The science fiction convention for first contact between humans and aliens is a face-to-face meeting in meatspace. This has the advantage of immediacy: No speed-of-light time lags to contend with! In-person meetings do have the disadvantage of proximity, should it turn out that humans and aliens cannot (or choose not to) peacefully co-exist. Therefore, while distant detection does not offer immediate gratification, it is not nearly as dangerous as in-person first contact. Or at least, so it would appear…
What brought this to mind was an arXiv paper with the catchy title “What no one has seen before: gravitational waveforms from warp drive collapse.” The question raised was straightforward: Assuming for the sake of argument that warp drives were possible1, just how far away would they be detectable by our civilization? The authors consider the extreme (and from the warp drive user’s perspective, undesirable) case of a warp bubble collapse. Their conclusion? With the right equipment, a warp bubble collapse could be spotted as far away as a megaparsec (somewhat farther than the Andromeda Galaxy).
While overhearing the gravitational scream of a dying starship is not as information-rich as a conversation, detecting a warp bubble collapse would still provide valuable information. We’d know that warp drives were possible and that at least one other technologically sophisticated species existed2, at least at the time of the mishap3.
There are other signals that might hint at the presence of other intelligent beings in this universe. Let me count the ways.
The presence of certain atmospheric pollutants could reveal (or at least hint at) the presence of intelligent-tool-users. Take lead, for example. Roman silver smelting produced lead vapor as an unintended by-product. The Romans put enough lead into the atmosphere that the evidence was preserved in Greenland ice, over four thousand kilometers away. Extraterrestrials noting the rise and fall of lead in the Earth’s atmosphere might deduce what they were seeing was the product of intelligent activity (though so incidentally unintelligent as to dump massive amounts of lead into the atmosphere).
The catch would be determining if the unusual pollutants were being produced by industrial activity by intelligent beings, or if some unfamiliar but purely natural phenomena were at work. Aliens intermittently monitoring Earth 66 million years ago might note a sudden spike in various pollutants (including iridium) combined with a dramatic drop in species diversity… all of which were purely natural in origin.
Less challenging and certainly longer range would be inadvertent electromagnetic signals. While the radio and television noise humans generate drops below detectability at inconveniently short distances, which would presumably be as true for aliens as it is for us, certain activities might be detectable across many light-years. For example, military radar could be detectable beyond 10,000 light-years, while Thomas Womack once calculated4 that exo-atmospheric nuclear explosions were in theory detectable by 10-metre telescopes anywhere in the Milky Way.
Yeah, deducing that there used to be an alien civilization a few thousand light-years away because we picked up decades of military radar emissions followed by several thousand x-ray flashes over a few hours, then silence, would be a bit depressing. But at least we would surely learn an important lesson!5 And if signals began again after a few years, that too would be a valuable lesson.
Artifacts provide a special case of durable, potentially long-range signal. Aliens in the vicinity of Ross 248 might deduce from the passing Voyager probes that humans existed or at least existed thousands of years earlier, when the Voyagers were first launched. Scientist Nick Oberg concluded that the Golden Records on the Voyagers could remain at least partly legible for as long as five billion years.
The obvious implication of all of the above is that if unintentional signals can betray our existence or that of our alien counterparts to observers thousands of light-years away, then deliberate signals should be detectable at comparable distances. In fact, since the signals could be optimized for detectability, greater distances should be attainable6. There does not seem to be any inherent reason a civilization could not announce itself to the whole galaxy.
The fact that we see no evidence that anyone is trying to alert the galaxy to their existence is a bit concerning. There are many explanations as to why this is so, only some of which should keep you awake at night, wide-eyed with terror. The least alarming might be that we are alone (although then one has to wonder why), followed closely by the possibility that there is a superior means of communication we primitive humans have yet to discover.
Have I overlooked something obvious? Feel free to enlighten me in the comments below.
