It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Sunday, February 16, 2020
The Repeating Signals From Deep Space Are Extremely Unlikely to Be Aliens. Here's Why
The Repeating Signals From Deep Space Are Extremely Unlikely to Be Aliens. Here's Why
MICHELLE STARR
14 FEB 2020
There are many things in the Universe we are yet to understand. It's a big old machine just churning out mysteries, and we tiny specks crawling on the surface of a small blue dot are doing our darnedest to unravel them.
Recently, news emerged about one of the most tantalising mysteries. For the first time, a fast radio burst (FRB) has been detected emitting in a pattern - a 16-day cycle, with four days of intermittent bursts and 12 days of silence.
We still don't know what causes these extremely powerful, millisecond blasts of radio waves from up to billions of light-years away. Most of them haven't been detected repeating, most of them are wildly unpredictable, and only five out of over 100 have been traced to a source galaxy.
It's proven extremely tricky to find a cosmic phenomenon that fits the profile of FRBs. Violent, highly magnetised neutron stars called magnetars are pretty close, but there's some doubt as to whether they can emit the nova-scale energies detected in fast radio bursts.
But the absence of a solid explanation thus far doesn't mean we should automatically turn to aliens, as so many headlines have done. When unusual cosmic phenomena appear, rampant speculation arrives at this suggestion all too quickly.
"Invoking aliens has become too systematic, too easy, and too sensationalist a way to get the public's attention ... [It] reminds me of the way we used to invoke gods," planetary scientist and astrobiologist Charley Lineweaver of the Australian National University (ANU) told ScienceAlert.
"Instead of 'gods of the gaps' we now have 'aliens of the gaps'."
Alien communication problems
In 2017, some physicists proposed that the fast radio burst signals could be produced by radiation leaking from alien spaceship propulsion systems. Others have put forward that it could be one-way alien communication.
"My understanding is that those explanations are not excluded by the available evidence," physicist Paul Ginsparg of Cornell University, and the founder of arXiv, told ScienceAlert.
"But also that they are not required by it, in the sense that there remain equally or more plausible explanations that don't employ extraterrestrial intelligence."
One big problem for the alien idea is the variety of locations and distances involved. Of the FRBs that have been localised, some are from billions of light-years away; others are from hundreds of millions.
As astronomer Seth Shostak of the SETI Institute has noted, that alone is reason enough to discount the hypothesis that FRBs are extraterrestrial communications.
"How could aliens organise so much of the Universe to engage in broadcasting the same sort of signal?" he wrote in a blog post last year.
"There's hardly been enough time since the Big Bang to coordinate such widespread teamwork, even if you can think of a reason for it!"
For the bursts to have an artificial origin, at least 100 different alien species would have to be technologically advanced to produce such a powerful signal that it can move across space and still be detected by us.
For context, here on Earth, we only developed technology that could beam radio waves into space just around 125 years ago. That means that any radio transmission from Earth would only have travelled, at a maximum, 125 light-years. By the time the signal has propagated that far, it would have become too attenuated to be detected.
That's not to say that a more advanced civilisation couldn't produce a powerful signal... but there's another problem. All these hypothetical alien civilisations would've had to have developed their technologies at just the right time, so that all their signals are reaching Earth in the same handful of years.
Are we alone?
To date, we have had no credible evidence that there are other intelligent, advanced civilisations out there. This lack of evidence for other civilisations seems paradoxical in the context of the Drake Equation, which suggests there should be quite a few of these civilisations around.
But should there? Of all the multitudinous species on Earth, only humans have human-like intelligence. In turn, this suggests that our kind of intelligence is a very long way from inevitable.
"My reading of biological evolution on Earth is that human-like intelligence is not a convergent feature of evolution," Lineweaver told ScienceAlert.
"The bottom line to my thinking is that the best data we have (data from evolution here on Earth) strongly suggest that our closest relatives in the Universe are here on Earth."
So, there are logistical reasons to think that fast radio bursts are natural in origin. As was also eventually found with interstellar object 'Oumuamua, another target of enthusiasm for alien presence - there is actually evidence in the data that the phenomenon is a natural one.
