What if I could see in radio instead of light?

  • #1
DaveC426913
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Summary:
What would the world look like if I could see it with "eyes" that detected radio wavelengths?
If my eyes were sensitive to radio wavelength instead of visible wavelengths (and were large enough to resolve an image), what would the world look like?

I assume that my brain would interpret different frequencies in a way that is analogous to colours, such that I could distinguish them from each other.

I think that, as I sat here in my living room:
  • My house would be virtually transparent, like a ghost. I would be able to make out portions of it, where it was dense enough to interfere with radio signals, but everything would be very fuzzy. For example, a block of metal would look like a fuzzy blob because it is too small compared to the radio wavelengths to be resolved and the signals would just diffract around it.
  • I would be able to see my (fuzzy) phone flashing brightly as it sent and received signals.
  • I would be able to see the transmitter towers as beacons in the distance.
  • Everything else would be dark but not black, as radio waves would pass through most things but with at least some reflection.
  • The sun would shine brightly of course.
  • Would the sky be dark? I guess it would be dark enough that I could see stars.
  • My cell phone would light up so bright (and omnidirectional) that it could be easily seen by a cell tower a mile away.
  • A faraday cage would be a blob with black at its centre.
  • I guess my microwave (which I can see in my kitchen, right through my living room wall) would be opaque inside.
  • What colour would radio antennae, like on cars, be? I guess they would be black? They would have to be resolveable (if weren't at least partially opaque to radio waves, they couldn't receive radio signals.)

What other weird things might I see?
 
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  • #2
sophiecentaur
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Summary:: What would the world look like if I could see it with "eyes" that detected radio wavelengths?

  • A faraday cage would be a blob with black at its centre.
  • I guess my microwave (which I can see in my kitchen, right through
Those objects would 'look' highly reflective because their surfaces would be highly conductive. But for longer wavelengths they would slightly scatter the radio waves which would largely pass by, unaffected.

We're talking of many octaves of frequency here, as opposed to the single octave of visible frequencies so the range of effects would be huge, from almost optical definition to merely very fuzzy.

How big were you envisaging your eyes to be?
 
  • #3
Baluncore
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What colour would radio antennae, like on cars, be? I guess they would be black? They would have to be resolveable (if weren't at least partially opaque to radio waves, they couldn't receive radio signals.)
It would depend on the impedance matching of the antenna to the radio over frequency.
Antennas would be coloured like beetles, or Dichroic filters.

We see only the universe of impedance mismatches that are illuminated.
 
  • #4
sophiecentaur
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We see only the universe of impedance mismatches that are illuminated.
That's a reasonable way to put it.

What we would 'see' would depend on the source of the illumination (as in optics). With the source behind us and the object in front of us, with empty space behind, we would see a 'reflection' of the object, the fuzziness would depend on the width in wavelengths.

With the object between us and the illumination, we would see a fuzzy shadow (the inverse of the above). The amount of disturbance would depend on the impedance mismatch.

For a ball park figure of the depth of the 'shadow' of a small object, a half wave dipole has an effective area (in the max direction) of about 1/100 of a wavelength squared. I think that means it would intercept about 1/100 of the passing flux. (This assumes that the dipole is matched to the receiver.) Here is a link to a calculator. I think I've driven it correctly. The reflection for a total mismatch would be similar.
 
  • #5
tech99
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Summary:: What would the world look like if I could see it with "eyes" that detected radio wavelengths?

If my eyes were sensitive to radio wavelength instead of visible wavelengths (and were large enough to resolve an image), what would the world look like?

I assume that my brain would interpret different frequencies in a way that is analogous to colours, such that I could distinguish them from each other.

