IMAGINE a place far from here, deep in the emptiness of space. This point is light years from Earth, vastly distant from any nebula, star or lonely atom. We have many words for what you would find in such a place: a void, a vacuum, a lacuna. In fact, this nothingness is a sea of activity.
According to quantum theory, empty space is filled with virtual particles. They are always there, keeping reality ticking over smoothly. They are also completely undetectable – unless, that is, you have an incredibly powerful searchlight. “Usually when people talk about a vacuum, they mean something that’s empty,” says theorist Mattias Marklund at the Chalmers University of Technology in Gothenburg, Sweden. “But a laser can show you the vacuum’s secrets.”
To expose virtual particles, to transform them into something tangible, takes one serious laser. But that is exactly what physicists are putting the finishing touches to in Romania. Switched on for the first time a few months ago, this machine could not only reveal the truth about empty space, but also teach us about another big mystery: dark energy, the unknown entity accelerating the expansion of the cosmos. It is time to rip nothingness apart and see what is inside.
The notion that nothingness is full of virtual particles might sound fanciful. After all, no astronaut swims in a virtual sea, no satellite is hindered by virtual drag. Virtual particles just aren’t tangible. The reason we believe they exist goes back to the foundations of quantum electrodynamics (QED), the branch of quantum theory used to calculate what happens when photons, particles of light, interact with electrons. …
