Re: [Vo]:Colours with a twist

[H L V]

Good observation, but I don't think the angle of the light source is great
enough to account for the number of helical turns within the
given length of the tube.

harry

On Thu, Sep 21, 2023 at 6:20 PM MSF  wrote:

> One other thing. If you aim a laser into the inside of a transparent tube,
> you get that barber pole effect spiraling around at a greater or lesser
> frequency depending on the angle of the beam into the interior of the tube.
> So that may explain the barber pole in the video.
>
> --- Original Message ---
> On Thursday, September 21st, 2023 at 9:05 PM, MSF <
> foster...@protonmail.com> wrote:
>
> I can't even begin to express how conceptually and experimentally wrong
> this demonstration is. The first thing is the perpetuation of the mistaken
> idea that photons are wiggling in a sinusiodal fashion. When you see that
> sine wave, it's a graph of the varying field as the wave propagates. It's
> not the wave itself. This is such a common miscommunication that physics
> students often have a hard time getting over it.
>
> Just for the sake of context, this guy should have at least mentioned the
> practical application of this phenomenon, which is the polarizing
> saccharimeter. Wine makers, for example, use this device to measure the
> amount of dextrose (glucose) in grape juice so they can harvest the grapes
> at their peak. So next time you're enjoying that glass of wine, think,
> "Mmm...saccharimeter."
>
> The experimental setup in this demonstration has, in my opinion, a fatal
> flaw. The light source seems to be too broad to test the phenomenon.
> Furthermore it appears to be tilted at an angle at the entrance to the
> tube. Both of these factors will have the light glancing off the interior
> of the tube. At least some of the light will be at Brewster's angle for the
> interface between the sugar solution and the tube. So the interior of the
> tube becomes its own polarizer.
>
> Another thing that should have been mentioned is that the light, while
> circularly polarized  in the sugar solution, emerges linearly polarized.
> Maybe that's obvious, but it should have been stated.
>
> Having said all that, it's a hell of a beautiful demonstration. It should
> be repeated with a narrow beam of light just to see the results.
>
> --- Original Message ---
> On Sunday, September 10th, 2023 at 1:15 AM, H L V 
> wrote:
>
> The well known mathematics youtuber 3Blue1Brown recently published two
> interesting videos on polarized light passing through a clear glass tube
> filled with dissolved sugar in water. (He is working on a third video.)
> Normally he explains mathematical concepts with nicely rendered visual
> explanations so the inclusion of a physical demo is something new for his
> channel. The mathematical explanation offered in part 2 seems to
> qualitatively account for what is observed in part 1 but there is a lively
> discussion in the comment section on part 2 where it is pointed out that
> his explanation makes a prediction that he acknowledges is not actually
> observed. I enjoy it when textbook science bumps up against reality! It
> will be interesting to see if he can account for this theoretical weakness
> in his third video.
>
> This demo tests your understanding of light | Barber pole, part 1
> https://www.youtube.com/watch?v=QCX62YJCmGk
> This demo tests your understanding of light | Barber pole, part 2
> https://www.youtube.com/watch?v=aXRTczANuIs=0s
>
> Harry
>
>
>
>

Re: [Vo]:Colours with a twist

[MSF]

One other thing. If you aim a laser into the inside of a transparent tube, you 
get that barber pole effect spiraling around at a greater or lesser frequency 
depending on the angle of the beam into the interior of the tube. So that may 
explain the barber pole in the video.

--- Original Message ---
On Thursday, September 21st, 2023 at 9:05 PM, MSF  
wrote:

> I can't even begin to express how conceptually and experimentally wrong this 
> demonstration is. The first thing is the perpetuation of the mistaken idea 
> that photons are wiggling in a sinusiodal fashion. When you see that sine 
> wave, it's a graph of the varying field as the wave propagates. It's not the 
> wave itself. This is such a common miscommunication that physics students 
> often have a hard time getting over it.
>
> Just for the sake of context, this guy should have at least mentioned the 
> practical application of this phenomenon, which is the polarizing 
> saccharimeter. Wine makers, for example, use this device to measure the 
> amount of dextrose (glucose) in grape juice so they can harvest the grapes at 
> their peak. So next time you're enjoying that glass of wine, think, 
> "Mmm...saccharimeter."
>
> The experimental setup in this demonstration has, in my opinion, a fatal 
> flaw. The light source seems to be too broad to test the phenomenon. 
> Furthermore it appears to be tilted at an angle at the entrance to the tube. 
> Both of these factors will have the light glancing off the interior of the 
> tube. At least some of the light will be at Brewster's angle for the 
> interface between the sugar solution and the tube. So the interior of the 
> tube becomes its own polarizer.
>
> Another thing that should have been mentioned is that the light, while 
> circularly polarized in the sugar solution, emerges linearly polarized. Maybe 
> that's obvious, but it should have been stated.
> Having said all that, it's a hell of a beautiful demonstration. It should be 
> repeated with a narrow beam of light just to see the results.
>
> --- Original Message ---
> On Sunday, September 10th, 2023 at 1:15 AM, H L V  
> wrote:
>
>> The well known mathematics youtuber 3Blue1Brown recently published two 
>> interesting videos on polarized light passing through a clear glass tube 
>> filled with dissolved sugar in water. (He is working on a third video.) 
>> Normally he explains mathematical concepts with nicely rendered visual 
>> explanations so the inclusion of a physical demo is something new for his 
>> channel. The mathematical explanation offered in part 2 seems to 
>> qualitatively account for what is observed in part 1 but there is a lively 
>> discussion in the comment section on part 2 where it is pointed out that his 
>> explanation makes a prediction that he acknowledges is not actually 
>> observed. I enjoy it when textbook science bumps up against reality! It will 
>> be interesting to see if he can account for this theoretical weakness in his 
>> third video.
>>
>> This demo tests your understanding of light | Barber pole, part 1
>> https://www.youtube.com/watch?v=QCX62YJCmGk
>>
>> This demo tests your understanding of light | Barber pole, part 2
>> https://www.youtube.com/watch?v=aXRTczANuIs=0s
>>
>> Harry