I think that, as I sat here in my living room:
  • My house would be virtually transparent, like a ghost. I would be able to make out portions of it, where it was dense enough to interfere with radio signals, but everything would be very fuzzy. For example, a block of metal would look like a fuzzy blob because it is too small compared to the radio wavelengths to be resolved and the signals would just diffract around it.
  • I would be able to see my (fuzzy) phone flashing brightly as it sent and received signals.
  • I would be able to see the transmitter towers as beacons in the distance.
  • Everything else would be dark but not black, as radio waves would pass through most things but with at least some reflection.
  • The sun would shine brightly of course.
  • Would the sky be dark? I guess it would be dark enough that I could see stars.
  • My cell phone would light up so bright (and omnidirectional) that it could be easily seen by a cell tower a mile away.
  • A faraday cage would be a blob with black at its centre.
  • I guess my microwave (which I can see in my kitchen, right through my living room wall) would be opaque inside.
  • What colour would radio antennae, like on cars, be? I guess they would be black? They would have to be resolveable (if weren't at least partially opaque to radio waves, they couldn't receive radio signals.)

What other weird things might I see?
Your eyes would need to be a few wavelengths in diameter to be able to make out directional information. I think a more plausible comparison would be with hearing, where wavelengths are similar.
 
  • #6
sophiecentaur
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I think a more plausible comparison would be with hearing, where wavelengths are similar.
Our directional sense of sound is still pretty approximate. But the audible frequency range is more along the lines of a communications receiver.
 
  • #7
DaveC426913
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OK, I think I see the problem with my premise.
Everything's gonna be fuzzy and indistinct. (which knew I, but not so bad as this.)
Radio wavelengths are near the size of much of the human-scale world. The experience of seeing in radio wavelengths would be similar to the experience of my light-resolving eyes - if I had no corneae or lenses.


It's analogous to having my regular light-sensitive eyes that are no bigger than molecules, and wandering around looking at atoms and molecules. The wavelengths involved are to large to resolve anything.
 
  • #8
DaveC426913
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I guess things like streetlights would be dark even when on.

And most electronics should be dark as well (at least, the ones that aren't wireless-enabled). The FCC guidelines for devices require that they don't emit a troublesome amount of stray radio noise.

In fact, I'm thinking almost all objects and structures would be either mostly transparent or dark (depending on their metallic density), and the only things that would be bright and visible would be things that are designed to emit radio (or are natural emitters).

What would the ground look like?
 
  • #9
berkeman
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Don't look at the AM radio transmitter towers! You'll go blind!
 
  • #10
jim mcnamara
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Insects can see in UV, flowers have pigments that show up below 440nm and bees see them.
Canids can see into the very, very near infared, dogs have a rhodoposin peak at 510nm-540nm, tailing of past the red limit for human past.

FWIW dogs are dichromats. We are trichromats, having photo-pigments with sensitivities at three peak wavelengths, birds have photo-pigments with sensitivities at four or five peak wavelengths. So they are tetrachromats perhaps even pentachromats.

The point is all the above retinas see the world differently.

FWIW mantis shrimp win the polychromacy vision gold medal. Sixteen.

How the mantis shrimp sees the world, a shrimp-eye camera:
https://www.theatlantic.com/science/archive/2018/04/mantis-shrimp-eye-camera/557195/

I do not see how you could possibly survive with radio wavelength vision. Resolution is a function of wavelength. You could probably resolve asteroid sized objects. As a guess.
From the FCC, (www.fcc.gov ) AM radio wavelengths:
The wavelengths of AM radio signals vary from a maximum of 555 meters (1821 feet) at 540 kilohertz (kHz), the lowest AM carrier frequency used in the United States for broadcast stations, to a minimum of 176 meters (579 feet) at 1700 kHz, the highest carrier frequency at the upper end of the AM expanded
-- biological eyes cannot resolve objects that are smaller than the wavelength.

Good luck crossing a road at a crosswalk. If you could find it to start off.
 
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  • #11
DaveC426913
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I do not see how you could possibly survive with radio wavelength vision. Resolution is a function of wavelength. You could probably resolve asteroid sized objects. As a guess.
From the FCC, (www.fcc.gov ) AM radio wavelengths:
Right. So.
From 1cm to 1m.
Radar, TV, FM.
 
