Weirdest/things that blew your mind when you learned them

[Dr_Nate]

Jocelyn Bell Burnell, who co-discovered the first pulsar PSR B1919+21 in 1967, relates that in the late 1950s a woman viewed the Crab Nebula source at the University of Chicago's telescope, then open to the public, and noted that it appeared to be flashing. The astronomer she spoke to, Elliot Moore, disregarded the effect as scintillation, despite the woman's protestation that as a qualified pilot she understood scintillation and this was something else.
View attachment 260602

Thanks, I had never heard this anecdote before. I'll have to check out the Crab Nebula sometime.

 

[sysprog]

From walking my dog at night, I learned that I can tell from a distance whether the colour from xmas lights are made from two different LEDs or not, or whether a car's brake lights are incandescent or an LED. I think it has to do with persistence of vision and the pulse rate of LEDs.

I just flutter my eyes back and forth. For brake lights, I can see dots for the LEDs and a line of red for the incandescent. I never took apart someone's brake lights to truly confirmed it, but I think it's true because I think I tell the difference normally. For the xmas lights I see dots of different colour that when added together would produce the colour I normally see.

The fastest fast-twitch muscles in the body are those that you use for this purpose: "I just flutter my eyes back and forth" -- such fluttering eyes can move fast enough to cause perturbation from the normal frame rate of visual processing -- that can allow you distinguish visual inputs the differences between which might otherwise be not perceived.

 

[pleeb]

Well, only grey scales of different frequencies (which are real), which the brain codes as different colors (to represent that reality).
The fact that natural selection has selected for these mechanisms gives credence to that reality as well as its significance to the organism's survival.

Agreed; it's how sighted organisms distinguish dangers, poisons, threats, and mates. When I was young I could read only 5 of the 38 Ishihara color plates other than the two neutral standards. Now that I'm in my seventies I can't read any of them. I had no idea I was RG color blind until I was tested when I joined the army, the doctor falsified my record so I could enlist. It was the Vietnam era and they took anybody they could.

 

[Dr_Nate]

Agreed; it's how sighted organisms distinguish dangers, poisons, threats, and mates. When I was young I could read only 5 of the 38 Ishihara color plates other than the two neutral standards. Now that I'm in my seventies I can't read any of them. I had no idea I was RG color blind until I was tested when I joined the army, the doctor falsified my record so I could enlist. It was the Vietnam era and they took anybody they could.

I was told that colour blind snipers are less fooled by camouflage and are thus more valuable.

 

[pleeb]

I like to show my students a visible spectrum and ask them to point out where the color white is. Then I show them that their minds are tricking themselves(?) by using a handheld spectroscope and looking at the emission lines from white fluorescent lights.

But aren't they just seeing frequencies of what we call light? For instance; why is there no magenta in a rainbow? Birds, insects, and fish in the dark zone see in the UV spectrum but they still see colors although sunlight doesn't penetrate the depths. All heating coils produce the same hue of red. I'm no physicist but I can still do research and I've yet to find any claim of innate color on any object. Astrophysicists claim the sun is green, but I've never seen that. I grew up under a yellow sun, millennials have never seen a yellow sun due to the atmospheric changes in gas composition. Superman's powers came from our yellow sun, isn't it odd that his cultural influence waned when the sun turned white? Is our atmosphere filled with kryptonite now? LMAO!

 

[Ibix]

I've yet to find any claim of innate color on any object

The reflectivity of an object as a function of frequency is certainly an objectively measurable thing, as is its emission spectrum. So is the frequency spectrum of the light incident on the object and any filtering between the object and you, although these aren't properties of the object. So the frequency spectrum of light incident on your eyes from an object is a measurable and meaningful thing, over and above the intensity. Neither spectrum nor overall intensity is purely a property of the object, at least in general. I think it's difficult to claim that one is more real than the other.

To me, the only question is whether "green" is only a name for your sensation of your mid-wavelength photoreceptors being stimulated, or also for light that does that stimulating.

