The Fermi Paradox was first posed by the physicist Enrico Fermi: why with such a large number of stars in the universe, and with the great age of the universe allowing enough time for life to evolve and slowly propagate across a galaxy, are there no civilizations
In 2014 in the prestigious Physical Review Letters, astrophysicists Tsvi Piran and Raul Jimenez argue that most planets in the universe have been wracked by frequent galactic-scale environmental catastrophes that probably would destroy nascent life more complex than a single-celled organism.
The sources of these catastrophes are so-called long gamma ray bursts (LGRBs). Gamma rays are electromagnetic radiation of an extremely high frequency and are therefore high energy photons. Gamma rays are ionizing radiation, and are thus biologically hazardous. They have the smallest wavelengths and the most energy of any wave in the electromagnetic spectrum. Unlike optical light and x-rays, gamma rays cannot be captured and reflected by mirrors. Gamma-ray wavelengths are so short that they can pass through the space within the atoms of a detector. LGRBs are enormously violent events occur upon the collapse of a massive star which runs out of fuel, collapses, and sprays out more energy and radiation than a supernova along a highly directional beam.
A long gamma ray burst lasts for just a few seconds, but it ejects so much energy it would ruin the biosphere of any nearby planet in the direction of its beam. Gamma-ray bursts are the most energetic and luminous electromagnetic events since the Big Bang and can release more energy in 10 seconds than our Sun will emit in its entire 10-billion-year expected lifetime. The surface of a close-by planet might be fried by the gamma rays themselves. But even at a distance of a few thousand light years, a LGRB would destroy the protective ozone layer in the atmosphere of an Earth-like planet for several weeks or even months. Without ozone, ultraviolet light from a planet’s star would irradiate biological life and completely degrade the biosphere. Any complex surface life forms would be doomed. Simple life might survive, but its evolution to more complex forms would be set back by millions or billions of years.
Their conclusion: In any 500 million year period, a planet within about 13,000 light years of the center of the Milky Way has a 95% chance of getting blasted by a lethal LGRB. And early in the development of the universe the stars were more closely packed and the risk from LGRB was worse.
Interestingly, the Earth has a privileged area in the universe; it is not well populated with stars so the risk for sterilization is less.
In 2014 in the prestigious Physical Review Letters, astrophysicists Tsvi Piran and Raul Jimenez argue that most planets in the universe have been wracked by frequent galactic-scale environmental catastrophes that probably would destroy nascent life more complex than a single-celled organism.
The sources of these catastrophes are so-called long gamma ray bursts (LGRBs). Gamma rays are electromagnetic radiation of an extremely high frequency and are therefore high energy photons. Gamma rays are ionizing radiation, and are thus biologically hazardous. They have the smallest wavelengths and the most energy of any wave in the electromagnetic spectrum. Unlike optical light and x-rays, gamma rays cannot be captured and reflected by mirrors. Gamma-ray wavelengths are so short that they can pass through the space within the atoms of a detector. LGRBs are enormously violent events occur upon the collapse of a massive star which runs out of fuel, collapses, and sprays out more energy and radiation than a supernova along a highly directional beam.
A long gamma ray burst lasts for just a few seconds, but it ejects so much energy it would ruin the biosphere of any nearby planet in the direction of its beam. Gamma-ray bursts are the most energetic and luminous electromagnetic events since the Big Bang and can release more energy in 10 seconds than our Sun will emit in its entire 10-billion-year expected lifetime. The surface of a close-by planet might be fried by the gamma rays themselves. But even at a distance of a few thousand light years, a LGRB would destroy the protective ozone layer in the atmosphere of an Earth-like planet for several weeks or even months. Without ozone, ultraviolet light from a planet’s star would irradiate biological life and completely degrade the biosphere. Any complex surface life forms would be doomed. Simple life might survive, but its evolution to more complex forms would be set back by millions or billions of years.
Their conclusion: In any 500 million year period, a planet within about 13,000 light years of the center of the Milky Way has a 95% chance of getting blasted by a lethal LGRB. And early in the development of the universe the stars were more closely packed and the risk from LGRB was worse.
Interestingly, the Earth has a privileged area in the universe; it is not well populated with stars so the risk for sterilization is less.
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