Fortunately, in the process of searching for signs of extraterrestrial civilization in the real world, we do not have to encounter the alien fleet heading to the earth like in "Three Body". "The Three-Body Problem" is a Netflix streaming TV series adapted from the award-winning novel by Chinese science fiction writer Liu Cixin. But the trajectory of the search is almost as winding as the warp-driven journey from the fictional Trisolaris galaxy.
Take the Breakthrough Starshot Project as an example: back in 2016, the project’s billionaire founder Yuri Milner teamed up with physicist Stephen Hawking to announce a A $100 million project to use light sails to send a large number of nanoprobes into the Alpha Centauri star system. The concept, called "breakthrough starshot," is similar to the swarms of space sails envisioned by Liu Cixin in the book, but with propulsion provided by powerful lasers rather than nuclear bombs.
Today, Breakthrough Starshot is focusing on projects closer to home. In addition to spending millions of dollars to support the search for radio or optical signals from distant planetary systems, it is working with partners on a small space telescope to identify planets around Alpha Centauri, a radio station that may be built on the far side of the moon. telescope, and a low-cost mission to search for traces of life in the clouds of Venus.
However, the Breakthrough Starshot project was shelved. "It looks very doable," said Pete Worden, executive director of the Breakthrough Initiative. "However, it still seems very, very expensive and probably won't be achievable until the end of the century. So, we've been pausing for a while to try to see Are there any applications for this technology in the near future? There may be."
In the latest episode of the Fiction Science podcast, Pete Worden provides a status report on the search for extraterrestrial intelligence, teasing out science fiction Scientific facts.
The "three-body problem" takes its name from a long-standing challenge in orbital mechanics: except in some special circumstances, predicting the gravitational interactions of three massive objects in a system is extremely difficult. In the Netflix series and the original book, a Chinese radio astronomer makes contact with an alien civilization that is constantly in crisis because its home planet is in an unstable three-star system.
When aliens learned of our existence, they began a 400-year mass migration to Earth—an onslaught that brought our own planet to the brink of destruction. A key concept in the book is: the dark forest theory. This view holds that civilizations should not broadcast their presence to the rest of the galaxy for fear that other inhabitants of the "dark forest" will eventually come looking for them.
Pete Worden acknowledges the influence of the Dark Forest theory on Breakthrough Starshot's agenda.
“We originally had a project called Breakthrough Messages. … It wasn’t that we were going to send something away, but we were going to think about it,” he recalls. "We met a lot of resistance when we even considered sending the message. Interestingly, one of the key people who was skeptical about this was Professor Stephen Hawking. It was because of the Dark Forest that he believed, this was a bad idea. In contrast, Lord Martin Rees, Astronomer Royal, who chairs our advisory committee, takes the opposite view. He doesn't think it's a big problem."
Peter Worden's personal view is that we are always sending out signs of our presence - — from radio transmissions to pollutants in the atmosphere — for so long that “it may be too late to hide in the forest and quiet down.”
The Breakthrough Project hopes that civilizations in other planetary systems will respond in this way or Screaming that way. Since 2015, Breakthrough Listen has supported projects looking for radio signals, or optical flashes, that may be transmitted by aliens. One signal in particular, known as "blc1," got hearts racing in 2019, but astronomers ultimately traced its origin to radio interference from Earth, not Proxima Centauri.
Another initiative, called Breakthrough Watch, is working with Australian astronomers to use a space telescope to monitor the motion of three stars in the Alpha Centauri galaxy, looking for very small gravitational wobbles that led to the discovery The existence of Earth-like planets a little more than 4 light years away from Earth. The telescope is called "toliman," the Arabic name for Alpha Centauri and the acronym for Orbital Interferometry Monitoring Astronomical Neighbors.
Pete Worden said launch is currently planned for the first half of 2025. "We are still negotiating for a launch vehicle, but the most likely one is a launch mission, probably a SpaceX mission."
