Hank Green: Cloak of Invisibility! Always wanted one of these.

(Intro)

Listen up, muggles, because today I'm talking about cloaking devices first made famous by those pesky Romulans in Star Trek but perfected by the Demiguise. You don't know what a Demiguise is? Well, it's a small animal in the world of Harry Potter that's fur is woven into the Cloak of Invisibility that Harry Potter uses.* You thought it was just a Deathly Hallow? Also made of Demiguise fur. So in case you thought my cred as a Harry Potter nerd was in question, you can evacuate all of those thoughts from your brain right now.

The fact is, there's real research going on in the real world right now that could, one day, make things like me, for example, invisible. And who doesn't want to be invisible every once in a while? Like you, dear viewer, that time that your mom walked into you re-enacting the scene from Spider Man with the upside-down kiss with a wig head.

So, let's get the big question out of the way first: Do the laws of nature allow this to happen, allow for a thing that's there to appear to not be there? And the answer is yes, kinda. And two, Do those technologies currently exist, and the answer to that is no, kinda.

The key to making a real invisibility cloak is not to actually make the thing itself vanish. The key is to make light waves bend around that thing or refract around it so that you're basically seeing what's behind it. You know, like this.

The first research on this stuff was actually started in the 1950s and it focused on plasma, kind of like ionized gas. Scientists found that plasma was really great at reflecting or absorbing radiation as it comes in, and so they spent a lot of time and money figuring out how to surround vehicles and people with clouds of plasma. It doesn't make things invisible to our eyes, but it does make them invisible to things like radar.

But more recently, cloaking research has actually made progress creating materials that can bend light. In 2009, for example, two separate research teams came up with two very similar methods for cloaking using nanomaterials. One team at Berkeley drilled millions of tiny tiny tiny tiny tiny little holes in silicon-based materials, and these little holes allowed infrared light to bend around microscopic objects. Another team at Cornell was able to achieve similar effects by studding the surface of materials with tiny nanopillars.

And then there's this. Last year, in 2011, it seemed nanoscientists (yes, they are actually tiny tiny scientists) used heated sheets of carbon to make nanotubes in a pool of water create what's known as the mirage effect. This is like when you're driving on a hot summer road and the road in front of you looks like a pool of water. That's because the hot air you see just over the road surface is refracting the light you see to reflect the sky above. What you saw there is a lot like that -- refracting light to create a reflection.

Scientists have also gotten similar results using calcite and other kinds of crystal stuff, but the problem... well, okay, there are a lot of problems. A lot of these techniques only work when you're, like, underwater or in a certain color light or from a certain angle, and usually it only works with very small objects. And so far the research focused on nanomaterials hasn't been able to cloak anything that is very big because these nanomaterials are so extremely expensive to make, so until they get cheaper to create there's no way we're gonna be able to build a whole cloak out of it. So for now, all you wallflowers and wig-head-kissers... you're just gonna have to find different ways to blend into the background, unless of course you manage to score yourself a Demiguise pelt like me.

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Goodbye.

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* Editor's note: Harry Potter does not actually use a Demiguise cloak. Those are imperfect invisibility cloaks which will become opaque with time (although a living Demiguise can always turn invisible). Harry's cloak is the one true Invisibility Cloak, being a Hallow, and is not made of Demiguise fur because it does not fail with time.