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What is the most common way to measure the speed of light?
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The most common way to measure the speed of light is by using a technique called interferometry. This involves sending a laser beam through two different paths, and then recombining them at a detector. If the path lengths are equal, then the beams will interfere constructively, producing a bright spot at the detector. If they’re not equal, then the beams will interfere destructively, resulting in a dark spot at the detector. By measuring the brightness of the spot, we can determine the difference in length between the two paths, which gives us an estimate of the speed of light.