- · Rings
- · Cloaks
- · Amulets
- · Magical potions
- · Magical spells
- · Mythical creatures (making themselves invisible at will, like leprechauns and Chinese dragons)
But now there are actually devices, claiming to create invisibility fields around objects in real life. But real life invisibility cloaks don’t look like a Harry Potter style robe that completely erases visual presence in an environment, which is what usually comes to your mind when you hear the term. In more realistic movies, invisibility cloaks tend to bend light around an object, making it look as if it’s covered in liquid mirror. In real life, for instance, they often tend to be solid objects that simply play perspective or reflective tricks on the eye( which isn’t even close to what is shown in the movies)
Secret ingredients? Not so secret…
To become invisible, an object must do two things:
- · It has to be able to bend light around itself, so that it casts no shadow, (Meaning: you have to return the light to the same path it was pursuing before it hit the cloak; otherwise it casts a shadow.)
- · It must produce no reflection.
While naturally occurring materials are unable to do this, a new class of materials called METAMATERIALS is now making it possible. These materials are composed of metal and dielectric composite films, created using a nano-transfer printing method. The films are layered in such a way as to create a fishnet-like pattern, which in turn allows the control of visible-spectrum light.
Limitation: “It won’t work for every frequency.”
· The "invisibility shield," created by David R. Smith of Duke University and colleagues, inevitably set the media buzzing with talk of H. G. Wells's invisible man and 's Romulans. Using rings of printed circuit boards, the researchers managed to divert microwaves around a kind of "hole in space"; even when a metal cylinder was placed at the center of the hole, the microwaves behaved as though nothing were there.
The shield consists of concentric circles of fiberglass circuit boards, printed with C-shaped split rings. Microwaves of a particular frequency (limitation alert!!!) behave as if objects inside the cylinder aren’t there--but everything remains in plain view.
· the Rochester Cloak is a surprisingly low-tech response to what is traditionally considered a high-tech problem: making objects invisible.The Rochester Cloak could make anything invisible, as long as the lenses can cover it. Theoretically, that means it's possible to make a military base "disappear" from the visible spectrum if you surround it with big enough lenses.
· A researcher at the University of Texas at Austin has devised an invisibility cloak that could work over a broad range of frequencies, including visible light and microwaves. This is a significant upgrade from current invisibility cloaks that only cloak a very specific frequency — say, a few hertz in the microwave band — and, more importantly, actually make cloaked objects more visible to other frequencies. The UT Austin cloak would achieve this goal by being active and electrically powered.
Recipe 101: make it invisible!
You can make a small invisibility device ( a Rochester cloak) at your home for around $100:
- 1. Obtain two sets of two lenses with different focal lengths. The first set will have one focal length while the other set will have a different focal length. You will have four lenses in total, which should cost you no more than $30. The lens provider will include the focal length information (sometimes denoted as FL) so you don't have to calculate it yourself.
- 2. Using an optics bench, select one lens with the first focal length and a second lens with the second focal length. Separate them by a distance that is the sum of their focal lengths. For example, if your first lens has a focal length of 50 centimeter and your second lens has a focal length of 30 centimeters, then separate these lenses by 5+3 = 8 centimeters.
- 3. Now, do the same with your remaining two lenses.
- 4. Lastly, you need to know how far apart to separate your two sets. This will take a little math, but here's an example using the same measurements in Step 2 D=[2 (3) (5+ 3) ]/ (5- 3) = 12 centimeters should be the distance between your two lenses with the focal length of 3 centimeters.
Why does the world need to be invisible?
The practical applications of an invisibility cloak are exciting in their own right.
· Imagine nurses who can make their hands invisible so they don't obstruct a doctor's view during surgery,
· Trucks kitted with cloaks so they can see right through their blind spots on the highway.
Cloaking technology has more revolutionary applications than just turning a Klingon Bird of Prey invisible. Hopefully we'll see more of this technology for the betterment of human lives.