The USA physicist Frank Wilczek provides an excellent state of the art for
Particle Physics, and his own favorite solution to the dilemma of "grand
unification". I found three themes particularly interesting.
Newton's mass was an arbitrary concept. Einstein tried to explain it in terms of energy. Quantum Chromodynamics suggests that most of what we call "matter" is not all that material, because a body is made of elementary "particles" that are almost mass-less (for example, the proton is made of two quarks, whose combined masses are about 1% of the mass of the proton, and of gluons, which are mass-less). Newton believed that mass could not be created: it was always conserved. Einstein showed that energy can turn into mass and viceversa. That opened the possibility that mass might not be a primitive element, but might be "created"; that there is an origin of mass. Wilczek visualizes the origin of mass in a compromise that Nature has to strike between two opposing principles: on one hand Nature wants a quark and an anti-quark to be as near as possible to minimize the energy required (the strong/color force increases with distance) but pinpointing an anti-quark's position next to its quark would require an infinite amount of energy (as per Heisenberg's uncertainty principle); and viceversa (the energy is minimal when the two particles are let loose in the universe, but then the strong force between them would become infinite). The compromise between these two extremes is the mass of the proton.
Noting that photons become heavy inside (electric) superconductors (or, better, that an observer inside a superconductor would perceive a photon as a massive particle), Wilczek derives the analogy that we live inside a (non-electric) superconductor into which particles (and then objects) acquire mass. That "superconductor" is made of the Higgs condensate, which is made from the Higgs particle.
Space has been another hotly debated concept in the history of science. Since Quantum Physics predicts that empty space is inherently unstable, both Newton's absolute space and Einstein's relative spacetime (that defied common sense by assuming action at a distance) are being replaced by the vision of a space that is full of spontaneous activity, that seems to have a life of its own. In fact, there seems to be layers of activity that take place in spite of the laws of Physics at our layer. That activity is not irrelevant: it might determine what happens at our layer. These "condensates" arise from empty space, which behaves like a superconductor of a new kind. One theory is that the metric field of General Relativity should also obey the same laws, and therefore be "inhabited" by quantum fluctuations, and be made of yet another kind of "condensate". After all, Einstein's cosmological constant (if it is indeed needed) would de facto represent an intrinsic property of space.
TM, ®, Copyright © 2009 Piero Scaruffi