Re: [Vo]:Colours with a twist

[MSF]

I can't even begin to express how conceptually and experimentally wrong this 
demonstration is. The first thing is the perpetuation of the mistaken idea that 
photons are wiggling in a sinusiodal fashion. When you see that sine wave, it's 
a graph of the varying field as the wave propagates. It's not the wave itself. 
This is such a common miscommunication that physics students often have a hard 
time getting over it.

Just for the sake of context, this guy should have at least mentioned the 
practical application of this phenomenon, which is the polarizing 
saccharimeter. Wine makers, for example, use this device to measure the amount 
of dextrose (glucose) in grape juice so they can harvest the grapes at their 
peak. So next time you're enjoying that glass of wine, think, 
"Mmm...saccharimeter."

The experimental setup in this demonstration has, in my opinion, a fatal flaw. 
The light source seems to be too broad to test the phenomenon. Furthermore it 
appears to be tilted at an angle at the entrance to the tube. Both of these 
factors will have the light glancing off the interior of the tube. At least 
some of the light will be at Brewster's angle for the interface between the 
sugar solution and the tube. So the interior of the tube becomes its own 
polarizer.

Another thing that should have been mentioned is that the light, while 
circularly polarized in the sugar solution, emerges linearly polarized. Maybe 
that's obvious, but it should have been stated.
Having said all that, it's a hell of a beautiful demonstration. It should be 
repeated with a narrow beam of light just to see the results.

--- Original Message ---
On Sunday, September 10th, 2023 at 1:15 AM, H L V  wrote:

> The well known mathematics youtuber 3Blue1Brown recently published two 
> interesting videos on polarized light passing through a clear glass tube 
> filled with dissolved sugar in water. (He is working on a third video.) 
> Normally he explains mathematical concepts with nicely rendered visual 
> explanations so the inclusion of a physical demo is something new for his 
> channel. The mathematical explanation offered in part 2 seems to 
> qualitatively account for what is observed in part 1 but there is a lively 
> discussion in the comment section on part 2 where it is pointed out that his 
> explanation makes a prediction that he acknowledges is not actually observed. 
> I enjoy it when textbook science bumps up against reality! It will be 
> interesting to see if he can account for this theoretical weakness in his 
> third video.
>
> This demo tests your understanding of light | Barber pole, part 1
> https://www.youtube.com/watch?v=QCX62YJCmGk
>
> This demo tests your understanding of light | Barber pole, part 2
> https://www.youtube.com/watch?v=aXRTczANuIs=0s
>
> Harry

Re: [Vo]:Colours

[H L V]

Sorry, there was a missing character in the final link. Here is the correct
link.
_Goethe’s Theory of Colors from the Perspective of Modern Physics_
https://www.physikdidaktik.uni-wuppertal.de/fileadmin/physik/didaktik/Forschung/Publikationen/Grebe-Ellis/Mack_und_Goethe_Seite_124-137_freigegeben-low.pdf

Harry

On Thu, Aug 31, 2023 at 4:05 PM H L V  wrote:

