field based effect. The new effect is a sort of dual to Faraday's induction: Not only do changing magnetic fields create electric fields, but also changing electric fields create magnetic fields.
With Maxwell’s addition, fields take on a life of their own; they no longer need particles as their sources. Changing electric fields produce (changing) magnetic fields, which produce changing electric fields, and so forth, in a self-renewing cycle. Maxwell found that his new, improved equations—known today, of course, as Maxwell’s equations—have pure-field solutions of this kind, that move along in space at the speed of light. Climaxing a grand synthesis, he concluded that these self-renewing disturbances in electric and magnetic fields are light—a conclusion that has stood the test of time.
There is a persistent myth that Einstein, with his special theory of relativity, eliminated the ether. As with most myths, this one is based on a kernel of truth. Einstein indeed discredited some clunky models, popular at the time, which postulated mechanical underpinnings for the electric and magnetic fields. Those crude “ethers” are gone. But the implicit message, that Einstein emptied out space, is dead wrong. Einstein did not eliminate space-filling fields as the primary ingredients of physical theory. On the contrary, his special theory of relativity built on the physics of Faraday and Maxwell, and left Maxwell's equations, with its space-filling fields, just as they were.
It is natural to consider entities that fill all space, and have the same properties everywhere, as aspects of space itself.
Radio receivers, satellite dishes, or Wi-Fi Internet hookups sense various sorts of excitations in electromagnetic fields; our eyes sense other kinds. Generally, we can track down some source for these signals, e.g., broadcasting stations, the Sun’s reflected light, radio and light emission from astronomical bodies. A very special signal, in microwaves, is radiation from far-away hot gas (plasma), finally arriving here after a journey that began just a hundred thousand years after the big bang; this is, of course, the famous microwave background radiation. We can systematically eliminate that and all other sources, say by taking our receiver into a cold, dark, thick-walled cave underground. Having done that, still an ineradicable, faint hum remains. It is random “noise.” This irreducible signal represents spontaneous activity of electric and magnetic fields, intrinsic to their nature. It is another, direct indication of the rich inner life of space.
According to the rules of quantum theory, all dynamic entities exhibit spontaneous activity. In particular, fields do. This activity goes by various names: zeropoint motion, quantum fluctuations, or virtual particles. Like most quantum effects this spontaneous activity is barely noticeable in the macroworld, where it is hidden beneath much larger effects from ambient heat (thermal fluctuations). It does, however, become a limiting factor when one designs instruments to detect
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