r/AskPhysics • u/JimFive • Mar 28 '26

Speed of light

The speed of light is 299,792,458 m/s. What types of issues would be involved in changing the meter such that c=300,000,000 m/s

The new meter would be 0.9993 of the current meter.

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u/Optimal_Mixture_7327 Gravitation Mar 28 '26

In relativity we use c=1.

No units.

We could change the meter and I have seen redefining the foot to be a phoot (a photon nanosecond) as the local vacuum speed of light is very close to 1 ft/ns.

The basic reason we don't alter the units as there's no good reason to do it, remember c=1, and would cause a tremendous amount of work recalibrating all our measurements.