Hello, I am reading Planck's Unit. What I understand is that what is the need for Planck's unit. Kilogram, meter and second are measurement, rather arbitrary measurement, which humans have done in the past. The question is what do we know that is constant throught the universe? We know (1) The gravitational constant (2) Planck's constant and (3) The speed of light. So if we could measure, say mass M, in terms of gravitational constant and Planck's constant and speed of light, then we can get something which is fundamental. My question is what is fundamental? G,c and h bar, how can they be called universal constants if they are again measured by us, human beings? Thanks.