"I think the best argument against the extraterrestrial hypothesis is that we see FRBs with all sorts of weird properties (some wide, some narrow, some polarised, others not, some have multiple pulses, some are a single pulse)," an FRB astronomer, who wished to remain anonymous for concern of being targeted by conspiracy theorists, told ScienceAlert.
"If I were designing a spacecraft propulsion system (which would be bloody good fun), I'm not sure some of those properties (e.g. changing polarisation over the pulse), would make a better spacecraft engine.
"On the other hand, we do see a similar diversity of properties in pulsars, which everyone agrees are a natural phenomenon."
This line of thinking is also supported by astronomer Andy Howell of Las Cumbres Observatory and the University of California Santa Barbara.
Why #FRBs aren't aliens, part 3. The frequency sweep predicted how far away #FRBs would be, and then they were found to be consistent with those distances. That's explained by a natural process. For communication you want something unnatural. 14/
All that isn't to say there's no value in considering the alien explanation. It's important for scientists to keep an open mind, to be receptive to possibilities, even if they are small ones.
Consider the cases - even though they only constitute a small percentage - of hypotheses initially derided by the scientific community, only later to be widely accepted. The existence of tectonic plates comes to mind.
Wild ideas can also help to engage the public with science; not just the discoveries themselves, but the work scientists do to present the hypothesis, provide evidence for it, and generate a theory.
And there are practical possibilities, too.
"These discussions give non-scientists an indication of the sorts of the amazing observations being made, the fun that scientists have thinking about them, and the possibilities that are out there," Ginsparg told ScienceAlert.
"Wild speculation can sometimes inform the next generation of instrumentation, which can then either confirm or refute the wild hypothesis, or see something else entirely and unexpected. And that too is what makes science fun."
The difficulty lies in understanding the difference between pondering wild ideas as a thought exercise, and evidence based on data and prior experience, observation and conclusions.
Or, as Ginsparg put it, "in a discussion about string theory, a senior physicist once argued to me that one can't 'prove' there's no Santa Claus, but we have alternative ways of explaining the observed phenomena with fewer unnecessary assumptions."
So, for now, we'll be holding off on the aliens until the aliens tell us otherwise.
A radio signal is coming from space every 16 days. What the hell is it?
Scientists don’t know what to make of fast radio bursts. Some think they come from aliens.
Astronomers use radio telescopes like this one, part of the Very Large Array observatory in New Mexico, to listen to the cosmos. Getty Images
Fast radio bursts are one of astronomy’s tantalizing unsolved mysteries. These sudden pulses of radio waves come from far outside our galaxy. They last about a millisecond. And sometimes, the signals repeat.
Until recently, that’s about all scientists could tell you about fast radio bursts, or FRBs. Our radio telescopes, which pick up noise rather than light, first detected them in 2007; since then, we’ve recorded a few dozen more, but not enough to be able to put together a compelling theory of what causes them.
With the origin of these signals still unknown, some scientists — notably the chair of the Harvard astronomy department, Avi Loeb — speculate aliens could be sending them.
Now, researchers based in Canada, where a radio telescopeexceptionally well equipped to detect FRBs began operating in 2018, have added a new piece to the puzzle. A few previously detected FRBs had been shown to repeat sporadically, without any regular pattern. But by observing the sky from September 2018 through October 2019, the researchers in Canada found 28 bursts — including one that repeats with a very regular pattern indeed: It appears every 16.35 days, to be exact.
This is the first time scientists have detected such a pattern in an FRB source. The peculiar signal is coming from a massive spiral galaxy 500 million light-years away. The source sends out one or two bursts of radio waves every hour, over four days. Then it goes quiet for 12 days. Then the whole process repeats.
So why is a radio signal repeating every 16 days like clockwork, and what can that teach us about its origins?
That’s the central question ofa new paper authored by the Canadian Hydrogen Intensity Mapping Experiment in collaboration with the Fast Radio Burst Project (CHIME/FRB).
There are a couple of things we know for sure. The 16-day “periodicity” cannot be occurring “by chance coincidence,” the scientists write, and it’s “an important clue to the nature of the object.” It’s clear that the FRB can’t be originating from a cataclysmic event, like a star going supernova, since that’s a one-time affair.
