Radio signals from space – and a controversial interview by a Harvard astrophysicist – make people wonder again whether we are alone in the universe or not.
First, a new study, published in Nature examined rapid bursts of radioactivity, an astronomical riddle some of which argued could be of artificial origin. We discovered the first rapid radio impulses in 2007, but thanks to the new technology we can see many more and confirm that some are repeating. The origin of these repetitive signals is unknown, which is why some scientists speculate that aliens could send them.
Every time we discover inexplicable phenomena in space, people wonder: is that a sign of extraterrestrials? There are good reasons to conclude that these phenomena are of natural origin. However, some scientists – including the Loeb chief – insist that we reject the possibility of foreigners too quickly.
Much of the disagreement seems to be rooted in different priorities over ordinary life in the universe. Scientists who believe space should be crowded with alien life will find aliens the most likely explanation for a variety of astronomical phenomena. Scientists who think we are probably out there alone will interpret the same data differently.
But the debate is more than just pointless, fun speculation. Some conclusions that we can draw from the search for aliens have profound implications for our own world. In particular, some people are worried that civilizations like ours are inevitably wiping out – and wondering if the view of the universe can signal us what lies ahead.
When there's life out there, it's dark, distant and hard to spot. A sophisticated, technologically advanced alien civilization would probably leave more reliable traces. For example, a civilization that has enjoyed millions of years of technological innovation could build man's Dyson bullets (a massive structure that encircles a star to use it as an energy source) and much more systematic and identifiable signals and probes with energy send out produce. It is hard to guess what exactly they are doing, but it is very unlikely that their actions would shape the universe.
The traces observed so far are not nearly as good as evidence that could prove an alien civilization. This means that there may be hard-to-predict hurdles that prevent the development of advanced galactic civilizations or destroy such civilizations before they reach a size they can reach. Or it could only mean that life itself is a spectacular coincidence.
Fast radio impulses: natural events or signals from extraterrestrials?
A fast radio pulse is a sudden burst of radio waves that can be detected by our telescopes and originates from space. They are typically about a millisecond long. The first rapid radio burst was discovered in 2007. In the 12 years since then, we've picked up a few dozen more, but not enough to put together a compelling theory.
This can change quickly with a new telescope, which was just put into operation in the summer of 2018. The Canadian Hydrogen Intensity Experiment (CHIME), operated by the Dominion Radio Astrophysical Observatory of the Canadian National Research Council, in collaboration with the University of British Columbia. McGill University and the University of Toronto were developed for the exploration of the early universe (they can map the density of interstellar hydrogen) and proved to be exceptionally good at detecting FRBs.
The Nature paper written by the CHIME / FRB Collaboration reports on the first results of the FRBs observed with CHIME. The telescope is not fully operational yet, and still 13 FRBs were observed within just two months when it started operations. This is an important asset to our understanding of the phenomenon, as we have had only about 50 or 60 examples since 2007. CHIME also observed the second repetitive burst and the lowest frequency most known bursts.
We do not know much about the causes of FRBs yet. More primitive speculations among astrophysicists are that they are caused by neutron stars, fused stars or black holes. Until the first repeat signals were found, one theory was that they were caused by catastrophic events of some sort – for example, by a star-shaped supernova. But since the signals have now repeated, sometimes to repeat themselves, this can not be the case.
The theory that has taken public imagination is that they are caused by intelligent extraterrestrial life. A study by Avi Loeb and Manasvi Lingam of Harvard University, published in 2017, argued that the patterns could plausibly come from transmitters controlling interstellar light sails. The paper is theoretical; There is no evidence for the "aliens" hypothesis, but merely argues that it is compatible with previously recorded data. You conclude that physically it would be possible to build such a transmitter – at least if you had a solar-powered, water-cooled unit twice the size of Earth .
The hypothesis raises obvious questions. FRBs come from space, not just from a specific region. Should we assume that these aliens are highly developed and spread over many galaxies, that there are no signs of them apart from these outbreaks of energy? Or that many civilizations independently have committed to the strange style of the outbreak of energy?
The article argues for the latter possibility: Many civilizations have built such massive transmitters separately and are broadcasting FRBs. "The latest estimates assume that there are about 10 ^ 4 [10,000] FRBs per day," the newspaper notes, suggesting an implausible number of extremely busy scattered alien civilizations. To clarify this, the paper argues that "not all FRBs may be of artificial origin – only a fraction of that could be equivalent to foreigners' activity." But as soon as we admit that FRBs can occur naturally and come to the conclusion that at least some of them occur Why, therefore, come to the conclusion that one of them is artificial?
And if a civilization had the astonishing technical capacity to build solar-powered, planet-sized transmitters, would not they do other things we could discover and the less ambiguous?
"The possibility that FRBs are produced by extragalactic civilizations is more speculative than an astrophysical origin," the newspaper admits.
Is Oumuamua a foreign body?
