Invisibility

[TJWDD]

Invisibility, is it possible? If so how would you suggest doing it? Answers including active/optical camouflage as well as real invisibility welcome! Thanks

[RyanJ]

Such a thing has been done, with microwaves anyway. Look up negative refractive index or metamaterial on the internet and you'll find plenty of interesting articles about it.

[DrP]

There is also the James Bond style cloack that used conducting polymers to project an image on one one side of his car that cameras took from the other side. The Japanease done this with a coat. http://www.howstuffworks.com/invisibility-cloak.htm

[happy snapper]

Invisibility, is it possible? If so how would you suggest doing it? Answers including active/optical camouflage as well as real invisibility welcome! Thanks

 

Take a flat object cover it with a lcd display.Tiny cameras on back of same object.As the lcd display will show exactly what is behind object then object itself can not be seen..Or make an object from very thin glass and you cant see it.Have an object move away from you at the speed of light and you wont see it as the light will never reach you..Id say there are 2 problems with invisibility 1st You must stop the object from reflecting light..2nd You must capture any light that falls on the object and bend it around the object so that apears as if from the same sorce as if the object isnt there.Or make an object transparent..Beam me up SCOTTY

[TJWDD]

Thanks 4 the response could sum1 explain what a negative refractive index is?

[Mr Skeptic]

Proper invisibility is probably impossible.

[Phi for All]

Invisibility, is it possible? If so how would you suggest doing it? Answers including active/optical camouflage as well as real invisibility welcome! Thanks

Did you have an idea of a specific object you want to make invisible? That would help guide practical suggestions quite a bit.

[TJWDD]

Did you have an idea of a specific object you want to make invisible? That would help guide practical suggestions quite a bit.

your head or your torso

[Ouroboros]

Proper invisibility is probably impossible.

 

Mr Skeptic living up to his name there.

 

In terms of bending light around an object, a huge gravitational force would do the trick. Though given we are talking about cloaking your head, black holes probably aren't the best solution. (Maybe try standing next to the LHC and crossing your fingers..)

 

Travelling along another time line. Or travelling along the same timeline at a slightly faster/slower speed.

 

I can imagine its easy to alter the way the observer sees the object, than altering the object its self. Try exploiting the flaws of the mind through optical illusions or psychological trickery.

 

Failing that, the more materialist and obvious solution is fibre optics. the 007 suggestions above etc

[Cap'n Refsmmat]

Black holes would bend light around them, but the light on a direct path through the hole would never make it through, so there would be a noticeable dark spot. There are simulated images of what you'd see looking at a black hole somewhere on the Internet...

[Phi for All]

your head or your torso

Camouflage is probably the most practical method. You would need to think about where you want this invisibility to take place, the background, light sources and your audience. Your camouflage needs to break up the normal recognizable pattern of your head and torso. The human eye is always looking for patterns so you can use makeup and mottled coloring in your clothing to make yourself blend into a different recognizable pattern. Dark grays mixed with black are better than all black at night.

[Mr Skeptic]

Mr Skeptic living up to his name there.

 

Very well, let me state my reasoning. Suppose you want to make an invisibility cloak transparent to all wavelengths of light. Then it would need to be invisible to, for example, gamma rays. Now meta materials can be used to have an index of refraction lower than that of a vacuum. However, the ones we have would only work for a very small range of wavelengths. The smaller your wavelength, the smaller the meta materials must be. That's all well and good when you have a wavelength larger than say molecules. But if you want to be invisible to gamma rays as well, you'd need to have structures smaller than the atoms you build them with, which is not going to happen. So as far as we know it is impossible to be invisible to all electromagnetic waves. There may be a different way to do it.

 

Of course, you could also make something that changes its appearance like a chameleon based on the stuff behind it. However, to do it for a full 360 degrees you would need to be covered with cameras while also being covered with a screen that can change appearance. This seems unlikely. In addition, you would need to be able to generate a very wide spectrum of electromagnetic waves at varying brightness, and have a material that reflects absolutely no light. Both of these seem unlikely. At least with this method you wouldn't be blind.

 

And if you are warmer than your surroundings, you will be showing up on infrared regardless.

 

And that's just for light. After going through all that trouble it would be a shame if people could detect you via other methods, such as sound you produce, a disturbance in the air flow, gravitational effects, etc.

[Ouroboros]

Camouflage is probably the most practical method. You would need to think about where you want this invisibility to take place, the background, light sources and your audience. Your camouflage needs to break up the normal recognizable pattern of your head and torso. The human eye is always looking for patterns so you can use makeup and mottled coloring in your clothing to make yourself blend into a different recognizable pattern. Dark grays mixed with black are better than all black at night.

 

In dim light we predominantly see with the rod cells of the retina (those responsible for black and white), so under cover of night, the best camouflage would definitely be a grey blend/pattern.

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Of course, you could also make something that changes its appearance like a chameleon based on the stuff behind it.

 

Maybe not if your looking for an invisibility cloak, but genetics could certainly be the way to go! There has been a lot of research over the last decade looking into the genetic make-up of jelly fish and other translucent deep sea creatures...

[Klaynos]

I work in metamaterials....

 

And my comment is, give up... If you want to hid your head/torso you want camouflage, you also want to stop yourself giving off too much heat so some kind of IR absorber in the clothing as well... Now if you want to be really clever you could think of active camouflage that changes the pattern to better match what you are against. DPM 95 which is the standard British camourflag isn't too great in urban environments, green stands out against gray, but I've used it in very wet, muddy European wooded areas and you pretty much walk into people before you see them if they are stood still.

[bigbadjesus]

There are a variety of ways. Google photonic bandgap and metamaterials, for a start. Photonic bandgaps also allow for the conversion of environmental light into electricity much more efficiently than photovoltaics.