> What is yellow? by PehrSall
> https://www.youtube.com/watch?v=X_1WiWGndZw
>
> PehrSall is a physicist who is interested in the history and science of
> color theory. He has many video's in which he investigates Newton's and
> Geothe's color theories experimentally.
>
> He also has a video on Land's two color investigations.
> https://www.youtube.com/watch?v=YG4bzGNc1E0
>
> In this beautiful investigation
> _Goethe's Purple Ray - alias Monochromatic Rays of Shadow, the
> Rehabilitation of Darkness_
> https://www.youtube.com/watch?v=vu_7uG6KlsU
> he argues that Newton did not demonstrate that white light consists of
> variously coloured lights  any more than he was able to demonstrate the
> 'absurd' thesis that darkness consists of variously coloured shadows.
> (Personally I am not sure that the absurdity of one thesis should be
> regarded as proof that both theses are unjustified. I am inclined to ask
> what if the absurd thesis were true?)
>
>
> This paper supports my opinion that there is still much to learn about the
> nature of radiation.
>
> Power  Area Density in Inverse Spectra
> https://arxiv.org/ftp/arxiv/papers/1706/1706.09063.pdf
>
> An informal discussion of the results of the same paper in german and
> english with more pictures:
>
> https://www.physikdidaktik.uni-wuppertal.de/fileadmin/physik/didaktik/Forschung/Publikationen/Grebe-Ellis/Mack_und_Goethe_Seite_124-137_freigegeben-low.pd
>
>
> Harry
>
>
> On Sun, Aug 27, 2023 at 2:59 AM MSF  wrote:
>
>> The delay? I don't think we're in a hurry. And clearly no one else on the
>> list has an interest in our discussion.
>>
>> Spectral colors and their perception are my business. I've made literally
>> billions of square meters of diffraction gratings, mostly decorative
>> patterns. Yellow and magenta have been particularly interesting to me for a
>> few reasons. I am of the controversial opinion that yellow doesn't exist
>> except in human perception.
>>
>> Years ago, before lasers became unbelievably inexpensive, I was
>> interested in creating a light source to view transmission holograms
>> without a laser or filtered mercury arc.  I had a lot of slide projectors
>> left over from my "psychedelic light show" so I thought I could use one to
>> make such a light source. I put a slit into the projector where the slide
>> would normally go and a high efficiency Bragg diffraction grating in front
>> of it.  This projected  a nice broad spectrum.  I then used another slit to
>> isolate whatever color I wanted and a cylinder lens to spread it out. This
>> worked quite well, but not very bright. I settled on what would normally be
>> called the yellow part of the spectrum.
>>
>> But people viewing the holograms this way would say that the color was
>> white, or perhaps gray. I thought the same thing.  You have to see this to
>> appreciate it. So maybe Roy G Biv  should change his name. Another example
>> of the phenomenon is a pressure tuned krypton laser.  At just the right gas
>> pressure it makes four more or less equally spaced colors if sent through a
>> prism: red, yellow, green, and two tightly spaced blues. The yellow looks
>> yellow when the other colors are present, but by itself it appears to be
>> colorless. A lot of people smarter than I have argued about these things
>> for a very long time.
>>
>> If you really want to see some strangeness as regards color perception,
>> look up Land color theory. I played around with this when I was a child,
>> and my family thought I was nuts.
>>
>> I just think it's a gift to us that we can perceive color the way we do.
>>
>> --- Original Message ---
>> On Thursday, August 24th, 2023 at 9:10 AM, H L V 
>> wrote:
>>
>> Sorry about the delay.
>>
>> I am not sure. If you think about it, overlapping colours don't go along
>> with the topology of stress lines.
>> However, cellophane tape is a different situation. It could be that the
>> perception of the colour magenta is situational like
>> the perception of yellow.
>>
>>
>> Did you know that a third class of mammalian photoreceptors was
>> discovered in the 1990's?
>> Intrinsically photosensitive retinal ganglion cell were only shown to be
>> definitively present in humans in 2007 in people who were born without rods
>> and cones.
>>
>> From wikipedia " ipRGCs were only definitively detected in humans during
>> landmark experiments in 2007 on rodless, coneless humans.[15]
>> [16]
>>  As
>> had been found in other mammals, the identity of the non-rod non-cone
>> 

Re: [Vo]:Colours

[H L V]

What is yellow? by PehrSall
https://www.youtube.com/watch?v=X_1WiWGndZw

PehrSall is a physicist who is interested in the history and science of
color theory. He has many video's in which he investigates Newton's and
Geothe's color theories experimentally.

He also has a video on Land's two color investigations.
https://www.youtube.com/watch?v=YG4bzGNc1E0

In this beautiful investigation
_Goethe's Purple Ray - alias Monochromatic Rays of Shadow, the
Rehabilitation of Darkness_
https://www.youtube.com/watch?v=vu_7uG6KlsU
he argues that Newton did not demonstrate that white light consists of
variously coloured lights  any more than he was able to demonstrate the
'absurd' thesis that darkness consists of variously coloured shadows.
(Personally I am not sure that the absurdity of one thesis should be
regarded as proof that both theses are unjustified. I am inclined to ask
what if the absurd thesis were true?)


This paper supports my opinion that there is still much to learn about the
nature of radiation.

Power  Area Density in Inverse Spectra
https://arxiv.org/ftp/arxiv/papers/1706/1706.09063.pdf

An informal discussion of the results of the same paper in german and
english with more pictures:
https://www.physikdidaktik.uni-wuppertal.de/fileadmin/physik/didaktik/Forschung/Publikationen/Grebe-Ellis/Mack_und_Goethe_Seite_124-137_freigegeben-low.pd


Harry


On Sun, Aug 27, 2023 at 2:59 AM MSF  wrote:

