This discussion centers on the existence of naturally occurring holograms, with participants debating the definition and examples of holography in nature. Key examples include the interference patterns observed in butterfly wings, oil slicks, and peacock feathers, which exhibit color through constructive interference, akin to holographic effects. Additionally, some starfish possess periodic structures that function as holographic lenses, although the discussion concludes that true holography, defined as wavefront reconstruction from an object, does not occur naturally. The conversation highlights the distinction between holography and other optical phenomena such as diffraction.
PREREQUISITESResearchers in optics, biologists studying structural coloration, and anyone interested in the intersection of natural phenomena and holographic technology will benefit from this discussion.
berkeman said:I'm not aware of too many naturally occurring monochromatic light sources and interfernce within the coherence length.
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).tech99 said:I believe the colour on the wings of butterflies is caused by interference and so may be classed as a hologram.
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.sophiecentaur said:I seem to remember being shown hologram slides in the 60s which were only visible with laser light (in the laser lab at Uni).
sophiecentaur said:I seem to remember
I certainly hope so!sophiecentaur said:Me too.
I seem to remember hoping that, too!Vanadium 50 said:I certainly hope so!
That's quite a stretch. Holography (wavefront reconstruction) generates an image of the original object; what do you propose is the original object here?tech99 said:I believe the colour on the wings of butterflies is caused by interference and so may be classed as a hologram.
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.Mr Green T said:TL;DR Summary: holograms, light, illusions, nature
Do naturally occurring holograms exist?
Can you provide a reference for this?Joe M said: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".
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.Andy Resnick said:generates an image of the original object; what do you propose is the original object here?
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.Joe M said:IIRC, some starfish have periodic structures that are actually holographic lenses, which would be an example of the more typical holographic usage.
I call that diffraction.tech99 said:I believe the colour on the wings of butterflies is caused by interference and so may be classed as a hologram.
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?Hornbein said:I call that diffraction.