In the vicinity of black holes, space is so warped that even light rays may curve around them several times. This phenomenon may enable us to see multiple versions of the same thing. While this has ...

Congratulations on noticing an effect called superluminal expansion, a phenomenon we see in a light echo. The echo appears to us to expand at many times the speed of light, seemingly violating the ...

Everyday experience tells us that light reflected from a perfectly flat mirror will give us the correct image without any deformation. Interestingly, this is not the case when the light field itself ...