Matter is built on flaky foundations. Physicists have now confirmed that the apparently substantial stuff is actually no more than fluctuations in the quantum vacuum.
The researchers simulated the frantic activity that goes on inside protons and neutrons. These particles provide almost all the mass of ordinary matter.
Each proton (or neutron) is made of three quarks - but the individual masses of these quarks only add up to about 1% of the proton's mass. So what accounts for the rest of it?
Theory says it is created by the force that binds quarks together, called the strong nuclear force. In quantum terms, the strong force is carried by a field of virtual particles called gluons, randomly popping into existence and disappearing again. The energy of these vacuum fluctuations has to be included in the total mass of the proton and neutron.
But it has taken decades to work out the actual numbers. The strong force is described by the equations of quantum chromodynamics, or QCD, which are too difficult to solve in most cases.
So physicists have developed a method called lattice QCD, which models smooth space and time as a grid of separate points. This pixellated approach allows the complexities of the strong force to be simulated approximately by computer.