When ET calls, can we be sure we're not being spoofed?
New SETI technique filters out Earth interference to focus on extraterrestrial signals only
Peer-Reviewed PublicationIMAGE: BREAKTHROUGH LISTEN USES RADIO TELESCOPES TO MONITOR EMISSIONS FROM HUNDREDS OF STAR SYSTEMS NEAR EARTH IN SEARCH OF NARROWBAND SIGNALS THAT COULD BE INTENTIONAL COMMUNICATIONS OR RADIO LEAKAGE FROM CIVILIZATIONS ON OTHER PLANETS. view more
CREDIT: ZAYNA SHEIKH, BREAKTHROUGH LISTEN
Scientists have devised a new technique for finding and vetting possible radio signals from other civilizations in our galaxy — a major advance in the search for extraterrestrial intelligence (SETI) that will significantly boost confidence in any future detection of alien life.
Most of today's SETI searches are conducted by Earth-based radio telescopes, which means that any ground or satellite radio interference — ranging from Starlink satellites to cellphones, microwaves and even car engines — can produce a radio blip that mimics a technosignature of a civilization outside our solar system. Such false alarms have raised and then dashed hopes since the first dedicated SETI program began in 1960.
Currently, researchers vet these signals by pointing the telescope in a different place in the sky, then return a few times to the spot where the signal was originally detected to confirm it wasn't a one-off. Even then, the signal could be something weird produced on Earth.
The new technique, developed by researchers at the Breakthrough Listen project at the University of California, Berkeley, checks for evidence that the signal has actually passed through interstellar space, eliminating the possibility that the signal is mere radio interference from Earth.
Breakthrough Listen, the most comprehensive SETI search anywhere, monitors the northern and southern skies with radio telescopes in search of technosignatures. It also targets thousands of individual stars in the plane of the Milky Way galaxy, which is the likely direction a civilization would beam a signal, with a particular focus on the center of the galaxy.
"I think it's one of the biggest advances in radio SETI in a long time," said Andrew Siemion, principal investigator for Breakthrough Listen and director of the Berkeley SETI Research Center (BSRC), which operates the world's longest running SETI program. "It's the first time where we have a technique that, if we just have one signal, potentially could allow us to intrinsically differentiate it from radio frequency interference. That's pretty amazing, because if you consider something like the Wow! signal, these are often a one-off."
Siemion was referring to a famed 72-second narrowband signal observed in 1977 by a radio telescope in Ohio. The astronomer who discovered the signal, which looked like nothing produced by normal astrophysical processes, wrote "Wow!" in red ink on the data printout. The signal has not been observed since.
"The first ET detection may very well be a one-off, where we only see one signal," Siemion said. "And if a signal doesn't repeat, there's not a lot that we can say about that. And obviously, the most likely explanation for it is radio frequency interference, as is the most likely explanation for the Wow! signal. Having this new technique and the instrumentation capable of recording data at sufficient fidelity such that you could see the effect of the interstellar medium, or ISM, is incredibly powerful."
The technique is described in a paper appearing today in The Astrophysical Journal by UC Berkeley graduate student Bryan Brzycki; Siemion; Brzycki's thesis adviser Imke de Pater, UC Berkeley professor emeritus of astronomy; and colleagues at Cornell University and the SETI Institute in Mountain View, California.
Siemion noted that, in the future, Breakthrough Listen will be employing the so-called scintillation technique, along with sky location, during its SETI observations, including with the Green Bank Telescope in West Virginia — the world’s largest steerable radio telescope — and the MeerKAT array in South Africa.
Distinguishing a signal from ET
For more than 60 years, SETI researchers have scanned the skies in search of signals that look different from the typical radio emissions of stars and cataclysmic events, such as supernovas. One key distinction is that natural cosmic sources of radio waves produce a broad range of wavelengths — that is, broadband radio waves — whereas technical civilizations, like our own, produce narrowband radio signals. Think radio static versus a tuned-in FM station.
Because of the huge background of narrowband radio bursts from human activity on Earth, finding a signal from outer space is like looking for a needle in a haystack. So far, no narrowband radio signals from outside our solar system have been confirmed, though Breakthrough Listen found one interesting candidate — dubbed BLC1 — in 2020. Later analysis determined that it was almost certainly due to radio interference, Siemion said.
