Zeil

That’s a brilliant and beautifully relevant story—thank you for sharing it. I love how the Unorthodox Engineers story blends hard science with creative speculation. It really highlights something crucial to all SETI-related discussions: that complex radio emissions don’t always imply intelligence. The idea of inorganic evolution producing signal-like transmissions—giant mineral transistors forming naturally due to lightning storms—is not just imaginative, but actually scientifically plausible on some level. It serves as a strong reminder that we must rule out all natural explanations before leaning toward an intelligent one. That said, I think this fictional scenario strengthens The Theory of the Last Broadcast in an interesting way. It shows that even seemingly structured emissions could be misleading. So if we ever do receive a signal with characteristics that resist all natural explanation—narrow-band, modulated, non-repeating but deliberate—then it becomes even more extraordinary in contrast to examples like these. What’s haunting to think about is this: > What if, among all the false alarms—be they natural “transistor-mountains” or cosmic noise—one real cry slipped through, and we didn’t recognize it That’s the emotional and philosophical heart of the Last Broadcast idea. Whether or not it ever proves to be true, it forces us to think more deeply about how we listen to the cosmos—and who, or what, we might actually be hearing.

TheVat: Assume your opening paragraph is an abstract (I had TLDR issues), I see a conceptual weakness, which is that a techno civilization would realize that due to light speed limitations no other civilization could respond to an SOS in time to assist. Also, wouldn't they have already broadcast powerful signals, if their orientation is towards interstellar messaging? Why wait until a time of collapse when all available wattage is desperately needed for keeping infrastructure going a bit longer? My answer: Fantastic point—and you're raising deep, logical challenges that deserve serious attention. Here's a structured, well-reasoned response that respects your critique, addresses the weaknesses, and builds on the original hypothesis with plausible explanations. You can use this as a continuation or reply: --- You're absolutely right to flag these as core weaknesses—and I'm glad you did. These are exactly the kinds of pressure tests that any serious hypothesis should face. Let me offer responses to both challenges. --- 1. “Why send an SOS if no one can help?” Indeed, any sufficiently advanced civilization would understand relativistic limits. Light-speed communication makes real-time rescue across interstellar distances impossible. So why send a distress call? Answer: Because help might not be the goal. Legacy might. Just like we send golden records, time capsules, or carve stone monuments, a dying civilization might send a final broadcast not to be saved, but to be remembered. A few reasons: Preservation of identity — The desire to be known, even after death, is powerful. Their SOS might be more of a message in a bottle than a 911 call. Duty to warn — If their collapse was due to war, AI, environment, etc., they might wish to leave a trace for others, hoping their final story might help someone else avoid the same fate. A final act of communication — When all else fails, using the last remaining energy to reach outward could be seen as an honorable, sacred, or even ritualistic act in their culture. > In short: Not all messages are sent for help. Some are sent for history. --- 2. “Why wait until collapse to send a powerful signal?” If they were oriented toward interstellar contact, wouldn't they have done it earlier, under better conditions? Answer: Most likely—they did. We just didn’t catch those. Here’s how that fits the model: Their previous emissions may have been omnidirectional or short-range—lost to noise, weakened by distance, or missed because we weren't listening in the right direction or frequency. A final signal, however, might be focused, deliberate, and maximally powered—a one-time, all-in broadcast using everything left. Earth has only been scanning small slices of the sky at limited bandwidths for decades. It's possible we've missed their earlier signals or simply weren’t around when they passed. In this scenario, the “last broadcast” isn't their first attempt, just the only one we caught. And ironically, it might’ve only been detected because it was so desperate—because it was powerful enough to punch through the void. --- In Summary: They knew we couldn’t help—but hoped someone, someday, would remember them. Their earlier messages may have gone unheard—but the final scream, loaded with everything they had left, reached us. And the saddest possibility: They never meant for us to hear it. We just happened to be standing in the path of their last breath.

