# Why can't we define fundamental unit of mass? [duplicate]

In my physics textbook of class $11^{th}$ The kilogram was defined as :-

mass of the platinum-iridium standard cylinder kept at Sevre's France

But this isn't a proper and scientific definition of an important fundamental unit.
When we have advanced so much in atomic physics that we are creating matter, Then why are we unable to define unit of mass?

• @JohnForkosh i am small to understand that May 25, 2018 at 9:58
• Possible duplicate of Why do we still not have an exact (constants-based) definition for a kilogram? May 25, 2018 at 10:08
• @EmilioPisanty Sorry but title was not clear so this happened May 25, 2018 at 10:21
• @Abhishek No need to apologize, asking duplicates is just something that happens. May 25, 2018 at 12:25
• @EmilioPisanty My question was genuine but its ok May 25, 2018 at 12:26

The definition of the kilogram is to be changed in 2019, see Proposed redefinition of SI base units (wiki).

The current proposal is to indirectly define the kilogram via an exact specification of the Planck constant: this is possible because the dimension of that constant can be expressed as a combination of mass, time and distance. The kilogram would then be defined via the second and the meter.

• is it nice for a definition to depend on other definitions? May 25, 2018 at 9:29
• How would you do otherwise? May 25, 2018 at 9:30
• using exact value of avogadro's number? May 25, 2018 at 9:31
• So you would be using the definition of the mole. May 25, 2018 at 9:35