A functional invisibility cloak is one of those things that physicists keep chasing, and every six months or so we see an update that brings us one step closer to being able to sneak around without being seen. Today's major breakthrough comes from an undergraduate student at the University of St Andrews who figured out how to get around the fundamental problem of light taking too long to travel around the hidden object.
Here's the problem: when you have an object hidden by an invisibility cloak, the light has to be warped around it so that the object is invisible, right? But now the light has to take a longer path, making it slower than it should be. If everything's dead still, you won't notice the difference, but as soon as there's movement, the warping shows up.
So how do you fix this? You either make the light travel faster than the speed of light (very hard) or you do what this kid did, and make a large bubble of space where the speed of light is slower than normal, so you don't look out of place. By slowing down the speed of light over a larger area, it's possible to match the speed around the cloak with comparative ease.
This is all mathematics right now, but if the theory holds up, we're one step closer to making invisibility cloaks without that Predator shimmer in the background.