- At the risk of being a complete buzzkill, I must add that warp drives are probably not possible. ↩︎
- Evidence of a civilization in command of energies far beyond ours. To quote “for a 1 km sized warp bubble traveling at v=0.1, the magnitude of the energy carried by the matter waves, of order 10−2 [R], would be around 1/100 times the mass-energy of the sun.” ↩︎
- Obviously, we’re more likely to spot evidence of aliens if they didn’t have an effective analog of the Transportation Safety Board of Canada, because TSBC-analogs would do their best to reduce or eliminate warp bubble mishaps. Might be best not to base our warp bubble designs on data gathered from Andromedan starship calamities, as by definition those are the designs that fail. ↩︎
- Thomas Womack said this on Usenet, which means that the original comment is forever lost to time. Well, practically. ↩︎
- That lesson being that humans do not learn important lessons. ↩︎
- For example, a Nicoll-Dyson laser can communicate one civilization’s desire for another civilization to get off the first civilization’s lawn at a distance of a million light-years, with the message arriving in the form of enough energy to evaporate the second civilization’s planet. ↩︎
It would be best to keep in mind that the Earth’s astronomical community cannot observe the sky 360 degrees in every direction, at every frequency of the the electromagnetic spectrum, 24/7.
1.) There are simply not enough assets (expensive, limited optimal locations for observatories, etc.).
2.) Physics dictates that telescopes and detectors for different parts of the electromagnetic spectrum have to be built differently, so you need different telescopes and/or detectors and/or receivers for different parts of the spectrum.
3.) The signal may not be a continuous one.
For Earth to detect an intelligent extraterrestrial signal, we would have to happen to be looking in exactly the right direction, at exactly the right frequency, at exactly the right time.
For now, we will have to rely on luck to detect an extraterrestrial signal (if it is out there).
Which of course raises the issue exemplified by the WOW! signal: if we only see something that might be a signal once, how can we be sure it was a signal?
I hear a lot about a mission to the solar Foci.
Fly to the far side of the Sun 500 AU—on the side of the Sun opposite our galactic core—you can get a good view of a black hole.
Part of me wonders if Earth flew through a focal line…get back to that rough location…maybe we can hear something.
The Great Daylight Fireball of 1972 spooked me a bit.
I remember Peekskill, Chelyabinsk, etc.
But the Teton event reminded me most of the Stardust backshells in how smooth and laminar the trail was behind it.
Teton stayed in atmosphere for 1,500 km and was expected to make a resonant return.
It had made a de facto aerobrake maneuver.
That—and how Miranda looks strip-mined—still had me scratching my head.
If any good comes out of the Musk presidency—I hope at least one SLS core gets outfitted for an interstellar probe/Project Lyra deal.
SLS might be 4 billion a pop—but we know Oumuamua is an extrasolar object.
Probably not a probe itself—but it is a body from a different Star system—thus SLS can give us an interstellar mission without having to fly an interstellar distance.
Such a probe would be worth killing Artemis for.
Elon and other can rag on my guys at Marshall, but we at least build HLLVs that don’t tumble.
“We focus our attention on you, may this gift of light find you well.”
with the message arriving in the form of enough energy to evaporate the second civilization’s planet.
Which would certainly get them off the lawn!
And would get the lawn off them.
In James White’s “Sector General” galactic hospital sci-fi novels, some technology is stuck somewhere around the time the series started – Wikipedia says 1957 – although they have real-time computer speech translation. The computer is really big, though. Anyway… When a spaceship wrecks, a hyperspace beacon is released to call help. It’s just a loud signal, no message. You can identify a ship if you know that it was where the beacon is. But not all of the beacons are known to the Federation… and while there’s active exploration to contact new alien civilisations, rescuing and treating unknown space accident victims is… cheaper. As long as you put the pieces back together right, of course. “Sector General” doctors usually do.
1). This is obviously an example of Canadian optimism, because is for further and say FTL travel is pure fantasy, albiet a fantasy writers are truly reluctant to discard.
It’s not as though science fiction can’t be written without FTL, but still, FTL is considered a mainstay, while more reasonable concepts like ESP are not.
Warp drive is not “pure fantasy,” it’s a rigorously derived solution to the equations of General Relativity, although one that poses potentially insurmountable practical difficulties due to the extreme energies and conditions it would require. In recent years, theorists have managed to find ways around some of the seemingly insurmountable obstacles (such as the need for negative energy), so we can’t rule out that some far more advanced civilization might surmount the others.
