A New Determine for the Cosmic Pace Restrict – Science Information, December 2, 1972
A gaggle on the Nationwide Bureau of Requirements at Boulder, Colo., now studies an especially correct [speed of light] measurement utilizing the wavelength and frequency of a helium-neon laser.… The end result offers the pace of sunshine as 299,792.4562 kilometers per second.
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That 1972 experiment measured the two-way pace of sunshine, or the typical pace of photons that traveled from their supply to a reflective floor and again. The end result, which nonetheless holds up, helped scientists redefine the usual size of the meter (SN: 10/22/83, p. 263). However they weren’t performed placing gentle by way of its paces. Within the late Nineteen Nineties and early 2000s, photons set a file for slowest measured pace of sunshine at 17 meters per second and froze of their tracks for one-thousandth of a second (SN: 1/27/01, p. 52). For all that success, one main hurdle stays: instantly testing the one-way pace of sunshine. The measurement, which many scientists say is unattainable to make, may resolve the long-standing query of whether or not the pace of sunshine is uniform in all instructions.