Nov 27, 2023 06:53 PM
https://www.washingtonpost.com/science/2...b80uSE5LNc
EXCERPTS: ...For SETI experts, two arguments grounded in science bolster the conjecture that aliens are surely out there somewhere: Big Numbers and the Copernican principle.
The Big Numbers argument notes that our galaxy, the Milky Way, has something like 400 billion stars, and it’s just one of untold billions of galaxies in a universe that might be infinite. Moreover, in the past 30 years, astronomers have discovered that planets of all shapes and sizes are common in the universe.
With so much turf out there, even the most frowny-faced skeptic must admit it’s hard to run the numbers in a 13.8 billion-year-old universe like ours and wind up with just one self-aware, technological, telescope-constructing species.
The Copernican principle is inspired by 16th-century astronomer Copernicus, whose revolutionary model of the solar system put the sun and not Earth at the center. The principle suggests that, in the same way that Earth is not in a privileged place in the universe, humanity should not presume itself special, or unique. The universe is not about us, and what happened on this planet over the past 4 billion years could happen elsewhere.
“Otherwise you have to believe that Earth is a miracle. I don’t,” said Seth Shostak, an astronomer at the SETI Institute in Mountain View, Calif. “It’s just never true that you only find one example of something in nature.”
Shostak is right, with an asterisk: So far, science has found only one example of a habitable planet with intelligent life. Despite decades of hunting for signs of another civilization, in scientific parlance, N=1.
[...] The discovery of exoplanets injected new optimism into the equation. There’s surely an Earth twin out there somewhere. The closest thing found so far, according to planet-hunting NASA astrophysicist Knicole Colón, is Kepler-452b, a planet 1,800 light-years away. It orbits in the “habitable zone” of a sun-like star, which means water could be liquid on its surface. It’s not our galactic doppelgänger, however: It is 50 percent larger than Earth, putting it in a class known as a “super-Earth.”
[...] “I do think it’s impossible for Earth to be the only place with life, even if it’s just bacterial or microbiological life,” Colon said, adding, “I would be shocked if we were the only intelligent civilization out there.”
[...] But the evolution of complex life is fraught with unknowns. Emily Mitchell, a paleobiologist at the University of Cambridge, points out that, while there is fossil evidence of life on Earth at least 3.5 billion years ago, no large multicellular creatures appeared until about 600 million years ago. Life on Earth took roughly 3 billion years to learn to crawl.
“I think there’s a massive, massive difference between being able to find life elsewhere, and being able to find evidence of intelligent life and being able to contact them,” Mitchell said.
At Green Bank, Jay Lockman is a sage presence, a former director of the observatory who is eager to discuss all angles of radio astronomy — including SETI. He thinks it is “silly” to say we are alone in the universe. “There’s no killer barrier in the Drake equation that we know of,” he said.
But Lockman adds a caveat: If intelligence evolves on a world covered entirely by an ocean, “you wind up with all these super-intelligent dolphins who will never build a radio transmitter.”
Which raises a philosophical question: What do we mean when we ask “Are we alone?”
The bible for alien-life pessimists is the 2000 book “Rare Earth: Why Complex Life Is Uncommon in the Universe,” by Peter D. Ward and Donald E. Brownlee. The controversial book argued that Earth is unusually blessed with conditions that make complex life possible, such as having the giant planet Jupiter in just the right spot to run interference against dangerous comets.
But the book does not argue there are no aliens out there. Here’s where the debate gets subtle. Ward told The Washington Post that he assumes aliens do exist somewhere in the vast universe, but we’ll never know because they’re just too far away to make contact. We’re not literally alone, in his scenario, but we’re functionally alone.
“The chances that there’s one close enough to ever interact with is vanishingly small,” Ward said.