Here’s an article that goes into a bit more detail: https://www.centauri-dreams.org/2024/06/18/the-physics-of-starship-catastrophe/
This again. Look, just because you can derive a solution to a given equation is no indication that it has any applicability to the real world. Any high school student knows that the Quadratic Equation can give solutions to equations that are positive and negative-and in many real world applications, the negative values while correct, don’t apply.
Look, I’ll make it even simpler for you. V=h×π×r². If I’m calculating the dimensions of a cylinder from volume, I can get negative results for the radius that are equally “valid” as he positive ones. But if I’m working with an actual cylinder, the negative values don’t apply.
The sane applies to relativity. Just because you can fiddle the equations to come up with a nonsensical solution doesn’t mean it actually has a real-world result. Saying its a solution to the equations means nothing.
The bottom line is that relativity is extremely well tested. Causality is extremely well tested. There is no requirement for relativity that requires FTL travel, and there is no real world evidence for anything that requires FTL as an explanation. The only thing FTL has going for it is the continued magical thinking of various people who desperately want their galactic empires and libertarian interstellar trading conglomerates.
I didn’t say it had applicability to the real world. I said it’s not “pure fantasy.” Words have meanings. Pure fantasy would be something with zero basis in real science. Everything about the idea of warp drive comes from General Relativity. The very idea of spacetime as something that can be warped comes straight from Einstein. The only part of the theory that the fiction leaves out is the part saying that it would be prohibitively impractical to achieve in real life instead of on paper. That makes it science fiction — something that’s rooted in known theory and fact, with only as much poetic license as necessary to allow the story to happen.
Where you’re off-base is assuming that science fiction needs to have real-world results. That’s why it’s fiction. It doesn’t have to be real; it just has to draw on reality as a starting point, enough to create a credible illusion. The goal is to have enough realistic elements to earn the audience’s goodwill and their willingness to suspend disbelief about the unreal parts.
“The bottom line is that relativity is extremely well tested.”
Yes, and the idea that spacetime can be distorted to allow effectively superluminal displacement comes from relativity, specifically General Relativity. Laypeople make the mistake of assuming that Special Relativity’s absolute speed limit is the entire story, rather than just a specialized case of unaccelerated motion. General Relativity shows that speed limit to be local, because spacetime itself can expand at any speed, as it must have done in the inflationary era just after the Big Bang.
Is warp drive practically achievable? No, of course not. I’m sure you don’t need to explain that to anyone here. But we’re not talking about reality, we’re talking about storytelling. The difference between fantasy and science fiction is not whether it can really happen, but where the ideas come from. Fantasy gets its ideas from mythology, superstition, lore, wishful thinking, etc. Science fiction gets its ideas from science, even if it applies them in loose or fanciful ways. And the idea underlying warp drive, the idea that spacetime topology is alterable, comes from General Relativity. The principle is real even if the application is not.
I just read an sf novel in which the average speed at which humans are spreading is about 1 ly per millennium…
That’s very similar to the percolation theory, which has humans spreading via going from one iceball to the other in the Oort Cloud. Eventually they reach the next star over.
Of course one consequence is that humans spread across the galaxy in a “mere” 100 million years. Or only 25 times as long as hominids have existed…
The argument that aliens must not exist because they would have colonized the whole galaxy by now is based on an oversimplification. There’s no reason to assume that an expanding civilization would expand without limit. There could be social or economic factors that would make it preferable to stay within a certain range of other colonies and the homeworld. And since every society goes through changes over time, the factors that created the impetus for expansion in the first place might fade in favor of stability or retreat. Some colonies might thrive to the point of becoming new centers of expansion, while others might have social or economic conditions that make further expansion unnecessary or undesirable. Some colonies might fail before they can become new centers of expansion. So over time and distance, the number of new centers of expansion would diminish, so the wave of a single species’s expansion might die out before it spreads galaxywide, the same way a ripple in the ocean is damped out well before it reaches the shore.
Poul Anderson’s Starfarers deals with this in some depth.
“I must add that warp drives are probably not possible”.
So you’re saying there’s a chance!
