A Leap in the Dark


Paradoxically, a shadow can go even faster than light! We can [cast a shadow] first at one star and then toward another star. We can take two stars more or less the same distance from Earth, such as Acrux in the Southern Cross and Bellatrix in Orion (both are 360 light-years away from us). We point the flashlight at Acrux and then we make the beam slide slowly toward Bellatrix. Three hundred sixty years later, the shadow … (which will at this point have become huge and very fast) will reach Acrux, and just a few seconds later it will be at Bellatrix, after having crossed one quarter of the vault of the sky far faster than the speed of light. Can shadows do things that are physically impossible?

— Roberto Casati, Shadows, 2000