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Quantum glow shows the way
The vacuum is not what it seems. The ephemeral phenomena occurring in it will help merge two great, but separate, descriptions of the world.
Vacuum is unequal to vacuum. In common parlance, there is one, and it is what fills the free spaces of the Universe. But the solid state physicist sees a whole range of them. And none is perfect. But suppose there is one in which there is nothing known — no molecule, no atom. That wouldn’t be a vacuum, either. Rather, it is a foam of illusions. Unusual and counterintuitive things happen in it — particles are born, only to disappear after a while, jump backwards and forwards in time.
Something else is happening. Vacuums are sometimes relative. They are something slightly different for observers who are stationary or moving at a constant speed, and something different for those who are accelerating. The former may have the impression that space is empty. The latter, that it is filled with particles. And the more of them they will see, the greater the acceleration. This phenomenon, commonly known as the Unruh effect, was described independently by three scientists — Stephen Fulling in 1973, Paul Davies in 1975, Bill Unruh in 1976.
The appealing image illustrating it is a thermometer. In a vacuum devoid of heat sources, it will indicate zero. But subjected to acceleration it will indicate a higher temperature…
