Today, Moti Fridman and buddies, at Cornell University in Ithaca, go a step further. These guys have designed and built a cloak that hides events in time.
Time cloaking is possible because of a kind of duality between space and time in electromagnetic theory. In particular, the diffraction of a beam of light in space is mathematically equivalent to the temporal propagation of light through a dispersive medium. In other words, diffraction and dispersion are symmetric in spacetime.
I don't really understand how this is different then regular cloaking. I mean, if something is normal cloaked for some amount of time, then it is implicitly time cloaked as well. I mean, are those space-time events not hidden? Also, their space-time diagram makes no sense. They have rays going sideways which would mean they are not moving, and then rays going backward in time.
