Invisibility

[Modelworks]

I was watching science channel and they had a segment on is it technologically possible to make someone invisible. They had a lot of good info. They did one experiment where you place a pyrex beaker inside a larger pyrex beaker. Then fill the little one with vegetable oil first until it overflows and the bigger beaker is filled too. The smaller beaker will appear to disappear because the index of refraction of the oil and pyrex are the same so it bends the light hiding the smaller one.

They also showed that they discovered how light is transmitted through mediums like glass by it stimulation electrons so they supposed you could gnd the atom causing no light to transfer and that atom becomes invisible. Some labs are doing test but can't do it for longer than a split second and only very very small areas.

Then they did another segment where they brought up something I had never thought about before. If you made someone invisible , how would they see ? The light is not entering the eyes anymore but bending around the person. So they suggested you would have to have some sort of filter for the eyes to allow some light through.

I don't think it is technologically possible with what we have right now, maybe something like a suit made of billions of optical fiber cables bending the light might work. Was wondering what others thought.

 

[MStele]

There is a difference between making something invisible, and making them invisible to the eye. What you saw was an advanced form of camouflage. I think its reasonable to assume that at some point technology will allow the ability to refract light in such a way to prevent its return to source (in much the same way Stealth does with radio waves). I highly doubt they could do it with 100 percent efficiency, but it would prob be enough as long as you don't get close. Also, the entire body would have to be covered with whatever material is used.

True invisibility of a solid object? Can't happen under physics as we currently understand and define it.

 

[cheesehead]

True invisibility of a solid object? Can't happen under physics as we currently understand and define it.

Yes and no.

In theory, a complicated setup of cameras and an OLED poncho could render you invisible to the naked eye, and it's relatively simple (note the use of the word "relative") to make a person invisible to thermal imaging.

However, sonar poses a unique conundrum - you don't know you're being seen by sonar until the sound pulse has already reflected off you. Similarly, X-rays are almost impossible to produce from a small source you can turn on and off quickly (like an OLED), so you'd still show up if anyone was looking.

 

[MStele]

Yes and no.

In theory, a complicated setup of cameras and an OLED poncho could render you invisible to the naked eye, and it's relatively simple (note the use of the word "relative") to make a person invisible to thermal imaging.

However, sonar poses a unique conundrum - you don't know you're being seen by sonar until the sound pulse has already reflected off you. Similarly, X-rays are almost impossible to produce from a small source you can turn on and off quickly (like an OLED), so you'd still show up if anyone was looking.

True invisibility is impossible. What your describing are just more examples of camouflage.

cam⋅ou⋅flage

1. the act, means, or result of obscuring things to deceive an enemy, as by painting or screening objects so that they are lost to view in the background, or by making up objects that have from a distance the appearance of fortifications, guns, roads, etc.

2. concealment by some means that alters or obscures the appearance

3. a device or stratagem used for concealment

4. clothing made of fabric with a mottled design, usually in shades of green and brown, similar to that used in military camouflage.

 

[jackofalltrades]

I believe if you were truly invisable you would also be blind since the eyes need to be struck with photons for you to see. i also do not believe this is possible anyway since you would have to have an enormous power source to bend the light around an object.

 

[DrPizza]

1st - the disappearing beaker - it's not invisible because light rays are bent around the beaker - actually it's the opposite. You can make out the glass because the light rays are bent (refraction) as they travel from one medium to another (pyrex to air to pyrex to air.) Since the index of refraction is very close, the light rays AREN'T refracted - that's why you can't tell there's a surface or edge there where the beaker starts.

2: light can be bent around an object, rendering it invisible through the use of metamaterials. I only have a second to google at the moment - here's an old link:http://physicsworld.com/cws/article/news/24975
If I'm not mistaken, they've done this successfully in the lab with x-rays.

I wouldn't say that it's "technically possible" at the present time, rather I'd say that physics has proven that it isn't impossible.

 

[MStele]

1st - the disappearing beaker - it's not invisible because light rays are bent around the beaker - actually it's the opposite. You can make out the glass because the light rays are bent (refraction) as they travel from one medium to another (pyrex to air to pyrex to air.) Since the index of refraction is very close, the light rays AREN'T refracted - that's why you can't tell there's a surface or edge there where the beaker starts.