  • #12
Baluncore
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Our directional sense of sound is still pretty approximate. But the audible frequency range is more along the lines of a communications receiver.
The cochlea in our ear performs a mechanical analysis of audio frequency. The high frequencies are detected first at the thin end of the taper and become the central neurons in the nerve bundle. The low frequencies are detected last and form the outer layer of neurons in the auditory nerve, which also helps allocate neurons to the wide range of octaves we hear.
So our auditory system it is not like a tuned communications receiver so much as a parallel analyser or FFT. Direction finding is by phase comparison of the low frequencies only in neurons from both ears. Different people have and learn different frequency and harmonic resolution, which helps play a part in their ability to sing, and in knowing which way to look when they hear a loud bang.

Your eyes would need to be a few wavelengths in diameter to be able to make out directional information. I think a more plausible comparison would be with hearing, where wavelengths are similar.
With the eye, the centre of the optic nerve carries the centre of vision from near the fovea of the retina. The outside of the optic nerve contains the peripheral vision. So there is no spatial frequency analysis performed by the eye. It is the spiral paths taken by the neurons in the optic nerve that decides how the image on the retina will be mapped to the brain. The brain must then do the image analysis. That is why sight is our key directional sense.

To use our eyes for radio frequency identification we would need to replace our three colour detectors with very broad band long, medium and short wavelength detectors that slightly overlapped in the radio spectrum. I know our eyes are too small to resolve radio wavelengths, but we could make a much bigger antenna array, with an RF spatial analyser and a colour screen that we could view with our eyes.

Imagine looking at a crowd, a landscape or the sky, and seeing bright spots on the TV image where RF energy was being emitted. The closest I have come to that was an antenna array with an analyser/correlator that produced a spatial image, with false colour and brightness determined by the energy received from that direction, for a very narrow radio frequency channel. In a world where different spot frequencies come from so many very different directions, the ability to see a specific frequency RF source was more valuable to my employer than the ability to sense broadband energy distribution.
 
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  • #13
tech99
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Remember that our surroundings are warm so emit noise; the only dark things would be conductors and good insulators. The sky is shiny at all frequencies below about 30 MHz due to the ionosphere, and sparkling with reflected signals. At higher frequencies, the sky will be full of light pollution due to satellites, which will look like stars. The interior of houses and offices will be bright due to computer interference.
 
  • #14
Baluncore
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Remember that our surroundings are warm so emit noise; the only dark things would be conductors and good insulators.
Good conductors make very good mirrors, so they would reflect RF energy from other sources, and so would not necessarily appear black. Attenuation of RF in insulators is more difficult to predict, but they would appear darker, unless they had a multiple of λ/2 thickness.
 
  • #15
sophiecentaur
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Direction finding is by phase comparison of the low frequencies only in neurons from both ears.
You could say that we do much better than the Rayleigh criterion with sound would suggest. We can resolve (that's the relevant thing for Rayleigh) sound sources with an error of not many tens of degrees with an aperture of about 20cm.
Remember that our surroundings are warm so emit noise; the only dark things would be conductors and good insulators.
This scaling exercise is very hard.
There are very few objects that would appear invisible (black) by reflection (stealth vehicles). Everything else would reflect (whether or not they happen too be matched aerials). An open window would be the only 'object' to appear black (if the Sun is not shining through).
Judging by the performance of radio receivers, we would be more subject to interference from outside transmitting sources than received noise at many frequencies. Also, the internally generated noise in our (warm) bodies would often be the limiting factor.
Good conductors make very good mirrors, so they would reflect RF energy from other sources, and so would not necessarily appear black.
I think they would necessarily appear 'whiter' than the background of free space. After all, that's how RADAR works./
 
  • #17
DaveC426913
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The interior of houses and offices will be bright due to computer interference.
I don't think so. Computers, by themselves shouldn't be emitting radio signals. They're supposed to be damped. Though any wireless devices will glow.
 
