Author Topic: Why evolution by natural selection didn't make use of RF?  (Read 7699 times)

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Online coppercone2

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #50 on: August 30, 2023, 12:23:44 am »
please stay on topic about spark snakes
 

Online BrianHG

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #51 on: August 30, 2023, 01:48:45 am »
I thought that electric eels could make some signals which were detected from a pond to a pond after a flooded rain storm which may have isolated individuals.  I don't remember how, (it was a National Geographic or David Attenborough docu) but a particular signal they sent was designed to attract mates and one pond within the right size could trigger a sexual response of an electric eel of opposite sex in the next pond of similar size.

This means the charge they sent out had a tuned amplitude and frequency and the mate was attuned to that pattern for searching for sexual mates.  It was also said that other signals, like defensive electrical attacks would not trigger the sexual response in other eels.  So, by close definition, we have a signal with selective amplitude and frequency characteristics developed by natural selection.  Perhaps with a few million years of guided evolution, this effect can be further attuned to something like a radio transceiver we are accustomed to.

Maybe the OP's title is wrong...
« Last Edit: August 30, 2023, 01:51:52 am by BrianHG »
 
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Offline TimFox

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #52 on: August 30, 2023, 02:26:15 am »
Since the electric eel's discharges are pulsed, it is more likely that pulse patterns and rates form the code, rather than carrier frequency.
 

Offline T3sl4co1l

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #53 on: August 30, 2023, 02:28:54 am »
Yeah, nothing wrong with signaling at low frequencies, likely well under 1kHz given the depolarization rate of neurons.  Also well serves predators, like sharks sensitive to myoelectric fields.  E-fields don't go far in water (sea or otherwise), but that's enough when it's very dark (abyssal) or murky (several river species) -- eyes offer no improvement!

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Offline Tomorokoshi

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #54 on: August 30, 2023, 04:18:23 am »
And then there are these things. Keywords: quarter-wave plates, Stokes parameters:

https://en.wikipedia.org/wiki/Mantis_shrimp
 

Offline tggzzz

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #55 on: August 30, 2023, 08:41:02 am »
...
If you subscribe to Fourier's theories, then
...

Doesn't everybody?

Oh, wait.... given some of the earlier posts in this thread, that is probably beyond some posters :(
There are lies, damned lies, statistics - and ADC/DAC specs.
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Offline JPortici

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #56 on: August 30, 2023, 12:55:12 pm »
I've read some articles that suggest that bird flocks could use magnetic fields to coordinate and to decide which direction they need to go
 

Offline SiliconWizard

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #57 on: August 30, 2023, 08:30:29 pm »
...
If you subscribe to Fourier's theories, then
...

Doesn't everybody?

Oh, wait.... given some of the earlier posts in this thread, that is probably beyond some posters :(

If we get that kind of "lunacies" on an engineering forum, imagine what it's like in the general population. :popcorn:
 

Offline tggzzz

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #58 on: August 30, 2023, 08:36:09 pm »
...
If you subscribe to Fourier's theories, then
...

Doesn't everybody?

Oh, wait.... given some of the earlier posts in this thread, that is probably beyond some posters :(

If we get that kind of "lunacies" on an engineering forum, imagine what it's like in the general population. :popcorn:

Unfortunately we don't have to imagine.

All we have to do is look at the news and see how people are being persuaded that something that looks blue is actually red because a random crackpot says that <insert conspiracy here>.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Online BrianHG

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #59 on: August 30, 2023, 08:48:59 pm »
I've read some articles that suggest that bird flocks could use magnetic fields to coordinate and to decide which direction they need to go

Not just birds.  Even some forms of bacteria have magnetic navigation.
 
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Offline T3sl4co1l

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #60 on: August 31, 2023, 02:47:59 am »
Static fields are easy: electric fields make your hairs stand on end, or other things; magnetic fields by magnetite crystals usually, I think.  Anything faster than nerve response rate though, good luck.  Actual "RF", in the MHz to say 10s of THz, far harder to do.

Also arguably in the 10s-100s THz, there's thermal radiation, but this is getting into the quantum range, in this case by way of phonons; heat.  Bolometry works for anything, of course, I mean, you can certainly feel various wavelengths if they're strong enough (from diathermy to direct microwaves, to the warmth of the sun), and the sensor isn't too thin for the wavelength.  Not very sensitive though.

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Offline RoGeorgeTopic starter

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #61 on: August 31, 2023, 04:47:32 pm »
...
If you subscribe to Fourier's theories, then
...

Doesn't everybody?

That's far from obvious, nor trivial.  The continuous sinusoids calculated with Fourier are not really there.  The sinusoids are as if it were to be a bunch of added together sinusoids instead of the given shape of a signal, but they are not really there.  One can see with an oscilloscope that there is some other wiggly form and no sinusoid in an arbitrary signal.

