It’s confirmed: Matter is merely vacuum fluctuations

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.

Ab Initio Determination of Light Hadron Masses
Dürr, et al. Science 21 November 2008:Vol. 322. no. 5905, pp. 1224 – 1227

(h/t to Martin)