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This question already has an answer here:

Imagine a species of eusocial arthropoids, each about the size of a dog, that live in complex, multilayered nests. Each individual has very little brain - a brain about the size of a tic-tac, to be precise - but as a whole, the nest is powerful sentient mind.

An individual needs to be able to perform a complex task in real time in order to operate some technologies. Rather than the individual knowing how to do the task, it would receive a series of subtle radio signals from the other individuals nearby, a cascade of meaningless pulses from thousands or millions of individuals that converge on this individual to give it the impulse needed to carry out its task, moment by moment.

What physical structures would an individual need in order to send and receive these radio signals?

To clarify: By 'radio', I don't mean 'any form of electromagnetic radiation'. I'm referring to the range of frequencies known as 'radio waves', that is up to around 300GHz. This is because the signals need to be able to go through the solid walls of the nest. Basically biological wi-fi.

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marked as duplicate by JDługosz May 27 '17 at 0:04

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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    $\begingroup$ For an example of a fictional species which communicates using naturally produced radio waves, see Verpines from the Star Wars expanded universe. $\endgroup$ – Thriggle May 26 '17 at 18:28
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    $\begingroup$ Since radio waves are part of the electromagnetic spectrum, the way one would receive radio waves is through vision. So the real trick is transmitting it. You might be interested in microwave auditory effect. (It's not radio waves, but it's close.) $\endgroup$ – Mea quidem sententia May 26 '17 at 18:36
  • $\begingroup$ I've seen ham radio enthusiasts with business cards reading "500THz band communication" and fireflies and cephalopods are natural examples for light. But while it is all EM waves, generally "radio" is used for 0.3 to 3000MHz bands $\endgroup$ – user25818 May 26 '17 at 18:54
  • $\begingroup$ @Meaquidemsententia We already do transmit. It is just very weak. Perhaps it is not required to be a strong signal for the OP? If so, then an increase in the electromagnetic components of thought that we can currently pick up (see virtual reality Brain Computer Interface) by some technobabble chemical process? $\endgroup$ – Enigma Maitreya May 26 '17 at 19:14
  • $\begingroup$ this has been asked before, worldbuilding.stackexchange.com/questions/27108/… $\endgroup$ – John May 26 '17 at 22:31
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The very simplest radio is a crystal radio receiver, and are available for children to play with and build themselves. The key element of the design is the crystal which demodulates the radio signal to get the audio signal. The complete design is described here: https://en.wikipedia.org/wiki/Crystal_radio#Design

The transmission side of a radio is a little more complicated, and in addition to an oscillator (also a crystal) requires a transformer to modulate the radio waves so as to carry the signal. Take for example this simple AM transmitter: http://sci-toys.com/scitoys/scitoys/radio/am_transmitter.html

Your alien species would then need to biologically grow a crystal (possible, with access to the right elements, using mechanisms like a mix of kidney stones and spider web weaving), as well as wiring and some way of producing an electrical potential (also possible, like a more advanced design of electric eels, except contained and directed into circuits) to form the tuning inductor and transformer.

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If you consider a radio signal as the electromagnetic spectrum, then you already have an answer with "visible" light. What human perceive through our eyes is nothing more than a specific range of the spectrum, the one the sun emits light in. Other species are able to perceive outside the human range : bees see in the ultraviolet range to spot flowers, and some predators can see in the infrared. So you can imagine evolution that led to other wavelengths use if it give an advantage (being social is an advantage).

On the emitter part, bio-luminescence exist. You can imagine other chemical or physical reactions to emit in other ranges. Storing specific isotopes and releasing small amounts of them, or maybe moving iron organs to generate magnetic fields. Note that torpedoes and other fishes have the ability to deliver electric shocks. Such organs could be suitable for lighter electric emissions as well.

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  • $\begingroup$ Hum, bio-luminescence is really good. Lets change the frequency to a specific radio frequency and add an amplifier chemical process. $\endgroup$ – Enigma Maitreya May 26 '17 at 19:16
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Exactly for radiowaves, some sort of low-resistant material (metals for best results) close to body surface, with it's size as close as possible to wavelength of signal. Maybe, dipole antenna shaped.. antennas on their heads, with copper rich nerves? Problem is, well, three problems.

1) Radio transmission and recieving. If recieving is relatively simple, transmission - not so much. Due to certain magnetic field laws, field strenght is divided on cube of distance - for unfocused emitting. And to focus radiowaves, you need something alike to satellite dishes or even more complicated antennas. So, issue is that they need a lot of energy to emitt comprehensible message. Can they have really, really keen senses? They can. But then, second problem arises.

2) Noises. Stone brick lets Wi-Fi through. Dense tree crown kills it without remorse. If we imagine that your species have really, really sensitive nerve systems to recieve even faintest messages, we end up with other problem. On our world living species haven't developed radio-recieving capabilities, despise of such waves abundance being similar to light - because radio range is unreliable. Light is almost entirely consumed-reflected by leaf. Radio wave - reflects and goes through at the same time. On a sunny day, you will be blinded because of sun radiation (yes, in radio wavelengths) flooding your surroundings, partitially reflected, particially going through everything - even air provides some resistance. Imagine living in a world of a bit smoky lenses and prisms, and trying to see your neighboor in it. On a cloudy day, EMP burst of a thunderstorm will burn any sensitive apparatus just like blastwaves make us deaf, and flashes of light - blind. This sun and storm problem becomes less of a problem if they live underground, that's right. But this gives us even bigger problem.