> The delay? I don't think we're in a hurry. And clearly no one else on the
> list has an interest in our discussion.
>
> Spectral colors and their perception are my business. I've made literally
> billions of square meters of diffraction gratings, mostly decorative
> patterns. Yellow and magenta have been particularly interesting to me for a
> few reasons. I am of the controversial opinion that yellow doesn't exist
> except in human perception.
>
> Years ago, before lasers became unbelievably inexpensive, I was interested
> in creating a light source to view transmission holograms without a laser
> or filtered mercury arc.  I had a lot of slide projectors left over from my
> "psychedelic light show" so I thought I could use one to make such a light
> source. I put a slit into the projector where the slide would normally go
> and a high efficiency Bragg diffraction grating in front of it.  This
> projected  a nice broad spectrum.  I then used another slit to isolate
> whatever color I wanted and a cylinder lens to spread it out. This worked
> quite well, but not very bright. I settled on what would normally be called
> the yellow part of the spectrum.
>
> But people viewing the holograms this way would say that the color was
> white, or perhaps gray. I thought the same thing.  You have to see this to
> appreciate it. So maybe Roy G Biv  should change his name. Another example
> of the phenomenon is a pressure tuned krypton laser.  At just the right gas
> pressure it makes four more or less equally spaced colors if sent through a
> prism: red, yellow, green, and two tightly spaced blues. The yellow looks
> yellow when the other colors are present, but by itself it appears to be
> colorless. A lot of people smarter than I have argued about these things
> for a very long time.
>
> If you really want to see some strangeness as regards color perception,
> look up Land color theory. I played around with this when I was a child,
> and my family thought I was nuts.
>
> I just think it's a gift to us that we can perceive color the way we do.
>
> --- Original Message ---
> On Thursday, August 24th, 2023 at 9:10 AM, H L V 
> wrote:
>
> Sorry about the delay.
>
> I am not sure. If you think about it, overlapping colours don't go along
> with the topology of stress lines.
> However, cellophane tape is a different situation. It could be that the
> perception of the colour magenta is situational like
> the perception of yellow.
>
>
> Did you know that a third class of mammalian photoreceptors was
> discovered in the 1990's?
> Intrinsically photosensitive retinal ganglion cell were only shown to be
> definitively present in humans in 2007 in people who were born without rods
> and cones.
>
> From wikipedia " ipRGCs were only definitively detected in humans during
> landmark experiments in 2007 on rodless, coneless humans.[15]
> [16]
>  As
> had been found in other mammals, the identity of the non-rod non-cone
> photoreceptor in humans was found to be a ganglion cell in the inner
> retina. The researchers had tracked down patients with rare diseases wiping
> out classic rod and cone photoreceptor function but preserving ganglion
> cell function.[15]
> [16]
> 
> Despite having no rods or cones the patients continued to exhibit circadian
> photoentrainment, 

Re: [Vo]:Colours

[MSF]

The delay? I don't think we're in a hurry. And clearly no one else on the list 
has an interest in our discussion.

Spectral colors and their perception are my business. I've made literally 
billions of square meters of diffraction gratings, mostly decorative patterns. 
Yellow and magenta have been particularly interesting to me for a few reasons. 
I am of the controversial opinion that yellow doesn't exist except in human 
perception.

Years ago, before lasers became unbelievably inexpensive, I was interested in 
creating a light source to view transmission holograms without a laser or 
filtered mercury arc. I had a lot of slide projectors left over from my 
"psychedelic light show" so I thought I could use one to make such a light 
source. I put a slit into the projector where the slide would normally go and a 
high efficiency Bragg diffraction grating in front of it. This projected a nice 
broad spectrum. I then used another slit to isolate whatever color I wanted and 
a cylinder lens to spread it out. This worked quite well, but not very bright. 
I settled on what would normally be called the yellow part of the spectrum.

But people viewing the holograms this way would say that the color was white, 
or perhaps gray. I thought the same thing. You have to see this to appreciate 
it. So maybe Roy G Biv should change his name. Another example of the 
phenomenon is a pressure tuned krypton laser. At just the right gas pressure it 
makes four more or less equally spaced colors if sent through a prism: red, 
yellow, green, and two tightly spaced blues. The yellow looks yellow when the 
other colors are present, but by itself it appears to be colorless. A lot of 
people smarter than I have argued about these things for a very long time.

If you really want to see some strangeness as regards color perception, look up 
Land color theory. I played around with this when I was a child, and my family 
thought I was nuts.

I just think it's a gift to us that we can perceive color the way we do.

--- Original Message ---
On Thursday, August 24th, 2023 at 9:10 AM, H L V  wrote:

> Sorry about the delay.
>
> I am not sure. If you think about it, overlapping colours don't go along with 
> the topology of stress lines.
> However, cellophane tape is a different situation. It could be that the 
> perception of the colour magenta is situational like
> the perception of yellow.
>
> Did you know that a third class of mammalian photoreceptors was discovered in 
> the 1990's?Intrinsically photosensitive retinal ganglion cell were only shown 
> to be definitively present in humans in 2007 in people who were born without 
> rods and cones.
>
> From wikipedia " ipRGCs were only definitively detected in humans during 
> landmark experiments in 2007 on rodless, coneless 
> humans.[15](https://en.wikipedia.org/wiki/Photoreceptor_cell#cite_note-ns1-15)[16](https://en.wikipedia.org/wiki/Photoreceptor_cell#cite_note-mnt-16)
>  As had been found in other mammals, the identity of the non-rod non-cone 
> photoreceptor in humans was found to be a ganglion cell in the inner retina. 
> The researchers had tracked down patients with rare diseases wiping out 
> classic rod and cone photoreceptor function but preserving ganglion cell 
> function.[15](https://en.wikipedia.org/wiki/Photoreceptor_cell#cite_note-ns1-15)[16](https://en.wikipedia.org/wiki/Photoreceptor_cell#cite_note-mnt-16)
>  Despite having no rods or cones the patients continued to exhibit circadian 
> photoentrainment, circadian behavioural patterns, melanopsin suppression, and 
> pupil reactions, with peak spectral sensitivities to environmental and 
> experimental light matching that for the melanopsin photopigment. Their 
> brains could also associate vision with light of this frequency."
> Harry

Re: [Vo]:Colours

[H L V]

Sorry about the delay.

I am not sure. If you think about it, overlapping colours don't go along
with the topology of stress lines.
However, cellophane tape is a different situation. It could be that
the perception of the colour magenta is situational like
the perception of yellow.


Did you know that a third class of mammalian photoreceptors was discovered
in the 1990's?
Intrinsically photosensitive retinal ganglion cell were only shown to be
definitively present in humans in 2007 in people who were born without rods
and cones.

>From wikipedia " ipRGCs were only definitively detected in humans during
landmark experiments in 2007 on rodless, coneless humans.[15]
[16]
 As had
been found in other mammals, the identity of the non-rod non-cone
photoreceptor in humans was found to be a ganglion cell in the inner
retina. The researchers had tracked down patients with rare diseases wiping
out classic rod and cone photoreceptor function but preserving ganglion
cell function.[15]
[16]
 Despite
having no rods or cones the patients continued to exhibit circadian
photoentrainment, circadian behavioural patterns, melanopsin suppression,
and pupil reactions, with peak spectral sensitivities to environmental and
experimental light matching that for the melanopsin photopigment. Their
brains could also associate vision with light of this frequency."

Harry



https://arxiv.org/abs/1706.09063

On Wed., Aug. 16, 2023, 5:31 p.m. MSF,  wrote:

> Would it change your mind if you saw the real thing instead of a digital
> representation? All of color photography, both on film and now with digital
> cameras and LCD or OLED screens depend upon acceptable approximations of
> the real colors.  This varies among different cultures.
>
> And now, I delve once more into my misty past. In the late 60s I made a
> meager living doing what was then called a "psychedelic light show" with
> rock bands.  One of the effects I used was a rotating polarizer combined
> with various crystals and injection molded styrene. I used to search
> grocery and hardware stores for suitable pieces. I would then use them as
> is or further stress them by heating and stretching. You can definitely see
> edges of red and blue around the magenta. Something even more definitive
> could be seen when making patterns from the original Scotch cellophane
> tape. After they switched to polypropylene, much to my disappointment at
> the time, the effect was no longer possible. As you rotate the polarizer
> slowly you could see a washed out red, fading into magenta and then blue.
>
> Again, probably more than you wanted to know.
>
>
>
> --- Original Message ---
> On Wednesday, August 16th, 2023 at 2:16 AM, H L V 
> wrote:
>
> Cool. Your story got me to watch videos of stress visualization in plastic
> using polarized light.
> Noticing how readily the colour magenta (a.k.a. pink ) is produced in this
> video as the plastic is rotated.
> https://www.youtube.com/watch?v=-6U4uembaNQ
>
> Watching how the magenta patches come and go as the viewing angle changes
> got me thinking about the common teaching that since magenta does not
> appear in Newton's spectrum it is made up by the brain whenever red and
> blue light overlap. (By contrast magenta does appear in Goethe's spectrum
> a.k.a the dark spectrum).
>
> Although it is certainly possible to trick the brain into seeing colours
> which aren't there such as when red and green light overlap to create the
> illusion of yellow light, this is not proof that magenta is just made up by
> the brain. On the contrary if magenta were just made up by the brain then
> _every_ instance of magenta in the above video should show signs of red and
> blue around its perimeter which is not the case.
>
> Harry
>
>
> On Mon, Aug 14, 2023 at 5:16 PM MSF  wrote:
>
>> More polarized fun...
>>
>> A much more easily viewed demonstration of the effect we are discussing
>> here is looking at clear glass table tops outside. If you happen to have
>> some lawn furniture that includes a clear tempered glass table top, all you
>> have to do is stand to the east or west of of the glass and look down at it
>> at an angle of approximately 56 degrees and you will see beautiful pools of
>> color. The colors outline the birefringence caused by the strains in the
>> tempered glass.
>>
>> Once in a while a random observation at my back yard of the phenomenon by
>> a friend or family member will be alarmed at "something wrong with the
>> glass". And of course, their eyes glaze over when I try to explain it.
>>
>> You might wonder why I immediately recognized Harry's noticing of
>> mysterious color effects during his walk. It's simple. When I was very
>> young, I used to see these colors in the 

Re: [Vo]:Colours

[MSF]

Would it change your mind if you saw the real thing instead of a digital 
representation? All of color photography, both on film and now with digital 
cameras and LCD or OLED screens depend upon acceptable approximations of the 
real colors. This varies among different cultures.