I’m reminded of an article I wrote for Plokta a quarter century ago which pointed out the fundamental problem with SETI and other real-world attempts to find and communicate with aliens:
1 – a distinct lack of Jacobs Ladder devices, bubbling retorts, and other fundamental equipment
2 – nobody wore lab coats and safety glasses while their equipment was crunching it’s 5000th data packet
3 – no spinning reels and punched tape on the computers
4 – Not enough scientists with nubile daughters as their assistants
In short, we are not conforming to the wisdom and aesthetics we have sent out to the universe in old movies etc., and the aliens rightly consider us hypocrites and want nothing to do with us!
The article is here, if anyone wants to read it.
Calling Occupants of Interplanetary Craft
https://www.plokta.com/plokta/issue20/calling.htm
Elsewhere here, I suggested that 1972’s Teton fireball might have been a Bracewell probe…in that it stayed in atmosphere 1,500km.
A good story would have a supposed MOL Titan III actually be something of a tug.
In this timeline, the size and shape of Columbia shuttle orbiters had nothing to do with HEXAGON and KH-11/13s.
Instead, the payload bay was to match the probe-an ancient wreck.
Sometimes a lack of evidence is compelling evidence in its own right. It seems pretty obvious to me that extraterrestrial life throughout the galaxy has realized we’re on the cusp of inventing an FTL drive and all hunkered down out of sight – ie, that they spotted us first – and who could blame them?
On the plus side we now know – (1) that it is possible to detect extraterrestrial life over great distances (2) that extraterrestrial life exists & (3) that we’re going to invent an a FTL drive in the (relatively) near future!
“Sometimes a lack of evidence is compelling evidence in its own right.”
Sometimes, perhaps, but not in this case. We’ve only been looking for a paltry few decades and we don’t even know precisely how to look for it. Our primary methods of searching have been chosen, not because they’re the most likely ways for aliens to communicate, but simply because they’re the easiest ways for our limited methods to detect. It’s way, way too early to assume our search has been remotely exhaustive.
Also, we’re nowhere remotely near the cusp of inventing FTL drive. Even if the theorists cracked the problem in our lifetimes, achieving the actual technology would probably require millennia of further advancement, due to the vast energies and exotic materials that would probably be required. Although it’s vastly more likely that FTL is impossible and any interstellar travel would be sublight.
Besides, why would they be bothered if we were about to invent FTL? If it’s possible at all, then presumably they would’ve had it far longer and wouldn’t have reason to see us primitive upstarts as a threat.
Space is big. Really big. You might think it’s a long way down the road to the chemist’s, but that’s peanuts compared to space.
Radar beams might be detectable at considerable distance if they happen to intersect a place containing an active radio receiver. Nuclear detonations might be visible if a telescope happens to be pointed at the right area of sky during the right 10-second period. The vast majority of space contains no radio receivers or telescopes, a fact that would remain true even if 99% of solar systems contained planets inhabited by tool users with a tech base at least as good as ours.
We really need to hope for an alien Elon Musk whose warp-capable spacecraft undergo rapid unscheduled disassembly frequently enough that we have a good chance of spotting their collapsing warp bubbles.
Unfortunately, it’s possible that billionaires are actually the Great Filter, and that any civilization that develops them will quickly succumb to societal and climatic collapse. A species that is able to evolve an Elon Musk may not live to leave its mark on the galaxy. It could be that the only truly long-lived species are those that are able to invent guillotines and apply them judiciously. In my TED talk I will …
I think the people making jokes about Musk’s rockets exploding are forgetting how many hundreds of NASA rockets exploded before they figured out how to make them not explode. That’s just a natural part of the development process, providing valuable data about what not to do next time. Certainly there’s plenty of evidence of Musk’s incompetence elsewhere, but I think it’s premature to call this an example, because test rockets blowing up is normal enough.
I’m no fan of billionaires, but one thing I learned in my Frontiers in World History course in college is that the development of new frontiers never really takes off in earnest until governments partner with private enterprise that takes on the expense and risk so that the governments don’t have to — the fur traders in North America, the Cossacks in Siberia, the East India Companies, etc. Frontiers only take off once they start earning a profit, so like it or not, we probably need private industry to take the lead in settling space. (Though not Musk, who’s an incompetent charlatan who got rich by stealing credit for the innovations of the companies he bought.) Although it requires a partnership, industry working on the government’s behalf and under its authority in service to the overall interests of the nation, rather than billionaires running around unfettered and serving only their own bottom line. As with most things in life, the key is a healthy balance.