3) Radiowaves sit between sound and light on wavelength scale - and they travel through hard matter with bigger success than light, but with less success than sound. In fact, raw, timid soil will easily eat your radio signal - just like sheet of grounded metal does.

It boils to question - aren't sounds better? They travel reasonably fast and really far through hard substances, and are much more reasonable to transmit - just tap the floor.

By the way, don't forget that known nerve cells tramsfer a hundred of pulses per second at most - so radiowaves are in no way densier as data carriers than sound for organic reciever, unless such species develop really, really wide range of antennas - or their nerves work on different principle, which is carte blanche on many, many fronts. They might be more metallic in nature, since arthropoids don't need to bend them much, which makes their nerve system into wide-range antenna while not even needing centralised brain - since body can be directly controlled from outside. Which, otoh, will be major vulnerability to exploit in conflict.

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  • $\begingroup$ electromagnetic waves and sound waves, while they may share certain characteristics, are entirely different phenomena that propagate through entirely separate media. Trying to use 2.4 GHz electromagnetic waves for communication underground wouldn't work well, I agree. But 100KHz would probably work reasonably well, and would be easier to generate with biological systems anyway. $\endgroup$ – Perkins May 31 '17 at 18:33
  • $\begingroup$ Any sort of radio waves is catched by conductors. Raw, timid soi is a poor conductor, but still good enough to "eat" radio waves, 100kHz or 2.4GHz. Dry soil will be penetrated better, but still it's 20m at best. $\endgroup$ – Dat.N Jun 9 '17 at 22:03
  • $\begingroup$ The longer the wavelength, the more penetration you get. When you get into the ELF bands, you can talk to submarines, practically anywhere in the world, and under hundreds of feet of otherwise radio-opaque seawater. Bandwidth sucks at frequencies that low, but penetration is impressive. ULF radios used in mines can penetrate 500 feet of rock at about 3KHz. Newer systems with carefully designed transmission modes are usable through 1500 feet of rock. And yes, they fit in hand-held devices. $\endgroup$ – Perkins Jun 12 '17 at 23:50
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Well, firstly, if you want optimal transmission through walls, longer wavelengths are better. The higher the frequency, the more the waves tend to hit things. This is countered by the fact that longer wavelengths require larger antennas. If you want long range, shorter wavelengths work better because you can do fancy things like bounce them off the ionosphere or the moon to get around the curvature of the planet. (All this is a gross oversimplication, I know, but it's good enough for these purposes.)

Now, as for what kind of structures they'd need, it's actually pretty simple. If your dentist messes up a metallic filling, it's quite possible for you to end up being able to hear one of the local AM radio stations through your teeth. Tooth enamel is a piezoelectric material. (albeit not a particularly good one.) Running electricity through it makes it vibrate, and vibrating it makes it produce small amounts of electricity. Get a conductive bridge with just the right inductance in there and put it between the right spots, and you get a basic circuit that can pick up radio waves of a particular frequency range.

As for transmitting, don't make it too complicated. The simplest kind of transmitter is the "spark gap" and it's exactly what it says on the tin. Jump an electric arc between two conductors and you get radio waves on a variety of frequencies. (You can make it more complicated for greater efficiency, but a very basic one is little more than that.) It's unmodulated, so they'll have to use some kind of pulse-code similar to the way Dolphins click at each other. Electric eels can produce enough voltage and current to be able to do something like that if they weren't water creatures (and would tolerate having some bits of wire taped to their bodies...), so it's within the realm of possibility.

The data rate will be dependent mostly on how fast their brains can process incoming clicks, and how much metabolic energy they can devote to electricity generation. Probably on the order of a skilled telegraph operator. And keep in mind that it's a very broad-band signal, so while you can tune it somewhat, you don't get to put very many channels in your bandwidth, so they'll have to have some kind of protocol about who gets to talk when to avoid congestion and interference.

If you need nitty-gritty details of how it works for some reason, check the wikipedia page on spark gap transmitters, it's pretty comprehensive.

Side note: From an evolutionary point of view, the most likely way for this to arise would be for the creature to have developed an electric shock based defense mechanism, similar to various aquatic creatures, and then slowly developed it into a radio transmitter. Odds are reasonable that the original defense mechanism is also still available to them. If they are intelligent, then the development of radio could also be external to their bodies and simply be a radio device they build and carry and power with their nervous system.

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There might be something for you to build based on how an MRI works. Basically, spinning magnets produce radio waves. See: Does waving a magnet around create light? Unfortunately, it seems that creating the frequencies you're hoping for might be too far of an imaginative stretch to be believed as an evolved, biological structure.

Maybe instead of being in their bodies, they "build" the transmitters as part of their nest (or rather, I mean to say that the interesting way they build the nest creates a transmitter, but it's not really an intentional thing), then some organ that receives the signals is easily hand-waved as plausible, considering eyes are a common structure.

In real life here on Earth, such nesting creatures depend heavily on sound and smell (pheromones). Those are pretty effective, as evidenced by the nearly universal use. I know the radio waves makes your creatures more interesting, but if it's not vital to the story, perhaps it's worth reconsidering its inclusion.

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