Light doesn’t always travel at the speed of light. A new experiment reveals that focusing or manipulating the structure of light pulses reduces their speed, even in vacuum conditions.
A paper reporting the research, posted online at arXiv.org and accepted for publication, describes hard experimental evidence that the speed of light, one of the most important constants in physics, should be thought of as a limit rather than an invariable rate for light zipping through a vacuum.
“It’s very impressive work,” says Robert Boyd, an optical physicist at the University of Rochester in New York. “It’s the sort of thing that’s so obvious, you wonder why you didn’t think of it first.”
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