We're one step closer to cloaking Devices, now they can be scientifically theorized; but they're not sapping your sentry just yet.
One of the main failings of games and science fiction in general is that whilst some inventions (like teleportation, androids, and so forth) are really cool, they fail to deal with real physical laws and are sniffed at by 'proper' scientists. Now, however, scientists have found a theory to produce invisibility whilst still remaining within physical laws.
The original research here, is very heavy on the physics, so I'll do my best to translate.
Two years ago, an Anglo-US team managed to create a 'cloak' which could hide an object from microwaves. As microwaves are part of the electromagnetic spectrum, along with visible light, something that could cloak visible light would allow invisibility without all that bumping around in bandages.
The cloak was made out of a Metamaterial, of copper wires fastened around fiberglass. As the microwaves struck the cloak, they flowed through the copper without affecting the surface.
Earlier this year, scientists in California built a cloak that could negatively refract visible light, in the same way that water does. They were nearly there, but it took a team from Scotland and the Czech Republic to finally nail the starting point.
The breakthrough came when they started using Non-Euclidian geometry to describe how such a cloak would work.
In essence, the new cloak would present a surface similar to a sphere, where the light coming towards the object would be streamlined around it, in the same way that an aircraft diverts air around its wings. The beauty of this theory is that it will divert light from all sides, whilst leaving the person underneath the cloak able to see.
So Team Fortress's Spy doesn't yet exist, but the theory to create him does.
Watch this space. And if you don't see anything, you know it's worked.