The Theory of Invisibility
Invisibility is a state of which an object cannot be seen, and is a myth that has dated back to many fantasy and science fiction books, such as Harry Potter's cloak of invisibility, or Artemis Fowl's high-vibration suit. To have the ability to turn invisible would be a great advantage in almost all situations, for both government and everyday issues. In most of the traditional fantasy books, an invisible substance is something that either does not reflect light, or absorbs light (allows light to pass through it), although there are no naturally recurring objects that are 100% transparent. However although it seems impossible, scientists have revealed they developing a new material, one that acts as a shawl of invisibility, much like in Harry Potter. This may seem far fetched but when you look at the evidence, it seems that in the distant future, this type of state maybe possible.
As you well know, light is the source of life, and without it earth would not be "The Green Planet". A Muslim scientist called Ibn al-Haytham provided the first correct description of how vision works, stating that it is not caused by light rays emanating from the human eye as Ptolemy and Euclid had thought, but due to light rays entering the eyes. Al-Haytham described light as "streams of minute particles that lack all sensible qualities except energy, and travel at a finite speed". He also argued that the ability to see was because of the sun's rays of light reflecting off objects, and travelled in straight lines. Modern science proves this, and gives us a better understanding of al-Haytham's theories. Basically, we can see an object when light reflects off it. Light travels in straight lines, and shadows are caused by an object blocking the rays of light, making them cut-outs on a surface with light. Imagine a black wall. If you shine a torch on the wall, it will make a circle of yellow light on the wall. However, if you put an object between the light source (the torch) and the receiving object (the wall), this will make the light shine on the object in-between, and since light travels in straight lines, it will block the rays that reach the object between from reaching the wall. This creates a black cut-out among the yellow light. Rays of light alone cannot normally be seen. Try this. shine a torch onto a wall, and you can only see faint light in the path of it, but there is a circle of light on the wall. The visible ray of light is because the dust and small particles in the air are reflecting the light, making it visible. However very powerful beams can be seen, creating a beautiful display.
So how are they attempting to achieve this great feat of invisibility? They intend to bend light around an object. Logically, if the light never reflects off the object, it will never be seen. but since light travels straight and cannot turn without reflecting, scientists think that making "Light waves" are possible, much like radio waves. It is thought by the British that eventually they will be able to produce visible light. The idea of a stone in a river appealed to scientists. A rock in the current of a stream makes the water part, but further downstream there is no evidence at all of a parting of the waters. The believe that if scientist could do that with light, they would be able to make a device that would allow the rays of light to pass around the object, leaving no evidence of it being there and possibly making no shadow whatsoever. Xiang Zhang for the University of California said: "In the case of invisibility cloaks or shields, the material would need to curve light waves completely around the object like a river flowing around a rock. An observer looking at the cloaked object would then see light from behind it, making it seem to disappear."
According to the laws of physics, a perfectly invisible man would have to be blind, no matter which way invisibility was achieved. This is because if no light were to reflect off him, no light would be absorbed by the retinas, allowing him no site. This leaves a mutual blindness, which does not give much advantages in most situations. However if the user was only to stand and hide for a time, letting the danger pass, then take off/turn off the device and regain sight. Although this physical barrier renders the invisibility nearly useless, there are practical ways around it. If the user was to wear goggles that would allow infrared vision and only allow physical light to pass, this would allow him to remain invisible to the human eye, while the user could still see heat sources. There is also the tactic of being practically invisible, so enough light is absorbed to see, but makes the careful observer wary of his position.
In the Thrawn Trilogy of Star Wars, Admiral Thrawn's ship would be able to turn invisible at any time, however everyone inside the ship would not be able see out. This tactic was used to power up invisibility shields until right before battle. In popular video game HALO, the user can earn a cloaking device which leaves only a faint transparent outline visible, to allow enough light to reach the retina. In the video game Quake, the user can find a ring which allows him to be unseen by monsters. In multi-player, only his eyes are visible. With eyes visible, this allows light to be absorbed by the eyes only. In the movie series Predator, the cloaking device is similar to HALO's, except this is debatable, as in the movie it is said that the Predator's see in infrared. However this may be to allow the target a fairer fight, as the Predator's are known to be an honourable race.
So is invisibility possible? Maybe in the far future, when scientists have finished developing cloaking software. But one thing is certain... It will happen, and soon movies won't need special affects to render the actor invisible. With technology advancing faster and faster, so is science, and it will be proved that science is useful for the future of mankind.