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Research sheds new light on intelligent life existing across the Galaxy
Is there anyone out there? This is an age-old question that researchers have now shed new light on with a study that calculates there could be more than 30 intelligent civilizations throughout our Galaxy. This is an enormous advance over previous estimates which spanned from zero to billions.
One of the biggest and longest-standing questions in the history of human thought is whether there are other intelligent lifeforms within our Universe. Obtaining good estimates of the number of possible extraterrestrial civilizations has however been very challenging.
A new study led by the University of Nottingham and published today in The Astrophysical Journal [DOI: 10.3847/1538-4357/ab8225] [DX] has taken a new approach to this problem. Using the assumption that intelligent life forms on other planets in a similar way as it does on Earth, researchers have obtained an estimate for the number of intelligent communicating civilizations within our own galaxy -the Milky Way. They calculate that there could be over 30 active communicating intelligent civilizations in our home Galaxy.
The abstract:
We present a cosmic perspective on the search for life and examine the likely number of Communicating Extra-Terrestrial Intelligent (CETI) civilizations in our Galaxy by utilizing the latest astrophysical information. Our calculation involves Galactic star formation histories, metallicity distributions, and the likelihood of stars hosting Earth-like planets in their habitable zones, under specific assumptions which we describe as the Astrobiological Copernican Weak and Strong conditions. These assumptions are based on the one situation in which intelligent, communicative life is known to exist—on our own planet. This type of life has developed in a metal-rich environment and has taken roughly 5 Gyr to do so. We investigate the possible number of CETI civilizations based on different scenarios. At one extreme is the Weak Astrobiological Copernican scenario—such that a planet forms intelligent life sometime after 5 Gyr, but not earlier. The other is the Strong Astrobiological Copernican scenario in which life must form between 4.5 and 5.5 Gyr, as on Earth. In the Strong scenario (under the strictest set of assumptions), we find there should be at least 36 (+175/-32) civilizations within our Galaxy: this is a lower limit, based on the assumption that the average lifetime, L, of a communicating civilization is 100 yr (since we know that our own civilization has had radio communications for this time). If spread uniformly throughout the Galaxy this would imply that the nearest CETI is at most 17,000(+33,600/-10,000) lt-yr away and most likely hosted by a low-mass M-dwarf star, likely far surpassing our ability to detect it for the foreseeable future, and making interstellar communication impossible. Furthermore, the likelihood that the host stars for this life are solar-type stars is extremely small and most would have to be M dwarfs, which may not be stable enough to host life over long timescales. We furthermore explore other scenarios and explain the likely number of CETI there are within the Galaxy based on variations of our assumptions.
Somewhere between 4 and 211 (or 0 and 1) civilizations.
Also at The Guardian and USA Today.
(Score: 5, Informative) by takyon on Tuesday June 16 2020, @10:47AM (4 children)
Researchers can't help taking a crack at the Drake equation now that we have decent estimates for exoplanet and potentially habitable exoplanet prevalence. Things will get more interesting once we have good imaging of (considered to be) potentially potentially habitable exoplanets. If we see evidence of life/vegetation on many exoplanets, including exoplanets orbiting red dwarfs, then it could mean that life is embarrassingly common and arises quickly when conditions are favorable (or that panspermia gets things started). It already seems that life arose very early on Earth, as the date keeps getting pushed back [wikipedia.org].
The 100 year broadcasting window could be a conservative estimate and doesn't necessarily mean that a civilization will get snuffed out or go dark after that time. Even if we move away from high powered OTA broadcasts and stop doing active SETI, Earth is still EM noisy. And if we don't wipe ourselves out, our window of being findable increases.
I would like for this estimate to be correct. If our ability to detect alien civilizations simply sucks right now [cosmosmagazine.com], there are obvious improvements that can be made to increase our radio and optical telescope capabilities by orders of magnitude. Alien civilizations will probably be found within this century if they are in our galaxy.
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(Score: 2) by coolgopher on Tuesday June 16 2020, @11:16AM (1 child)
By that reasoning, isn't it more likely that we would be found by others, rather than the other way around?
(Score: 4, Interesting) by takyon on Tuesday June 16 2020, @11:32AM
Does it matter? Unless they manage to land on the White House lawn or communicate with us, being found from a distance doesn't tell us anything. I think we have a decent chance of turning on the right spec'd telescope(s) and just finding evidence of life (not necessarily intelligent/broadcasting) very quickly.
It's possible that the lush environment of Earth has been detected numerous times by alien civilizations and that it has been visited or is currently being visited. But we don't have compelling proof of that, and if faster-than-light travel is not possible, traveling to a Blue Marble hundreds or thousands of light years away isn't convenient, especially if there are many of them much closer.
That leaves questions like "why hasn't the entire galaxy been colonized by slow-moving ships?" and "are we living in a zoo?" That's not anything we can answer until we improve our own space technologies and/or make contact with alien civilizations.
For now, we need to focus on not wiping out humanity in a nuclear war, and launching better space telescopes. Then we can get more data. It seems to be going well so far.
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(Score: 1, Insightful) by Anonymous Coward on Tuesday June 16 2020, @01:37PM (1 child)
OP here...
Sure, but the point is that there are some variables in this equation that we have limited knowledge about, mostly because of lack of proof (the only proof being our own planet). From an astronomical point of view the research seems relevant (how else would this get through peer review), but as a biologist it seems to me mostly wishful thinking until we find more proof of life in other places.
(Score: 2) by takyon on Tuesday June 16 2020, @02:49PM
There is some value to this rampant speculation in the field. For example, astrobiologists are speculating about what kind of biosignatures they need to look for to attempt to find life. But a powerful tool for doing that has been delayed by years: the James Webb Space Telescope. Once that's launched, the hunt is on.
Maybe messing around with the Drake equation will help others to decide what kind of radio telescopes should be built.
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