Which is an unsatisfying situation. We are a social species. And finding others out there would give us hope, demonstrating that this remarkable evolutionary adaptation of intelligence is sustainable and is not ultimately self-destructive... (MORE - missing details)
EXCERPTS: ...For SETI experts, two arguments grounded in science bolster the conjecture that aliens are surely out there somewhere: Big Numbers and the Copernican principle.
The Big Numbers argument notes that our galaxy, the Milky Way, has something like 400 billion stars, and it’s just one of untold billions of galaxies in a universe that might be infinite. Moreover, in the past 30 years, astronomers have discovered that planets of all shapes and sizes are common in the universe.
With so much turf out there, even the most frowny-faced skeptic must admit it’s hard to run the numbers in a 13.8 billion-year-old universe like ours and wind up with just one self-aware, technological, telescope-constructing species.
The Copernican principle is inspired by 16th-century astronomer Copernicus, whose revolutionary model of the solar system put the sun and not Earth at the center. The principle suggests that, in the same way that Earth is not in a privileged place in the universe, humanity should not presume itself special, or unique. The universe is not about us, and what happened on this planet over the past 4 billion years could happen elsewhere.
“Otherwise you have to believe that Earth is a miracle. I don’t,” said Seth Shostak, an astronomer at the SETI Institute in Mountain View, Calif. “It’s just never true that you only find one example of something in nature.”
Shostak is right, with an asterisk: So far, science has found only one example of a habitable planet with intelligent life. Despite decades of hunting for signs of another civilization, in scientific parlance, N=1.
[...] The discovery of exoplanets injected new optimism into the equation. There’s surely an Earth twin out there somewhere. The closest thing found so far, according to planet-hunting NASA astrophysicist Knicole Colón, is Kepler-452b, a planet 1,800 light-years away. It orbits in the “habitable zone” of a sun-like star, which means water could be liquid on its surface. It’s not our galactic doppelgänger, however: It is 50 percent larger than Earth, putting it in a class known as a “super-Earth.”
[...] “I do think it’s impossible for Earth to be the only place with life, even if it’s just bacterial or microbiological life,” Colon said, adding, “I would be shocked if we were the only intelligent civilization out there.”
[...] But the evolution of complex life is fraught with unknowns. Emily Mitchell, a paleobiologist at the University of Cambridge, points out that, while there is fossil evidence of life on Earth at least 3.5 billion years ago, no large multicellular creatures appeared until about 600 million years ago. Life on Earth took roughly 3 billion years to learn to crawl.
“I think there’s a massive, massive difference between being able to find life elsewhere, and being able to find evidence of intelligent life and being able to contact them,” Mitchell said.
At Green Bank, Jay Lockman is a sage presence, a former director of the observatory who is eager to discuss all angles of radio astronomy — including SETI. He thinks it is “silly” to say we are alone in the universe. “There’s no killer barrier in the Drake equation that we know of,” he said.
But Lockman adds a caveat: If intelligence evolves on a world covered entirely by an ocean, “you wind up with all these super-intelligent dolphins who will never build a radio transmitter.”
Which raises a philosophical question: What do we mean when we ask “Are we alone?”
The bible for alien-life pessimists is the 2000 book “Rare Earth: Why Complex Life Is Uncommon in the Universe,” by Peter D. Ward and Donald E. Brownlee. The controversial book argued that Earth is unusually blessed with conditions that make complex life possible, such as having the giant planet Jupiter in just the right spot to run interference against dangerous comets.
But the book does not argue there are no aliens out there. Here’s where the debate gets subtle. Ward told The Washington Post that he assumes aliens do exist somewhere in the vast universe, but we’ll never know because they’re just too far away to make contact. We’re not literally alone, in his scenario, but we’re functionally alone.
“The chances that there’s one close enough to ever interact with is vanishingly small,” Ward said.
Which is an unsatisfying situation. We are a social species. And finding others out there would give us hope, demonstrating that this remarkable evolutionary adaptation of intelligence is sustainable and is not ultimately self-destructive... (MORE - missing details)