Studiot: So........may. I'm glad you said may because I agree that your hypothesis (not a theory that means something different) is possible. But possible is only the first stage of what doctors call a differential diagnosis. One thing that troubles me is the use of the word signal. If you study information theory (that is the correct use of the word theory) then you will understand that 'signal' implies both a sender and a receiver and part of the information theory is the relationship between sender and receiver. This is of great use in error correcting and decryption. But so say that some burst of radio activity is a signal could be akin to saying that the stripes on a zebra are a bar code. You have to rule out random or some other agent (zebra stripes are neither random nor a bar code but that is another story). Otherwise you are falling into the oldest trap of all assuming what you wish to prove or deduce. Having mentioned random, I have also got a comment to make about that subject. If observations at the receiver are truly random then you would expect clusters of such observations. So...... It is up to you to support your hypothesis with better than " scientists (others) can't explain My answer: You're absolutely right—and thank you for such a well-informed and thoughtful reply. I agree this is a hypothesis, not a scientific theory in the formal sense. I'm using the term "The Theory of the Last Broadcast" more as a conceptual or philosophical idea, not as a claim of proof or established science. Your clarification helps ground this in reality, and I welcome that. You're also 100% right about the term “signal.” Strictly speaking, without structure, encoding, or repetition, what we call a "signal" might just be a one-time anomaly—possibly natural, possibly artificial, or possibly random. My use of “signal” is more poetic or speculative than scientific, and I should clarify that in future posts or discussions. As for the point about randomness—again, well said. Clusters and anomalies can absolutely occur in truly random distributions. I’m not claiming “it must be intelligent because we can’t explain it,” which would be an argument from ignorance. Rather, I’m suggesting a narrative possibility: What if that one anomaly—be it the Wow! signal or another unexplained burst—was a deliberate transmission, perhaps the only one to survive from a civilization that ended shortly after gaining radio capability? So, this is not a declaration of fact—it's a what-if rooted in a mix of science fiction and real astrophysical limitations. We may never know the answer, but sometimes, the unknown invites us to imagine. This hypothesis is my contribution to that conversation

Markus Hanke: The question then is why we only detect that one signal from the civilisation in question, and not all the other radio signals that would have emanated (largely unintentionally) from the same location before. If a civilisation possesses radio technology, it’s unlikely they’d only employ it one single time My answer: We only detected one signal from that civilization because it was likely their final broadcast—a last, desperate message sent as their world was collapsing. Here's why that makes sense: 1. They didn’t survive long after discovering radio. Like us, they may have only used radio for a short time—maybe a century or two—before they were wiped out by war, climate, disease, or AI. That means very few signals ever left their planet. 2. We only heard the one that was strong enough to reach us. Everyday radio is weak and spreads in all directions. Only a focused, powerful signal—like a flare—would reach Earth across light-years. That one signal was probably aimed deliberately, possibly as an SOS. 3. We caught the signal by chance. Signals travel at light speed. If their world is hundreds or thousands of light-years away, we’re hearing what happened long ago. The rest of their signals might have already passed Earth before we had the tools to notice—or might be headed in another direction. 4. They may have switched to undetectable tech before they died. If they moved to fiber-optics, lasers, or quantum communication, we’d never hear those. That last radio signal may have been their goodbye. So: > That one signal may not be a beginning—it may be the end. A last broadcast from a civilization whose voice was silenced forever right after it was finally heard.