And now, I delve once more into my misty past. In the late 60s I made a meager 
living doing what was then called a "psychedelic light show" with rock bands. 
One of the effects I used was a rotating polarizer combined with various 
crystals and injection molded styrene. I used to search grocery and hardware 
stores for suitable pieces. I would then use them as is or further stress them 
by heating and stretching. You can definitely see edges of red and blue around 
the magenta. Something even more definitive could be seen when making patterns 
from the original Scotch cellophane tape. After they switched to polypropylene, 
much to my disappointment at the time, the effect was no longer possible. As 
you rotate the polarizer slowly you could see a washed out red, fading into 
magenta and then blue.

Again, probably more than you wanted to know.

--- Original Message ---
On Wednesday, August 16th, 2023 at 2:16 AM, H L V  wrote:

> Cool. Your story got me to watch videos of stress visualization in plastic 
> using polarized light.
> Noticing how readily the colour magenta (a.k.a. pink ) is produced in this 
> video as the plastic is rotated.
> https://www.youtube.com/watch?v=-6U4uembaNQ
>
> Watching how the magenta patches come and go as the viewing angle changes got 
> me thinking about the common teaching that since magenta does not appear in 
> Newton's spectrum it is made up by the brain whenever red and blue light 
> overlap. (By contrast magenta does appear in Goethe's spectrum a.k.a the dark 
> spectrum).
>
> Although it is certainly possible to trick the brain into seeing colours 
> which aren't there such as when red and green light overlap to create the 
> illusion of yellow light, this is not proof that magenta is just made up by 
> the brain. On the contrary if magenta were just made up by the brain then 
> _every_ instance of magenta in the above video should show signs of red and 
> blue around its perimeter which is not the case.
>
> Harry
>
> On Mon, Aug 14, 2023 at 5:16 PM MSF  wrote:
>
>> More polarized fun...
>>
>> A much more easily viewed demonstration of the effect we are discussing here 
>> is looking at clear glass table tops outside. If you happen to have some 
>> lawn furniture that includes a clear tempered glass table top, all you have 
>> to do is stand to the east or west of of the glass and look down at it at an 
>> angle of approximately 56 degrees and you will see beautiful pools of color. 
>> The colors outline the birefringence caused by the strains in the tempered 
>> glass.
>>
>> Once in a while a random observation at my back yard of the phenomenon by a 
>> friend or family member will be alarmed at "something wrong with the glass". 
>> And of course, their eyes glaze over when I try to explain it.
>>
>> You might wonder why I immediately recognized Harry's noticing of mysterious 
>> color effects during his walk. It's simple. When I was very young, I used to 
>> see these colors in the pavement all the time, directly on, not peripherily. 
>> The reason is my brother and I were blessed, or cursed, with vision that was 
>> so sharp and light sensitive that we were accused all the time of "seeing 
>> things". We tested out at 20-05 on the eye charts. Our retinas must have 
>> been so stuffed withe rods and cones, I'm surprised they didn't explode. I 
>> could see close to 7th magnitude stars. That's all gone now that I'm old. 
>> Down to 20-20 with lens implants.
>>
>> Please pardon my self-indulgent nostalgia.
>>
>> MSF
>>
>

Re: [Vo]:Colours

[H L V]

The demonstrations given by this lecturer are more refined so it is easier
to observe how magenta arises in proximity to other colours.
https://www.youtube.com/watch?v=PqZ1THDGD34

The idea that real or objective colour is reducible to a single parameter
known as wavelength seems to me simplistic and wrong. Even with the domain
of the hard sciences, colour should be treated as
a multidimensional phenomena.

Harry

On Tue, Aug 15, 2023 at 10:16 PM H L V  wrote:

> Cool. Your story got me to watch videos of stress visualization in plastic
> using polarized light.
> Noticing how readily the  colour magenta (a.k.a. pink ) is produced in
> this video as the plastic is rotated.
> https://www.youtube.com/watch?v=-6U4uembaNQ
>
> Watching how the magenta patches come and go as the viewing angle changes
> got me thinking about the common teaching that since magenta
> does not appear in Newton's spectrum it is made up by the brain whenever
> red and blue light overlap. (By contrast magenta does appear in Goethe's
> spectrum a.k.a the dark spectrum).
>
> Although it is certainly possible to trick the brain into seeing colours
> which aren't there such as when red and green light overlap to create the
> illusion of yellow light, this is not proof that magenta is just made up by
> the brain. On the contrary if magenta were just made up by the brain then
> _every_ instance of magenta in the above video should show signs of red and
> blue around its perimeter which is not the case.
>
> Harry
>
>
> On Mon, Aug 14, 2023 at 5:16 PM MSF  wrote:
>
>> More polarized fun...
>>
>> A much more easily viewed demonstration of the effect we are discussing
>> here is looking at clear glass table tops outside. If you happen to have
>> some lawn furniture that includes a clear tempered glass table top, all you
>> have to do is stand to the east or west of of the glass and look down at it
>> at an angle of approximately 56 degrees and you will see beautiful pools of
>> color. The colors outline the birefringence caused by the strains in the
>> tempered glass.
>>
>> Once in a while a random observation at my back yard of the phenomenon by
>> a friend or family member will be alarmed at "something wrong with the
>> glass".  And of course, their eyes glaze over when I try to explain it.
>>
>> You might wonder why I immediately recognized Harry's noticing of
>> mysterious color effects during his walk. It's simple. When I was very
>> young, I used to see these colors in the pavement all the time, directly
>> on, not peripherily. The reason is my brother and I were blessed, or
>> cursed, with vision that was so sharp and light sensitive that we were
>> accused all the time of "seeing things". We tested out at 20-05 on the eye
>> charts. Our retinas must have been so stuffed withe rods and cones, I'm
>> surprised they didn't explode. I could see close to 7th magnitude stars.
>> That's all gone now that I'm old. Down to 20-20 with lens implants.
>>
>> Please pardon my self-indulgent nostalgia.
>>
>> MSF
>>
>>
>>
>>
>>
>>>
>>>
>>

