Without going into all the colorful details, the central premise is that a hugely advanced and ancient race of artificially intelligent machines ‘harvests’ all sentient, space-faring life in the Milky Way every 50,000 years. These machines otherwise lie dormant out in the depths of intergalactic space. They have constructed and positioned an ingenious web of technological devices (including the Mass Effect relays, providing rapid interstellar travel) and habitats within the Galaxy that effectively sieve through the rising civilizations, helping the successful flourish and multiply, ripening them up for eventual culling. The reason for this? Well, the plot is complex and somewhat ambiguous, but one thing that these machines do is use the genetic slurry of millions, billions of individuals from a species to create new versions of themselves.
It’s a grand ol’ piece of sci-fi opera, but it also provides a neat solution to the Fermi Paradox via a number of ideas: a) The most truly advanced interstellar species spends most of its time out of the Galaxy in hibernation. b) Purging all other sentient (space-faring) life every 50,000 years puts a stop to any great spreading across the Galaxy. c) Sentient, space-faring species are inevitably drawn into the technological lures and habitats left for them, and so are less inclined to explore.
Nextbigfuture believes we do not know enough to conclude anything about the Fermi Paradox and need to really search the whole galaxy before making any conclusions. At the very least make hyper telescopes and put some space telescopes at gravitational lensing points the we can examine many exoplanets in detail out a thousand light years.
Goat Guy's Fermi Paradox Musing
I’ve been thinking about this for years, it seems. Avid SciFi reading caused most of the contemplation. I probably have no less right to speak my opinion than anyone else … so I might as well.
I hypothesize three fundamental things have, and will prevent us from [a] discovering other sentient civilizations, [b] hooking up with them, and [c] having them come fetch us and gobble us up (or play Monopoly, or give us eternal life, or … whatever)
FIRST - 1/R² diminution - Electromagnetic signals, as they spread over interstellar distances, diminish as a function of 1/R². The power drops by 100 times at 10 times the distance. This strictly limits the opportunity of discovering other sentient species by “EM leakage” to within a few dozen light-years – tops.
The math isn’t hard to do, really. The electromagnetic background at every frequency from megameter wavelengths all the way up to the X-Ray regime has random noise coming from all directions. With very large parabolic antennae, we can concentrate the incoming EMR (electromagnetic radiation) by thousands and even millions of times. But we also concentrate the noise, thousands to millions of times. Ultimately, our sensitivity becomes signal-to-noise limited. S/N ratios and Nyquist’s criteria strictly limit how many “bits” of information can be detected in a noisy signal per unit time.
Further, advanced civilizations won’t be using Morse Code at a few hundred bits per minute, to be sure. Just as we have recently retired Morse Code from ship-to-shore communication after about 150 years of its Hayday and replaced all communications with near-gigabit highly compressed (and outwardly “noisy”) signals, so too would advanced civilizations prize bandwidth so much that they too would be coding all their communications in highly compressed, gigabit to terabit streams. We would have to detect this at such high power that the “aliens” could not be very far away. Indeed: the Pioneer craft, which are barely at the heliopause, have been instructed to “send” at only a few actual bits per second, because the signal-to-noise has become so weak. And they’re bloody pointed at us intentionally!
Pioneer 10 is approximately 7 billion miles (11 billion km) away. 70 AU, or 0.00119 light years away. Its 8 watt transmission is focused by a high-gain (highly directional) parabolic antenna that delivers most of its power to a beam about 1 spherical degree in divergence (1/3200 of a full sphere). This is multiplies intensity by the same 3200 times, to an equivalent of 26,000 watts per steradian. The receiving antennas here have 1 arcminute pointing accuracy, and offer directional gains of about 30,000,000 times over omnidirectional antennae. At the last transmission that we could detect useable information from, at 67 AU in 2003 from Pioneer 10, the transmission rate was down to 20 bits per second.
Theoretically, in a detector-limited but otherwise noiseless universe, we could detect Pioneer 10 at Alpha Centauri (4.37 LY, or 26 trillion miles, 40 trillion kilometers) transmitting 0.13 bits per day. About a week per bit. A very long time to be staring at one speck in the heavens to receive … count them … one bit of information.
THE MATH: But let’s say we think our alien bro’s are using slow-bits (say a few kilobits per second) to communicate with each other over their inner solar systems (not unreasonable). They would need to be transmitting at about the 350 GIGAwatt-persteradian level in our direction exactly, in order for us to receive it. What kind of systems transmit with these directed intensity levels?