Aside: some of the old Star Trek novels had Klingons having vision in the yellow-to-near-ultraviolet range. Thus they see Starfleet's redshirts as clad head-to-toe in black...

 

[pleeb]

I was told that colour blind snipers are less fooled by camouflage and are thus more valuable.

I'd do a fact check on that. In fact, I did and it's not true. 20/20 vision or better is what you'd need. That, and good peripheral vision. And night vision. Colorblind people are more sensitive to bright light and even a rifle flash can produce black or purple spots in their eyes. Artillery flashes can temporarily blind them. If the sun is rising behind their target, forget it. In my day the military wouldn't take you if you're colorblind.

 

[Dr_Nate]

To me, the only question is whether "green" is only a name for your sensation of your mid-wavelength photoreceptors being stimulated, or also for light that does that stimulating.

To expand on @Ibix 's good answer: your brain can be stimulated to perceive green by having photons of around 440 nm be absorbed by your cones, or have only two wavelengths corresponding to red and blue photons be absorbed in the right ratio on the same area of your retina.

 

[Jarvis323]

Maybe the existence of tree Kangaroos; why has nobody told me about this until now?

 

[Ibix]

To expand on @Ibix 's good answer: your brain can be stimulated to perceive green by having photons of around 440 nm be absorbed by your cones, or have only two wavelengths corresponding to red and blue photons be absorbed in the right ratio on the same area of your retina.

Fair enough - I was just meaning to distinguish between colour being a word that labels a sensation versus being one that labels the stimulus (or stimuli, as you note) that causes the sensation. It seems to me to be a matter of semantics, at least if one is claiming that an object is or is not "really" a particular colour. If the colour only labels the sensation then the light isn't green, it just has a spectrum that causes you to perceive green. If the colour also labels the light and/or an object that sends that light to you then the light and the object are green.

 

[Jarvis323]

Also, that animals seem to use quantum entanglement for sense of smell, and to sense magnetic fields.

And also that humans, apparently, are also "selectively processing directional input from magnetic field receptors,”

https://www.popularmechanics.com/science/a31755545/humans-detect-earth-magnetic-field/

 

[sysprog]

The so-called 'wholphin' (I generally dislike portmanteau words) who is a fertile offspring of 2 closely related species, the so-called 'false killer whale' and a dolphin, has 66 teeth -- the arithmetic mean average between the 88 teeth of her dolphin father and the 44 teeth of her false-killer-whale mother.

I was trying to discuss this remarkable macro-emergence from a micro-(DNA-level)-fact with a Chinese woman who was a comp-sci PhD candidate, and I said that I thought that it was interesting that the 2 species were far enough apart that their offspring were usually infertile, but yet they were close enough that in this rare instance, the offspring was fertile.

To clarify the point to the nice gal, I said that this was unlike a horse and a donkey, who are close enough to have offspring together, but not close enough to have fertile offspring.

She said, "well, horse, he have a bad eye, so he don't know that's not a horse".

That was pretty much the entirety of her response.

 

[sysprog]

I'd do a fact check on that. In fact, I did and it's not true. 20/20 vision or better is what you'd need. That, and good peripheral vision. And night vision. Colorblind people are more sensitive to bright light and even a rifle flash can produce black or purple spots in their eyes. Artillery flashes can temporarily blind them. If the sun is rising behind their target, forget it. In my day the military wouldn't take you if you're colorblind.

I was completely colorblind for about a month or so 'way back in the day'. Then I began to see red clearly. Shortly thereafter I was able to experience the full range of colors.

Spoiler: early

Neonates are colorblind. Red comes first. Then the other colors arrive in all their splendor.

 

[Dr_Nate]

For instance; why is there no magenta in a rainbow?

I don't know how to describe magenta, but if we pick brown instead we might be able to just call it dark orange. Perception is a tricky thing.

 

[sysprog]

I don't know how to describe magenta, but if we pick brown instead we might be able to just call it dark orange. Perception is a tricky thing.

Conventionally, you can specify ordinary 'magenta' or 'fuchsia' with 24 bits of RGB accuracy as #FF00FF (max red, no green, max blue).