Re: [Vo]:Colours

[H L V]

Cool. Your story got me to watch videos of stress visualization in plastic
using polarized light.
Noticing how readily the  colour magenta (a.k.a. pink ) is produced in this
video as the plastic is rotated.
https://www.youtube.com/watch?v=-6U4uembaNQ

Watching how the magenta patches come and go as the viewing angle changes
got me thinking about the common teaching that since magenta
does not appear in Newton's spectrum it is made up by the brain whenever
red and blue light overlap. (By contrast magenta does appear in Goethe's
spectrum a.k.a the dark spectrum).

Although it is certainly possible to trick the brain into seeing colours
which aren't there such as when red and green light overlap to create the
illusion of yellow light, this is not proof that magenta is just made up by
the brain. On the contrary if magenta were just made up by the brain then
_every_ instance of magenta in the above video should show signs of red and
blue around its perimeter which is not the case.

Harry


On Mon, Aug 14, 2023 at 5:16 PM MSF  wrote:

> More polarized fun...
>
> A much more easily viewed demonstration of the effect we are discussing
> here is looking at clear glass table tops outside. If you happen to have
> some lawn furniture that includes a clear tempered glass table top, all you
> have to do is stand to the east or west of of the glass and look down at it
> at an angle of approximately 56 degrees and you will see beautiful pools of
> color. The colors outline the birefringence caused by the strains in the
> tempered glass.
>
> Once in a while a random observation at my back yard of the phenomenon by
> a friend or family member will be alarmed at "something wrong with the
> glass".  And of course, their eyes glaze over when I try to explain it.
>
> You might wonder why I immediately recognized Harry's noticing of
> mysterious color effects during his walk. It's simple. When I was very
> young, I used to see these colors in the pavement all the time, directly
> on, not peripherily. The reason is my brother and I were blessed, or
> cursed, with vision that was so sharp and light sensitive that we were
> accused all the time of "seeing things". We tested out at 20-05 on the eye
> charts. Our retinas must have been so stuffed withe rods and cones, I'm
> surprised they didn't explode. I could see close to 7th magnitude stars.
> That's all gone now that I'm old. Down to 20-20 with lens implants.
>
> Please pardon my self-indulgent nostalgia.
>
> MSF
>
>
>
>
>
>>
>>
>

Re: [Vo]:Colours

[MSF]

More polarized fun...

A much more easily viewed demonstration of the effect we are discussing here is 
looking at clear glass table tops outside. If you happen to have some lawn 
furniture that includes a clear tempered glass table top, all you have to do is 
stand to the east or west of of the glass and look down at it at an angle of 
approximately 56 degrees and you will see beautiful pools of color. The colors 
outline the birefringence caused by the strains in the tempered glass.

Once in a while a random observation at my back yard of the phenomenon by a 
friend or family member will be alarmed at "something wrong with the glass". 
And of course, their eyes glaze over when I try to explain it.

You might wonder why I immediately recognized Harry's noticing of mysterious 
color effects during his walk. It's simple. When I was very young, I used to 
see these colors in the pavement all the time, directly on, not peripherily. 
The reason is my brother and I were blessed, or cursed, with vision that was so 
sharp and light sensitive that we were accused all the time of "seeing things". 
We tested out at 20-05 on the eye charts. Our retinas must have been so stuffed 
withe rods and cones, I'm surprised they didn't explode. I could see close to 
7th magnitude stars. That's all gone now that I'm old. Down to 20-20 with lens 
implants.

Please pardon my self-indulgent nostalgia.

MSF

>>>

Re: [Vo]:Colours

[Jürg Wyttenbach]

Here a practical link for optical calculations like Brewster angle


https://refractiveindex.info/?shelf=main=Ni=Johnson



J.W.


Thanks for the feedback.
I had not heard of Brewster's angle.
I will need time to consider these suggestions.

