Jul 9, 2023 05:43 PM
(This post was last modified: Jul 9, 2023 05:43 PM by C C.)
https://www.astronomy.com/science/is-ear...ks-planet/
EXCERPTS: In 2000, paleontologist Peter Ward and astronomer Donald Brownlee of the University of Washington in Seattle penned a controversial book, Rare Earth: Why Complex Life Is Uncommon in the Universe (Copernicus). In it, they propose that Earth is an unusual world where complex life-forms developed over an extended period. They further assert that though simple, unicellular life may be abundant in the universe, complex life must be exceedingly rare.
In sharp contrast, noted Harvard-Smithsonian Center for Astrophysics astrophysicist Avi Loeb passionately argues in his book Extraterrestrial: The First Sign of Intelligent Life Beyond Earth (Mariner Books, 2021): “Given the ubiquity of habitable planets, it is the height of arrogance to conclude that we are unique.”
The debate about habitability and life in the universe remains wide open. In the past, astronomers spoke of finding “Goldilocks worlds” — planets in the habitable zone (HZ) of their stars, where the temperature was just right for liquid water on the surface. But the past two decades of research have shown that just because a planet lies in the HZ doesn’t mean it’s necessarily habitable.
[...] In their soon-to-be-published new book, The Rare Earth Hypothesis, Ward and Brownlee double down on their thesis with what they consider even stronger supporting evidence. They posit that “from what we know now, rare might not be a restrictive enough word for describing the frequency of complex life in the Cosmos.”
Their conclusion is based on comparisons of most of the exoplanetary systems so far characterized and that “no potentially habitable planet will remain so for long in almost every case without several crucial aspects.” Foremost is an ability to maintain a temperature allowing the existence of liquid water for almost unimaginable periods of time — which, they maintain, is perhaps the most important aspect of life-supporting planetary systems.
The authors also state that had a body the size of Comet Hale-Bopp (C/1995 O1) struck us, “there probably would not be a single microbe alive on Earth right now, let alone animals... (MORE - missing details)
EXCERPTS: In 2000, paleontologist Peter Ward and astronomer Donald Brownlee of the University of Washington in Seattle penned a controversial book, Rare Earth: Why Complex Life Is Uncommon in the Universe (Copernicus). In it, they propose that Earth is an unusual world where complex life-forms developed over an extended period. They further assert that though simple, unicellular life may be abundant in the universe, complex life must be exceedingly rare.
In sharp contrast, noted Harvard-Smithsonian Center for Astrophysics astrophysicist Avi Loeb passionately argues in his book Extraterrestrial: The First Sign of Intelligent Life Beyond Earth (Mariner Books, 2021): “Given the ubiquity of habitable planets, it is the height of arrogance to conclude that we are unique.”
The debate about habitability and life in the universe remains wide open. In the past, astronomers spoke of finding “Goldilocks worlds” — planets in the habitable zone (HZ) of their stars, where the temperature was just right for liquid water on the surface. But the past two decades of research have shown that just because a planet lies in the HZ doesn’t mean it’s necessarily habitable.
[...] In their soon-to-be-published new book, The Rare Earth Hypothesis, Ward and Brownlee double down on their thesis with what they consider even stronger supporting evidence. They posit that “from what we know now, rare might not be a restrictive enough word for describing the frequency of complex life in the Cosmos.”
Their conclusion is based on comparisons of most of the exoplanetary systems so far characterized and that “no potentially habitable planet will remain so for long in almost every case without several crucial aspects.” Foremost is an ability to maintain a temperature allowing the existence of liquid water for almost unimaginable periods of time — which, they maintain, is perhaps the most important aspect of life-supporting planetary systems.
The authors also state that had a body the size of Comet Hale-Bopp (C/1995 O1) struck us, “there probably would not be a single microbe alive on Earth right now, let alone animals... (MORE - missing details)