 

[Klystron]

In my experience the military thoroughly checks recruit's vision including color perception in order to match people with appropriate occupations. The USAF and USN required electronic technicians with excellent color discretion in order to distinguish markings on resistors and the oft-dramatized 'red and green wires'.

I trained and worked with an excellent but partially color-blind tech who had methods to overcome this slight disability. He was originally trained and operated as a photographic analyst with success. Apparently good color vision was not required to distinguish rocket launchers from steam pipes in high speed fly-over photos. His ability to recognize distant aircraft through telescope images was amazing, along with selecting targets from 'grass' (noise) in raw radar returns.

The color blind PF member's insistence that color remains an illusion corresponds to comments from other people who see the world in shades of grey. One color blind brother-in-law, a successful city editor at large newspapers, understood the majority fascination with color but with an amused skepticism similar to discussing an obscure philosophy or belief system. He conceded that other people valued color but dismissed the concept with a sports analogy. A talented quarterback can distinguish movement and angles on the playing field and throw a pass (or kick a soccer ball) down field far better than he; but he still enjoys watching the game.

 

[sysprog]

@Klystron In HS electronics the prof, who had a PhD in propulsion systems, taught us a somewhat awful mnemonic for the BBROYGBVGW resistor color codes -- I think I shouldn't repeat it here.

 

[Merlin3189]

... your brain can be stimulated to perceive green by having photons of around 440 nm be absorbed by your cones, or have only two wavelengths corresponding to red and blue photons be absorbed in the right ratio on the same area of your retina.

A mixture of red and blue light (yes pleeb, light is coloured!) will give the sensation of a shade of magenta. A redish colour like orange and a bluish colour like cyan might give a very desaturated greenish white.
Some saturated greens can be approximated only by mixtures of greens which are already very close to that green.

What may be confusing, is that colour names are very broad categories. Many colours which we would call "green" are easily discriminable. We can tell they are different, but call them all green.

... we have cones that give us the illusion of color. But nothing is actually colored.

I would suggest the opposite: most macroscopic objects are coloured. You don't even need colour vision to see this. A red object and a green object which looked similar to a monochrome camera when illuminated with a white light, would look very different when illuminated with red or green light. That is due to the properties of the object, not the camera.

If you want an interesting account of colour properties of objects, Why Things Are Coloured is a comprehensive and very understandable site.

We simply interpret shades of gray as color. There is only light and the absence of light to various degrees. ...

There is the prescence to various degrees of lights of different colours.
Your view seems rather like trying to do chemistry while believing that all atoms are equal. Water is 3 atoms, methane is 5 atoms,: their differences are due to the presence or absence of atoms to various degrees, ignoring the differences between atoms.

... All heating coils produce the same hue of red. ...I've yet to find any claim of innate color on any object. ...

Depends on the temperature. Hot objects have a broad spectrum, whose peak moves as the temperature rises. The subjective hue also shifts with temperature.

Look at the Why Things Are Coloured site, if you want to find a claim of innate colour of objects.

To be fair to you, the colour of an object that we see, is also dependent on the illumination, but that doesn't mean it isn't determined by properties of the object. We usually think of objects in terms of their colour in broad spectrum daylight, but are aware that this can be changed say under narrow band low pressure sodium street lights, where everything is a shade of yellow. This is all predictable from the properties of the object.

What is less predictable is how humans see colour in context. This could be regarded as a deficiency of our vision. I think we could build robots who were not fooled by context and saw light objectively.

 

[BillTre]

the colour of an object that we see, is also dependent on the illumination, but that doesn't mean it isn't determined by properties of the object.

It has occurred to me that objects with the color most tied to their composition are fluorescent.
Although fluorescence depends upon an exciting illumination in order to fluoresce, but the single wavelength they emit is a function of their emitting molecules which do not change much (unless they are over-illuminated and get oxidized or otherwise chemically modified).
They can however, be quenched by neighboring molecules that can absorb their emitted wavelength.

 

[sysprog]

Well, as long as we're being specific, aren't the stimulated emitters more precisely the atoms rather than more coarsely the molecules?

