50 years ago, physicists found the speed of light.
A group at the National Bureau of Standards at Boulder, Colo., now reports an extremely accurate [speed of light] measurement using the wavelength and frequency of a helium-neon laser.… The result gives the speed of light as 299,792.4562 kilometers per second.
That 1972 experiment measured the two-way speed of light, or the average speed of photons that traveled from their source to a reflective surface and back.
The result, which still holds up, helped scientists redefine the standard length of the meter ( SN: 10/22/83, p.
But they weren’t done putting light through its paces.
In the late 1990s and early 2000s, photons set a record for slowest measured speed of light at 17 meters per second and froze in their tracks for one-thousandth of a second ( SN: 1/27/01, p.
For all that success, one major hurdle remains: directly testing the one-way speed of light.
The measurement, which many scientists say is impossible to make, could resolve the long-standing question of whether the speed of light is uniform in all directions.
Foreign [Music] Years ago physicists found the speed of Light a group at the National Bureau of Standards at Boulder Colorado now Reports an extremely accurate speed of Light measurement using the wavelength And frequency of a helium neon laser the Result gives the speed of light as 299 792.4562 kilometers per second that 1972 Experiment measured the two-way speed of Light or the average speed of photons That traveled from their source to a Reflective surface and back the result Which still holds up helped scientists Redefine the standard length of the Meter SN 10 2283 page 263. but they weren't done putting light Through its Paces in the late 1990s and Early 2000s photons set a record for Slowest measured speed of light at 17 Meters per second and froze in their Tracks for one thousandth of a second SN 12701 page 52 dot for all that success One major hurdle remains directly Testing the 1 one-way speed of light the Measurement which many scientists say is Impossible to make could resolve the Long-standing question of whether the Speed of light is uniform in all Directions to stay up to date with Latest top stories make sure to Subscribe to this YouTube channel by Clicking the button above this video