Astronomers claim in a new paper that star motions should make it easy for civilizations to spread across the galaxy, but still we might find ourselves alone.
As
far as anyone knows, we have always been alone. It’s just us on this
pale blue dot, “home to everyone you love, everyone you know, everyone
you ever heard of,” as Carl Sagan so memorably put it. No one has called
or dropped by. And yet the universe is filled with stars, nearly all
those stars have planets, and some of those planets are surely livable.
So where is everybody?
The Italian physicist Enrico Fermi was purportedly the first to pose this question, in 1950, and scientists have offered a bounty of solutions for his eponymous paradox since. One of the most famous came from Sagan himself, with William Newman, who postulated in a 1981 paper that we just need patience. Nobody has visited because they’re all too far away; it takes time to evolve a species intelligent enough to invent interstellar travel, and time for that species to spread across so many worlds. Nobody is here yet.
Other researchers have argued that extraterrestrial life might rarely become space-faring (just as only one species on Earth ever has). Some argue that tech-savvy species, when they arise, quickly self-destruct. Still others suggest aliens may have visited in the past, or that they’re avoiding us on purpose, having grown intelligent enough to be suspicious of everyone else. Perhaps the most pessimistic answer is a foundational paper from 1975, in which the astrophysicist Michael Hart declared that the only plausible reason nobody has visited is that there really is nobody out there.
Now comes a paper that rebuts Sagan and Newman, as well as Hart, and offers a new solution to the Fermi paradox that avoids speculation about alien psychology or anthropology.
The research, which is under review by The Astrophysical Journal, suggests it wouldn’t take as long as Sagan and Newman thought for a space-faring civilization to planet-hop across the galaxy, because the movements of stars can help distribute life. “The sun has been around the center of the Milky Way 50 times,” said Jonathan Carroll-Nellenback, an astronomer at the University of Rochester, who led the study. “Stellar motions alone would get you the spread of life on time scales much shorter than the age of the galaxy.” Still, although galaxies can become fully settled fairly quickly, the fact of our loneliness is not necessarily paradoxical: According to simulations by Carroll-Nellenback and his colleagues, natural variability will mean that sometimes galaxies will be settled, but often not — solving Fermi’s quandary.
The question of how easy it would be to settle the galaxy has played a central role in attempts to resolve the Fermi paradox. Hart and others calculated that a single space-faring species could populate the galaxy within a few million years, and maybe even as quickly as 650,000 years. Their absence, given the relative ease with which they should spread, means they must not exist, according to Hart.
Sagan and Newman argued it would take longer, in part because long-lived civilizations are likelier to grow more slowly. Faster-growing, rapacious societies might peter out before they could touch all the stars. So maybe there have been a lot of short-lived, fast-growing societies that wink out, or a few long-lived, slowly expanding societies that just haven’t arrived yet, as Jason Wright of Pennsylvania State University, a coauthor of the new study, summarized Sagan and Newman’s argument. But Wright doesn’t agree with either solution.
“That conflates the expansion of the species as a whole with the sustainability of individual settlements,” he said. “Even if it is true for one species, it is not going to be this iron-clad law of xenosociology where if they are expanding, they are necessarily short-lived.” After all, he noted, life on Earth is robust, “and it expands really fast.”
In their new paper, Carroll-Nellenback, Wright and their collaborators Adam Frank of Rochester and Caleb Scharf of Columbia University sought to examine the paradox without making untestable assumptions. They modeled the spread of a “settlement front” across the galaxy, and found that its speed would be strongly affected by the motions of stars, which previous work — including Sagan and Newman’s — treated as static objects. The settlement front could cross the entire galaxy based just on the motions of stars, regardless of the power of propulsion systems. “There is lots of time for exponential growth basically leading to every system being settled,” Carroll-Nellenback said.
But the fact that no interstellar visitors are here now — what Hart called “Fact A” — does not mean they do not exist, the authors say. While some civilizations might expand and become interstellar, not all of them last forever. On top of that, not every star is a choice destination, and not every planet is habitable. There’s also what Frank calls “the Aurora effect,” after Kim Stanley Robinson’s novel Aurora, in which settlers arrive at a habitable planet on which they nonetheless cannot survive.
When Carroll-Nellenback and his coauthors included these impediments to settlement in their model and ran many simulations with different star densities, seed civilizations, spacecraft velocities and other variations, they found a vast middle ground between a silent, empty galaxy and one teeming with life. It’s possible that the Milky Way is partially settled, or intermittently so; maybe explorers visited us in the past, but we don’t remember, and they died out. The solar system may well be amid other settled systems; it’s just been unvisited for millions of years.
Anders Sandberg, a futurist at the University of Oxford’s Future of Humanity Institute who has studied the Fermi paradox, said he thinks spacecraft would spread civilizations more effectively than stellar motions. “But the mixing of stars could be important,” he wrote in an email, “since it is likely to spread both life, through local panspermia” — the spread of life’s chemical precursors — “and intelligence, if it really is hard to travel long distances.”