 

[BillTre]

Well, as long as we're being specific, aren't the stimulated emitters more precisely the atoms rather than more coarsely the molecules?

Its my somewhat vague understanding that it is the molecule (in modern engineered fluorophores) that determine the absorption and emission properties.
Things like neighboring aromatic groups can be involved.
Wikipedia article here.

There are more fluorophores than there are different kinds of atoms.

 

[Keith_McClary]

Maybe the existence of tree Kangaroos; why has nobody told me about this until now?

 

[sysprog]

You know that this is a fake, and intended as a joke, right?

 

[TeethWhitener]

To expand on @Ibix 's good answer: your brain can be stimulated to perceive green by having photons of around 440 nm be absorbed by your cones, or have only two wavelengths corresponding to red and blue photons be absorbed in the right ratio on the same area of your retina.

Fun fact: the chromophores in the cone cells in your eyes actually have overlapping absorption spectra. Which means even the most intense green you’ll ever see on an object will still involve signals from all three types of cones.

In color theory, there’s even a concept called “supergreen,” which is the hypothetical color that you would see if only your green cone cells were allowed to fire. The really neat thing is that you can actually experience this color:
http://therefractedlight.blogspot.com/2010/09/imaginary-and-impossible-colors.html?m=1

Some colors will saturate your red and blue cones such that you can subsequently preferentially stimulate only the green cones (as seen in the demo at the link above). As the link states, you can’t buy a paint swatch in this color, and you can’t display it on a screen. It’s only a transient phenomenon, as your eyes recover quickly. But the impression is quite vivid.

I for one would welcome a cinematographer taking full advantage of this phenomenon (I haven’t been able to find anyone who’s done this extensively). Simply have a focal character with a vivid monochrome background and suddenly shift to a different monochrome background. The audience then gets the supergreen (or related supercolors) and the filmmaker gets a dramatic visual effect.

 

[pleeb]

I don't know how to describe magenta, but if we pick brown instead we might be able to just call it dark orange. Perception is a tricky thing.

Yes, it is. It's like pressing your fingers against your eyelids and seeing amazing geometries. It no longer works for me I suppose because of my age? I had a friend with a box attached to eyeglasses. When I wore them he fired up the box and I saw colors and geometries that were spectacular. He then revealed that the glasses had only red LEDs in them. The frequencies he dialed up were responsible for the colors I saw.

 

[sysprog]

Yes, it is. It's like pressing your fingers against your eyelids and seeing amazing geometries. It no longer works for me I suppose because of my age? I had a friend with a box attached to eyeglasses. When I wore them he fired up the box and I saw colors and geometries that were spectacular. He then revealed that the glasses had only red LEDs in them. The frequencies he dialed up were responsible for the colors I saw.

Pressing your fingers against your eyelids shows dark inversions (if you try this, please be gentle). Red LEDs cannot show other colors, e.g. blue. What do you mean by "the frequencies he dialed up"? LEDs are color-specific; they're not variable-frequency devices.

From: https://www.lrc.rpi.edu/programs/NLPIP/lightingAnswers/led/color.asp

The material used in the semiconducting element of an LED determines its color. The two main types of LEDs presently used for lighting systems are aluminum gallium indium phosphide (AlGaInP, sometimes rearranged as AlInGaP) alloys for red, orange and yellow LEDs; and indium gallium nitride (InGaN) alloys for green, blue and white LEDs. Slight changes in the composition of these alloys changes the color of the emitted light.​

I hope that you'll re-examine, and appropriately discard, your incorrect input-signal-box variability theory of LED color variegation.

 

[BillTre]

I for one would welcome a cinematographer taking full advantage of this phenomenon (I haven’t been able to find anyone who’s done this extensively). Simply have a focal character with a vivid monochrome background and suddenly shift to a different monochrome background. The audience then gets the supergreen (or related supercolors) and the filmmaker gets a dramatic visual effect.

Interesting idea.
A related phenomena is how certain object-background color combinations can make the object colors really pop.

