A beam from the sun may seem to you one smooth, continuous flow of light. Yet in reality, scientists have known for over a century that light, mass, and all forms of energy actually exist in discrete packets. Light comes to us in photons, for instance. Something that has mass is mostly the sum of its subatomic protons and neutrons. Time and space is also, on the face of it, smooth and continuous. But it needn't necessarily be so.

One of the wilder ideas to come from string theory is that space and time might exist in jumpy packets itself—in essence, the universe might be pixelated. An experiment based at the Fermi National Accelerator Laboratory in Illinois, has tested one theory of how this "hologram universe" might work. The appropriately named Holometer uses a pair of laser interferometers to test for any slight jittering. After a year of taking data, the Holometer did not, alas, find any evidence that we're living in a jumpy reality of two-dimensional bits. The Holometer is just getting started though, say researchers. They've also investigated high-frequency gravitational waves and have other space-time models to fire their lasers at.