2: light can be bent around an object, rendering it invisible through the use of metamaterials. I only have a second to google at the moment - here's an old link:http://physicsworld.com/cws/article/news/24975
If I'm not mistaken, they've done this successfully in the lab with x-rays.

I wouldn't say that it's "technically possible" at the present time, rather I'd say that physics has proven that it isn't impossible.

I have to make an important point here that some keep stepping over. If your "invisibility" relies on ANY technology to facilitate said invisibility then the assumption is that your original object in which you are "making invisible" actually is not changed in any way. Intrinsic invisibility (i.e. The fact that it is invisible without the help of external forces) does happen in the natural word (various gases, air, etc..), but any object that is visible cannot be made invisible without changing its very physical nature, which would change what your trying to hide in the first place (if you make a person intrinsically invisible, it would not be a person anymore).

Physics has proven that its possible to cause perceived invisibility via the use of technology (defined as camouflage), but it is impossible to cause intrinsic invisibility, unless you plan on converting whatever your trying to hide into a gas of some sort, which would suck if your trying to hide a person haha.

 

[Born2bwire]

As Dr. Pizza mentioned, we know theoretically how to create a perfect invisibility cloak using metamaterials. This cloak refracts all incident light around the object so that the object's presence does not affect the light at all, it is perfectly invisible. However, in response to previous questions about the matter, the enclosed object is blind because no light is allowed to reach the object, it is refracted around and back out again. They have been able to experimentally replicate the effect in the microwave region. I doubt they have done so in the x-ray region using metamaterials because I have not heard of metamaterials being made for frequencies higher than RF. However, high energy radiation does not interact very much with materials (hence how x-ray's are so bloody useful). So in a way, I can always choose a high enough frequency of light, shoot it through something, cause large amounts of DNA damage but for the most part have a negligible impact on the radiation.

The main problem with making the invisibility cloak is bandwidth, making a 3D structure, and for general polarizations. Metamaterials are currently very narrow bandwidth and low frequency. It will be a very long time before we could think about doing anything in the visual spectrum. Metamaterials' effects are also very sensitive to loss which is inherent in any medium. A true invisibility cloak would be a spherical ball of metamaterials, which would be an interesting problem to do. This is coupled with the fact that most metamaterials are polarization dependent. For example, we can do a TM metamaterial and a TE but I do not know if we can do TE and TM at the same time yet.

So all of these present very difficult challenges for this to be a truly realizable. Right now, they can only do 2D TE/TM cloaks within a narrow bandwidth.

Interestingly enough, I saw a paper that talked about how Cherenkov radiation can be used to detect the cloak. If we pass relativistic charges through the cloak, the change in the index of refraction can cause Cherenkov radiation. Since the radiation is sourced inside the cloak it will travel through and can be detected. But then again, if you hit the bloody thing with any physical object you should be able to detect it. Might as well just shoot a machine gun in all directions and see what sticks.

 

[Kyanzes]

Without any seriousness, I would like to add that we will probably (assumption) find an alternate solution to this problem. E.g., what if we discover a method which allows for shifting back and forth between dimensions? It would probably render invisibility an outdated concept. Ofc this is some *HEAVY* assumption, I'm just saying.

Also, what if we could teleport between places? It's probably somewhat similar to the previous concept but it would also dethrone invisibility.

Further, what is the real advantage of invisibility? One could say that "Whoa, imagine invisible military assets dewd! And what about invisible observers?"

Well, I assume that everybody reading this thread have already seen the Invisible Man. Inivisiblity has a lot of disadvantages. To list more mundane stuff: rain/snow makes you visible, others bump into you, people who are on your side also can't see you which can be dangerous, invisiblity is susceptible to detection methods other than visual observation.

Now, of course, I also realize that one could always give some reason as to why something shouldn't be done, but I think these are some reasonable concerns. I don't think that there's much to invisibility. Ofc perhaps there's more to it than the eye can see

 

[disappoint]

I believe if you were truly invisable you would also be blind since the eyes need to be struck with photons for you to see. i also do not believe this is possible anyway since you would have to have an enormous power source to bend the light around an object.

Eyes without a face....got no human grace, your eyes without a faa aa a a ce.

Ok assuming you could make a suit that makes you invisible, you'd either have the eyes visible or use a pinhole camera to 'see out of the inviso suit'.

Will it ever be possible? Maybe as theoretically you don't have to break any laws of physics to do so. But technologically we are not there yet.