Well, certainly the Areceibo-scale antennas, with only a few dozen kilowatts of drive power. 350 GW/srad with an antenna divergence of 1 arcminute (1/60th of a degree) would require a 30 kilowatt transmitter at the exact focal point of the Big Dish, as it sweeps past our target star. Again, not that amazing a power level. They they could hear us, or we could hear them, … for a few blips of time, as we/they tried to communication with each other. What’s the likelihood of us having our limited resources of big dishes (way fewer than reasonably close stars to observe) mutually pointed at each other in that few-seconds-per-day window of coalignment? NOT very high. Its one of those miserable “and” statistics. If we point at each star once a minute, for a minute, there is 1/1440 of-a-day pointed at each star. If they’re doing the same, then square that… 1 in 2,000,000 chance.
IF EVERY target star – every blasted one of them – has a civilization that’s doing the same darn thing (transmitting and listening), then it is still about 2,000,000 minutes 1,400 days (4 years) before we just happen upon ONE communication. Given that and the almost certainty of observing technological duds (not yet “there”), then the chances are virtually zero of ever detecting a local entity that’s more or less on par with ours technologically.
Second – pencil beam communication – the idea is that just like the above, to effectively communicate useful amounts of information over the startlingly great distances of interstellar space, the power levels need to be very high indeed. Light in the form of lasers is very easy to get down to arcsecond divergence where a 25 watt source would have an effective power of 1000 gigawatt per steradian directional intensity, accommodating kilobits per second communication pretty trivially. But if it isn’t pointing exactly at us, we’d never see it at all. One arcsecond is 7 trillionth’s of a unit sphere. If the target planet has gone completely over to pencil-beam communication at obvious laser frequencies ( solid state, as we’ve discovered and now happily use all the time ), and they’re transmitting millions of them in all sorts of wild-assed directions to talk to millions of “local” spacecraft (which isn’t implausible for a really advanced civilization), then we’d still have a 1-in-a-million chance of catching millisecond long “sweeps” our system due to intercepted traffic.
But wait. That’s less than a bit’s worth of information.
And moreover, they’re going to be transmitting gigabits or higher.
Which (again) due to signal-to-noise will get lost entirely at our distance.
Third – and most important – is my hypothesis that inter-stellar space travel isn’t statistically possible at high speed. With the almost uncountable gazillions of chunks of Oort and Kuiper Cloud objects ranging down to foot-ball sized hunks of junk, and the very high likelihood of a lumpy continuum of similar stellar nursery “leftovers” sluicing about between the star systems indefinitely, the likelihood of having a critical part of a large interstellar space-craft hitting a hunk of junk seems very high.
In other words, Space is too junky to wing around in at near speed-of-light speeds. A single walnut at 50% of c would explode with the force of a 14 kiloton nuclear bomb on impact. Think about that and weep! And we can be assured that there are quintillions of the little chunks out there. Between there, and “here”. A single kilogram hunk of primordial ices carries 2.7 megatons of kinetic energy.
FINAL THOUGHTS – the issue is this: space, through our telescopes, is amazingly rich and apparently clear and without detectable evidence of #3’s space junk. But telescopes wouldn’t be able to “see” the junk at all, given the interferometric halo or “fog” that it would cause. And that’s what causes all science fiction to assume that we “could” chug along at near-c velocities – the clarity of space to observation, and the induction that therefore space must be gloriously free of such obstructions and chunks. Well, it is that which I challenge.
The likelihood of there being advanced civilizations all over the place – to my mind is actually pretty significant. We’re learning that to no statistical surprise, virtually all F and G stars (and by induction the rest too) have planets. We’re very likely to learn within a few decades that some show chlorophyll and rhodopsin type fluorescence signatures, indicating life. It only took 4.7 billion years for us to evolve, through a remarkable childhood of Snowball Earth glaciation, pummeling by many wicked bolides (observe Moon), of great tectonic forces, and having the Goldy Locks set of conditions that kept life evolving every so often.
But we’ve only been “communicative” for a hundred years or so out of 4.7 billion. There isn’t any evidence [here] that great civilizations evolved and were snuffed somehow in that 4.7 billion. We appear to be the first. There also is no reason to believe that our peculiar dynamics is unique – especially for planets of the Goldi-locks size. But it IS probabilistically slim that there’d be ANY similarly communicative-at-this-stage radio beacon civilizations within the local 25 light-years. Very slim.
And then the probabilities of coincident communications objectives, pencil-beams and so on … diminishes that slim probably by millions of times. Then further – because I’m convinced that interstellar space travel is fraught with “itsy-bitsy-nuke-bomb-walnuts”, the probability further diminishes that anyone MORE advanced than us hairless apes would be blithely traversing the galaxy in their space-faring days. Too high of a probability of becoming more space dust. Way too high.
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