In 2017, we discovered Oumuamua, an interstellar object on a tumbling trajectory that brought it into our solar system and around the sun. Oumuamua was exceptionally fast – twice as fast as the Voyager 1 probe. It hurled around the sun, slid within the reach of Earth's telescopes, and disappeared into space.
The speculation about it began earnestly when scientists noticed that it was flung faster than possible around the sun. The most likely explanation is that he lost ground like a comet as he moved around the sun and increased his speed. We were previously surprised by the motion of objects in space without aliens involved. Sometimes our calculations are just a little bit wrong.
But researchers studying Oumuamua, including Loeb, have been the subject of controversial discussions and aroused fascination for the media as they mentioned in their article that Oumuamua could instead be of artificial origin and even be an awning.
What is a sunshade? My colleague Brian Resnick discusses this in an article about Oumuamua:
You can think of a light sail as a kite, but instead of being forced into our atmosphere by air, it pushes the sun's radiation forward. People have designed these sails (in the works, there is a pretty gonzo plan called Breakthrough Starshot) to develop awnings that are powered by lasers to send tiny spacecraft to the star Alpha Centauri. As The Verge points out, Loeb is the chairman of the Advisory Board of This Project.) You may think, "Well, an advanced alien species could also make these things."
In an interview published on Monday with Haaretz, Loeb expressed his view that the "aliens" interpretation of Oumuamua is plausible. Many scientists agree with him, he argues, and they are too nervous to say, "The article I have published has been written in part based on my discussions with colleagues whom I respect scientifically. Higher-status scientists said themselves that this object was peculiar, but that they were worried about making their thoughts public. "
Of course many other scientists contradict him. "You can provide [Oumuamua’s movement] with an uncomplicated comet-like object," said Michele Bannister, an astronomer who studied Oumuamua at Queen's University Belfast, opposite the Verge when Loeb and Bialy's newspaper first came out. A Nature article last fall has made the case that Oumuamua is perfectly explainable as a comet. Comets are far more common than extraterrestrial awnings and thus the most likely explanation.
In fact, while Loeb argues that he has more allies in the private sector, most of the articles with headlines turn out against scientists who claim they could be intelligent aliens, as articles in which Loeb the scientist in question is – what the readers might leave to the reader impression that there are more scientists on the "aliens" side of the argument than there really is.
This does not mean that Loeb is not qualified or marginalized: he is a professor of astrophysics at Harvard University, founding director of the Harvard Black Hole Initiative, and director of the National Academies' Board of Physics and Astronomy. However, his attitude is hardly consensus among foreigners.
The Broader Debate on Extraterrestrial Life
As the case makes clear to Oumuamua, scientists disagree on how these phenomena are to be interpreted because they disagree on how plausible extraterrestrial life is in the first place , Statistically, they have different priorities, which means that the background assumptions they use to interpret the new evidence are different.
From one perspective, the universe is amazingly large and full of habitable planets like the earth on which life could develop so here. Sometimes this life would become intelligent. We expect that such a universe will have many flourishing civilizations – and many extinct.
This is clearly the expectation that motivates Avi Loeb. "As soon as we leave the solar system, I think there will be a lot of traffic outside," he said in an interview with Haaretz. "We may receive a message saying" Welcome to the interstellar club. "Or we may discover several dead civilizations-that is, we will find their remains."
If you believe that space is right for you, it is teeming with aliens that astronomical phenomena are less than the remains of these aliens.
However, if you look at the same data with the expectation that we are alone in the universe, you are more likely to believe that there is a natural explanation for the rapid bursts of radio and Oumuamua.
It's strange, given the fact that the universe is so big that we seem to be alone in it. The physicist Enrico Fermi was the first to express this dilemma, and it was named after him: the Fermi paradox. The paradox is that, with sound assumptions about how often life arises and technological sophistication is achieved, we should be able to see signs of thousands or millions of other civilizations. And yet we do not have it. Recent research suggests that the paradox could have an earthly resolution – with more accurate assumptions about the origin of life, we are very plausibly alone.
The disagreement between researchers who think that advanced civilizations are extremely rare, and those who think they are, is a pretty substantial one. If advanced civilizations are common then why can not we see them? We may be forced to conclude that they are quite short-lived. This is Loeb's thesis: "The technological window of opportunity may be very small," he told Haaretz. "Sails like these are started, but they have no one to send back to."
That would have some consequences for us. If there is a danger that destroys any technological civilization that plunges into it, we might expect to live in a "vulnerable world" where future technological progress will also destroy us.
In this way, disagreements over foreigners have a big impact. But that's probably not why everyone cares about her. As Resnick has noted for Vox, offensive speculations about aliens in astronomy are much more affected than anything else. Whether we are alone in the universe feels like a deeply important issue because of its impact on human civilization, but also for its own sake. The lack of evidence to suggest that these phenomena are alien is not enough to keep people from wondering.
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