On the big screen, in video games and in our imaginations, lightsabers flare and catch when they clash together. In reality, as in a laser light show, the beams of light go through each other, creating spiderweb patterns. That clashing, or interference, happens only in fiction—and in places with enormous magnetic and electric fields, which happens in nature only near massive objects such as neutron stars. Here, the strong magnetic or electric field reveals that a vacuum isn't truly a void. Instead, when light beams intersect here, they scatter into rainbows. A weak version of this effect has been observed in modern particle accelerators, but it is completely absent from our daily lives or even normal laboratory environments.