Siemion and his colleagues realized, however, that real signals from extraterrestrial civilizations should exhibit features caused by passage through the ISM that could help discriminate between Earth- and space-based radio signals. Thanks to past research describing how the cold plasma in the interstellar medium, primarily free electrons, affect signals from radio sources such as pulsars, astronomers now have a good idea how the ISM affects narrowband radio signals. Such signals tend to rise and fall in amplitude over time — that is, they scintillate. This is because the signals are slightly refracted, or bent, by the intervening cold plasma, so that when the radio waves eventually reach Earth by different paths, the waves interfere, both positively and negatively.
Our atmosphere produces a similar scintillation, or twinkle, that affects the pinprick of optical light from a star. Planets, which are not point sources of light, do not twinkle.
Brzycki developed a computer algorithm, available as a Python script, that analyzes the scintillation of narrowband signals and plucks out those that dim and brighten over periods of less than a minute, indicating they've passed through the ISM.
"This implies that we could use a suitably tuned pipeline to unambiguously identify artificial emission from distant sources vis-a-vis terrestrial interference," de Pater said. "Further, even if we didn’t use this technique to find a signal, this technique could, in certain cases, confirm a signal originating from a distant source, rather than locally. This work represents the first new method of signal confirmation beyond the spatial reobservation filter in the history of radio SETI."
Brzycki is now conducting radio observations at the Green Bank Telescope in West Virginia to show that the technique can quickly weed out Earth-based radio signals and perhaps even detect scintillation in a narrowband signal — a technosignature candidate.
"Maybe we can identify this effect within individual observations and see that attenuation and brightening and actually say that the signal is undergoing that effect," he said. "It's another tool that we have available now."
The technique will be useful only for signals that originate more than about 10,000 light years from Earth, since a signal must travel through enough of the ISM to exhibit detectable scintillation. Anything originating nearby — the BLC-1 signal, for example, seemed to be coming from our nearest star, Proxima Centauri — would not exhibit this effect.
Other co-authors of the paper are James Cordes of Cornell, Brian Lacki of BSRC and Vishal Gajjar and Sofia Sheikh of both BSRC and the SETI Institute. Breakthrough Listen is managed by the Breakthrough Initiatives, a program sponsored by the Breakthrough Prize Foundation.
JOURNAL
The Astrophysical Journal
METHOD OF RESEARCH
Computational simulation/modeling
ARTICLE TITLE
On Detecting Interstellar Scintillation in Narrowband Radio SETI
ARTICLE PUBLICATION DATE
17-Jul-2023
Why people tend to believe UFOs are extraterrestrial
Most of us still call them UFOs—unidentified flying objects. NASA recently adopted the term "unidentified anomalous phenomena," or UAP. Either way, every few years popular claims resurface that these things are not of our world, or that the U.S. government has some stored away.
I'm a sociologist who focuses on the interplay between individuals and groups, especially concerning shared beliefs and misconceptions. As for why UFOs and their alleged occupants enthrall the public, I've found that normal human perceptual and social processes explain UFO buzz as much as anything up in the sky.
Historical context
Like political scandals and high-waisted jeans, UFOs trend in and out of collective awareness but never fully disappear. Thirty years of polling find that 25%-50% of surveyed Americans believe at least some UFOs are alien spacecraft. Today in the U.S., over 100 million adults think our galactic neighbors pay us visits.
It wasn't always so. Linking objects in the sky with visiting extraterrestrials has risen in popularity only in the past 75 years. Some of this is probably market-driven. Early UFO stories boosted newspaper and magazine sales, and today they are reliable clickbait online.
In 1980, a popular book called "The Roswell Incident" by Charles Berlitz and William L. Moore described an alleged flying saucer crash and government cover-up 33 years prior near Roswell, New Mexico. The only evidence ever to emerge from this story was a small string of downed weather balloons. Nevertheless, the book coincided with a resurgence of interest in UFOs. From there, a steady stream of UFO-themed TV shows, films, and pseudo-documentaries has fueled public interest. Perhaps inevitably, conspiracy theories about government cover-ups have risen in parallel.