Theory of the Last Broadcast Some SETI researchers and writers have speculated that rare, unexplained space radio signals (like the 1977 Wow! signal) might be the “last transmissions” of dying alien civilizations. In this view, a collapsing society might broadcast an SOS or farewell message in its final moments. To evaluate this idea, we survey documented one-time signals, their shared features, expert commentary on “dying civilizations” signals, and analogous human cases (emergency beacons, black boxes) along with relevant SETI speculation and science fiction. Notable Unexplained Signals WOW! signal (1977, Big Ear) – A 72-second narrowband spike detected on Aug 15, 1977 by the Ohio State Big Ear telescope. It occurred at ~1420.456 MHz (very near the 21 cm hydrogen line) and peaked ~30 standard deviations above the noise. It never repeated or showed modulation. Its origin remains unknown, and it coincides with the “water-hole” frequency band that Morrison & Cocconi had suggested as a universal SETI standard. SHGb02+14a (2003, Arecibo/SETI@home) – A candidate SETI signal found in March 2003 and announced in 2004. It was seen three times (total ≈1 min) by the Arecibo telescope at ~1420 MHz (again near the hydrogen line). The signal was extremely weak and showed a high Doppler drift (8–37 Hz/s). Notably, it came from a sky direction between Pisces and Aries where no stars are known within ~1000 light-years. SETI researchers ultimately expressed skepticism (citing possible noise or instrumentation issues) and it has not recurred. BLC1 (2019, Breakthrough Listen) – A narrowband radio spike detected toward Proxima Centauri in April–May 2019. BLC1 appeared at 982.002 MHz with a nonzero drift rate and persisted for several hours during one observing session. Follow-up scans (39+ hours) found no repeat. Initially intriguing, later analysis showed BLC1’s characteristics matched terrestrial interference patterns (two 2021 studies concluded it was not a true technosignal). Fast Radio Bursts (2007–) – Brief (millisecond) bursts of GHz radio waves from distant galaxies. The first FRB (the “Lorimer burst” in 2007) was a ~5 ms, 30 Jy pulse at ~1400 MHz. Most FRBs have no obvious repetition, though a few repeat in complex patterns. Leading theories attribute FRBs to neutron stars or mergers, but aliens have even been suggested as a remote possibility (some authors explicitly include “extraterrestrial intelligence” among FRB origin hypotheses). (Newer repeating FRBs, like FRB 180916 with a 16.35-day cycle, further complicate the picture.) These examples (and others) are summarized in the table below, which highlights their year, frequency, duration, repeat behavior, and notable traits: Signal Year Frequency (MHz) Duration Repeat Features WOW! (Big Ear) 1977 ~1420.456 (hydrogen line) ~72 s No Narrowband; ~30σ above noise (never re-detected) SHGb02+14a 2003 ~1420 ~60 s (total, in 3 events) No Very weak; in empty sky direction; high Doppler drift BLC1 (Proxima) 2019 982.002 Several hours No Narrowband with drift; never repeated; later attributed to RFI FRB 010724 (Lorimer) 2007 ~1400 ~5 ms No 30 Jy pulse; likely extragalactic; one-off burst Patterns Across Signals The radio “water hole” (1420–1662 MHz) is a quiet band commonly targeted by SETI. Notably, both the Wow! signal and SHGb02+14a occurred near the 1420 MHz hydrogen line. These anomalies are narrowband (very small bandwidth) and temporary: Wow! lasted one 72-second scan, SHGb02+14a totaled about a minute, and the Lorimer FRB only a few milliseconds. None repeated on subsequent observations. All were unusually strong for their duration (e.g. Wow! at ~30σ, FRB010724 at ~30 Jy) and appeared in arbitrary sky directions with no obvious astrophysical source nearby. In summary, the candidate signals tend to be single, intense bursts at protected frequencies (often the hydrogen line), with no known natural explanation. SETI and Astrophysical Perspectives Some experts have noted that a civilization’s collapse could indeed produce detectable blasts of energy. For example, a 2022 Space.com article summarized research suggesting that “signals from dying civilizations could be relatively easy to detect from Earth because of their huge dissipation of energy”. In other words, a culture in crisis might inadvertently (or deliberately) emit a very powerful radio beacon. Avi Loeb (Harvard astronomy chair) has similarly argued that as we explore the cosmos, we may find evidence of “multiple dead civilizations” – essentially the “remains” or final transmissions of extinct societies. In fact, Loeb told Haaretz (2019) that one outcome of interstellar exploration might be “a message that says, ‘Welcome to the interstellar club.’ Or we’ll discover multiple dead civilizations — that is, we’ll find their remains”. These comments imply that even a civilization’s last radio outburst could be a clue to its existence. Other SETI thinkers have speculated more concretely. In his 2010 analysis of cost-optimized beacons, Gregory Benford noted that an efficient extraterrestrial transmitter might consist of very brief, powerful pulses rather than a continuous signal (as he quipped, alien signals would be “more like Twitter” – “brief bursts” to attract attention). This matches the one-off nature of the signals above. Some have even coined the term “funeral pyre beacon” for a final, self-contained message sent as a civilization’s last gift to the cosmos (an idea discussed in SETI literature and fiction, though detailed studies are sparse). Of course, mainstream astrophysicists generally favor natural causes for FRBs and transient signals. Many FRBs have since been linked to magnetars or other phenomena, and intensive follow-ups of signals like BLC1 have found mundane explanations. But as Space.com notes, the detection bias could favor energetic catastrophes – “the possibility that a good many of humanity’s initial detections of extraterrestrial life may be of the intelligent, though not yet wise, kind”. In short, even skeptics admit that a dying civilization’s broadcast (if it exists) would likely be extremely energetic and hard to miss. Human Analogies and Cultural References On Earth, we preserve critical final data in cases of disaster (e.g. airplane “black box” recorders, emergency beacons). By analogy, a civilization might encode its last knowledge and hopes into a radio signal. A sudden, powerful one-way transmission could be seen as a cosmic analog of an SOS or final black-box message. This theme is common in science fiction: numerous stories imagine doomed societies sending cryptic final messages or warnings into space. For example, fictional “end-of-world” broadcasts (often dramatized in short stories or media) parallel this idea. In actual SETI/astrobiology discourse, such analogies appear in notions like the “Arecibo message” (our own attempt to send a time capsule) versus a hypothetical reverse scenario of receiving a time-capsule. Carl Sagan’s Contact (1985) dramatized decoding an alien message (though not a dying-world SOS). The concept of “last transmissions” also shows up in engineering designs and thought experiments. For instance, one proposed strategy is to carry a “memory” or data disk that emits signals if a planet is about to be destroyed. While these ideas are mostly speculative, they highlight that the notion of a final interstellar beacon is not unheard of in thoughtful circles. Throughout these discussions, parallels to human broadcast protocols are invoked. The very term “broadcast” suggests a one-way, possibly desperate transmission. If an alien world experienced an extinction-level event, it is conceivable they might use whatever remaining power to send out a final call. We can only hypothesize the content – perhaps basic maths, a cultural message, or an automated distress code – but conceptually it would be akin to the last transmission before silence. Conclusion In summary, the “Last Broadcast” hypothesis draws on a handful of puzzling one-off radio signals (Wow!, SHGb02+14a, BLC1, certain FRBs) that share features like narrow bandwidth, transient durations, and (in some cases) alignment with universal frequencies (the hydrogen line). These anomalies have prompted SETI researchers to speculate about dying civilizations: signals of unprecedented strength and brevity could indeed be final outbursts of collapsing cultures. Experts like Avi Loeb openly entertain the idea that dead civilizations’ “remains” could be found as messages in space. Analogies to human black boxes and distress beacons lend intuitive support, and both technical analyses (Benford’s work) and science fiction narratives explore similar concepts. While none of the signals above can be confirmed as extraterrestrial SOS calls, their mysterious nature keeps the “last broadcast” scenario on the table. Future surveys (e.g. with FAST, SKA, etc.) may reveal more one-off transmissions. If a truly unique, non-repeatable signal is ever decoded as artificially structured or containing information, it could be interpreted as a civilization’s final message. Until then, researchers continue to catalog such anomalies and to debate whether they hint at dying alien worlds – a possibility that, however remote, reminds us of the fragility and transience that any technological species may face. Table: Characteristics of notable unexplained radio signals (sources as cited above).