Greetings, in the physics forum we've had a discussion on how to make a person invisible. Many people suggested complicated invisibility suits which I won't get into. I had an idea of how we could possibly biologically engineer a human body to be invisible without the need for a suit. I'm hoping you guys can give some input into its plausibility. Its a pretty fun read, enjoy! NON-SUIT SOLUTION Most color as we know it arises from the properties of molecules when their Carbon backbone structure has 'conjugated dienes'. This means in lay terms that there are Carbon atoms strung together with alternating single and double bonds (ie. -C=C-C=C-C=C- etc.). The molecule in Rods and Cones that allows us to 'see' light is also a conjugated diene, called 'cis-11-Retinal'. When a photon strikes 'cis-11-Retinal' it makes a conformational change (changes shape) into 'trans-11-Retinal' and essentially opens up a gate through which a tiny electrical current can now pass through and eventually reach the brain, where you perceive this signal as light. However, 'cis-11-Retinal' is always imbedded in an even larger molecule which is called 'Rhodopsin'. Rhodopsin is a large globular protein (globular basically means spherical) which always has the same basic structure, but there are a variety of Rhodopsin proteins which all vary slightly with the addition of a few atoms here and a few atoms there. Its these small variations that make all the difference to you and I when we perceive the wide variety of colors that we can perceive. For only a specific type of Rhodopsin will allow incident (incoming) light to pass through it and strike the all-important 'cis-11-Retinal' whereupon whenceforth the electrical signal is passed onwards up to the brain. That is why our 3 color sensing cones, namely the L-cone (Red), M-cone (Green) and S-cone (Blue) are only good at sensing the color of light that their specific 'Rhodopsin' protein lets through. With all of this background in mind, consider this possible solution for biological invisibility without the need for a suit: It is possible in theory that you could line your body with Rhodopsin proteins all along the epidermis of your skin and you could then use these proteins to detect all the incoming light around you from all directions (the INPUT part of the problem). Now we come to the more difficult problem of how to get the body to OUTPUT the colors of light we need to perfectly mimic the INPUT signals we have just received. Generating the proper OUTPUT of colors all over your body surface would require each skin 'pixel' to be a maximum size of say 0.1 mm to ensure that no human eye could be visual acute enough (have good enough vision) to see that you are not invisible, even when their proximity to you is within a foot. Recalling that molecules emit color based on their 'conjugated diene' structure, it is forseeable that we could genetically engineer proteins that produce molecules of all the required colors for our OUTPUT. These proteins could be place locally in the epidermis where they would be interspersed in a mosaic beside our INPUT 'Rhodopsins' and then an INPUT 'Rhodopsin' situated 180 degrees (opposite side of the body) could send an electrical signal through a nervous system (a special nervous system suited to connect INPUTS and OUTPUTS) to tell the OUTPUT protein to generate a molecule that's color mimics the 180 degree INPUT. This is my idea of how to create biologically induced invisibility. There are several little quarks that I can think of that would need to be smoothed out, for example since the body is not perfectly spherical, the INPUTS and OUTPUTS would not really be perfectly coupled by 180 degrees. Just think of a woman's breast and her back, clearly the INPUT 180 degrees from her breast would not correspond to the correct mimicry of her OUTPUT on her breast, since her breast is curved and her back flat. But I think that you can appreciate that this problem could be worked through by finding the proper INPUT/ OUTPUT mimicry angles needed for all of your body surfaces and its skin pixels. Other than that, there are a handful of other hurdles to overcome, however I think the guts of my solution is pretty good. What do you think?