  • #18
sophiecentaur
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@bob012345
That link serves to demonstrate how 'the world' is not restricted to a visual one. Sighted people seem to think that what they can 'see' and remember about a scene is somehow the 'truth' and they find it amazingly difficult to understand how blind people (and also many non-human animals) can get any meaningful information about their surroundings and the spatial layout of where they are.
AI can make up its own world image, using all the information it can gather and it often works out things and solve problems in a totally different way.
 
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  • #19
tech99
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I don't think so. Computers, by themselves shouldn't be emitting radio signals. They're supposed to be damped. Though any wireless devices will glow.
My experience is that all IT equipment, including computers, printers, power supplies, chargers and internet lines, all radiate high levels of interference. Try holding an AM radio near any IT equipment.
 
  • #20
DaveC426913
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My experience is that all IT equipment, including computers, printers, power supplies, chargers and internet lines, all radiate high levels of interference. Try holding an AM radio near any IT equipment.
I'm not sure if that's active radio interference or simply blocking the signal with metallic density. Many of those devices might have their own form of simple faraday cage.

I guess it depends on whether the problem still occurs when the equipment is turned off.
 
  • #21
sophiecentaur
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My experience is that all IT equipment, including computers, printers, power supplies, chargers and internet lines, all radiate high levels of interference. Try holding an AM radio near any IT equipment.
This is another problem in this exercise. Interference from nearby equipment won’t be by traveling waves. You’ll be in the near field up to at least tens of MHz so there’ll be no ‘optical’ images involved, just a mish mash of fields.
Although EM is always EM, the relevance of coherence and QM don’t scale.
 
  • #22
DaveC426913
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This is another problem in this exercise. Interference from nearby equipment won’t be by traveling waves. You’ll be in the near field up to at least tens of MHz so there’ll be no ‘optical’ images involved, just a mish mash of fields.
Although EM is always EM, the relevance of coherence and QM don’t scale.
Once again, in Laymanese?
 
  • #23
Baluncore
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I'm not sure if that's active radio interference or simply blocking the signal with metallic density. Many of those devices might have their own form of simple faraday cage.

I guess it depends on whether the problem still occurs when the equipment is turned off.
The only way to assess the level of RFI is with a radio receiver. Our receivers have variable gain front-ends that can often hear the noise floor. When inside a building, screened from outside signals, any minor source of RFI will be magnified to fill the audio channel.
 
  • #24
berkeman
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My experience is that all IT equipment, including computers, printers, power supplies, chargers and internet lines, all radiate high levels of interference. Try holding an AM radio near any IT equipment.
We are required in pretty much all countries to comply with one of two levels of EMI -- Level A or Level B. They are about 10dB apart. Level A is for industrial/commercial settings, and Level B is for residential settings.

The EM radiation levels are generally measured in the far field at 3m or 10m depending on the standard. The goal of the EMI regulations is to prevent interference with radio receivers that are practical distances away, not held up to the equipment. If you ever experience EMI stepping on your radio receiver you need to contact the FCC to have them find out who is causing the harmful interference. It is then up to the source of the EMI to fix the problem. If the source of the interference is not obvious, I may be one of the folks called in to hunt down the source. :smile:

[Update -- I just noticed that they seem to have gotten the red/blue colors reversed in the graph below. Level B is more restrictive than Level A, so the colors should be reversed]

1632268931478.png

https://e2e.ti.com/blogs_/b/powerhouse/posts/a-review-of-emi-standards-part-2-radiated-emissions
 
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  • #25
sophiecentaur
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Once again, in Laymanese?
OK. Radio sensing and receiving works on the classical wave model of EM. You can (ideally) determine the amplitude and phase of any signal you pick up. The individual photons of RF are very low energy and you basically can't see them but you can follow the Volts and Amps of the ensemble signal.

With a few exceptions (laser technology and astrophotography etc.) We can detect individual photons but the information at light frequencies is usually non-coherent (we just see the total energy arriving).

The OP is trying to compare and contrast the two regimes and the differences are massive.
 

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