I’m catching up with plenty of papers in my backlog, prompted by a rereading yesterday of David Kipping’s 2022 paper on the Wow! Sign, the intriguing, one-off reception on the Large Ear radio telescope in Ohio again in 1977 (Kipping quotation under). I had simply completed checking Abel Mendez’ work at Arecibo, the place the Arecibo Wow! mission has introduced a brand new evaluation primarily based on examine of beforehand unpublished observations utilizing up to date sign evaluation strategies. No enormous surprises right here, however each Kipping’s work and Arecibo Wow! are proof of our persevering with fascination with what Kipping calls “essentially the most compelling candidate for an alien radio transmission we have now ever obtained.”
Additionally they remind us that regardless of what number of instances this intriguing occasion has been checked out, there are nonetheless new methods to strategy it. I give the quotation for the Mendez paper, written with a staff of collaborators (one among whom is Kipping) under. Let me simply pull this from Mendez’ assertion on the Arecibo Wow! website, displaying how the brand new work has refined the unique Wow! Sign’s properties:
Location: Two adjoining sky fields, centered at proper ascensions 19h 25m 02s ± 3s or 19h 27m 55s ± 3s, and declination –26° 57′ ± 20′ (J2000). That is each extra exact and barely shifted from earlier estimates.
Depth: A peak flux density exceeding 250 Janskys, greater than 4 instances increased than the generally cited worth.
Frequency: 1420.726 MHz, inserting it firmly within the hydrogen line however with a larger radial velocity than beforehand assumed.
Main Mendez (College of Puerto Rico at Arecibo) to remark:
“Our outcomes don’t clear up the thriller of the Wow! Sign. “However they provide us the clearest image but of what it was and the place it got here from. This new precision permits us to focus on future observations extra successfully than ever earlier than…. This examine doesn’t shut the case,” Méndez mentioned. “It reopens it, however now with a a lot sharper map in hand.”
Picture: Comparability of the beforehand estimated areas of the Wow! Sign (grey bins) with the refined positions from the Arecibo Wow! Challenge (yellow bins). The sign’s supply is presumed to lie inside one among these bins and past the foreground Galactic hydrogen clouds proven in brilliant crimson. Credit score: PHL @ UPR Arecibo.
Homing in on fascinating anomalies is after all a method for SETI to proceed, though the host of later one-off detections from different areas (none evidently as highly effective a sign as Wow!) doesn’t yield optimism that one among these will ultimately repeat. A sweeping beam that by sheer probability swept throughout Earth from some type of ETI set up? Works for me, if solely we had repeating proof. Within the absence of it, we proceed to dig into current information utilizing new strategies.
We are able to additionally proceed with focused searches of close by stars of curiosity each due to their proximity in addition to the presence of surprising planetary configurations. The TRAPPIST-1 system isn’t remotely like ours, with its seven Earth-sized planets crammed into tight orbit round an M8V crimson dwarf star, however the truth that every of those transits makes the system of big worth. Now a staff led by Guang-Yuan Tune (Dezhou College, China) has used the FAST instrument (5 hundred meter Aperture Spherical Telescope) to seek for SETI alerts, delving into the frequency vary 1.05–1.45GHz with a spectral decision of ~7.5Hz. No alerts detected, however the scientists plan to proceed to go looking different close by programs and don’t rule out a return to this one. Quotation under.
The Elements Resulting in Expertise
The frustration over lack of success at discovering an extraterrestrial civilization is comprehensible, so it’s no shock that theoretical work explaining it from a wholly wrong way continues to seem. As witness a brand new examine simply introduced on the EPSC-DPS Joint Assembly 2025 in Helsinki. Right here we’re asking what elements go into making a technological society doable, assuming an evolutionary historical past one thing like our personal, and probing whether or not modifications to any of the parameters that helped us emerge would have made us unimaginable.
All this goes again to the Nineteen Sixties and the unique Drake Equation, which makes a unfastened try at sizing up the chances. Manuel Scherf and Helmut Lammer of the Area Analysis Institute on the Austrian Academy of Sciences in Graz paint a distressing image for these intent on plucking a sign from ETI out of the ether. Their work has centered on plate tectonics and its relationship with the essential gasoline carbon dioxide, which governs the carbon-silicate cycle.
CO2 is a large think about sustaining photosynthesis, however an excessive amount of of it creates greenhouse results that may likewise spell the tip of life on a planet like ours. The fine-tuning that goes on via the carbon-silicate cycle ensures that CO2 will get launched again into the environment via plate tectonics and volcanic emissions, recycling it again out of the rock by which it had been beforehand locked. Scherf identified to the EPSC-DPS gathering that if we wait someplace between 200 million and one billion years, lack of atmospheric CO2 will carry an finish to photosynthesis. The Solar might have one other 5 billion years of life forward, however the surroundings that sustains us received’t final almost as lengthy.
Certainly, the researchers argue, floor partial pressures and mixing ratios of CO2, O2, and N2 likewise have an effect on things like combustion, wanted for the smelting of metals that underpins the expansion of a technological civilization. Think about a planet with 10 p.c of its environment taken up by CO2 (versus the 0.042 p.c now discovered on Earth). This world produces a biosphere that may maintain itself towards a runaway greenhouse if additional away from its star than we’re from the Solar, however it might additionally require at least 18 p.c oxygen (Earth now has 21 p.c) to make sure that combustion can happen.
If we get rid of plate tectonics, so essential to the carbon-silicate cycle, we likewise restrict liveable situations on the floor. So we want this in addition to sufficient oxygen to offer combustion to make know-how doable. In different phrases, we have now astrophysical, geophysical, and biochemical standards that should be met even when a planet is within the liveable zone if we hope to search out lifeforms which have survived lengthy sufficient to create know-how. Uncommon Earth?
