c = 299792458 m/s Einstein's Constant
The speed of light in a vacuum. [Exact, by definition of the meter (m)]
The great power possessed by the general principle of relativity lies in the comprehensive limitation which is imposed on the laws of nature.
Albert Einstein (1916)
In April 2000, Kenneth Brecher (of Boston University)
produced experimental evidence, at an unprecedented level of accuracy,
which supports the main tenet of Einstein's
Special Theory of Relativity,
namely that the speed of light (c)
does not depend on the speed of the source.
When he announced his results, Brecher declared that
the constant c appears "even more fundamental than light itself"
and he urged his colleagues to give it a proper name and
start calling it Einstein's constant.
The proposal was well received and has only been gaining momentum ever since,
to the point that the "new" name seems now fairly well accepted.
Since 1983, the constant c has been used to define the meter in terms of
by enacting as exact the above value of 299792458 m/s.