Harry

On Fri, Aug 11, 2023 at 3:11 PM MSF  wrote:

We call them "colors" down here south of the border, Harry. But to
your question, yes I have experienced the same phenomenon. Keep in
mind that peripheral vision is more light sensitive than foveal
vision.

I can think of two possibilities to explain the phenomenon. Light
from the clear sky is partially polarized along a north to south
axis. So if you are walking in a mostly north or south direction
you would see these colors to your left or right as the angle to
the area you are observing is around Brewster's angle. They would
be secondary colors.

Alternatively, it might just be a very thin oil slick formed from
the asphalt and you need the more sensitive peripheral vision to
perceive it.

More than you wanted to know, probably.

--- Original Message ---
On Wednesday, August 9th, 2023 at 7:36 PM, H L V
 wrote:


This summer I have been walking to work in the morning during
twilight just before the sun rises.
As I walk across asphalt paved streets which are old and
cracking, sometimes I see very faint bands of colour
in my peripheral vision when I am looking at the pavement. When
it happens I am walking roughly southward ( at 46 degrees north
latitude) and the bands seem to appear on the left side of my
peripheral vision. The colours remind more of those found in the
Goethe spectrum rather than the rainbow spectrum. I wondered if
it might be an effect of LED street lighting reflecting off the
pavement but sometimes it seems to arise far from any LED street
lights. Has anyone else experienced this?

Harry






--
Jürg Wyttenbach
Bifangstr. 22
8910 Affoltern am Albis

+41 44 760 14 18
+41 79 246 36 06

Re: [Vo]:Colours

[H L V]

Thanks for the feedback.
I had not heard of Brewster's angle.
I will need time to consider these suggestions.

Harry

On Fri, Aug 11, 2023 at 3:11 PM MSF  wrote:

> We call them "colors" down here south of the border, Harry. But to your
> question, yes I have experienced the same phenomenon. Keep in mind that
> peripheral vision is more light sensitive than foveal vision.
>
> I can think of two possibilities to explain the phenomenon. Light from the
> clear sky is partially polarized along a north to south axis. So if you are
> walking in a mostly north or south direction you would see these colors to
> your left or right as the angle to the area you are observing is around
> Brewster's angle. They would be secondary colors.
>
> Alternatively, it might just be a very thin oil slick formed from the
> asphalt and you need the more sensitive peripheral vision to perceive it.
>
> More than you wanted to know, probably.
>
> --- Original Message ---
> On Wednesday, August 9th, 2023 at 7:36 PM, H L V 
> wrote:
>
> This summer I have been walking to work in the morning during twilight
> just before the sun rises.
> As I walk across asphalt paved streets which are old and cracking,
> sometimes I see very faint bands of colour
> in my peripheral vision when I am looking at the pavement. When it happens
> I am walking roughly southward ( at 46 degrees north latitude) and the
> bands seem to appear on the left side of my peripheral vision. The colours
> remind more of those found in the Goethe spectrum rather than the rainbow
> spectrum. I wondered if it might be an effect of LED street lighting
> reflecting off the pavement but sometimes it seems to arise far from any
> LED street lights. Has anyone else experienced this?
>
> Harry
>
>
>
>
>

Re: [Vo]:Colours

[MSF]

We call them "colors" down here south of the border, Harry. But to your 
question, yes I have experienced the same phenomenon. Keep in mind that 
peripheral vision is more light sensitive than foveal vision.

I can think of two possibilities to explain the phenomenon. Light from the 
clear sky is partially polarized along a north to south axis. So if you are 
walking in a mostly north or south direction you would see these colors to your 
left or right as the angle to the area you are observing is around Brewster's 
angle. They would be secondary colors.

Alternatively, it might just be a very thin oil slick formed from the asphalt 
and you need the more sensitive peripheral vision to perceive it.
More than you wanted to know, probably.

--- Original Message ---
On Wednesday, August 9th, 2023 at 7:36 PM, H L V  wrote:

> This summer I have been walking to work in the morning during twilight just 
> before the sun rises.
> As I walk across asphalt paved streets which are old and cracking, sometimes 
> I see very faint bands of colour
> in my peripheral vision when I am looking at the pavement. When it happens I 
> am walking roughly southward ( at 46 degrees north latitude) and the bands 
> seem to appear on the left side of my peripheral vision. The colours remind 
> more of those found in the Goethe spectrum rather than the rainbow spectrum. 
> I wondered if it might be an effect of LED street lighting reflecting off the 
> pavement but sometimes it seems to arise far from any LED street lights. Has 
> anyone else experienced this?
>
> Harry

[Vo]:Colours

[H L V]

This summer I have been walking to work in the morning during twilight just
before the sun rises.
As I walk across asphalt paved streets which are old and cracking,
sometimes I see very faint bands of colour
in my peripheral vision when I am looking at the pavement. When it happens
I am walking roughly southward ( at 46 degrees north  latitude) and the
bands seem to appear on the left side of my peripheral vision. The colours
remind more of those found in the Goethe spectrum rather than the rainbow
spectrum. I wondered if it might be an effect of LED street lighting
reflecting off the pavement but sometimes it seems to arise far from any
LED street lights. Has anyone else experienced this?

Harry