But beyond that, the scientists really aren’t sure. They propose a few possibilities.
One explanation is orbital motion. Celestial bodies are known to orbit on regular timescales, so a pair of objects — like a star and a black hole — could account for the 16-day pattern. “Given the source’s location in the outskirts of a massive spiral galaxy,” the paper says, “a supermassive black hole companion seems unlikely, although lower-mass black holes are viable.”
The authors say FRBs could be generated if giant radio pulses from an energetic neutron star are eclipsed by a companion object. They also note that periodicity could arise from the rotation of a star, but that’s a tricky hypothesis: Previously observed sources have had way shorter periodicities (a few hours, not a couple of weeks) and way less strength (we’re talking nine orders of magnitude less) than FRBs have.
In short, the authors don’t know what’s causing FRBs. But aliens are not on their list of possibilities. They end their paper calling for more research.
Are aliens causing fast radio bursts? Probably not.
While grounded speculation among astrophysicists suggests that FRBs are caused by neutron stars, stars merging, or black holes, it’s a different theory that has caught hold of the public imagination: Maybe they’re caused by intelligent alien life.
The hypothesis raises some obvious questions. FRBs come from all over space, not just from one particular region. Are we to assume that these aliens are sophisticated enough to have spread across many galaxies, but that there are no signs of them other than these energy bursts? Or that many civilizations independently settled on the same odd style of energy burst?
The 2017 paper argues for the latter possibility: that many civilizations have separately built such massive transmitters and are sending out FRBs. “The latest estimates suggest that there are ∼ 10^4 [10,000] FRBs per day,” the paper observes, which would suggest an implausible number of extremely busy, scattered alien civilizations. To resolve that, the paper argues that perhaps “not all FRBs have an artificial origin — only a fraction of them could correspond to alien activity.”
But once we concede that FRBs can occur naturally, and conclude that at least some of them are occurring naturally, why conclude that any of them are artificial?
And if a civilization had the astounding technical capacities to build solar-powered, planet-size transmitters, wouldn’t it be doing other things we could detect that would be less ambiguous?
“The possibility that FRBs are produced by extragalactic civilizations is more speculative than an astrophysical origin,” the paper concedes.
Indeed, that’s what the CHIME/FRB researchers behind the new paper think. “We conclude that the periodicity [of the FRB] is significant and astrophysical in origin.”
The broader debate over alien life
Scientists disagree about how to interpret phenomena like FRBs in large part because they disagree about how plausible alien life is in the first place. In statistical terms, they have different priors, meaning that the background assumptions they are using to interpret the new evidence are different.
From one perspective, the universe is astonishingly large, full of habitable planets like Earth where life could evolve as it did here. Sometimes, that life would become intelligent. We’d expect such a universe to have lots of flourishing civilizations — as well as lots of extinct ones.
This is clearly the expectation that motivates Harvard’s Loeb. “As soon as we leave the solar system, I believe we will see a great deal of traffic out there,” he said in a 2019interview with Haaretz. “Possibly we’ll get a message that says, ‘Welcome to the interstellar club.’ Or we’ll discover multiple dead civilizations — that is, we’ll find their remains.”
If you think that space is teeming with aliens, it’s not so much of a stretch to interpret astronomical phenomena as remnants of those aliens.
But if you’re looking at the same data with the expectation that we’re alone in the universe, you’re much likelier to conclude that there’s a natural explanation for FRBs.
It’s weird, given that the universe is so vast, that we seem to be alone in it. Physicist Enrico Fermi was the first to spell out this dilemma, and it’s named after him: the Fermi paradox. The paradox is that, under some reasonable assumptions about how often life originates and reaches technological sophistication, we should be able to detect signs of thousands or millions of other civilizations. And yet we haven’t. Recent investigations suggest that the paradox may have a mundane resolution — under more accurate assumptions about how life originates, we are very plausibly, alone.
