  Planck thought that physics can go beyond psychological dependency by basing itself on psychologically independent universal constants: “the constants appearing in the laws of heat radiation in free ether, like the constants of gravity, have a universal character and involve no reference to any special substance or any special body” [1909]. They are human-independent in a way that a unit like a centimeter is not. These constants can be used to “establish units of length, time, volume and temperature, which must of necessity retain their meaning for all time and for all cultures, even extra-terrestrial and extra-human ones” [1909].