Some UFO cases inevitably remain unresolved. But despite the growing interest, multiple investigations have found no evidence that UFOs are of extraterrestrial origin—other than the occasional meteor or misidentification of Venus.
But the U.S. Navy's 2017 Gimbal video continues to appear in the media. It shows strange objects filmed by fighter jets, often interpreted as evidence of alien spacecraft. And in June 2023, an otherwise credible Air Force veteran and former intelligence officer made the stunning claim that the U.S. government is storing numerous downed alien spacecraft and their dead occupants.
Human factors contributing to UFO beliefs
Only a small percentage of UFO believers are eyewitnesses. The rest base their opinions on eerie images and videos strewn across both social media and traditional mass media. There are astronomical and biological reasons to be skeptical of UFO claims. But less often discussed are the psychological and social factors that bring them to the popular forefront.
Many people would love to know whether or not we're alone in the universe. But so far, the evidence on UFO origins is ambiguous at best. Being averse to ambiguity, people want answers. However, being highly motivated to find those answers can bias judgments. People are more likely to accept weak evidence or fall prey to optical illusions if they support preexisting beliefs.
For example, in the 2017 Navy video, the UFO appears as a cylindrical aircraft moving rapidly over the background, rotating and darting in a manner unlike any terrestrial machine. Science writer Mick West's analysis challenged this interpretation using data displayed on the tracking screen and some basic geometry. He explained how the movements attributed to the blurry UFO are an illusion. They stem from the plane's trajectory relative to the object, the quick adjustments of the belly-mounted camera, and misperceptions based on our tendency to assume cameras and backgrounds are stationary.
West found the UFO's flight characteristics were more like a bird's or a weather balloon's than an acrobatic interstellar spacecraft. But the illusion is compelling, especially with the Navy's still deeming the object unidentified.
West also addressed the former intelligence officer's claim that the U.S. government possesses crashed UFOs and dead aliens. He emphasized caution, given the whistleblower's only evidence was that people he trusted told him they'd seen the alien artifacts. West noted we've heard this sort of thing before, along with promises that the proof will soon be revealed. But it never comes.
Anyone, including pilots and intelligence officers, can be socially influenced to see things that aren't there. Research shows that hearing from others who claim to have seen something extraordinary is enough to induce similar judgments. The effect is heightened when the influencers are numerous or higher in status. Even recognized experts aren't immune from misjudging unfamiliar images obtained under unusual conditions.
Group factors contributing to UFO beliefs
"Pics or it didn't happen" is a popular expression on social media. True to form, users are posting countless shaky images and videos of UFOs. Usually they're nondescript lights in the sky captured on cellphone cameras. But they can go viral on social media and reach millions of users. With no higher authority or organization propelling the content, social scientists call this a bottom-up social diffusion process.
In contrast, top-down diffusion occurs when information emanates from centralized agents or organizations. In the case of UFOs, sources have included social institutions like the military, individuals with large public platforms like U.S. senators, and major media outlets like CBS.
Amateur organizations also promote active personal involvement for many thousands of members, the Mutual UFO Network being among the oldest and largest. But as Sharon A. Hill points out in her book "Scientifical Americans," these groups apply questionable standards, spread misinformation and garner little respect within mainstream scientific communities.
Top-down and bottom-up diffusion processes can combine into self-reinforcing loops. Mass media spreads UFO content and piques worldwide interest in UFOs. More people aim their cameras at the skies, creating more opportunities to capture and share odd-looking content. Poorly documented UFO pics and videos spread on social media, leading media outlets to grab and republish the most intriguing. Whistleblowers emerge periodically, fanning the flames with claims of secret evidence.
Despite the hoopla, nothing ever comes of it.
For a scientist familiar with the issues, skepticism that UFOs carry alien beings is wholly separate from the prospect of intelligent life elsewhere in the universe. Scientists engaged in the search for extraterrestrial intelligence have a number of ongoing research projects designed to detect signs of extraterrestrial life. If intelligent life is out there, they'll likely be the first to know.
As astronomer Carl Sagan wrote, "The universe is a pretty big place. If it's just us, seems like an awful waste of space."
Provided by The Conversation
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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