Frank views his and his colleagues’ new paper as SETI-optimistic. He and Wright say that now we need to look harder for alien signals, which will be possible in the coming decades as more sophisticated telescopes open their eyes to the panoply of exoplanets and begin glimpsing their atmospheres.
“We are entering an era when we are going to have actual data relevant to life on other planets,” Frank said. “This couldn’t be more relevant than in the moment we live.”
Seth Shostak, an astronomer at the SETI Institute who has studied the Fermi paradox for decades, thinks it is likely to be explained by something more complex than distance and time — like perception.
Maybe we are not alone and have not been. “The click beetles in my backyard don’t notice that they’re surrounded by intelligent beings — namely my neighbors and me,” Shostak said, “but we’re here, nonetheless.”
Rebecca Boyle
Source news
Comment by Oliviero Mannucci: I want to remind all of you who read this blog a document decrypted by the FBI in which we talk about extraterrestrial life forms as multidimensional life forms. The problem is that most Earth scientists have difficulty accepting as real everything that comes from the limited perception of our limited five senses. By opening the mind, and by ceasing to divide science from spirituality, science could understand that not only do extraterrestrials exist, but that they come from innumerable dimensions of existence. But on Earth we are still in the Middle Ages unfortunately.
After all, there are still people who, despite all the evidence, continue to maintain that the Earth is flat. Scientists who reject the UFO phenomenon as a real phenomenon are exactly like these people who are not so good.
With this document declassified the FBI indirectly wanted to alert us to the presence of aliens who could manifest with their spaceships, opening the distance between the dimensions.
FBI Link here: vault.fbi.gov/...
1. One part of the vessel sighted contained passengers inside, while another part was under remote control (remote control).
2. The mission is peaceful, visitors are planning to stay on the planet.
3. The type of race in question, the "visitors", has enormous dimensions, but human facets.
4. They are not earthly and come from your world.
5. They come from an "Etheric World" that we do not know, so they do not come from any other known planet.
6. The bodies of visitors and their ships materialize through vibrations with the dense matter of the Earth.
7. Your ships have beams of energy that can disintegrate any aircraft and can suddenly disappear from our vision without a trace.
8. The region from which they come is the astral plane corresponding to Loka or Talas. The esoteric will understand these words. In fact, the Loka-Talas, which are not physical or metaphysical places, are different levels of consciousness. Each plane of consciousness different from ours is a parallel dimensional plane.
9. Visitors use a radar system that allows you to capture the opening location to move from one dimension to another.
Source news
The Italian physicist Enrico Fermi was purportedly the first to pose this question, in 1950, and scientists have offered a bounty of solutions for his eponymous paradox since. One of the most famous came from Sagan himself, with William Newman, who postulated in a 1981 paper that we just need patience. Nobody has visited because they’re all too far away; it takes time to evolve a species intelligent enough to invent interstellar travel, and time for that species to spread across so many worlds. Nobody is here yet.
Other researchers have argued that extraterrestrial life might rarely become space-faring (just as only one species on Earth ever has). Some argue that tech-savvy species, when they arise, quickly self-destruct. Still others suggest aliens may have visited in the past, or that they’re avoiding us on purpose, having grown intelligent enough to be suspicious of everyone else. Perhaps the most pessimistic answer is a foundational paper from 1975, in which the astrophysicist Michael Hart declared that the only plausible reason nobody has visited is that there really is nobody out there.
Now comes a paper that rebuts Sagan and Newman, as well as Hart, and offers a new solution to the Fermi paradox that avoids speculation about alien psychology or anthropology.
The research, which is under review by The Astrophysical Journal, suggests it wouldn’t take as long as Sagan and Newman thought for a space-faring civilization to planet-hop across the galaxy, because the movements of stars can help distribute life. “The sun has been around the center of the Milky Way 50 times,” said Jonathan Carroll-Nellenback, an astronomer at the University of Rochester, who led the study. “Stellar motions alone would get you the spread of life on time scales much shorter than the age of the galaxy.” Still, although galaxies can become fully settled fairly quickly, the fact of our loneliness is not necessarily paradoxical: According to simulations by Carroll-Nellenback and his colleagues, natural variability will mean that sometimes galaxies will be settled, but often not — solving Fermi’s quandary.
The question of how easy it would be to settle the galaxy has played a central role in attempts to resolve the Fermi paradox. Hart and others calculated that a single space-faring species could populate the galaxy within a few million years, and maybe even as quickly as 650,000 years. Their absence, given the relative ease with which they should spread, means they must not exist, according to Hart.
Sagan and Newman argued it would take longer, in part because long-lived civilizations are likelier to grow more slowly. Faster-growing, rapacious societies might peter out before they could touch all the stars. So maybe there have been a lot of short-lived, fast-growing societies that wink out, or a few long-lived, slowly expanding societies that just haven’t arrived yet, as Jason Wright of Pennsylvania State University, a coauthor of the new study, summarized Sagan and Newman’s argument. But Wright doesn’t agree with either solution.
