Perfect Floating Ball Illusion (inspired by Jeff Koons' Art)

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Discussion Overview

The discussion revolves around the creation of a "floating ball illusion" inspired by Jeff Koons' art. Participants explore the physical principles involved, particularly focusing on the refractive indices and densities of different fluids used to achieve the illusion. The scope includes conceptual exploration and technical reasoning regarding the materials and methods that could replicate the effect.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant notes the difference in refractive indices between tap water and saline water, suggesting this is a key factor in replicating the illusion.
  • Another participant proposes that Koons likely used a fluid mix that is clear, more dense than water, and has the same refractive index as water, though they express uncertainty about the feasibility of such a mixture.
  • It is mentioned that Koons used sodium chloride dissolved in water to achieve the desired density, but glycerol is also suggested as an alternative for tuning density.
  • A participant points out that while glycerol can adjust density, it would still result in a noticeable difference in refractive indices, which they wish to avoid.
  • One participant speculates that the ball might not be a solid object but rather a thin-skinned sphere, which could help in hiding distortions due to background differences.
  • There is a suggestion that the difference in refractive index might be negligible at certain degrees, implying that a better-balanced ball could enhance the illusion.

Areas of Agreement / Disagreement

Participants express various hypotheses about the materials used to create the illusion, with no consensus on the exact method or composition. The discussion remains unresolved regarding the best approach to replicate the illusion without noticeable refractive index differences.

Contextual Notes

Participants acknowledge limitations in their understanding of the materials and methods used by Koons, as well as the potential for perceptual factors to influence the effectiveness of the illusion.

Wrichik Basu
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Recently I chanced upon a video from the Royal Institution. The host has tried to replicate a piece of art by Jeff Koons (snapshot from video):

Annotation 2019-08-02 221728.png


At Ri, they have tried to produce the same thing by balancing the ball filled with water, in a tank containing saturated saline water at the bottom, and tap water on top:

Annotation 2019-08-02 221516.png


However, as you can see from the above picture, there is a clear difference in refractive indices between tap water and saline water. But this is not present in the original version.

Any other ideas to create this kind of "floating ball illusion"?
 
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Wrichik Basu said:
Any other ideas to create this kind of "floating ball illusion"?
I assume Koons created a fluid mix that is (1) as clear as water and (2) is more dense than water and (3) has the same refractive index as water. I don't even know if you CAN make such a thing but that's what seems most likely.
 
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Wrichik Basu said:
Recently I chanced upon a video from the Royal Institution. The host has tried to replicate a piece of art by Jeff Koons (snapshot from video):

Any other ideas to create this kind of "floating ball illusion"?

Koons dissolved salt (sodium chloride) in water to achieve the desired density, but you could also use glycerol to tune the density.
 
Andy Resnick said:
Koons dissolved salt (sodium chloride) in water to achieve the desired density, but you could also use glycerol to tune the density
Actually, we don't know what Koons used. The host in the video used salt in water. Glycerol can be used as well, but there will again be a marked difference in refractive indices, which is what I want to eliminate.
 
Wrichik Basu said:
However, as you can see from the above picture, there is a clear difference in refractive indices between tap water and saline water. But this is not present in the original version.
Maybe it is just a matter degree. At some point the difference in refractive index might become not perceivable, but requires a better balanced ball.
 
As this was an illusion, the 'football' may not have been a football but a very thin skinned sphere (balloon), made of a material with a density very near to the mean between fresh and low concentration salt water.
Add to that, the different background in the original image, the distortion could be better hidden.
Illusions make us assume certain things about the situation and that's where the showman sneaks things past our critical faculties. Is there a link to the actual video?
 
sophiecentaur said:
Is there a link to the actual video?
I have put a link in post #1. In that video, you can see the illusion. Other than that, I don't have a link to any other video on the original illusion.