often in the history of the universe has life evolved to an advanced state?"
That still leaves huge uncertainties in calculating the probability for advanced life to evolve on habitable planets. It's here that Frank and Sullivan flip the question around. Rather than guessing at the odds of advanced life developing, they calculate the odds against it occurring in order for humanity to be the only advanced civilization in the entire history of the observable universe. With that, Frank and Sullivan then calculated the line between a Universe where humanity has been the sole experiment in civilization and one where others have come before us.
"Of course, we have no idea how likely it is that an intelligent technological species will evolve on a given habitable planet," says Frank. But using our method we can tell exactly how low that probability would have to be for us to be the ONLY civilization the Universe has produced. We call that the pessimism line. If the actual probability is greater than the pessimism line, then a technological species and civilization has likely happened before."
Using this approach, Frank and Sullivan calculate how unlikely advanced life must be if there has never been another example among the universe's ten billion trillion stars, or even among our own Milky Way galaxy's hundred billion.
The result? By applying the new exoplanet data to the universe's 2 x 10 to the 22nd power stars, Frank and Sullivan find that human civilization is likely to be unique in the cosmos only if the odds of a civilization developing on a habitable planet are less than about one in 10 billion trillion, or one part in 10 to the 22th power.
"One in 10 billion trillion is incredibly small," says Frank. "To me, this implies that other intelligent, technology producing species very likely have evolved before us. Think of it this way. Before our result you'd be considered a pessimist if you imagined the probability of evolving a civilization on a habitable planet were, say, one in a trillion. But even that guess, one chance in a trillion, implies that what has happened here on Earth with humanity has in fact happened about a 10 billion other times over cosmic history!" (visualizing one billion - the height of a stack of one billion one dollar bills measures 358,510 feet or 67.9 miles. This would reach from the earths surface into the lower portion of the troposphere. - W)
For smaller volumes the numbers are less extreme. For example, another technological species likely has evolved on a habitable planet in our own Milky Way galaxy if the odds against it evolving on any one habitable planet are better than one chance in 60 billion.
But if those numbers seem to give ammunition to the "optimists" about the existence of alien civilizations, Sullivan points out that the full Drake equationwhich calculates the odds that other civilizations are around todaymay give solace to the pessimists.
"The universe is more than 13 billion years old," said Sullivan. "That means that even if there have been a thousand civilizations in our own galaxy, if they live only as long as we have been aroundroughly ten thousand yearsthen all of them are likely already extinct. And others won't evolve until we are long gone. For us to have much chance of success in finding another "contemporary" active technological civilization, on average they must last much longer than our present lifetime."
"Given the vast distances between stars and the fixed speed of light we might never really be able to have a conversation with another civilization anyway," said Frank. "If they were 20,000 light years away then every exchange would take 40,000 years to go back and forth."
But, as Frank and Sullivan point out, even if there aren't other civilizations in our galaxy to communicate with now, the new result still has a profound scientific and philosophical importance. "From a fundamental perspective the question is 'has it ever happened anywhere before?'" said Frank. Our result is the first time anyone has been able to set any empirical answer for that question and it is astonishingly likely that we are not the only time and place that an advance civilization has evolved."
Scientists discover potentially habitable planets
Just 40 light years from Earth, planets are best targets so far for search for extraterrestrial life.
May 2, 2016
https://news.mit.edu/2016/scientists-discover-potentially-habitable-planets-0502
Excerpts from that article and another:
Because the system is just 40 light years from Earth, co-author Julien de Wit, a postdoc in the Department of Earth, Atmospheric, and Planetary Sciences, says scientists will soon be able to study the planets atmospheric compositions, as well as assess their habitability and whether life actually exists within this planetary system.
These planets are so close, and their star so small, we can study their atmosphere and composition, and further down the road, which is within our generation, assess if they are actually inhabited, de Wit says. All of these things are achievable, and within reach now. This is a jackpot for the field.
Up to now, the search for Earth-like orbs in our Galaxy and beyond centred on stars like our Sun, more massive and hotter than the dwarf around which the newly-discovered worlds orbit.
But the discovery suggests that a significant fraction of ultracool dwarfs hold potentially habitable planets in their gravitational sway.
"At the scale of our Galaxy, this means billions of additional places where life might have developed," Gillon said.
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