15 October 2009

Artificial black holes!

Two Chinese researchers, Qiang Cheng and Tie Jun Cui, from the State Key Laboratory of Millimeter Waves at the Southeast University in Nanjing, China, have apparently created artificial black holes![1,2]

Bending light

Now everyone has heard of black holes (picture). Dense regions of matter, which are so dense that light cannot escape from them. Yadda yadda yadda. Booooooring! (Okay, not really. Black holes are pretty cool.)

Now if you want to bend light, there are two ways to do it. The one that comes to mind when thinking of black holes is gravitational lensing (picture), that is when a chunk of mass bends light because of its gravity. However there's a much simpler way to do so. Simply take something like a chunk of glass and witness Snell's Law (picture). Ta-dah!

If you have a dense enough chunk of mass, the lensing effect will be so big that light will start "bending inwards" (for lack of a better way to describe this), and light will not be able to escape. And that's your Grandma's black hole. An astute reader with a keen sense of inquiry (such as yourself) would at this point suspect that since this happens for mass, perhaps it also happens for optical materials as well.


Now these you might not have heard of. Metamaterials are essentially optical materials (glass is an optical material for example) that are specifically engineered to have uncommon properties (such as negative refractive indices). What a negative refractive index means is that a ray of light will bend inwards, as if the ray came from the opposite angle (picture) instead of bending in the usual way. What this means is that you can create a a material where light keeps "bending inwards", thus will never be able to get out, just like in Grandma's black hole.

The mathematical properties of these artificial black holes are exactly the same (as far as light is concerned) than for the "normal" black holes. So we now have black holes that we can build in labs, move around, experimentally study, and fits in your pocket. The really cool thing about them is since the mathematics are the same for the "artificial" or the "normal" black holes, then whatever knowledge we gain by studying the artificial ones yields knowledge about the normal ones.


[1] 14 October 2009. "Artificial Black Hole Created in Chinese Lab", Technology Review. Accessed 15 October 2009.
[2] Qiang Cheng, Tie Jun Cui (2009). "An electromagnetic black hole made of metamaterials", arXiv:0910.2159 [physic.optics]. (Lots of pretty pictures at the end.)

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