NOTHING is not what it seems. Or rather, the vacuum that exists throughout space and inside every atom is not empty at all. It has an intricate structure that determines how matter is built.
Sounds bizarre? Blame it on the fact that the vacuum is permeated by a gluon field, which is the glue that binds quarks 鈥� the fundamental units of matter 鈥� into protons and neutrons. This gluon field can stick to itself like sticky tape, curling up into knots called instantons. These four-dimensional vortices are distant relatives of wormholes, the space-time 鈥渢unnels鈥� that could act as short cuts through the universe. Instantons create the distorted vacuum-scape that quarks have to navigate.
We cannot directly observe all this, so how do we know instantons exist? So far, they鈥檝e only been seen in computer simulations. But new findings from the Brookhaven National Laboratory in Upton, New York, hint at their ghostly existence (Physical Review Letters, DOI: 10.1103/PhysRevLett.94.102302). In Brookhaven鈥檚 particle accelerator, a fireball 300 million times hotter than the surface of the sun 鈥渕elts鈥� the vacuum. As a result, the gluon field loses its stickiness, quarks break free from one another and the instantons unfurl and disappear. At least, the researchers assume this is what is happening, because a major effect that instantons have on the quarks suddenly disappears.
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What else do we know about instantons? They got their name because they blink in and out of existence, like twinkling stars or bubbles in soapy water. But despite their elusive nature, they have a powerful influence on quarks. Quarks have a property called spin; some spin to the left, others to the right. The equations that govern them stipulate that a left-handed quark can never turn into a right-handed quark, and vice versa 鈥� a rule called chiral symmetry. But instantons break the symmetry. When a quark that鈥檚 spinning one way passes through an instanton, it swirls around in the vortex and becomes so disoriented that it emerges spinning the other way round: imagine a right-handed glove swirling through a tornado so twisted that it comes out left-handed.
Why is this so important? Well, the result of all that twisting is that the quark gains mass. Quarks start out virtually massless, but when they loop through an instanton they gain energy, making them up to 60 times more massive. Since quarks make up the mass of protons and neutrons, which in turn comprise most of the mass of atoms, that means that more than 95 per cent of visible matter owes its mass to instantons.
