B Any examples of naturally occurring holograms?

[Mr Green T]

TL;DR Summary

holograms, light, illusions, nature

Just downloaded a very interesting trail camera video that appears to contain a holographic red dome on the ground. Highest probability it's internal to the lenses and some reflection. It caused me to do a bit of fruitless searching on the topic of naturally occurring holograms. Do naturally occurring holograms exist?

 

[berkeman]

How are you defining a hologram? What in the trail camera pictures reminded you of holography? I'm not aware of too many naturally occurring monochromatic light sources and interfernce within the coherence length...

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

 

[tech99]

I believe the colour on the wings of butterflies is caused by interference and so may be classed as a hologram.

 

[Joe M]

Mr. Green T has it. Butterfly wing colors, as well as those colored rings on oil-covered water and the color of peacock feathers, are all the result of constructive structured interference. This is mathematically identical to a hologram, creating a "false color" in white light, although not generating the displacement optical illusion we usually think of.

IIRC, some starfish have periodic structures that are actually holographic lenses, which would be an example of the more typical holographic usage. These are not the well-known eyespots on the tips of the arms, but scattered along the "skin".

 

[sophiecentaur]

I'm not aware of too many naturally occurring monochromatic light sources and interfernce within the coherence length.

I believe the colour on the wings of butterflies is caused by interference and so may be classed as a hologram.

I think it's only a matter of degree but that may be crucial for the definition of 'hologram' to apply. The bands of colour you see in a thin film have very low spatial frequency across the film and only require low coherence of the illumination (only the order of the thickness of the film).

OTOH, holograms that are created optically do not need high coherence of the light that they are viewed by. However, I seem to remember being shown hologram slides in the 60s which were only visible with laser light (in the laser lab at Uni).

Evolution is great though; it often (/always?) produces structures (variation of the hard chitin that insects are built of) in a way that 'designers' never would. It works by positive reinforcement of a design that gives a good result. (Hmm; a bit like some of my attempts at electronics along the lines of a blind watchmaker)

 

[JoshS]

https://zenodo.org/records/11269384

 

[sophiecentaur]

I seem to remember being shown hologram slides in the 60s which were only visible with laser light (in the laser lab at Uni).

Me too. Also, the 'apparently' special requirements for holography seem to have eased (thick concrete benches etc.). Maybe the coherence length of the source lasers is much higher and the chromatic aberration of the optics may be lower. That would affect the contrast range of the holograms.
Some of the staff seemed to have less than perfect understanding about the 'philosophy' behind holography. When we undergrads asked smartarse questions they went a bit wobbly. lol

 

[Vanadium 50]

I seem to remember

Me too.

I certainly hope so!

 

[sophiecentaur]

I certainly hope so!

I seem to remember hoping that, too!

 

[Baluncore]

After the escape of all the "curses upon mankind" from Pandora's box, nothing remained in the box but "Hope".
One of the curses released, was memory loss in the second childhood.

 

[Andy Resnick]

I believe the colour on the wings of butterflies is caused by interference and so may be classed as a hologram.

That's quite a stretch. Holography (wavefront reconstruction) generates an image of the original object; what do you propose is the original object here?

 

[Andy Resnick]

TL;DR Summary: holograms, light, illusions, nature

Do naturally occurring holograms exist?

No. A hologram is a recorded interference pattern that, when illuminated correctly, reconstructs a wavefront generated from a (previously illuminated) object. I am not aware of such a naturally occurring phenomenon.

 

[Andy Resnick]

IIRC, some starfish have periodic structures that are actually holographic lenses, which would be an example of the more typical holographic usage. These are not the well-known eyespots on the tips of the arms, but scattered along the "skin".

Can you provide a reference for this?

 

[sophiecentaur]

generates an image of the original object; what do you propose is the original object here?

But it is possible to generate holograms from a mathematical model. Structures of tens of nm can be made to achieve this but microwave and sound holograms are possible.
A search seems to throw up a lot of "AI generated hologram" hits but there's a lot of marketing nonsense all over that area. Princess Leia still has a lot to answer for, I think.

 

[Baluncore]

IIRC, some starfish have periodic structures that are actually holographic lenses, which would be an example of the more typical holographic usage.

Starfish do have photophores that can produce light from their skin. I found no details about the complexity of the organ in starfish. In cephalopods and fish, the photophore can flash and flicker, change colour and may have an optical lens.
https://en.wikipedia.org/wiki/Photophore

 

[Hornbein]

I believe the colour on the wings of butterflies is caused by interference and so may be classed as a hologram.

I call that diffraction.

 

[sophiecentaur]

I call that diffraction.

So would I. The term 'hologram' implies much more than mere interference; if not, then Newton's Rings would also be holograms. And, at longer wavelengths, so would electronically steerable radio antenna arrays. Where would oe stop?