Scherf and Lammer weigh these elements towards the period of time it takes know-how to emerge, assuming that the longer an ETI civilization exists, the extra seemingly we’re to watch it. Right here I don’t have a paper to work with, so I can solely report the conclusions introduced on the EPSC-DPS convention, that are acknowledged bluntly by Scherf:
“For 10 civilizations to exist similtaneously ours, the typical lifetime should be above 10 million years. The numbers of ETIs are fairly low and rely strongly upon the lifetime of a civilization.”
I may fall again on a 2024 paper from the identical staff discussing these issues, which delves not solely into the query of the maybe uncommon mixture of circumstances which permits for technological civilizations to emerge but additionally our use of the Copernican Precept in framing the problems:
…our examine is agnostic about life originating on hypothetical habitats apart from EHs. Any extra unique habitats (e.g., subsurface ocean worlds) might considerably outnumber planets with Earthlike atmospheres, no less than in precept. Lastly, we argue that the Copernican Precept of Mediocrity can’t be legitimate within the sense of the Earth and consequently advanced life being frequent within the Galaxy. Sure necessities should be met to permit for the existence of EHs and solely a small fraction of planets certainly meet such standards. It’s subsequently unscientific to infer advanced cardio life to be frequent within the Universe, no less than primarily based on the Copernican Precept. As an alternative, we argue, at most, for a mixed Anthropic-Copernican Precept stating that life as we all know it could be frequent, so long as sure standards are met to permit for its existence. Extremophiles, anaerobic and easy cardio lifeforms, nevertheless, could possibly be extra frequent.
Picture: An artist’s impression of our Milky Method Galaxy, displaying the placement of the Solar. Our Photo voltaic System is about 27,000 mild years from the centre of the galaxy. The closest technological species could possibly be 33,000 mild years away. Credit score: NASA/JPL–Caltech/R. Damage (SSC–Caltech).
All of which illuminates the paucity of knowledge. Lets say that it took 4 and a half billion years for know-how to emerge on Earth, however that’s our solely reference level. We additionally haven’t any information on how lengthy technological societies exist. It’s clear, although, that the longer the survival interval, the extra seemingly we’re to be current within the cosmos on the similar time they’re. For there to be even one technological civilization within the galaxy coinciding with our existence, ETI must have survived in a technological section for no less than 280,000 years. I believe that matches up with the case Brian Lacki has been making for a while now, which emphasizes the ‘home windows’ of time inside which we view the cosmos.
However Scherf provides this:
“Though ETIs is perhaps uncommon there is just one approach to actually discover out and that’s by looking for it. If these searches discover nothing, it makes our idea extra seemingly, and if SETI does discover one thing, then will probably be one of many largest scientific breakthroughs ever achieved as we’d know that we’re not alone within the Universe.”
Picture: This graph exhibits the utmost variety of ETIs presently current within the Milky Method. The stable orange line describes the situation of planets with nitrogen–oxygen atmospheres with 10 per cent carbon dioxide. On this case the typical lifetime of a civilization should be no less than 280,000 years for a second civilization to exist within the Milky Method. Altering the quantity of atmospheric carbon dioxide produces totally different outcomes. Credit score: Manuel Scherf and Helmut Lammer.
I’ll word in passing that Adam Frank (Rochester Institute of Expertise) and Amedeo Balbi (College of Rome Tor Vergata) have analyzed the query of an ‘oxygen bottleneck’ for the emergence of know-how in a current paper in Nature Astronomy. The memorable thought that if there are not any different civilizations within the galaxy, it’s an amazing waste of house sounds affordable provided that we have now absolutely labored out how seemingly any planet is to be liveable. This new course of astrobiological analysis tells me we have now an extended approach to go.
The Mendez paper is Mendez et al., “Arecibo Wow! II: Revised Properties of the Wow! Sign from Archival Ohio SETI Knowledge,” presently out there as a preprint however submitted to The Astrophysical Journal. The Kipping paper from 2022 is Kipping & Grey, “Might the ‘Wow’ sign have originated from a stochastic repeating beacon?” Month-to-month Notices of the Royal Astronomical Society, Quantity 515, Situation 1 (September 2022), pp.1122-1129 (full textual content). Due to my buddy Antonio Tavani for the heads-up on the Mendez paper. The paper on the FAST search of TRAPPIST-1 is Guang-Yuan Tune et al., “A Deep SETI Seek for Technosignatures within the TRAPPIST-1 System with FAST,” submitted to The Astrophysical Journal and out there as a preprint.
The Scherf and Lammer presentation is titled “How frequent are organic ETIs within the Galaxy?” EPSC-DPS Joint Assembly 2025, Helsinki, Finland, 7–12 Sep 2025, EPSC-DPS2025-1512. The summary is out there right here. The identical staff’s 2024 paper on these issues is “Scherf et al. “Eta-Earth Revisited II: Deriving a Most Variety of Earth-Like Habitats within the Galactic Disk,” Astrobiology 24 (2023), e916 (full textual content). The paper from Adam Frank is Frank & Balbi, “The oxygen bottleneck for technospheres,” Nature Astronomy 8 (2024), pp. 39–43 (summary / preprint).
And I need to you should definitely point out Robert Grey, Kipping’s co-author on his 2022 paper, who devoted years to the examine of the Wow! Sign and was variety sufficient to write down about his quest in these pages. When you’re not acquainted with Grey’s work, I hope you’ll learn my An Appreciation of SETI’s Robert Grey (1948-2021). I solely want I had gotten to know him higher. His loss of life was a loss to all the group. David Kipping’s fantastic video masking his work with Grey is out there at Cool Worlds. Keith Cooper additionally explicates this paper in One Man’s Quest to Examine the Mysterious “Wow!” Sign.