A given shape can be decomposed many ways.  One way is to write our shape as a sum of sin and cos functions, thus the Fourier spectrum.  But the same signal can be decomposed, for example, in a series of wavelets.  Or, maybe with some other kernel function instead of either sin/cos or wavelets.

Now, is our arbitrary signal a sum of wavelets?  Or a sum of sinusoids?  Or some other sum of some other kernel functions?

I think the correct answer is neither, our arbitrary signal is just the shape we see on the oscilloscope, not a sum of sinusoids, not a sum of wavelets, or any other sum.



It's a happy coincidence that Fourier is particularly useful in engineering, somehow overlaps with the idea of superposition (which only holds for linear systems).  Then we are all trained to apply Fourier only where it holds, and we turn a blind eye to what doesn't match, or we learn how to minimize Furrier side effects like the Gibbs artifacts, the need of windowing, the lost of causality.

We do that all the time and only consider what we need out of it, up to the point where we start to believe a square wave is made of odd harmonics in a certain ratio, which is not really so.  I consider that's just a form of gaslighting, though this time the gaslighting is just an innocent side effect with no malicious intent behind.  I consider the sinusoidal components aren't really there, and that can be proved in practice.

(An example of causality artifact can be seen in any digital oscilloscope, when sinx/x compensation is on, and the level of a constant 0 or 1 voltage starts to wiggle on the screen before an edge, as if the signal will somehow have premonitions and knows in advance when an edge will come - that's just a Fourier artifact, the logic level can not know the future.)



I think it can be proved in practice that the sinusoids from the Fourier spectrum are not really there.

For example, if we take a square wave of 1kHz, such a signal is supposed to have plenty of sinusoidal 3kHz in it, according to Fourier.  However, one can make a filter that will only respond to a sinusoidal shape of 3kHz, and no other shape than sinusoidal.

Such a 3kHz filter won't respond to a square wave of 1kHz, which indicates there is no sinusoidal 3kHz in our 1kHz square.  I'll say that's a proof Fourier spectrum is not really there.

Now, the funny thing is that what we casually call a 3kHz filter in EE will respond to a 1 kHz square, how so!?!  :o

But then, what's a filter?  And how/why does it work?
That's another simple yet difficult question to answer.
« Last Edit: August 31, 2023, 04:56:33 pm by RoGeorge »
 

Offline tggzzz

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #62 on: August 31, 2023, 06:57:17 pm »
...
If you subscribe to Fourier's theories, then
...

Doesn't everybody?

That's far from obvious, nor trivial.  The continuous sinusoids calculated with Fourier are not really there.  The sinusoids are as if it were to be a bunch of added together sinusoids instead of the given shape of a signal, but they are not really there.  One can see with an oscilloscope that there is some other wiggly form and no sinusoid in an arbitrary signal.

That last sentence is wrong, pure and simple. The earlier ones make no sense.

For similar reasons I suppose you would claim that the individual colours in white light are not really there.

Quote
A given shape can be decomposed many ways.  One way is to write our shape as a sum of sin and cos functions, thus the Fourier spectrum.  But the same signal can be decomposed, for example, in a series of wavelets.  Or, maybe with some other kernel function instead of either sin/cos or wavelets.

Now, is our arbitrary signal a sum of wavelets?  Or a sum of sinusoids?  Or some other sum of some other kernel functions?

I think the correct answer is neither, our arbitrary signal is just the shape we see on the oscilloscope, not a sum of sinusoids, not a sum of wavelets, or any other sum.

Observing something on one type of instrument (e.g. a scope) is irrelevant. Why not choose a spectrum analyser instead?

Fourier analysis is a mathematical concept. Ditto wavelet analysis. The validity of one does not invalidate the other.

You can also decompose a 2D shape into a set of triangles. Or squares. Or hexagons.

Quote
(An example of causality artifact can be seen in any digital oscilloscope, when sinx/x compensation is on, and the level of a constant 0 or 1 voltage starts to wiggle on the screen before an edge, as if the signal will somehow have premonitions and knows in advance when an edge will come - that's just a Fourier artifact, the logic level can not know the future.)

Sigh. You are missing many important concepts there, and I don't have time to attempt to enlighten you. I just refer you to textbooks.

The rest of your post isn't even wrong.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Offline RoGeorgeTopic starter

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #63 on: August 31, 2023, 07:44:55 pm »
I suppose you would claim

We are here to talk about ideas, not to disconsider each other.  Well, again, you start with ad hominem innuendos, assuming how you are smart and the others are not.  That attitude never made anybody look smart, quite contrary but arrogant.  I don't have the time to enlighten you either.