“That conflates the expansion of the species as a whole with the sustainability of individual settlements,” he said. “Even if it is true for one species, it is not going to be this iron-clad law of xenosociology where if they are expanding, they are necessarily short-lived.” After all, he noted, life on Earth is robust, “and it expands really fast.”
In their new paper, Carroll-Nellenback, Wright and their collaborators Adam Frank of Rochester and Caleb Scharf of Columbia University sought to examine the paradox without making untestable assumptions. They modeled the spread of a “settlement front” across the galaxy, and found that its speed would be strongly affected by the motions of stars, which previous work — including Sagan and Newman’s — treated as static objects. The settlement front could cross the entire galaxy based just on the motions of stars, regardless of the power of propulsion systems. “There is lots of time for exponential growth basically leading to every system being settled,” Carroll-Nellenback said.
But the fact that no interstellar visitors are here now — what Hart called “Fact A” — does not mean they do not exist, the authors say. While some civilizations might expand and become interstellar, not all of them last forever. On top of that, not every star is a choice destination, and not every planet is habitable. There’s also what Frank calls “the Aurora effect,” after Kim Stanley Robinson’s novel Aurora, in which settlers arrive at a habitable planet on which they nonetheless cannot survive.
When Carroll-Nellenback and his coauthors included these impediments to settlement in their model and ran many simulations with different star densities, seed civilizations, spacecraft velocities and other variations, they found a vast middle ground between a silent, empty galaxy and one teeming with life. It’s possible that the Milky Way is partially settled, or intermittently so; maybe explorers visited us in the past, but we don’t remember, and they died out. The solar system may well be amid other settled systems; it’s just been unvisited for millions of years.
Anders Sandberg, a futurist at the University of Oxford’s Future of Humanity Institute who has studied the Fermi paradox, said he thinks spacecraft would spread civilizations more effectively than stellar motions. “But the mixing of stars could be important,” he wrote in an email, “since it is likely to spread both life, through local panspermia” — the spread of life’s chemical precursors — “and intelligence, if it really is hard to travel long distances.”
Frank views his and his colleagues’ new paper as SETI-optimistic. He and Wright say that now we need to look harder for alien signals, which will be possible in the coming decades as more sophisticated telescopes open their eyes to the panoply of exoplanets and begin glimpsing their atmospheres.
“We are entering an era when we are going to have actual data relevant to life on other planets,” Frank said. “This couldn’t be more relevant than in the moment we live.”
Seth Shostak, an astronomer at the SETI Institute who has studied the Fermi paradox for decades, thinks it is likely to be explained by something more complex than distance and time — like perception.
Maybe we are not alone and have not been. “The click beetles in my backyard don’t notice that they’re surrounded by intelligent beings — namely my neighbors and me,” Shostak said, “but we’re here, nonetheless.”
Rebecca Boyle
Source news
Comment by Oliviero Mannucci: I want to remind all of you who read this blog a document decrypted by the FBI in which we talk about extraterrestrial life forms as multidimensional life forms. The problem is that most Earth scientists have difficulty accepting as real everything that comes from the limited perception of our limited five senses. By opening the mind, and by ceasing to divide science from spirituality, science could understand that not only do extraterrestrials exist, but that they come from innumerable dimensions of existence. But on Earth we are still in the Middle Ages unfortunately.
After all, there are still people who, despite all the evidence, continue to maintain that the Earth is flat. Scientists who reject the UFO phenomenon as a real phenomenon are exactly like these people who are not so good.
FBI Document Revealed: A Multidemsional Alien Race Visits Earth Since 1947
A few years ago an FBI document revealed the existence of extraterrestrial (multidimensional) creatures.
With this document declassified the FBI indirectly wanted to alert us to the presence of aliens who could manifest with their spaceships, opening the distance between the dimensions.
FBI Link here: vault.fbi.gov/...
1. One part of the vessel sighted contained passengers inside, while another part was under remote control (remote control).
2. The mission is peaceful, visitors are planning to stay on the planet.
3. The type of race in question, the "visitors", has enormous dimensions, but human facets.
4. They are not earthly and come from your world.
5. They come from an "Etheric World" that we do not know, so they do not come from any other known planet.
6. The bodies of visitors and their ships materialize through vibrations with the dense matter of the Earth.
7. Your ships have beams of energy that can disintegrate any aircraft and can suddenly disappear from our vision without a trace.
8. The region from which they come is the astral plane corresponding to Loka or Talas. The esoteric will understand these words. In fact, the Loka-Talas, which are not physical or metaphysical places, are different levels of consciousness. Each plane of consciousness different from ours is a parallel dimensional plane.
9. Visitors use a radar system that allows you to capture the opening location to move from one dimension to another.
Source news
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