I think it has to do with the brains opponent color system which should also explain the phenomena you described.
Center-surround neural circuits in the brain and retina are thought to underlie this.

 

[Swamp Thing]

What do you mean by "the frequencies he dialed up"?

I think this has to do with certain artifacts that arise in the brain's visual processing when pulsating light is seen. (And is connected to why flickering light can trigger epilepsy in susceptible people)

https://en.wikipedia.org/wiki/Audio-visual_entrainment#Evidence_of_sensory_effects

Huxley and Walter were among the first to articulate the subjective correlates of photic stimulation. They described subjective experiences of incessantly changing patterns, whose color was a function of the rate of flashing. Between ten and fifteen flashes per second, Walter reported orange and red; above fifteen, green and blue; above eighteen, white and grey.

The subjective visual experience depends on how the flicker frequency matches the brain's own activity in terms of the theta, delta etc. waves.

See also: https://en.wikipedia.org/wiki/Mind_machine

 

[phinds]

@Klystron In HS electronics the prof, who had a PhD in propulsion systems, taught us a somewhat awful mnemonic for the BBROYGBVGW resistor color codes -- I think I shouldn't repeat it here.

That was a completely normal mnemonic in my engineering student days and my early engineering days, but it reminds me that I once had to explain it to a young lady who had apparently had a rather sheltered upbringing before beginning engineering school. She was horrified, but when she then asked me what her lab instructor had meant in telling her that her results were off by just an RCH (a very common phrase those days for a small amount, particularly a small distance or width) and I told her that, I think she decided right then and there that EE was not for her.

 

[sysprog]

I think this has to do with certain artifacts that arise in the brain's visual processing when pulsating light is seen. (And is connected to why flickering light can trigger epilepsy in susceptible people)

https://en.wikipedia.org/wiki/Audio-visual_entrainment#Evidence_of_sensory_effects

The subjective visual experience depends on how the flicker frequency matches the brain's own activity in terms of the theta, delta etc. waves.

The poster (@pleeb) seemed to be claiming that, by use of different input frequencies, different colors were produced by a device which had red-only LEDs:

He then revealed that the glasses had only red LEDs in them. The frequencies he dialed up were responsible for the colors I saw.

Can he honestly say that he saw e.g. orange or green light emitted by a red-emitting LED? I would like him to clarify his claim if he would like to maintain it. It's in my view a fully absurd claim.

 

[Swamp Thing]

I would like him to clarify his claim if he would like to maintain it. It's in my view a fully absurd claim.

I have experimented with this phenomenon, and I have experienced it.

The visual effects are produced in the brain, so it has little to do with the color of the LEDs.

It works best when you have your eyelids closed and the light from the pulsing LEDs is bright enough that some of it gets through your eyelids. As the pulsation frequency varies, you get certain frequencies where you see vivid moving patterns like rotating spirals of small geometric shapes in orange, blue, green etc.

It is a very well known and well documented phenomenon. I first became aware of it from a book my father owned, "The Living Brain" by W. Gray Walter. It is available on archive.org. (I just found this copy a few minutes ago after getting into this discussion). Grey Walter was a pioneer of brain research. If you are interested, you can read the chapter on "Flicker" in that book.

Grey Walter even describes two cases where people experienced this kind of thing when driving / cycling along a road that was overshaded by an avenue of trees. The sunlight flickering through the trees caused them to nearly experience epileptic fits accompanied by vivid visual images.

edit: I think that one can describe it very roughly as a kind of "beat frequency" between the LED's pulsation frequency and the frequencies associated with brain activity. More subtly, the beat effect then modifies the brain's activity in potentially chaotic ways.

 

[sysprog]

That was a completely normal mnemonic in my engineering student days and my early engineering days, but it reminds me that I once had to explain it to a young lady who had apparently had a rather sheltered upbringing before beginning engineering school. She was horrified, but when she then asked me what her lab instructor had meant in telling her that her results were off by just an RCH (a very common phrase those days for a small amount, particularly a small distance or width) and I told her that, I think she decided right then and there that EE was not for her.

