Lorentz invariance says that the laws of physics are the same for an observer at rest on the Earth or one who is rotated through some angle or traveling at a constant speed relative to the observer at rest. Looking for a crack in the universe in the form of a very faint field pervading the Cosmos, one that exerts a force on electron spin, would mean the end of Lorentz invariance. An important ingredient in Einstein’s theory of special relativity, Lorentz invariance has been borne out in numerous experiments. A new experiment conducted at the University of Washington, in Seattle, has sought such an anomalous field and not found it even at an energy scale of 10-21 electronvolt. This is the most stringent search yet — by a factor of 100 — for Lorentz-invariance-violating effects involving electrons.
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