What would you do if you had the power to become invisible? Hiding in the changing room is too clichéd. How about getting free gas at the pump? Or no more hiding in the closet when your partner’s spouse comes home.
What wouldn’t we do to be invisible like the fictitious invisible girl.
Source: http://images.fanpop.com/images/image_uploads/Invisible-Girl-3-fantastic-four-244983_1280_800.jpg
Or Mr. India, for that matter.
Source: http://www.imdb.com/title/tt0093578/
We’ve got great news: Invisibility may soon be a reality.
Source: http://www.ibtimes.co.uk/invisibility-cloak-may-soon-be-reality-say-german-physicists-1452320
How is this all possible, you ask? Remember refraction? Well it’s going to help us do naughty things. 
Light travels something like this when it goes from air to water to air.
Source: http://www.thephysicsmill.com/2013/02/17/refraction-how-we-see-through-the-looking-glass/
It’s not so much that the light slows down — it just spends more time interacting with electrons in the water compared to air.
Imagine a wedding couple moving through a reception hall filled with guests. The wedding couple being the light beam and the guests being the electrons in the material of the receptions hall. They’d have to stop at each guest and exchange pleasantries right? They’re still travelling at the same pace but their net speed by the time they come out is much less, and thus they appear to slow down.
Source: http://fantasyweddingphotography.com/blog/wp-content/uploads/2012/09/Vancouver_Wedding_Dance_Party.jpg
Incidentally, this path of refraction is also the path that takes the least amount of time! So don’t worry, Mr. and Mrs. Newly Weds, you are doing the best job you can do! Cake is on the horizon.
Source: http://4.bp.blogspot.com/-FGOftt74gJg/UlmLDEFd4zI/AAAAAAAAAVI/NpqbqhHhS8w/s1600/vlcsnap-2013-10-12-12h53m20s174.jpg
Aha! Now how much time light takes interacting with all the material of something defines the refractive index of that something! And it’s this property of materials that scientists are trying to manipulate to make things invisible!
It’s also this property of materials that helps us see them! If everything had the same refractive index, we wouldn’t be able to distinguish one object from another. Don’t believe us? Try this at home.
The glass in the center disappears because glass and oil have the same refractive index! Bizzare!
Clever scientists have now created something called metamaterials that make light do some cool yoga stuff. They bend light backwards and create a negative refractive index to achieve this effect:
Source: http://www.berkeley.edu/news/media/releases/2008/08/11_light.shtml
Combining metamaterials with other cool light bending technology, researchers at Duke have made their first prototype of an invisibility cloak! We tried reaching the researchers for a statement, but they couldn’t be spotted. Get the joke? No? Moving on.
Source: http://www.forbes.com/sites/alexknapp/2012/11/14/duke-researchers-perfect-the-original-invisibility-cloak/
The Duke cloaking device comprises of concentric circles of metamaterial with a cylinder in the middle where the object is placed. The light beams then bend around the cloak, like a rock diverting water in a stream:
Source: http://3.bp.blogspot.com/_OJ-BHgBCY5w/TKDFSGKow8I/AAAAAAAAANU/kvYtaBKM7wM/s1600/BlurredStream2.jpg
The technology right now is limited to the type (wavelength) of light the object is invisible from and also the size of the object, but Michio Kaku is hopeful!
Think About It
With 3D printing technology on its up, in a not too distant future, we’ll be able to make invisibility cloaks at home! Now the real conundrum, how should scientists keep their science from going into the “wrong” hands?
Learn More
How invisibility cloaks work | How we see through the looking glass | Refraction | Secrets of Metamaterials | Duke Invisibility Cloak
About the Authors
Jaya Ramchandani works on several astronomy and physics outreach projects. She is also a co-founder of Sirius Interactive, a language solutions company for researchers.
Jonathan Dias freelances for magazines and papers like Maxim and the Herald, writing about women, food and gadgets. He is also attempting to write a cook book that involves a lot of bacon and beer.
