What are the four steps in deriving the unit of measurement? And why does it need to be taught in such order?

Here are the four steps in deriving a unit of measurement, and why they are taught in this order:

Steps in Deriving a Unit of Measurement:

1. Define the physical quantity: First, you must clearly identify and define the physical quantity you want to measure (e.g., length, mass, time, electric current). This establishes the concept.
2. Choose a reproducible reference: Next, select a natural phenomenon or an easily replicable object that can serve as a basis for the unit. This reference should be stable and accessible, making the unit practical for use.
3. Standardize the reference: Create a precise, agreed-upon standard or prototype based on the chosen reference. This involves setting specific conditions and methods for its realization, ensuring consistency and allowing for comparisons worldwide.
4. Link to a fundamental constant: Finally, redefine the unit in terms of an immutable physical constant (like the speed of light, Planck's constant, or the frequency of a specific atomic transition). This provides the highest level of accuracy, universality, and independence from any physical artifact.

Why this order?

This order is taught because it reflects a logical and historical progression from a conceptual idea to a highly precise and universal standard. It moves from understanding what needs to be measured, to finding a practical way to measure it, to ensuring global consistency, and ultimately to achieving fundamental accuracy that is independent of any specific object or location. This systematic approach ensures that measurements are reliable and comparable across different times and places.