Offline TimFox

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #64 on: August 31, 2023, 11:16:48 pm »
...
If you subscribe to Fourier's theories, then
...

Doesn't everybody?

That's far from obvious, nor trivial.  The continuous sinusoids calculated with Fourier are not really there.  The sinusoids are as if it were to be a bunch of added together sinusoids instead of the given shape of a signal, but they are not really there.  One can see with an oscilloscope that there is some other wiggly form and no sinusoid in an arbitrary signal.

A given shape can be decomposed many ways.  One way is to write our shape as a sum of sin and cos functions, thus the Fourier spectrum.  But the same signal can be decomposed, for example, in a series of wavelets.  Or, maybe with some other kernel function instead of either sin/cos or wavelets.

Now, is our arbitrary signal a sum of wavelets?  Or a sum of sinusoids?  Or some other sum of some other kernel functions?

I think the correct answer is neither, our arbitrary signal is just the shape we see on the oscilloscope, not a sum of sinusoids, not a sum of wavelets, or any other sum.



It's a happy coincidence that Fourier is particularly useful in engineering, somehow overlaps with the idea of superposition (which only holds for linear systems).  Then we are all trained to apply Fourier only where it holds, and we turn a blind eye to what doesn't match, or we learn how to minimize Furrier side effects like the Gibbs artifacts, the need of windowing, the lost of causality.

We do that all the time and only consider what we need out of it, up to the point where we start to believe a square wave is made of odd harmonics in a certain ratio, which is not really so.  I consider that's just a form of gaslighting, though this time the gaslighting is just an innocent side effect with no malicious intent behind.  I consider the sinusoidal components aren't really there, and that can be proved in practice.

(An example of causality artifact can be seen in any digital oscilloscope, when sinx/x compensation is on, and the level of a constant 0 or 1 voltage starts to wiggle on the screen before an edge, as if the signal will somehow have premonitions and knows in advance when an edge will come - that's just a Fourier artifact, the logic level can not know the future.)



I think it can be proved in practice that the sinusoids from the Fourier spectrum are not really there.

For example, if we take a square wave of 1kHz, such a signal is supposed to have plenty of sinusoidal 3kHz in it, according to Fourier.  However, one can make a filter that will only respond to a sinusoidal shape of 3kHz, and no other shape than sinusoidal.

Such a 3kHz filter won't respond to a square wave of 1kHz, which indicates there is no sinusoidal 3kHz in our 1kHz square.  I'll say that's a proof Fourier spectrum is not really there.

Now, the funny thing is that what we casually call a 3kHz filter in EE will respond to a 1 kHz square, how so!?!  :o

But then, what's a filter?  And how/why does it work?
That's another simple yet difficult question to answer.

In the real world, to see if there be 3rd harmonic power in a square wave, do the following simple experiment with real equipment.
I'm not aware of any realizable (in the technical sense) filter that would discriminate against non-sinusoidal waveforms in the way you suggest.

Experiment:  start with good square-wave generator, with reasonable rise and fall times, but with stable frequency (from a good clock oscillator); set frequency to 1.00 MHz.
Connect directly to modern spectrum analyzer, with synthesized local oscillators and selectable filter bandwidth ("RBW").
Set RBW to minimum value available in the SA, and let the sweep width be set by the default manufacturer's value for that RBW.
1.  Set center frequency to 1.00 MHz and observe signal level at 1 MHz.
2.  Set center frequency to 3.00 MHz and observe signal level at 3 MHz.
Will the ratio between those levels agree with the Fourier series of a 1 MHz square wave?
 

Online coppercone2

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #65 on: August 31, 2023, 11:29:55 pm »
some how derailing this thread to yell about harmonics is just not cool
 
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Offline Bud

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #66 on: September 01, 2023, 03:29:31 am »

For example, if we take a square wave of 1kHz, such a signal is supposed to have plenty of sinusoidal 3kHz in it, according to Fourier.  However, one can make a filter that will only respond to a sinusoidal shape of 3kHz, and no other shape than sinusoidal.
No, one cannot  :-DD
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Offline tggzzz

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #67 on: September 01, 2023, 07:48:19 am »

For example, if we take a square wave of 1kHz, such a signal is supposed to have plenty of sinusoidal 3kHz in it, according to Fourier.  However, one can make a filter that will only respond to a sinusoidal shape of 3kHz, and no other shape than sinusoidal.
No, one cannot  :-DD

How about capturing the signal, doing an FFT, and seeing if there is any frequency other than 3kHz :) Oops; that contains the "invalid" word "Fourier".