Regardless, astronomers have discovered a super-Earth orbiting Proxima Centauri - In 2021, a A team powered by Breakthrough Observations reports the discovery of the first signs of a giant planet around Alpha Centauri a.
Meanwhile, Peter Worden is working with the Australian government science agency CSRO to develop a different type of telescope.
He said: "We think we could put about $100 million of radio telescopes on the far side of the moon to look for transients over a broad spectrum, mainly at higher frequencies. It's a good place to be because Now it's undisturbed by Earth. Almost everything you see will be interesting stuff."
The Breakthrough Project team is also interested in alien life outside the solar system: a few years ago, Yuri Mir Yuri Milner studies the prospects of sending a probe to Enceladus. Enceladus, an icy moon of Saturn, may harbor oceans and possibly even marine life. Today, Worden and his colleagues are working with other interested parties—including Schmidt Scientific, researchers at MIT, and engineers at Rocket Lab—to launch a probe into the atmosphere of Venus, Look for organic matter. It will be launched as early as January next year.
Go to other planets
Even though Breakthrough Starshot is on hold, Peter Worden is still thinking about interstellar travel, and he's not the only one. Over the weekend, SpaceX founder Elon Musk mentioned the prospect of sending his company's Starship super rocket to travel beyond the moon and Mars.
Musk posted on his social media platform x/twitter: "This Starship is designed to travel across our entire solar system and beyond the cloud of objects around us. Future Starships, larger and more advanced, will go Other galaxies."
Musk may not be considering lightweight sails, but NASA is. A proposal funded in the latest round of NASA Advanced Innovation Concepts grants envisions developing a swarm of sail-equipped, laser-propelled micro-detectors that would use the same principles proposed by Breakthrough Starshot to reach the Alpha Centauri system. .
Lightweight sails may well begin to be used for travel to distant destinations in the solar system. Japan's space agency tested a solar sail in a 2010 experiment that flew the spacecraft past Venus and investigated a follow-up mission to a group of asteroids orbiting Jupiter. The idea was shelved, but Japanese scientists are considering other missions using solar sails.
Nuclear fusion could provide another route to interstellar travel. Researchers have been studying fusion propulsion technology for years—just this week, a company called Rocketstar reported that it successfully demonstrated an electric propulsion device that uses nuclear fusion to enhance pulsed plasma.
Pete Worden believes that the best long-term method for interstellar travel is a combination of light sails to get probes where they are going, plus nuclear fusion energy to slow them down once they get there. "I think ultimately, something along this line might be feasible in a century or so, maybe earlier," he said.
A century may sound like a long time, but when you're talking about reaching other stars When you launch a detector, you have to adjust your time scale. After all, even the super-advanced aliens in "The Three-Body Problem" would take 400 years to reach Earth.You can add interstellar travel to other multi-generational challenges facing humanity, such as climate change. In fact, The New Yorker's review of "Three-Body" noted that the aliens' approach is "an unexpectedly powerful metaphor for the looming dangers of climate change."
So, how long will it take for us to make contact with extraterrestrial civilizations? Such questions can cause problems for people looking for aliens. Twenty years ago, Seth Shostak of the SETI Institute speculated that we might receive signals from intelligent alien life by 2025—a possibility that now seems remote.
And Pete Worden prefers to think in terms of percentages.
"Within ten years we will almost certainly find life elsewhere," he said. "We may find a planet with life nearby. We may find life on Mars, Venus, or moons outside our solar system. But what about alien technological civilizations? I would say that in any given decade, Maybe just a few percent. But if you don't look, you won't find it."
He doesn't worry that he might not be able to answer one of life's ultimate questions. Pete Worden said: "One of the cool things about science is that the journey is the fun part, you never know what you're going to find. So, as a scientist, to me, you're pursuing something that's not quite Possible, but something crucial to our future. It's the most interesting thing I can imagine."
If aliens do come, let's hope they will discover that this human trait is the most Lovely.
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