The disagreement between researchers who think advanced civilizations must be extremely rare and those who think they’re common is a fairly substantive one. For one thing, if advanced civilizations are common, then why can’t we see them? We might be forced to conclude that they’re fairly short-lived. That’s Loeb’s take: “The technological window of opportunity might be very small,” he told Haaretz.
That take would have some consequences for us. If there’s some danger ahead that destroys every technological civilization that runs into it, we might expect that we’re living in a “vulnerable world” where future technological advances will destroy us, too.
In that way, disagreements over aliens have big implications. But that’s probably not the reason everyone cares about them. Offhand speculation about aliens tends to get vastly more coverage than anything else in astronomy. Whether we’re alone in the universe feels like a profoundly important question, for its implications for human civilization but also for its own sake. The lack of evidence suggesting phenomena like FRBs are alien in origin won’t be enough to stop people from wondering. Something in Deep Space Is Sending Signals to Earth in Steady 16-Day Cycles
Scientists have discovered the first fast radio burst that beats at a steady rhythm, and the mysterious repeating signal is coming from the outskirts of another galaxy.
A mysterious radio source located in a galaxy 500 million light years from Earth is pulsing on a 16-day cycle, like clockwork, according to a new study. This marks the first time that scientists have ever detected periodicity in these signals, which are known as fast radio bursts (FRBs), and is a major step toward unmasking their sources.
FRBs are one of the most tantalizing puzzles that the universe has thrown at scientists in recent years. First spotted in 2007, these powerful radio bursts are produced by energetic sources, though nobody is sure what those might be. FRBs are also mystifying because they can be either one-offs or “repeaters,” meaning some bursts appear only once in a certain part of the sky, while others emit multiple flashes to Earth.
Pulses from these repeat bursts have, so far, seemed somewhat random and discordant in their timing. But that changed last year, when the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst Project (CHIME/FRB), a group dedicated to observing and studying FRBs, discovered that a repeater called FRB 180916.J0158+65 had a regular cadence.
The CHIME/FRB team kept tabs on the repeating burst between September 2018 and October 2019 using the CHIME radio telescope in British Columbia. During that period, the bursts were clustered into a period of four days, and then seemed to switch off for the next 12 days, for a total cycle of about 16 days. Some cycles did not produce any visible bursts, but those that did were all synced up to the same 16-day intervals.
“We conclude that this is the first detected periodicity of any kind in an FRB source,” the team said in a paper published on the preprint server arXiv in late January. “The discovery of a 16.35-day periodicity in a repeating FRB source is an important clue to the nature of this object.”
Scientists recently tracked down this particular FRB to a galaxy called SDSS J015800.28+654253.0, which is a half a billion light years from Earth. That may seem like a huge distance, but FRB 180916.J0158+65 is actually the closest FRB ever detected.
But while we know where it is, we still don’t know what it is. To that point, the beat of the FRB suggests that it might be modulated by its surroundings. If the source of the FRB is orbiting a compact object, such as a black hole, then it might only flash its signals toward Earth at a certain point in its orbital period. That scenario could potentially match this recognizable 16-day cycle.
It’s also possible that we are witnessing a binary system containing a massive star and a super-dense stellar core known as a neutron star, according to a study published on arXiv on Wednesday by a separate team that looked at the same data. In that model, the neutron star would emit radio bursts, but those signals would be periodically eclipsed by opaque outflowing winds from its giant companion.
Another scenario is that the FRB rhythm isn’t tempered by another object, and is sending out the pulses directly from the source. Scientists have previously suggested that flares from highly magnetized neutron stars, called magnetars, might be the source of some FRBs. But since magnetars tend to rotate every few seconds, a 16-day cycle does not match the expected profile of a magnetar-based FRB.
Ultimately, the CHIME/FRB team hopes to find similar patterns in the handful of known repeating bursts to see if these cycles are common. The researchers also plan to keep a careful eye on FRB 180916.J0158+6 while it is active in order to spot any other details that might point to its identity.
FRBs have baffled scientists for more than a decade, but new facilities such as CHIME are revealing new details about these weird events every year. While we still don’t know what is blasting out these bizarre signals, the discovery of a clear tempo from one of these sources provides a significant lead for scientists to follow.
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