Or an analogue variant: a bandstop filter centered on 3kHz, plus a switch. If the filter's output is non-zero, the switch is opened. Oops; that depends on the concept of the equivalence of time and frequency domains, as defined by Fourier.
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Offline Bud

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #68 on: September 01, 2023, 12:45:13 pm »
Such a 3kHz filter won't respond to a square wave of 1kHz, which indicates there is no sinusoidal 3kHz in our 1kHz square.  I'll say that's a proof Fourier spectrum is not really there.
That is exactly what a 3kHz filter WILL DO, you just have not tried or have not measured properly.
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Offline coppice

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #69 on: September 01, 2023, 01:46:16 pm »
Its sad how many of the messages in this thread come down to "that can't happen. because I've never seen it happen", rather than "here is a physics road blocker which means that can't happen".
 

Offline Kim Christensen

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #70 on: September 01, 2023, 03:44:48 pm »
Can't think of a "filter" that only passes a 3Khz sine while ignoring the 3Khz harmonic from a 1Khz squarewave. But I can imagine a "detector" for a pure 3Khz sinewave. Basically a 3Khz filter, x2 RMS detectors, and comparators to compare the energy at 3Khz vs everything else.

But on the topic of organic RF, I don't think there's any creature that outputs electrical pulses with sufficient rise time to emit enough RF energy to be useful for anything.
« Last Edit: September 01, 2023, 03:50:38 pm by Kim Christensen »
 

Offline TimFox

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #71 on: September 01, 2023, 04:09:42 pm »
"RF" is a definition of a subset of electromagnetic radiation frequencies, not a physical definition such as "alpha particle radiation".
Different sources define "RF" starting somewhere between 3 to 10 kHz and ending somewhere between 1010 and 1011 Hz.
The FCC defines radio-frequency "RF" as between 3 kHz and 300 GHz and "microwave" as between 1 and 30 GHz.
Traditional subsets of RF use "3", since they were originally defined in terms of wavelength (in meters).
3 to 30 kHz is "VLF"
30 to 300 kHz is "LF"
0.3 to 3 MHz is "MF", where the broadcast band lies
3 to 30 MHz is "HF", called short wave
30 to 300 MHz is "VHF"
0.3 to 3 GHZ is "UHF"
until we reach 30 to 300 GHz, which is "extremely high frequency" EHF.
There are names for the decades below 3 kHz and above 300 GHZ.
The IEEE, NATO, and other agencies have other nomenclature, including the confusing radar bands (X, Ku, etc.).
 

Offline Kim Christensen

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #72 on: September 01, 2023, 05:32:28 pm »
Sure that's fine... But how would a creature effectively radiate or receive "RF" in the VLF, LF, or even MF bands? Giant organic loopstick? It would have to be a very big animal.
 

Offline TimFox

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #73 on: September 01, 2023, 06:48:20 pm »
I was just pointing out what "RF" is:  many postings above were about other electromagnetic fields or frequencies, such as visible light or the Earth's magnetic field.
Nobody mentioned how modern man, with metal fillings in his teeth, supposedly can demodulate and hear MF broadcast radio fields.
 

Offline CatalinaWOW

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Re: Why evolution by natural selection didn't make use of RF?
« Reply #74 on: September 01, 2023, 06:55:30 pm »
It seems to me possible that RF detection capability could have developed, but it is highly unlikely.  And full blown RADAR even less likely.  For a whole series of reasons.

Any capability that is retained by evolution has to provide some benefit (or at least do no significant harm) to survival.  So any systems which randomly occur must either be biologically nearly free, or provide significant benefit.

In my limited understanding all of the extant sensing systems started with a sensing capability, and then in some cases a transmitting capability came along later.  The oldest appear to be chemical, temperature and light sensing systems which began providing very simple approach or avoid data.  Quite useful to mobile organisms looking for food or avoiding hostile environments. 

In the entire spectrum from VLF through X-rays the highest power level on earth occurs in the visible spectrum and also has a very simple signal correlated to some biological survival (daily on-off).  So it is easiest of all to detect and is useful.  For reasons explained in several other posts detecting other bands is generally more difficult, and the immediate survival benefit is less obvious.  All subsequent development of vision systems are just riffs on this theme, with transmitters (various luminescence schemes) and modulators (colors and color changing capability) developing long after vision systems had become quite complex.

This theme occurs in all other sensing systems I am aware of.  Something simple with a strong available signal to detect that is survivability related happens and then gets elaborated over tens of thousands of generations. 

RF has at least three strikes against it.  Low ambient power.  Difficult detection.  And little obvious survivability benefit. 

Radioactive detection similar.  The strongest strike against it is that natural radioactivity strong enough to effect breeding success is extraordinarily rare. 



 


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