Here’s a BBC article on the success rate of rocket launches.
https://www.bbc.com/future/article/20230518-what-are-the-odds-of-a-successful-space-launch
Almost 70% of early attempts at spaceflight were failures. The current success rate is around 93%, with programs in their early stages experiencing the most spectacular failures.
Wikipedia cites a human space flight survival rate in space of around 97%.
With space barons funding rockets not because they are easy, but because they are profitable, we can only expect more things to move fast and break.
The human survival rate is beside the point, because what’s in question here is not the operation of crewed spacecraft, but the testing of prototypes before they’re cleared for human use. One expects frequent failures in the early testing stage, and indeed they’re desirable, because you need to find out all the ways a design can fail so that you can develop ways to prevent them. (I think I saw a comment the other day that a 50% failure rate is optimal for rocket prototypes.) Explosions of crewed spacecraft are tragedies; explosions of uncrewed prototypes are learning opportunities.
Now, if the billionaires get to the point of operating crewed spacecraft, they may well cut corners to the degree that lives are endangered. I’m not denying that. I’m just saying we’re not there yet. People are assuming these rocket explosions are analogous to the high failure rate of Tesla Cybertrucks, that both are the result of the same incompetence; but in this particular case, it’s jumping the gun to assume that, because prototype rockets exploding is a pretty normal part of the process.
Gregory Bedford, has a short story, Bow Shock, in which radio astronomers detect the distant disaster of a Bussard ramjet failure.
“It’s a . . . starship?”
“Was. It got into trouble of some kind these last few days. That’s why the wake behind it … got longer. Then, hours later, it got turbulent, and—it exploded.”
In the universe of Dave Duncan’s Hero! it is found that some quasars appear to move across the sky and therefore are not actually quasars but alien STL starships. Humans learn how to build similar ships but never do manage to contact the aliens – at least as far as the characters in the book know, as with STL travel and lightspeed communication no one on a given world really knows what’s going on anywhere else.
I used to be in the planetary science field and a friend of mine there once noted that Mars has proven remarkably successful at taking chemical signals that we come up with as potential evidence for life and forcing us to look harder until we figure out an abiogenic process that could cause that signal.
Many, if not most of the detection methods considered today rely on waste – radio signals going to space from communications, heat from computations, etc. and the more advanced civilizations, the lest waste they are likely to generate. I think our best chance is either to find a civilization like ours, that has not yet learned to be terribly efficient, or a communication from more advanced civilization that is specifically targeted at “retards” like us, fine-tuned to be discoverable by regular astronomical observations (as suggested by Jiil Tarter once, on the idea that a civilization spends more time on astronomy than on SETI). This argument of increased efficiency also questions the widely accepted opinion that there is no Kardashev Type 3 civilization in the Milky Way – there could be one or even more, if they are too efficient for us to detect. We wrote an article about this – search for: A qualitative classification of extraterrestrial civilizations
Yes, that’s what I’ve long assumed — that in order to become truly advanced, a civilization would need to learn to be efficient and leave a minimal footprint on its environment. It’s like how Earth’s own radio leakage has diminished over the decades as we’ve switched from broadcast signals to cable and satellite, so by now, the only signals an alien civilization could really pick up from Earth would be military or aviation radars.
Particularly over interstellar distances, you’d want tight-beam signals with as little spread and leakage as possible so you didn’t waste energy, so the only way we’d pick up such a signal is if we passed directly through a beam, in which case it would probably be unrepeatable.
Indeed, I think the whole Kardashev scheme is based on a flawed premise, that a civilization would inevitably keep using more and more energy without limit until it devoured all the energy in a galaxy. It stands to reason that if an advanced civilization got more efficient, its energy demands would not skyrocket without limit, and conceivably might even plateau or diminish if they find ways to do more with less energy. Perhaps we don’t detect Dyson shells because really advanced civilizations don’t need that much energy after all.