One of my Dad's faculty buddies. who taught Classical Greek, was sitting on my family's front porch chatting with me, and he told me that he had previously been fond of opening his first lecture with the remark "the Greek verb has over three thousand forms". Then he would ease the shock by going into ideas about permutations, combinations, prefixes, suffixes, infixes, inflections, etc.. But one time, a girl in the class, as soon as she heard the first sentence, loudly slammed her book shut, and prominently exclaimed "Greek's not for me", and stormed out of the classroom. The Professor with a laugh said that he thereafter stopped opening his first lecture quite that way.

 

[Dr_Nate]

It has occurred to me that objects with the color most tied to their composition are fluorescent.
Although fluorescence depends upon an exciting illumination in order to fluoresce, but the single wavelength they emit is a function of their emitting molecules which do not change much (unless they are over-illuminated and get oxidized or otherwise chemically modified).
They can however, be quenched by neighboring molecules that can absorb their emitted wavelength.

Well, as long as we're being specific, aren't the stimulated emitters more precisely the atoms rather than more coarsely the molecules?

Gaseous atoms, ions, and molecules all have discrete emission spectra. The excitation doesn't need to be from photons; it can also be from bombardment with electrons (in fluorescent tubes electron bombard mercury). There are also often multiple decay pathways so you get out a multiple characteristic emission lines.

 

[sysprog]

@Swamp Thing: That wasn't apparently the claim being made by @pleeb . Perhaps he could, as you did, clarificationally present the idea that the different perceived colors were being made by different rates of light impulse pulsation frequency, Merely asserting that "the frequencies he dialed up were responsible for the colors" I think is insufficient explanation to seem other than implausible.

 

[Keith_McClary]

mnemonic for the BBROYGBVGW

List of electronic color code mnemonics

 

[phinds]

List of electronic color code mnemonics

BORRRing.

 

[sysprog]

BORRRing.

Mr. Roy F. Biv sends his regards.

 

[phinds]

Mr. Roy F. Biv sends his regards.

I like his Russian half-brother Vib Gyor better. Also, you have Roy's middle initial wrong.

 

[DennisN]

List of electronic color code mnemonics

BORRRing.

What?! I've done quite a bit of DIY electronics and you are saying the small color bands on the resistors actually are codes? I thought they were advanced traffic lights for the electrons:

• Red = no electrons may pass
• Yellow = some electrons may pass
• Green = all electrons may pass
• Black = traffic light is not working, electrons may do what they please
• White = darn it's bright today, electrons wear sunglasses

 

[sysprog]

I like his Russian half-brother Vib Gyor better. Also, you have Roy's middle initial wrong.

Middle initial wrong was purposely. In a post, reference was made to 'magenta', which can also be called 'fuchsia' -- it's defined in html by '#ff00ff' -- Roy's correct middle initial, G for green, is defined by fuchsia's converse -- '#00ff00' -- my use of 'F' instead of 'G' was merely me playing around -- I'm glad that someone cared enough to notice . . .

 

[mattt]

I think "the experience of color" is best understood as certain states of parts of the nervous system. I think this way because my dreams are full of colors, even though no photons (of the visible band) hit my retinas at those moments.

Of course you can trigger those states of your nervous system by means of different mechanisms: exciting the cones and rods in your retina, dreaming or just imagining colors with your eyes shut.

 

[melissaa]

Green's theorem is the weirdest most mind¤#%& theorem I have learned about (yet). It doesn't matter how one picks $M$ or $L$, as long as they satisfy certain conditions the result holds. I don't even have the vocabulary to explain why it's so strange.

Same here!

 

[MikeeMiracle]

For me it's the Delayed Choice Quantum Eraser experiment, think about it every night before I sleep.

 

[Frigus]

Bacteriophages,
More appropriately they don't blew my mind but they give me goosebumps,
the thing which really amazes me is to think about the ongoing wars in our body and even on head and in normal life we don't even have any clue about these wars!
To me they seems like some secret agency that is constantly protecting Earth from aliens.