The search for ever-more fundamental understanding requires higher and higher energies and heavier and heavier particles. An example is the ATLAS experiment at CERN, shown in the image to the left. We also discover that space is not empty, but is better described as a foam of virtual particles that blink into and out of existence, constrained only by the Heisenberg uncertainty principle; that their energy multiplied by their lifetime is less than h/4𝜋, where h=6.62607015×10^−34 J⋅s. However ephemeral, these virtual particles have a dramatic effect on the properties of “real” particles, and must be included in calculations to get accurate results.